Electrical Components Blog

Electrical Components

The Electrical Components Blog is the place for conversation and discussion about power generation, distribution and protection; connectors and relays; sensors, RFID & passive components; and magnetics and transformers. Here, you'll find everything from application ideas, to news and industry trends, to hot topics and cutting edge innovations.

Previous in Blog: Government Bankrolled Power Projects?   Next in Blog: Buy Local or Buy Best?
Close
Close
Close
96 comments

Hydraulic Hybrids Race Against Electrics

Posted January 23, 2009 8:19 AM

With all the hoopla about gas/electric hybrid vehicles, a superior technology may be getting lost in the shuffle. Hydraulic hybrids have three main advantages over electrics. First, the gas engine can be run at its sweet spot because hydraulics decouple the engine from the wheels. Second, vehicles can be run with the engine off. Third, regenerative braking energy is captured more efficiently. Will hydraulic hybrids win the race against electric hybrids?

The preceding article is a "sneak peek" from Electrical Components, a newsletter from GlobalSpec. To stay up-to-date and informed on industry trends, products, and technologies, subscribe to Electrical Components today.

Reply

Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
United States - Member - USA! Hobbies - Musician - Sound Man Engineering Fields - Mechanical Engineering - More than a Hobby Technical Fields - Technical Writing - New Member

Join Date: Oct 2008
Location: City of Roses.
Posts: 2056
Good Answers: 99
#1

Re: Hydraulic Hybrids Race Against Electrics

01/23/2009 4:31 PM

I hope so, considering i work in the Hydraulics Industry.

I have seen some really impressive hydraulic hybrid vehicles, getting 100+ MPG (keeping in mind there not your average commuter vehicle, more like a aerodynamic go cart)

In my opinion we need to get every viable technology married together in order to achieve the highest level of success.

__________________
Don't believe everything you read on the Internet!
Reply
Guru

Join Date: Jul 2008
Posts: 928
Good Answers: 55
#2

Re: Hydraulic Hybrids Race Against Electrics

01/23/2009 11:36 PM

It must be at least 35 to 40 years since I was first introduced to Hydrostatic drive. It was my first experience of all wheel drive and not a drive shaft in the lot.

Unfortunately this new experience was in the form of a 40 ton earth mover so it's rather a stretch to envision a car with it.

A hydraulic "Motor" was in each hub and fed power by high pressure hoses from a centrally mounted, engine driven pump.

I suspect they are still in use moving ore from open pit mines.

One thing that was weird was the sound of the engine: constant. Very little RPM change. It was at it's optimum torque setting all the time.

It never caught on in Detroit, which given their lack of innovation, is hardly a surprise.

__________________
"Both the revolutionary and the creative individual are perpetual juveniles. The revolutionary does not grow up because he cannot grow, while the creative individual cannot grow up because he keeps growing." Eric Hoffer
Reply
Anonymous Poster
#3
In reply to #2

Re: Hydraulic Hybrids Race Against Electrics

01/23/2009 11:47 PM

You hit the nail on the head, hydrostatic drive are great for earthmoving were it does not matter so much if they dump 40 litres of oil on the ground through having a burst hose. On the highway what an almighty pile up it could cause, even little drops of oil build up on the road surface having thousands of cars with the possibility of slight leaks from hydrostic drives is not good for highways. Engine oil drips are already a problem electric is a much safer approach.

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#4
In reply to #3

Re: Hydraulic Hybrids Race Against Electrics

01/24/2009 1:23 AM

Since the 1950's we've had many automobiles on the road with automatic transmissions. Most, if no all, had external oil lines running from transmission to radiator and back. In addition we have had power steering systems with external oil lines as well as oil filled air conditioner lines. The biggest problem with these things has been fires in which oil was ignited by exhaust heat or major short circuits of batteries. When oil gets on the road it is easily cleaned up with absorbents similar to kitty litter. Just not a problem any bigger than a dozen other messy consequences of auto accidents.

Everyday oil drips on the roads are a fact of life and have been for 100 years. I don't think this issue rises to the level of a disqualifier of hydraulic drives.

Several weeks ago we had a good discussion of hydraulic hybrids on another automotive oriented forum and I gained some real appreciation for the possibilities. Much of the problems revolve around how high you can make the practical working pressures of the hydraulics (for energy storage and sizing of the pumps and motors) and still keep the costs of the pumps and motors and size of the oil storage tank(s) within reason. There is a fire safety issue with respect to the amount of petroleum based oil that can be sprayed out of a high pressure hydraulic line. But we seem to deal with that fairly well in industrial hydraulics use without having to revert to the costs and technical problems of fire resistant hydraulic fluids used in aircraft systems.

Ed Weldon

Reply Score 1 for Off Topic
3
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#5

Re: Hydraulic Hybrids Race Against Electrics

01/24/2009 2:21 AM

Hydraulics will win when they are built correctly, and combine the engine with the hydraulics in a synergistic manner, likely in a free piston engine and NOT a diesel or Otto cycle (a large subject...).

There are a few companies that see what needs to happen in part, but the typical hydraulic motor system just will not do. For example, the typical hydraulic motor, such as an axial piston, has a rotary valve plate that pressurizes and depressurizes the fluid, causing a ringing noise. The valve needs to be closed just before Top Dead Center to repressurize the fluid before opening to the high pressure side, or by other means. If you don't do this, which most all don't, then you get a loss and slamming and pressure spikes.

I think that "water" hydraulics will prove the best because when you get into it long and deep enough with synergies you realize that water solves a lot of problems, one of which is high pressure injections. If oil is used, a person could be injected with oil and this is very dangerous and potentially fatal. If a person is injected with water then the risk is much less. Water is eco friendly and can be changed easily. There are some additives that can solve the freeze problem. Typically water is limited to 2000 psi (DanFoss water motors).

The end game is an engine that takes in air, produces water for drinking in the car, gets 60% efficiency at all times down to 1% of peak power, allows waste heat use for heating and cooling and solar cycle off the roof for hydrogen storage while the car is parked. When you get that, which is what I am confident is possible, the electric car will be way behind. Such a system would get 3x highway and 6x city over an Otto none hybrid car, or 2x and 4x over a Diesel based car.

The power density of hydraulics is also very important over that of electrics. Potentially the (water) hydraulics can be combined with safety restraints allowing for truly safe and low weight cars that can also use CNG, Hydrogen, compressed air, and liquid fuels. I am making mine also use a battery because of the PC nature of electrics.

I don't see the UPS system based on Eaton hydraulics being what needs to happen.

Seaplaneguy

Reply Good Answer (Score 3)
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#9
In reply to #5

Re: Hydraulic Hybrids Race Against Electrics

01/24/2009 12:12 PM

seaplaneguy-- You may be on to something here. Anyone actually contemplating building real hardware?

The challenge I see, and I think you'll agree with me, is designing the high pressure pumping elements that can live in a low viscosity poorly lubricating water environment. Like so many of our other good ideas for new vehicle propulsion technologies this one may be waiting for materials science to catch up.

I grew up as a mechanical engineer during the first era of experimentation with new engine technologies. We watched the Wankel Rotary rise and then fall over short lived tip seals only to rise again in the hands of Mazda as that particular material problem was solved with good old engineering persistence.

The project I worked on was invented by an engineering manager from Curtis Wright, the North American Licensee for the Wankel Engine. It was called "Dynastar" and it failed basically because the mechanical engineering challenge outweighed the patience of the investors. I like to think that with persistence (engineeringspeak for rectangular dollars) it might have succeeded.

Another interesting story now lost but in the memories of a few old guys.

Ed Weldon

Reply
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#10
In reply to #9

Re: Hydraulic Hybrids Race Against Electrics

01/24/2009 3:11 PM

Weldon,

I plan on building hardware once I get past my "challenges" (like the Wankel) that I run into with my concepts. I thought I was onto something this week to solve a key problem, and that devil guy knocked me down again...for the 20th+ time...

The devil is in the detail, and the devil of the Wankel was as you say, and moreover, the real problem with the Wankel was that is was not any more efficient or better on fuel economy, AND it had that nasty seal issue that burned up lots of money and, oh, the emissions were "troubling" most of the time. If the Wankel was 60% efficient it would be the standard today.

Was the Dynaster like the Dyna-cam?

I called up all the hydraulics shops in my area with 30+ years of experience...you know...and none could help out. One gave me a reference. I talked with him to see if he could help...can't... The hydraulics industry has a niche that works and the issues to solve the engine problem just have not come up. Once you look into standard hydraulic equipment you start to see why they are NOT used on cars.

Seaplaneguy

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#12
In reply to #10

Re: Hydraulic Hybrids Race Against Electrics

01/25/2009 2:00 AM

quote seaplaneguy: "the real problem with the Wankel was that is was not any more efficient or better on fuel economy"

But wow!! Could they put out horsepower! I saw the Racing Beat RX-7 at Bonneville (including the 240mph dance in the air). And the sound of that engine......never heard anything like it before or since.

OK, back to water for hydraulic hybrids. At an optimistic 90% efficiency 100 hp out of a hydraulic motor will require 94 gpm of water at 2000 psi, 63 gpm at 3000 psi and 47 gpm at 4000 psi. So it'll take 47 gallons of water storage in high pressure cylinders (like oxygen cylinders at 4000 psi to give back 100 hp for one minute. That, 47 gallons, is about 390 pounds of water weight or 6.28 cubic feet or 10857 cubic inches. That's 32 linear feet of 6" ID pipe. 500+ pounds of 1/4" wall pipe. (that's a guess, I didn't do the pressure calculations on wall thickness.) Maybe one minute storage is too long.

OK, a 3000 lb car (2500 plus 500 for the water tanks) with 100 hp will reach 60 mph in around 15 seconds with near ideal transmission operation, 20.4 to 70 and 27 seconds to 80mph. You get power back into the tanks at the same rate. (about the same, the efficiencies will be a bit different). This all suggests that all we really need for most normal driving is maybe 1/3 the tank capacity. Now 4000 psi is pushing the envelope for ordinary piston pump technology. 3000 psi (maybe one step above your ordinary high quality pressure washer) sounds more realistic. That puts us at about 23 gallons of water storage (liquid and tanks will be about 190 water plus 275 steel = 465 and add 35 for brackets etc., say 500 pounds for 4, 48 inch long tanks.)

So we have a 100 hp turbocharged diesel (2-3 cylinder?) some kind of piston type water pump. There are other types of positive displacement pumps but virtually nothing that can handle pressure the way a piston pump can. Now another important concept is that pumps can run as motors in the same manner that electric motors can run as generators. So the same pump that pumps water to high pressure can extract the same energy and turn it into mechanical energy. Thus we need only one of these close tolerance machines to do the jobs of putting energy into the water and getting it back out.

So the next problem is the question of just how efficient will our piston pump be working water at 3000 psi? Will it be 90%? Likely it would except for one issue. Water doesn't have the viscosity of even the lightest hydraulic oils so every place where there are loads between two moving parts in close contact the bearing issue must be addressed and solved. Almost no case of boundary lubrication or even mixed film lubrication can be allowed to exist if the kind of reliability and life we expect in automotive applications is to be achieved.

Clearance will have to be an order of magnitude more precise as will surface finishes. Thermal effects of expansion and contraction of materials in the pump will have to be greatly reduced through a combination of temperature control and lower CTE's. And all of this must be done at lower costs and higher production volumes than such technologies have been executed before.

So that's where I see the challenge. I don't think this is any greater a hurdle than achievement of practical electric car batteries. But also I don't think it will be much easier. I think we are looking at superfinished low CTE high strength ceramics for piston/cylinder materials as well as valving. That means scaling up precision ceramics grinding technology to automotive volumes. And guess who are the leaders in ceramics technology? The Japanese. The folks who build those fantastic motorcycle engines among other things.

Again, seaplaneguy....... I'm not sure you'll agree with me and I'll understand if you are a bit shy talking about it in much more depth given your possible commercial interest in this technology. But I though it might be intesting to crunch some rough numbers to help keep the conversation going.

Oh yeah.....Dynastar. Interesting story. Keep reminding me. It's too long to add to this post and it's really a good subject for another topic.

Ed Weldon

Reply Score 1 for Good Answer
Anonymous Poster
#14
In reply to #12

Re: Hydraulic Hybrids Race Against Electrics

01/25/2009 6:26 AM

Weldon,

Thank you for the thoughtful reply. Interesting that the RX-7 sound was interesting to you. I prefer quiet, especially while in the air flying...I can always add in sound effects.

The concept you mention is what most people envision. You got the gist quite well.

I don't see a need for more than 5-10 seconds no-engine-on power, or around 10-15 gallons at most. If you can get higher efficiency, say 60%, then you don't need to carry as much fuel (1/2?). A water motor would have to be well over 90%, yes. I am not looking at ceramics now (was), due to a new design that won't need it. Yes, water does require 1/3 the tolerance, but that is if you use boundary layer sealing like on a gear motor, which I don't do.

I think this will actually be rather inexpensive if I can successfully eliminate all the "challenges" you so rightly mentioned. It takes a long time to write a short letter and a short time to write a long letter...same idea applies to engines. I am putting the time into simplicity in hopes of low cost in the long run. Sometimes, like with the Wankel, a simple concept ends up very costly because of "challenges" that arise.

By the way, if you know of any good "out of the box" hydraulics guys (does such a person exist?) who wants to help on designing a new type of motor, I am looking for consulting help to brainstorm with to speed this up. Had a guy with 30 years and he chickened out when I told him what was needed.

Dynastar? (reminder)

Seaplaneguy

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#6

Re: Hydraulic Hybrids Race Against Electrics

01/24/2009 3:12 AM

Will hydraulic hybrids win the race against electric hybrids?

No.

__________________
There is more to life than just eating mice.
Reply
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#7
In reply to #6

Re: Hydraulic Hybrids Race Against Electrics

01/24/2009 3:24 AM

yes

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#15
In reply to #7

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 1:13 AM

No.

__________________
There is more to life than just eating mice.
Reply
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 662
#16
In reply to #15

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 4:25 AM

You made me splarff my tea...
(Timing.... is everything)
Del

__________________
health warning: These posts may contain traces of nut.
Reply Off Topic (Score 5)
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#17
In reply to #15

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 9:26 AM

Yes, and raise ya two yeses...make that three...

Reply
Power-User

Join Date: Feb 2007
Location: Nebraska
Posts: 104
Good Answers: 2
#18
In reply to #17

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 1:17 PM

I'd like to see some kind of super hybrid. Hydraulic drive train with large accumulators. Battery powered multiple electric pumps because you can stage the pumps on to keep the accumulators charged. I like the electric pumps because you can run them only as needed and if you stage them then you don't need expensive speed controllers. You also don't need massive batteries. And then some sort of power plant, gas or what ever, to charge the batteries for the electric pumps and it could also be used to provide extra pumping power for the pesky LONG hills.

The hydraulic accumulators would provided the power for all the starts you have in the city and the regenerative breaking, all the stops you have in city driving, would mostly recharge the accumulators. The electric pumps would be sized for your highway driving. And the gas powered generator, or what ever I wish I could find something better, would keep the batteries charged. You can downsize the gas generator to the minimum HP required for your highway driving. I'm playing around with the idea of a small motorcycle engine to keep the batteries charged in my design.

I've been bouncing my idea's off of my uncle who has been an hydraulic engineer for at least 30 years. And his first answer is always, "No that won't work". Then we talk it over and he will go "Well if you do it this way you might be able to get that to work". So I understand about working with hydraulic engineers. They are pretty set in their ways.

I'm hoping to start my build here in a few weeks. And I agree I sure wish I could find a better hydraulic motor. It is a complicated system but I sure think that it would be efficient. And it has to be less expensive then an all electric. The big electric motors can run $1500 maybe more and the same if not more for the speed controller. And then there are the batteries, you can spend 3 to 4 thousand dollars on batteries easy. I'm thinking I can do my hydraulic/electric system for less then $3000. Maybe a lot less.

And no I don't ever see this design catching on in Detroit.

Reply
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#19
In reply to #18

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 1:39 PM

Fishpipes,

I'm not understanding you...What makes the electricity to run the electric pumps? Why have any electric stuff in there at all? I can turn an engine off and on just as well as an electric motor, no? UPS does it.

It would seem to me that one should stay in one "domain" or the other due to the support needed for each. Electric hybrid or hydraulic hybrid, but not an electric-hydraulic hybrid in power transfer. Yes, the control should be in electronics in either case, but the merit of electric pumps seems limited. No?

Seaplaenguy

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#20
In reply to #18

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 2:27 PM

Fishpipes -- go look at this.

http://science.howstuffworks.com/skid-steer.htm

Then check out ebay. Search on "skid steer" for the prices of used bobcats. Figure on using the diesel engine, variable speed pumps and hydraulic motors to power just the two driving wheels for an ordinary subcompact car or truck and sell off the rest for parts. (Use the other two wheels to steer rather than fool around with 4wd steering. OK, you could likely use an FWD setup if you could come up with a good way to mount it all in an actual car or truck chassis and connect up the unique skid steer drive belt system).

Remember that hydraulic motors are nothing but specialized hydraulic pumps with the inlet and outlets switched with valving. So when you hit the brake pedal the valving changes until the accumulator tanks are fully pressurized and ready for the next acceleration cycle. Regular brakes will have to take over when the accumulator pressure maxes out. On vehicle acceleration the same control would have to disconnect the accumulator once it empties and let the engine pump pick up the load to further accelerate the vehicle.

By the way I wonder if ordinary double acting hydraulic cylinders (a lot cheaper than purpose built hydraulic accumulators) would work and hold up long enough at least for "proof of concept". Just pressurize one end with 1500 psi nitrogen and close it off.

If you really want to complicate things with an electric motor/generator in the middle of all this stuff that's certainly possible. But you'll be adding weight and cost that really will have to pay for itself including the efficiency losses unless all you are interested in is the "gee whiz" factor.

Or you could "off" the diesel engine and adapt the hydraulic pumps to your electric motor. But that big an electric motor/generator might be more practical just driving the wheels direct through a conventional drive train; which is nothing new and more mechanically efficient and cheaper than the hydraulic drive.

Remember this about hydraulic motor drives: The idea has been around for a long time in construction equipment. It's only used where mechanical drive trains won't work as well. As a young engineer in 1961 I found myself designing and testing hydraulic pump and motor hardware for the packaged refrigeration setups on refrigerated truck trailers. (My employer wasn't low bidder so the project was shelved)

Ed Weldon

Reply
Power-User

Join Date: Feb 2007
Location: Nebraska
Posts: 104
Good Answers: 2
#29
In reply to #20

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 9:57 AM

Thanks for your reply to my post. I've thought about some of your ideas.

My first thought for an accumulator was to use a cylinder, I ended up buying a small one on E-bay for 10 dollars. There are two problems I see with it. The first is what the heck do you do with the push rod. It would be kind of in the way. The other is volume. You would need to use a big bore in order to get the volume I want to test with and those are expensive. I'm thinking I'll build my own out of some schedule 40 pipe, and I've got so tricks up my sleeve to make that work. I know everyone is going to tell me it can't be done. And does it really matter if it's perfect I'm just doing this for myself.

And my electric motor idea is that I'm going to use small DC electric motors around 1 hp. I'm thinking 3 or 4 of them. They will each drive a small pump. I'm thinking I'm also going to need a bigger pump on my motorcycle motor. By doing this I can shut the gas engine off during low demand. And I've already said this is a complicated system I'm planning on building. No one in their right mind would market anything like this, it would be way to expensive.

This discussion is getting pretty serious. It seems to me that everyone needs to lighten up. If someone wants to build something with hydraulics in their back yard give them advice don't knock them down. And yes hydraulics are dangerous and anyone playing around with it needs to know that. Put quite just saying "IT CAN'T BE DONE". We need people that are free thinkers not people that say thats the way it has always been done.

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#31
In reply to #29

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 11:42 AM

fishpipes -- Looks like a neat experiment. Even if you can't get any spectacular efficiency out of it there'll be some unusual performance capabilities of the machine you're thinking of building.

One thing to be aware of is that any oil leakage into the high pressure gas side of the accumulator will produce an explosive mixture if the gas is air. The hazard there may be overrated as long as there aren't any glow plugs or spark sources. But I just don't really know myself. Usually these things are pressurized with dry nitrogen. I wonder what pressure and temperature might cause an air and oil vapor mix to ignite spontaneously? I guess that depends on the blend of the oil and what kind of light fractions it contains.

Anyone out there who knows more about this than this dreamer (me) want to comment?

Ed Weldon

Reply
Anonymous Poster
#78
In reply to #31

Re: Hydraulic Hybrids Race Against Electrics

03/02/2009 10:39 AM

For what this is worth, when I was in the US Navy, I repaired (among other things) Model 28 Teletypes. They had a shock-absorber on the front plate of the printer, called a dashpot. It was about 3/4 inch diameter, and about 1 1/2 inch long, and had a piston driven by a shaft coming in one end. The piston was sealed by a spring-and-gasket arrangement, and there was a small, screw-adjustable port on the top at the other end from the piston. The port was used to adjust the amount of shock damping it provided. We NEVER used teletype oil (very light grade, but heavier than trumpet valve oil, maybe around a 120W or so) (or any other oil, for that matter) because the Teletype Corp. (their hardware, remember?) stated in their manuals that doing so raised a risk of explosion, due to the spontaneous combustion of the oil, in turn due to friction and energy-damping heating. We KNEW they weren't wrong, after blowing one off the face plate, tearing out 3 hardened (Grade 5) 4-40 stainless steel screws, and punching a hole in a sheet steel (1/4" thick) shop wall, about 5 feet away.

And that was a SMALL piston, with very little oil (lube amounts, not for power, not SUPPOSED to burn), and only the air that could be sucked back in the damper port, and what leaked around the piston. Doesn't take much. I suspect this hydraulics idea COULD, and WOULD work, but I also suspect that if this scenario ever occurred at the kinds of pressures and volumes you are talking about, it would be nothing short of spectacular!!

NEWS at 11:00


Micah

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#83
In reply to #78

Re: Hydraulic Hybrids Race Against Electrics

03/02/2009 10:07 PM

Micah - Just a great anecdote!! Sort of like a diesel engine. The difference is that the diesel gets it's heating from adiabatic compression rather than from friction and gas compression inefficiencies. BTW, this does suggest some fodder for creative thinking.

Ed Weldon

Reply
Power-User

Join Date: Feb 2007
Location: Nebraska
Posts: 104
Good Answers: 2
#84
In reply to #78

Re: Hydraulic Hybrids Race Against Electrics

03/05/2009 9:14 AM

It's funny you should bring this up. I was reading about intensifiers, it takes a small pressure and large volume and outputs a high pressure low volume, and that was one of the things they said you needed to guard against. They called it dieseling. Which makes sense since that's what a diesel engine does. It made me wonder if you could use that in some controlled manner. So can anyone think of a way to use diesel fuel in this manner and get rid of all the machinery of an ICE engine????

Thanks for the advise. Oh and I wasn't planning on using compressed air for just this reason. They use nitrogen.

Reply
Guru
Popular Science - Weaponology - New Member Engineering Fields - Engineering Physics - New Member Engineering Fields - Nuclear Engineering - New Member

Join Date: Dec 2007
Location: No. VA, USA (No, it does NOTu mean "won't go"!)
Posts: 1791
Good Answers: 75
#79
In reply to #31

Re: Hydraulic Hybrids Race Against Electrics

03/02/2009 10:41 AM

Sorry, folks. #78 was me. I forgot to log in.

Micah

__________________
Been away a while. Miss all my old friends. Some of you I KNOW are still around. Where are the rest?
Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#36
In reply to #17

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 3:32 PM

Well then... No No No and nah nah nah.

Actually the problems with hydraulics, other than the low storage density, seem to me to have to do with efficiency vs cost. In the simplest case, with a gear pump and a modulating valve and a gear motor, the fluid flow losses are too high to be worthwhile, but the cost is low. When you go to efficient controllable-volume pumps, then the cost goes up so quickly. On the other hand, the hydrostatic units in lawn tractors are pretty cheap, and perhaps efficiency could be bumped up sufficiently while retaining low cost, if the volume were high enough.

Years ago, I worked on a project at Ford in which they started to build their own fuel injection nozzles. Then, the precision required was so high that it seemed that the cost would have to be astronomical. But the volume is sky high, and with a lot of automation, the nozzles are at least reasonable in price, although not cheap.

__________________
There is more to life than just eating mice.
Reply
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 662
#8

Re: Hydraulic Hybrids Race Against Electrics

01/24/2009 4:09 AM

If you two want to wager....
I'll hold your stake money.
Del(I'll invest it wisely at the fish shop)

__________________
health warning: These posts may contain traces of nut.
Reply Off Topic (Score 5)
Guru

Join Date: Jul 2008
Location: Mallorca, Spain
Posts: 567
Good Answers: 15
#11
In reply to #8

Re: Hydraulic Hybrids Race Against Electrics

01/24/2009 4:41 PM

I reckon these two have been to a good old fashioned English pantomime......

Ooooh no it won't

Oooooooh Yes it will etc etc.

Personally I'm with Ken on this one

Chas

__________________
En la casa del herrero, cuchillos de palo!
Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 662
#13
In reply to #11

Re: Hydraulic Hybrids Race Against Electrics

01/25/2009 4:02 AM

Look out, he's behind you

__________________
health warning: These posts may contain traces of nut.
Reply Off Topic (Score 5)
Commentator

Join Date: Apr 2008
Posts: 73
Good Answers: 10
#21

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 4:57 PM

There is a very good reason for using hydraulics for earthmovers and so forth... cars not so.

First off, the government will never allow vehicles with 2000 plus psi bombs on board out on the roads to kill all, or at least several, on board in the event of an accident, and to kill those in neighboring cars with the shrapnel. And in the case of one of thoise pinhole leaks that can practically slice right through you, nope, government safety folks just don't like it. In fact, you probably wouldn't either if it happened to you or a loved one. In a big earth mover that goes slow and never sppeds down the interstate and most of the equipment of concern is covered with heavy metal plates, it is a different matter altoghether.

One of you said that the hydraulic car would be 60% efficient. Well, the hydraulic part is 60% efficient, which is great except for the fact that you had to use something else, like an internal combustion engine to generate the energy for the hydraulics, so in essence, we are throwing away 40% of our energy for the opportunity to use those manly hydraulics. Where is the sense or economy in that? You will be paying 40% more at the gas station for the same number of miles - actually fewer miles since your vehicle is heavier. Why not use all the energy provided by that internal combustion motor running your hydraulics to just move the vehicle? You will be able to be 40% more efficeint and get rid of a ton of weight from the vehicle which means you need less energy to move your vehicle in the first place. If you use an electric motor to run your hydraulics as someone also mentioned, why not use the same motor to directly move the car instead of throwing away 40% of the energy for the excitement of having highly pressurized equipment on board.

These exercises in hydraulic vehicles are good for one thing, improving the technology so that the earth movers and so forth, that belch forth copious quantities of smog become much more efficient. They will never be on the road as a family car because of cost (maintenance and lots of extra heavy duty equipment), weight (heavy high pressure equipment located throguhout), safety and comparitively abysmal efficiency. No Virginia, hydraulic vehicles will never win out over electric or even internal combustion. In fact, hydraulic needs one or the other to make it work in the first place.

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#22
In reply to #21

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 6:07 PM

Quoting the PhysicsProf: "First off, the government will never allow vehicles with 2000 plus psi bombs on board out on the roads to kill all, or at least several, on board in the event of an accident, and to kill those in neighboring cars with the shrapnel. And in the case of one of those pinhole leaks that can practically slice right through you…..."

The issue of high pressures needs to be tempered by the fact that high pressures already exist in modern vehicles:

2000psi in diesel fuel injection systems, 1200 psi (at 900 deg F) in engine combustion chambers, 1000 psi in hydraulic brake systems to name a few. Is the prospect of the release of gallons of sulphuric acid or exposure to potential hundreds of volts at high amperage in electric car accidents or the destructive explosion of a tire or a mass of spilled gasoline any less of a safety hazard? When did you ever hear of the failure of a compressed gas tank, air brake tank or the massive hydraulic cylinders on the sides of our ubiquitous garbage trucks failing and causing personal injury in an accident. How about the proposals for CNG and hydrogen as vehicle fuel? Proposed hydraulic accumulators are a non-issue by comparison.

Another PhysicsProf quote: "like an internal combustion engine to generate the energy for the hydraulics,"

Read closer. That's not what we are talking about. This is about capturing mechanical energy from the car's velocity and storing it as a high pressure fluid (nitrogen in the accumulator) with the energy transfer medium being a convenient fluid such as hydraulic oil and the conversion device a purpose designed positive displacement pump/motor with appropriate controls. The prime mover for the vehicle could be anything from a rocket engine to a team of horses. This is nothing but a First Law (of thermodynamics) reversible process with a different mechanical execution. BTW, typical mechanical efficiency of a swash plate axial piston hydraulic pump is 92-94% Allowing for two passes of fluid through the pump (one in and one out in the motor mode) and a bit for the mechanical drive connection to the driveshaft we are looking at about 80% efficiency or some less if the power has to go through the hypoid rear axle gears.

Some have suggested combining the energy conversion/storage device into the prime mover's main propulsion system. There may be possibilities for efficiency and cost improving ideas there, particularly if the entire engine and hydraulic system can be a single compact package. In the extreme perhaps the hydraulic pump could take the place of one of the combustion cylinders in the engine block. After all, the hardware for pump and diesel engine are similar, and it may even prove possible to make the hydraulic system working fluid be diesel fuel or lubricating oil if the additive blend for either to do both jobs is practical. This, course is a major engineering project that doesn't lend itself well to proof of concept efforts.

I have suggested using Bobcat skid steer components for a serious compact car size experiment primarily because this hardware is readily available at reasonable prices for a "hobby" scale project. Used Bobcats are readily available at prices in the $3000-$5000 range. This solves the problem of mating an engine and hydraulic pump together; a prodigious effort in the 25-30 hp range which is the bare minimum needed for a drivable auto. And as a bonus you get a diesel engine and a whole pile of hydraulics and auxiliary hardware with the complete Bobcat (plus the problem of getting rid of what you don't use.)

Another possibility is to adapt the simple hardware of a 16-25hp pressure sprayer pump and an accumulator made from a couple of large double acting hydraulic cylinders (with 1500 psi nitrogen on the closed end) to any small vehicle as a concept test. This is an outfit that could well be mounted behind the transmission of a rear wheel drive vehicle and adapted to the transmission and a shortened driveshaft in the same manner that aftermarket overdrives for light trucks and RV's are done. This is an actual possible product after some of the details like component longevity are worked out.

So I tell you what, Prof…… Look a little closer………

Ed Weldon

Reply
4
Anonymous Poster
#56
In reply to #22

Re: Hydraulic Hybrids Race Against Electrics

02/05/2009 6:30 PM

Hydraulic accumulators are one of the safest energy storage devices around, provided that they are anchored as well as an engine, battery pack, or other heavy vehicle part. The classical failure mode is a perforated bellows, which leads to a loss of effectiveness, and a tedious repair job. It would take quite a crash to bust one, thatnis for sure. Perhaps a 60MH T-bone hit.

The good thing abut hydraulic storage is that if you are careful with the design, it can store enegy as fast as you can deliver it. That just does not work with batteries of flywheels, (remember the flywheel craze).

A hydraulic dragster could be quite interesting, all-wheel drive and an external pressurizing pump, then 1000HP at each wheel for 4 seconds, then apply the brakes, turn around, and drive back silently. That would be a show.

I used to work at a hydraulics company, J.E. Myles, and I am sure that if you wanted the parts and peces they could provide them. And then, after the car was assembled, they could put in the plumbing and controls. Because the piping in a hydraulic system is ABSOLUTELY VITAL to getting the best performance. JUst because it looks good and does not leak don't mean that it will work the way you want. So the hydraulic vehicle will need just as much engineering as the electric.

BUT the SUPER SAFETY feature is that when you switch it off, a hydraulic system is easy to make safe, unlike batteries, which do not "switch off". That is a real-world plus that would make hydraulics a better choice. Very few service people are electrocuted by hydraulic fluid. Excessivly lubricated, yes, but not zapped.

William Ketel, unemployed engineer.

Reply Good Answer (Score 4)
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#57
In reply to #56

Re: Hydraulic Hybrids Race Against Electrics

02/08/2009 3:50 AM

Ketel,

I am looking for an "unemployed engineer" with hydraulics experience who wants some part-time work.

Interested?

Write me at seaplaneguy@msn.com

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#60
In reply to #56

Re: Hydraulic Hybrids Race Against Electrics

02/11/2009 5:12 PM

A hydraulic dragster could be quite interesting, all-wheel drive and an external pressurizing pump, then 1000HP at each wheel for 4 seconds, then apply the brakes, turn around, and drive back silently. That would be a show.

A college friend, back in 1970 or so, did essentially this. He used a VW flat four engine to pump up an accumulator which was essentially the whole car. He entered it as at the races as a VW. He didn't have a big budget to work with, but the car was very impressive for its day (maybe 11 seconds in the quarter -- a lot quicker than the typical air-cooled Bug of the day.) I'd guess that the motors at each wheel were delivering about 75-100 hp. If we assume 400 hp total (which would support the 11 second time for this fairly heavy and un-streamlined car) The the energy stored would be 4400 hp seconds, or about double that stored in the UPS trucks.

__________________
There is more to life than just eating mice.
Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#37
In reply to #21

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 3:50 PM

First off, the government will never allow vehicles with 2000 plus psi bombs on board out on the roads to kill all, or at least several, on board in the event of an accident, and to kill those in neighboring cars with the shrapnel.

CNG cars and buses have (relatively huge) 3500 psi tanks, which can not only rupture in an accident, but can release a highly flammable gas. The government is happy with those traveling around.

__________________
There is more to life than just eating mice.
Reply
Guru

Join Date: Dec 2005
Location: Queensland Coalfields Australia.
Posts: 697
Good Answers: 11
#47
In reply to #21

Re: Hydraulic Hybrids Race Against Electrics

01/28/2009 2:10 AM

At this point I think I should kill off the "Big Earthmover" story. Big Earthmovers are either Electric drive or straight mechanical (with a torque converter). Some small gear is still Hydrostatic. The Hydraulics on big gear are for Brakes, Steering, implements etc.

Electric drives in Off highway vehicles use approximately 1/2 the fuel of their mechanical counterparts ands are faster on grade (the torque converter being the main loss). The modern designs are all AC at the wheel motors including the new Caterpillar 795.

Reply
Associate

Join Date: May 2008
Posts: 39
Good Answers: 1
#54
In reply to #21

Re: Hydraulic Hybrids Race Against Electrics

02/05/2009 1:18 PM

"the government will never allow vehicles with 2000 plus psi bombs on board out on the roads to kill all"

I guess that shoots down my 5000psi compressed hydrogen plans.

__________________
The beatings will continue until morale improves.
Reply
Commentator

Join Date: Apr 2008
Posts: 73
Good Answers: 10
#23

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 6:54 PM

Hi Weldon,

You were not happy with the high pressure comment. Note that the braking systems in cars that you mention have nowhere close to the pressures in some of what we're talking about. The other things like diesel injection happens at the engine virtually immediately before injection to the cylinder. Quite a different thing than a high pressure system distributed to all the wheels etc. You may also want to look at some previous posts of mine about hydrogen vehicles - enough said there. Besides, do you really want to add one of those heavy duty tanks you're talking about to your car to haul around and reduce the very mileage you're trying to improve?

By the way, there actually are documented cases (in the newspapers and everything) about the hydraulic cylinders on garbage trucks flying off and killing people in nearby vehicles. There are even documented cases of hydraulic components on dump trucks doing the same thing (although the manufacturer redesigned to reduce the probability of the part leaving the truck in that case). Propane tanks splitting during accidents (explosion, shrapnel, fire) - yes, such lovely stuff does happen. You can read all about it in newspapers.

About "capturing energy from the car's velocity and storing it as a high pressure fluid (nitrogen in the accumulator) with the energy transfer medium being a convenient fluid such as hydraulic oil and the conversion device a purpose designed positive displacement pump/motor with appropriate controls." Sorry Charlie but nothing comes for free. You still have to use up energy to make the car move and harnessing some of that energy in a very inefficient way only means you have lost energy and now you have to push it even harder to maintain speed - using up more energy. So, we use the process of burning fuel to make the car move, use some of that energy collected by very inefficeint means (energy loss) as a high pressure fluid. Now we loose even more energy as we transfer that energy to a hydraulic fluid and then loose even more as we transfer that to yet another form to say do what - turn the wheels to run the car to make it more efficient?!!! You can't see the failed logic in that? I don't care how efficient your hydraulic pumps and whatever else are, you won't get more energy out than you put in, especially once you have transformed it several times over. Just use the motor to run the car. Adding the complexity of compressed air and then hydraulics aren't going to make anything more efficient. If you are using some of the cars "velocity" to do this, you have to burn more fuel to maintain that velocity. Essentially you are dumping energy so you can reuse a fraction of it. Makes no sense. By the way, this is not the first law for reversible processes. Note all the lost energy - this is not a truely reversible process. In fact it's not even close. Read up on your physics.

"So I tell you what, Prof…… Look a little closer………" Sorry Weldon, but I've got to give you the same advice.

It may be fun to play with and you may learn a lot about hydraulics, but because of the efficiency losses naturally built into this type of system, it will never receive serious attention except by those trying to improve already fielded or to be fielded hydraulic systems (sometimes you never know where or who a good design idea might come from).

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#26
In reply to #23

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 8:42 PM

" 'So I tell you what, Prof…… Look a little closer………' Sorry Weldon, but I've got to give you the same advice."

Prof --OK, I've done you the courtesy of a close look at your latest post. Perhaps closer than you looked at mine.
My only advocacy of the complete hydraulic drive system, that was also suggested by LaughingJaguar and fishpipes, was in the context of an intermediate step for proof of concept where a very important consideration is the cost and effort involved in building the prototype.

"Please read closely the title of the topic just one more time for me….. ' Hydraulic Hybrids Race Against Electrics' "

My part in this discussion is about hydraulic hybrids; i.e. using hydraulic hardware to capture and redeliver the mechanical energy normally lost in braking as heat. Electric hybrids such as the Toyota Prius use electric motor/generators and batteries to accomplish the same thing. I agree that hydraulic pump/motor drives are less efficient than mechanical drives. That's why my suggestion to use a hydraulic drive was strictly for the convenience of early testing. Your comments about inefficiencies of hydrostatic drives is interesting but could be more useful if you could quote some better qualified numbers.

OK -- answering your specific statements:

"The other things like diesel injection happens at the engine virtually immediately before injection to the cylinder."

High pressure injector lines are usually attached to injector pumps on the sides or tops of diesel engines close to where mechanics can work. That's a known hazard. We were all cautioned about that on the Dynastar program where injector line vibration could eat away the wall of a tube in an hour's time on the dyno.

"Quite a different thing than a high pressure system distributed to all the wheels etc."

Again, my posts are not suggesting hydrostatic drives for light consumer vehicles inasmuch as they are less efficient than mechanical drives and are likely to be more expensive. In the hybrid system the only high pressures at the wheels are brakeline pressures and tire inflation pressures. And again, a hybrid drive will only be active in braking and the early acceleration of the vehicle following a braking maneuver from which the energy came.

" ….do you really want to add one of those heavy duty tanks you're talking about to your car to haul around and reduce the very mileage you're trying to improve?"

The accumulator tanks I foresee should be lighter than the current generation of hybrid electric batteries. While future lithium or other battery technology may be lighter in the best setup the hydraulic option with it's tanks could still be more cost effective when viewed from the standpoint of lifetime system cost. I'd like to see the numbers on that one.

"hydraulic cylinders on garbage trucks flying off and killing people in nearby vehicles."

OK. I've heard of this stuff. Was it about mechanical failures of mounts or linkage pins? Were any significant number of injuries caused by leakage of hydraulic fluid or the rupture of the cylinders or lines? Also with regard to propane tanks and garbage trucks the explosions and fires appear to have resulted from filled propane tanks in the refuse stream being crushed by the garbage compactors. This has little to do with the vehicle systems.

"Sorry Charlie but nothing comes for free. You still have to use up energy to make the car move and harnessing some of that energy in a very inefficient way only means you have lost energy and now you have to push it even harder to maintain speed - using up more energy."

Like I said, this topic thread is not about hydraulic drives except insofar as the use of existing hardware may make the prototyping an easier effort.

"Adding the complexity of compressed air and then hydraulics aren't going to make anything more efficient."

May I suggest you read up on the design of hydraulic system accumulators? It's an easy Google search……..

"By the way, this is not the first law for reversible processes. Note all the lost energy - this is not a truly reversible process. In fact it's not even close. Read up on your physics."

I consider myself well versed in the subject of thermodynamics. Perhaps, and I forgive you for missing my points, you are also well read on that subject; but not as well read on the posted details of the topic under discussion here. The adiabatic pressurization of nitrogen gas by mechanical energy and the subsequent redelivery of that energy by depressurization of the gas (the ideal case that ignores 2nd order friction and thermal losses) in the accumulator is a reversible process.

Please, if you are going to pick apart the things we say at least take the time to read and understand them. Honest criticism is the best part of any engineering effort even in a place like this. But criticism based on casual misreading of a writers words or intent only serves to waste time and confuse the issue.

Ed Weldon

Reply
Power-User

Join Date: Feb 2007
Location: Nebraska
Posts: 104
Good Answers: 2
#55
In reply to #23

Re: Hydraulic Hybrids Race Against Electrics

02/05/2009 1:49 PM

You don't seem to have any idea how ineffecent a gas drive train can be. They are starting to get close to 30% but that's not to good in my book. And I don't know what you are talking about when you say you have to use energy to stop. Stopping energy is FREE. We just throw it away right now as heat in our brakes. Any type of regenerative braking is a good idea even if you can't reclaim part of it. You can reclaim almost 70% of the braking energy with hydraulics. And they are also using regeneritve braking in electric cars. The biggeest problem with that is that the batteries right now can't charge as fast enough. But no matter how much energy you reclaim at least you are not throwing it away. And from the sound of it you need to stay in doors. You seem to see the worst in everything. I always worry about driving by a garbage truck just in case it blows up.

Reply
Guru
United States - Member - USA! Hobbies - Musician - Sound Man Engineering Fields - Mechanical Engineering - More than a Hobby Technical Fields - Technical Writing - New Member

Join Date: Oct 2008
Location: City of Roses.
Posts: 2056
Good Answers: 99
#24

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 7:14 PM
__________________
Don't believe everything you read on the Internet!
Reply
Guru
United States - Member - USA! Hobbies - Musician - Sound Man Engineering Fields - Mechanical Engineering - More than a Hobby Technical Fields - Technical Writing - New Member

Join Date: Oct 2008
Location: City of Roses.
Posts: 2056
Good Answers: 99
#25

Re: Hydraulic Hybrids Race Against Electrics

01/26/2009 7:31 PM

I forgot to put the homepage to the valentine car

http://www.valentintechnologies.com/concept/default.asp

Interesting, if nothing else.

__________________
Don't believe everything you read on the Internet!
Reply
Anonymous Poster
#27
In reply to #25

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 1:34 AM

RVZ717,

The valentine concept is not new and has many "devils" that they do not disclose, and this is why, in part, the auto companies do not accept it.

1. Hydraulic motors are VERY inefficient at low speeds due to leaks. When you put such an axial motor in the wheel they must have a gear to increase the RPM, and if you only have one gear, the average efficiency will be very low due to the fact that the average speed of a car is 25 mph or about 250-300 rpm at the wheel. Most motors warn against operation below 500 rpm (40 mph direct drive) due to the lack of lubrication film breakdown, similar to that in a piston crank bearing. By putting the motor into a drive and differential, instead of the wheel, you can get the motor RPM up and avoid having "heavy" wheels that loose traction and high pressure lines in constant vibration in a wheel well that could "spray" someone, cutting off hands, etc.. Any leaks must be in an enclosure, and their design does not meet min safety requirements.

2. Hydraulic motor efficiency drops off rapidly at low variable output even at high speeds where they are usually efficient, due to compression and recompression at the valve. Below 40-50% of full, the efficiency drops rapidly.

3. The free piston used is limited by flow velocity and have not shown to be very efficient. The cycle used does not add anything to the base efficiency that would be required to make up for losses in the hydraulics.

4. The claimed range and mileage estimates are not founded in the energy of fuel, but in a comparison of other types of engines.

SPG

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#28
In reply to #27

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 3:26 AM

Guest -- You sound like one of Valentin's competitors. Also sounds like you know what you are talking about. Just curious about whether Valentin had demonstrated any hardware yet. Likely they are keeping it under wraps until the 2010 formal Xprize competition. Or maybe they are busy trying to raise more money to clear the technical hurdles they face. Like the free piston engine. Starting from scratch with a new engine technology is pretty ambitious. So is that carbon fiber 7000 psi oil tank.

After looking at the link about Ford's "Hydraulic Launch Assist" posted by RVZ717 I'm thinking the hydraulic hybrid thing has more potential as an add-on optional accessory like air conditioning than a deeply integrated part of the vehicle power train and structure the way Valentin visualizes it.

Ed Weldon

Reply
Anonymous Poster
#33
In reply to #28

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 12:05 PM

Weldon,

It's me. S..P....G.. CR4 limits my comments for some reason....

There are a lot of problems with the free piston. Rexroth and all the majors have some sort of "free piston" and none have been successful. There is a foundational flaw to the concept... Sandia Lab has an electric free piston that they claim gets over 50%. That is interesting, but, of course is not hydraulic... Any hydraulic free piston will have to get over 50% to be competitive, which none, to date, can make that claim. So, in free pistons...electrics is the winner of the race...but not for long...

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#40
In reply to #28

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 6:21 PM

After looking at the link about Ford's "Hydraulic Launch Assist" posted by RVZ717 I'm thinking the hydraulic hybrid thing has more potential as an add-on optional accessory...

This has been mis-reported many times. No Ford F150 will get 60 mpg as a result of hydraulic launch assist or as a result of a full hybrid well-sorted-out system. The Prius system is a good benchmark. Without the hybridizing it would be a 40 (combined) mpg car by virtue of its Atkinson cycle engine (which is equivalent to a good diesel in terms of engine efficiency) light weighting, good aero and low rr tires. The hybridizing adds substantially to its city efficiency (48 mpg), but adds nothing to its highway efficiency. Throw out the hybrid system and you'd get 35 city and 45 highway.

If, in designing a hybrid (non plug-in) nothing is done to change the engine, cruise fuel economy can only get worse, because of additional weight, the drag of idling hydraulic pump, etc. (An old Honda Insight with shot batteries cruises at the same mpg -- some have said slightly higher -- as it does with the hybrid system working). Launch assist, can only, at best, recapture a portion of the energy used to accelerate the vehicle the last time, and it is only in intense stop and go traffic that this makes enough difference to be measurable.

There are a lot of electric car enthusiasts who use only regen braking to come to a stop virtually all the time -- they have to plan in advance to avoid needing to stop fast. Even then, the range increase is about 15%, with 10% being more typical. Recapture, under these conditions, is quite efficient (80% or so) but still does not offer huge differences in range (i.e. energy usage).

I would be surprised if launch assist on an F150 took the mileage from 15 city to 18 city. The difference in the highway cycle would be unmeasurable, so the combined cycle difference might be 1 or 2 mpg. I suppose if you had a fleet, and if the added cost and maintenance burden was low...

(A bit of trivia: in the EPA urban cycle, many of the decelerations only involve backing off on the throttle, rather than braking, even in aerodynamically efficient cars. In trucks, aero drag alone slows the truck faster, leaving less energy to be recaptured.)

__________________
There is more to life than just eating mice.
Reply Score 1 for Good Answer
Anonymous Poster
#41
In reply to #40

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 6:48 PM

Ken,

I spoke with the program manager on the UPS project from the EPA and he said they get 19 city 12 highway, whereas they were getting 10 city 10-11 highway. In the UPS case they did get 10-20% better on the highway and 90% better in the city.

If a f-150 got 18 and 15 as you say, then it should get with an assist around 20-22 highway and 40-44 city. The assist, it would appear, does not work like the Prius, in that it has a program that forces it to run efficient on the highway. If the Prius does nothing on the highway than it would without electric, then these system are NOT the same in programming. The key is to run the engine at best efficiency all the time.

That said, if you had a cruise control that put the pedel down 1/2-2/3 and then let off to a gentle coast, and controled speed in a +-3-5 mph range, up and down, with a set point say at 65 and the speed would go from 60-70 up and down, you would run the engine at peak efficiency much more of the time and you would get 15-20% better economy. I have and can, at any time, demonstrate this in my minivan, and pointiac. So, by just pushing the gas on and off you can get as good or better than what is achieved by all the eletronics. What would a cruise control like that cost? Not much more than a normal one. If you did it in a 63-68 band, say, you would not notice it. So much for hybrids...

Reply Score 1 for Good Answer
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#44
In reply to #41

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 11:29 PM

The UPS highway improvement is due to the engine, which is both more efficient, (for a given hp output) and also more heavily loaded, which further improves efficiency. The same logic applies to the Prius, which gets 45 mpg highway, which has nothing to do with the hybrid strategy (per se) and everything to do with a highly-efficient engine that is also smaller than would normally be installed for the application. Where the hybridizing shows up is in the city routine, where the Prius would otherwise get about 35 mpg, but gets 48 because of the advantages of idle shutoff, regen braking, and heavier engine loading loading.

If the Prius does nothing on the highway than it would without electric, then these system are NOT the same in programming.

"On the highway" has variations in meaning, but in a steady state cruise on level ground, the Prius system does not help (at least as far as I can tell from only brief observation). In theory, the engine could charge the batteries a little, running at a slightly higher, slightly more efficient load, and then back way off for awhile as the electric motor maintained speed, etc. But in practice, that doesn't appear to happen, and having looked at the bsfc map for the Prius engine, I don't think there would be enough advantage to overcome the irritation of the sound level rhythmically changing. The advantage the Prius has on the highway over a similar non-hybrid, is in the smaller and more efficient Atkinson cycle engine*.

If a f-150 got 18 and 15 as you say, then it should get with an assist around 20-22 highway and 40-44 city.

It would only get the better highway mileage if Ford did what UPS (actually Eaton) did, by both downsizing the engine and also improving its specific consumption. I haven't seen any reliable specs on the Ford, and I think that the only truck that they are releasing this year with any high efficiency pretense is a model with lower numerical axle ratio and other traditional tweaks. That model gets 1 mpg better than the more standard models, if I recall.

The 19 mpg figure sounds high, and must reflect a route with unusually high stop-and-go rates. UPS officially claims 45% - 50% mpg improvement (or 30% reduction in fuel consumed and CO2 emitted). The Ford pickup, if it had similar energy storage relative to weight, could also get a 50% mpg improvement (from 15 to 22.5), but only if it is driven like a delivery truck.

That said, if you had a cruise control that put the pedel down 1/2-2/3 and then let off to a gentle coast...

You must have been driving with my wife! She is incapable of holding the throttle steady. Interesting thought, though. Add another clutch so the engine would disengage entirely on the coasts, and the improvement could be substantial. It would be interesting to see if you could make the transitions smooth enough to be not too annoying.

* This is a huge advantage, incidentally, with efficiency being about 37% vs 30% for pretty sophisticated gasoline engines, and 25% for run of the mill.

__________________
There is more to life than just eating mice.
Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#45
In reply to #44

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 11:58 PM

Quote Blink: "Add another clutch so the engine would disengage entirely on the coasts, and the improvement could be substantial."

Blink --I think that freewheeling is illegal in most states, a holdover law from the depression and WWII when people tried to save money on gas and brake systems were not that good; so you needed the "engine braking" on long hills. (like the 36 Ford I had when I was 19).

You could likely get away with it on your own car; but it would take changes in the laws before a manufacturer of a conventional vehicle would add that as a feature. However, for all I know there may be recent changes in some state laws in that area to accommodate new alternative vehicle propulsion technologies.

By the way, thanks for putting some real and credible numerical information in several of your posts. This is the stuff of GA's

Ed Weldon

Reply
Anonymous Poster
#46
In reply to #44

Re: Hydraulic Hybrids Race Against Electrics

01/28/2009 1:45 AM

Ken,

Have you seen www.innas.com?

Here is the engine mapping

http://www.innas.com/HD_enop.html

Here is the fuel consumption.

http://www.innas.com/HD_fuel.html

What do you think of their hybrid system? Can you see something wrong here?

SPG

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#48
In reply to #46

Re: Hydraulic Hybrids Race Against Electrics

01/28/2009 12:19 PM

Their engine mapping page makes sense, and their arguments there would apply equally well to a series electric hybrid with enough battery capacity/type to enable regen braking to the limit of traction. Their chart suggests about a 2:1 improvement in fuel efficiency in a city cycle.

Diesels suffer less from pumping losses, so that downsizing the engine doesn't help as much as it does with a spark ignition engine (downsizing being one method to get the efficiency of a spark engine closer to that of a diesel.) (In other words, you don't get the same percentage gain, because the diesel is already more efficient.)

So their fuel page is reasonable to the extent that they use the same engine on each side of the comparison. But their calculation of vehicle fuel efficiency , on that page, seems haywire. In a city cycle, a better than 4:1 difference (hybrid vs conventional) is not at all likely, especially with the same engine in both. Their own figures from the engine mapping page say that 2:1 would be reasonable.

The highway comparison seems completely wrong too, and their text doesn't support their graphs. You'd expect that highway hp would be about 15 kW for a 4wd vehicle equipped with a 100 kW engine. That equates to an engine efficiency of about 36%, just one percent less than the average from cycling. That very slight difference in engine efficiency would be more than canceled by the higher losses entailed in the total transmission efficiency. If we accept their 95% efficiency of the pump and similar for the motor, and then assume that piping losses are 5%, and that compressing the nitrogen also causes a 5% loss, then the transmission efficiency would be about (.95 x .95 x .95 x .95) 81%. An ordinary transmission would more likely be about 95% efficient. 37% x .81 = 29.9%. 36% x .95 = 34.2%. So you'd expect the hybrid to be more than 10% less efficiency on the highway, not substantially more efficient, as they claim.

This last figure (10% worse than straight through) applies approximately to my MC2 (or other electric or hydraulic series hybrids). The rule of thumb is that a series hybrid is great in a city cycle, but worse than a straight-through drive on the highway. On the MC2, I'll probably provide a cruise mode which bypasses the hybrid system. (Of course, if the engine is substantially downsized to keep the load up and to minimize weight, then cruising up a significant hill means either slowing down or calling again on the electric motors.)

If they didn't completely fabricate the highway data, it might have come from a 4x4 with very high (numerical) gearing, which would make the engine run fast, and also reduce torque, both of which would reduce efficiency. In that case it would be as if they are comparing their hybrid system (geared as if in sixth gear) vs a non-hybrid geared as if in 3rd gear. Not a fair comparison of the hybridizing technique.

If their engine were larger (250 hp+/-) gasoline, and old tech, then a series hybrid could reduce even highway fuel consumption (with the engine pulsing at it's peak load [minimum bsfc] with wide open throttle, operating on a 10% duty cycle.) Given those conditions, the bsfc could differ by 2:1 or more, so highway fuel efficiency would improve dramatically. But for their diesel, the bsfc does not vary enough to support any improvement.

Other news: The Shelby Super Car company is bringing out an electric car which, they claim, can be recharged in 10 minutes (such batteries do exist) from a standard 110V outlet (which is so far from being credible it make you wonder if they are deliberately trying to come across as snake oil salesmen). This car is supposed to have 200 mile range, would would require at least a 50 kWh battery pack. Even if you give them the benefit of the doubt, and call a 20 A 110 V circuit "standard" (even though most are 15 A) then 2200 watts would charge such a battery pack in 22.7 hours -- which, in my book, is substantially longer than 10 minutes.) They also have claimed that the battery could go for years between recharges -- also patently obvious nonsense.

Turns out they sent out a "correction" to the press release, saying that they meant 220 v not 110 v. Even that is wrong, of course: if you assumed a dryer outlet (30 A) you'd still need 8 hours.

So I wonder if there is anything real about the Shelby Super Car Company. (Some ill-informed bloggers have said, "Well, Shelby has done some impressive things before..." meaning Carrol Shelby [no relation] ) Maybe even the "World's fastest production car" (for their gas powered car) claim is bogus. Obviously it's not a "production" car anymore than a purpose-built Lemans car (or NASCAR car) is. It's odd that the record is in the Guinness Book rather than with the Bonneville people, apparently. The whole electric car thing is so far out there that it calls the whole operation into question.

__________________
There is more to life than just eating mice.
Reply
Anonymous Poster
#49
In reply to #48

Re: Hydraulic Hybrids Race Against Electrics

01/28/2009 2:10 PM

Ken,

SPG here. I have a simple program in excel that calculates mpg and efficiency. I would like to send it to you so we can get on the same page.

Your E-mail?

Mine is seaplaneguy@msn.om

Most houses could put out 25 kw, so the minimum charge time is 1-2 hrs depending on charge level, that's if you run nothing else.

I sent out for the Innas CD and watched their vids. Interesting. I think they show some of the best understanding of hydraulics and what needs to happen. I like their "transformer" concept, but, again, it goes around the issue and does not actually solve the problem. Their free piston engine weighs 198 lbs and only 17 kw. Ouch! that is brick heavy, almost 16 times heavier than a Lycoming, and that does not include the rest of the story....

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#50
In reply to #49

Re: Hydraulic Hybrids Race Against Electrics

01/28/2009 11:54 PM

Through the miracle of electronics (and with the help of Al Gore), an email is on the way.

__________________
There is more to life than just eating mice.
Reply Off Topic (Score 5)
5
Member

Join Date: Feb 2009
Posts: 8
Good Answers: 1
#58
In reply to #48

Re: Hydraulic Hybrids Race Against Electrics

02/11/2009 3:12 PM

Let me first introduce myself. I'm working at Innas and am deeply involved in the design of the hydraulic hybrid, or HYDRID as we call it. I have been designing, building and testing hydraulic components and motors for more than 20 years. Included are several hydraulic transformers, free piston engines, and axial piston pumps and motors. The design requirement of the HYDRID was to half the fuel consumption and the related CO2-emissions while performing the European NEDC, the Japanese 1015 mode or the US FTP75 cycle, without increasing the weight and the cost of the vehicle, and without compromising the performance. The reason for choosing the legislated cycles is that, especially in Europe, the CO2-legislation is based on the NEDC. Moreover these cycles allow a fair comparison to other transmission and drive train concepts. The HYDRID is a series system: all energy of the engine is converted to hydraulic pressure and flow. The new lay-out is like the electricity grid, having power plants, a grid, and a large variety of loads taken energy and power from the grid. Likewise in the hydraulic hybrid there is a power plant (the engine pump combination), a grid (the high and low pressure hydraulic lines), power converters (the hydraulic transformers) and loads (the wheel motors). In addition there are accumulators. Contrary to most opinions you don't need a large accumulator to recuperate most of the brake energy of an average passenger car: a 3 to 6 gallon accumulator is sufficient. The accumulators play a crucial role in the new drive train. They are not only needed for recuperating a large part of the brake energy, but also for allowing power management. The power plant is decoupled from the wheels an can now be operated at or around the sweet spot. The engine throttle no longer controls the vehicle speed and the wheel traction. The vehicle control is shifted to the transformers, not only during propulsion but also during braking (except emergency brake actions). The cost advantage of the series hybrid architecture is that it is not an add-on system: the hydraulic system replaces the complete mechanical transmission. The power, force and torque density of hydraulic components is 10 to 20 times as good as of electric components. Hydraulic accumulators might not have a high energy storage capacity but they are unparalleled if it comes to power density, robustness, temperature range and costs. The hydraulic hybrid has not been built yet, at least not as a passenger car (we did built a fork lifttruck with the same system architecture). In cooperation with universities and industries, several cycle analysis have been performed. The simulations are based on efficiency tests of the engine, the hydrostatic components, accumulators, pressure lines, valves, etc. The results are that for a mid-sized European car (a Volkswagen Passat sedan) the mileage for the combined NEDC has been increased from 36 MPG to 81 MPG. The efficiency improvement is largest for the city part of the cycle for which the mileage is increased from 27 to 126 MPG. But also for the highway part of the cycle the mileage is increased from 43 to 67 MPG. We als performed constant speed driving analysis. The fuel consumption of the HYDRID is better for speeds below 65 mph. For higher speeds the differences in fuel consumption are marginal. At 120 mph the fuel consumption is about 10% higher. The conventional vehicle has a manual gear shift. If it would have been an automatic transmission, the differences in mileage would be even larger. The comparison is also based on identical engines for both drive trains. The analysis was based on a diesel engine. If it would have been based on a gasoline engine, the difference in mileage would also be larger. The key for the HYDRID are the new hydrostatic components. The new pumps, motors and transformers need to be extremely efficient, especially for the average operating conditions. Moreover the hydraulic motors need to have an almost constant drive torque. Unlike internal combustion engines, the torque variations of hydraulic motors can't be taken away by means of balance shafts and flywheels. Conventional 7 and 9 piston pumps create unacceptable noise, vibration and harshness (NVH) levels, and a new multi piston design was required. Moreover the noise level has to be lower than the contact noise of the wheels driving on the pavement. Finally, to get some sense in this interesting discussion: - hydraulic motors can be extremely efficient, also at low operating speeds - hydraulic accumulators are pressure vessels with a very limited energy content (an average starter battery has 50 times as much energy and is much more dangerous) - the average cycle efficiency of the hydraulic drive train is as good as or even better than of a mechanical transmission (especially compared to an automatic transmission) if we include energy recuperation. - We didn't fabricate the highway data and no, we didn't go haywire. I'm looking forward to continue the discussion with you.

Reply Good Answer (Score 5)
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#61
In reply to #58

Re: Hydraulic Hybrids Race Against Electrics

02/11/2009 7:13 PM

Welcome to CR4! You should enter a vehicle with your system in the Progressive Automotive X Prize. You could hardly ask for better publicity. Entries are still open, til the end of this month.

I'd caution that you may find that there is a significant difference between computer models and the real world. Aptera originally quoted a CFD-determined aero Cd of .06 for their vehicle. They later revised this to .011 (essentially twice the original figure). Now, they are saying .015, i.e., 250% of the original figure.

It is always good to do a plausibility check. The UPS system, also a relatively sophisticated hydraulic series hybrid, shows negligible improvement at highway speeds and a 45-50% improvement in intense stop-and-go traffic, far more favorable for a series hybrid than our EPA urban cycle. In our urban cycle, this would translate to perhaps a 35%-40% percent improvement. Perhaps the cycle you used had a huge amount of what would otherwise be idle time? But even if your efficiency takes the UPS 90% efficient pumps and motors to 100%, we would expect the city gain for your system to be perhaps 45%, not the 466% of original (of 366% increase) you are claiming.

Even if I model my own vehicle without any efficiency losses in regen and consider all the hybridizing components to be 100% efficient, I cannot come up with an improvement figure remotely close to yours. (And if I did so, I would be producing a figure far higher than I could hope to achieve -- all these efficiency numbers multiply, so together, they can make a big difference.) In a theoretical, idealized model, the engine runs only at its sweet spot, or not at all, and all braking energy is recovered. Even in that theoretical world, which is a long way from real world, hybridizing does not provide a 366% increase. A 100% increase would be considered exceptional, and the UPS figure of 45%-50% would be a good target to shoot for. The Prius is perhaps 20% more efficient as a hybrid than it would be simply running on its very efficient gasoline engine. Does a 366% improvement really seem realistic to you? How has Eaton so profoundly missed the target, in your view?

You are correct that even an old lead acid starting battery has 50 times the energy storage capacity of a small hydraulic accumulator.

You are not claiming greater than 100% efficiency for your components are you? I'd be interested in hearing the specifics regarding exactly how your system is so much more efficient than the UPS/Eaton system.

You say: The power, force and torque density of hydraulic components is 10 to 20 times as good as of electric components. Although that is a generality which is occasionally true if you compare best case hydraulics with worst case electrics, the important consideration is overall system weight and efficiency. The UPS vs Fed X experience (with both versions -- the hydraulic UPS and the electric FedX -- having been built by the same company, Eaton) puts overall system effectiveness into perspective -- the Fed X system is claimed to be slightly more efficient.

I note that you say that your hybrid system is less efficient than a non-hybrid at speeds over 65, but claim that it is far more efficient in a highway cycle. Here, in the US, a constant 65 and a highway cycle produce very close figures for most cars, with 70 on a straight level road being a very good match. Therefore, the improvement you claim for the highway cycle is stunning. Your fuel consumption map graphic does not seem to support such a huge difference. It shows that your claimed average engine efficiency via hybridizing is 38%. In our highway cycle, at least, a diesel will operate at low rpm and moderate load, near the left side of your chart and (for a 4wd 100kw vehicle) above the 10 kw line. A good estimate is 36% efficiency, which squares well with the highway fuel efficiency ratings for our old VW Jetta diesels, which were more efficient on the highway than a Prius. Perhaps your highway cycle includes many more segments of very low load and more stops and starts than ours does. Perhaps your model does not adequately account for nonrecoverable losses in aerodynamic drag and tire heat.

It will be interesting to see how your real prototype performs. I hope to see you on the Progressive Automotive X Prize race circuit. If your system is even 1/3 as good as you say it is you should be in the winner's circle, and the publicity will no doubt help with acceptance by manufacturers.

Remember, your customers will like you better if you under-promise and over-deliver. When the Aptera was first introduced, they claimed 330 mpg at 65 mph. That has now dropped to 120 mpg. That's still very good, but many potential customers would have liked to see the progression go in the other direction.

__________________
There is more to life than just eating mice.
Reply
Member

Join Date: Feb 2009
Posts: 8
Good Answers: 1
#63
In reply to #61

Re: Hydraulic Hybrids Race Against Electrics

02/12/2009 4:55 AM

Thank you Ken, for warning me about computer models. I once started a presentation at a conference in the US saying that 'Simulation is like masturbation: the more you do it, the more you think it's the real thing'. I'm a strong advocate of running simulations and experiments in parallel.

The results we have presented are somewhere in between computer models and the real world. The car and the cycle we have applied are computer models. But these models are well known and also not too complex. Also the hydraulic system modeling is based on many test results and has been validated for many real world exercises. Even for the modeling of the new components we have built real iron. The efficience maps we are using are based on measurements performed by the independent IFAS-institute of Aachen University in Germany (http://www.ifas.rwth-aachen.de/index_e.html). The other thing you should be aware of is that we followed closely the conditions and parameters of a test cycle, like the NEDC. For instance we have the air-conditioning turned off during our cycle analysis. But this is fair since the benchmark is measured with the same standard.

We are well aware of the great work that EPA, Eaton and UPS have done. We have been involved in the development of hydraulic hybrids since the mid eighties, when we were working on hydraulic drive trains in city busses (the Volvo Cumulo system). You missed to mention the hydraulic hybrid that has been built as a demonstrator by Artemis IP in the UK (www.artemisip.com). It also features a full series hybrid drive train applying so called digital hydraulic pumps and motors. But also this vehicle seems to prove your point: the improvement of the mileage is entirely due to the city part of the cycle. For the highway part (of the NEDC) the mileage is identical or even somewhat worse.

Also with our components and system the biggest gain is in the city operation. This also makes sense. The real energy demand of driving a vehicle is because of the rolling resistance and the aerodynamic resistance. Accelerating a vehicle is not energy dissipation, until of course you convert this energy into heat in the brakes. The aerodynamic resistance is strongly dependent on the vehicle speed. It is hardly important for the low average operating speeds that occur during city driving. But the aerodynamic drag is dominant on the highway, and there is not much that a transmission system can do about it. That we are still having a reduction of fuel consumption, even on the highway is because we are able to improve the operating conditions of the engine, even when driving on the highway and because there is energy recuperation (you can recuperate much more energy when decelerating from 70 to 50 mph, than to brake from 20 mph to zero, although in both cases the velocity drop is only 20 mph). Only if you drive at a constant speed than we are about equal or (at high cruising speeds) have some increased fuel consumption.

You could also argue that for most passenger cars the internal combustion engine is too big for its needs. That is certainly true for average cycle conditions. While performing the NEDC the peak engine power demand is around 34 kW. During 80% of the time the wheel traction requires even less than 11 kW and for half the time less than 5 kW. So for half the time we are running a 100 kW engine at 5 kW or less. However, there are many reasons why automotive designers don't want to compromise the performance of a vehicle and install a smaller engine. For accelerating a 3000 lbs vehicle from 0 to 60 mph within 9 seconds, you need power and wheel torque. For having enough power available for speeding up a vehicle from 50 to 70 mph (the so called elasticity) in order to overtake another vehicle you need engine power and wheel torque. For climbing a slope of 40% or even more (the gradability) you need engine power and wheel torque. A vehicle is an island with its own supplies, which is designed for peak performance, but which needs only 10% or less of this peak performance during most of the time.

The fuel economy improvement of the HYDRID is for a large part due to the improved operating conditions of the engine (which more than doubles the average engine efficiency). Than again we lose some of this advantage because of the hydraulic transmission (at least compared to a manual transmission), but we compensate this loss by recuperating part of the kinetic energy of the vehicle. I wouldn't overestimate the value of energy recuperation for a passenger car, especially not for rather tame cycles like the NEDC. In a more aggressive drive cycle the benefits of energy recuperation become of course larger, but than again the engine is also operated at a higher load and therefore at a higher efficiency when driving more aggressive. Nevertheless we see an overall mileage improvement for more aggressive cycles.

The average cycle efficiencies of our hydraulic transmission components is around 92%. The best point is around 96%. But to understand the concept of the HYDRID you have to include the engine into the equation. Furthermore, the HYDRID only has a benefit is there is a large difference between the required peak performance of a car and the average driving conditions. In other words: if you are designing a small and light vehicle with a small engine which doesn't need to fulfil all the performance requirements of todays vehicles than you would not see a big gain and you might even end up with a lower mileage.

The other thing I should point out is that it is extremely difficult to achieve an average cycle efficiency of the hydraulic components of 92%. This is where we believe we are much better than Eaton. It is also extremely important that the efficiency of the transmission components is high. Again I'm talking about average efficiencies and not about peak efficiencies. Due to the many conversion steps the average efficiency should at least be higher than 80%. If it is lower than you will lose more in the hydraulic components than you'll be able to gain on the engine side. If you also want to have a high mileage while cruising on the highway, than the average efficiency should be higher than 90%.

There are two reasons why we have a high efficiency. First of all the floating cup principle we have applied is very efficient. But so is the pump/motor that EPA has applied in its truck. The second reason is the hydraulic transformer. The maximum wheel torque that can be generated by means of a hydraulic motor is dependent on the size of the motor (the displacement volume) and the pressure difference between the high and low pressure lines that are connected to the wheel motor. Without having a pressure transformer the wheel torque is therefore dependent on the pressure in the accumulators. If the pressure level is low (which should be before a brake action if you want to store energy in the accumulator) than you can only generate a high wheel torque by choosing a large hydraulic motor having a large displacement. During normal operating conditions the wheel torque is much lower than the peak torque requirement and the variable displacement motor has to run at very low displacement volumes. This results in a strong efficiency penalty. The hydraulic transformer however enables you to amplify pressures. With this ability you can create boost torque on the wheels, even if the accumulator pressure is low. As a result we can apply rather small hydraulic motors which are operated at much better efficiencies at normal operating conditions.

Concerning the power density of hydraulic versus electric components: My statement is based on a comparison of best case hydraulics and best case electric components. I'm quite aware that the power density of electric motors has increased over the years, but this is primarily because of an increase of the maximum speed of these motors. However, if you want apply an electric motor that is designed for a maximum operating speed of 16.000 rpm and you need to drive a wheel that only requires less than 500 rpm for most of the operating conditions than you will also need a gear transmission, which will increase the weight and reduce the power density. Electric components are simply too expensive and too heavy for automotive applications, even after years of development (see the presentation that Susan Rogers gave about a year ago: http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2008/adv_power_electronics/merit08_rogers.pdf).

I will not be joining the X-Prize, although I strongly support the initiative and the goals of the program. As you might have seen I'm consulting Ingo Valentin with his project. In the mean time, we at Innas work together with the industry to find new solutions for their bread and butter lines which are threatened by competition from China and India, uncertainties in fuel prices, new CO2-emission demands and a devastating economic situation. The new CO2-limits, which will be effective in Europe in a few years force the automotive industry to strongly reduce the fuel consumption and the Asian competition forces them to reduce the cost. The electric hybrid is by far the most expensive solution for CO2-abatement (see: http://www.mckinsey.com/clientservice/ccsi/pdf/US_ghg_final_report.pdf). The hydraulic hybrid offers a way out.

Reply Score 1 for Good Answer
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#69
In reply to #63

Re: Hydraulic Hybrids Race Against Electrics

02/13/2009 4:15 PM

Hi Peter,

I appreciate your detailed answer, even though it doesn't leave me convinced that your system can be several times as efficient as the other hydraulic hybrid systems. The efficiencies you quote are very close to those quoted for the Eaton system or the Artemis system, yet you are claiming integer multiples of their fuel efficiency gains. For example, Artemis claims a 30% improvement with their very sophisticated hydraulics, but you claim a 366% improvement. There is nothing on your website or in what you have written here that would justify such a huge difference. The generalities you have supplied re series hybridizing apply to all such hybrids, if reasonable well-designed, no matter whether they are hydraulic or electric.

Your summary of the benefits of hybridizing, and particularly serial hybridizing are essentially correct: the central theme in any series hybrid is to run the engine at its most efficient, or not at all. Electric serial hybrids are especially good at this because they do not suffer (to the same degree) from the problem that your transformer attempts to cure, namely that when the charge is low the refilling torque is low, and therefore the engine efficiency is low. The reverse is true with electric batteries -- if the battery is low, the charge current (and thus torque) is naturally high. Also, batteries can have a quite flat recharge curve (i.e. torque requirement) until they are getting quite close to fully charged, and as a result, the recharge algorithm is designed to keep the battery from getting to this low current (low engine efficiency) state.

For the reason you point out, significant engine downsizing is not possible in a system such as the one you describe with a tiny accumulator. One cannot dramatically downsize an engine if the accumulator only has energy enough for one trip to 60mph, because there is still a need for high power for minutes, not just seconds. To provide several minutes of high output, you either need a high-output engine or good energy storage. Here the advantages of a plug-in series hybrid (rather than than simple hybrid in which the only external energy source is a fossil fuel) are synergistic, because the larger battery bank means that you can regen to the point of traction loss without overheating the batteries, and you can also go up a long steep hill, passing trucks, at 70 or 75mph, easily. In a hydraulic hybrid, this is impossible -- the energy is simply not available. Therefore the engine must be larger, which is a reverse synergy: it is heavier, reducing efficiency, and it spends more time running at lower relative loads, decreasing efficiency. It is probably not reasonable to predict a large number of short cycles (full torque for ten seconds, stop for ten seconds, full torque for ten seconds, stop for ten seconds, ad infinitum) for going up a long hill as being realistic, for many reasons such as the irritation to passengers, the repetitive thermal shocks to the engine, etc. So then, with such limited energy storage, you must be forced to run the engine at lower power (less efficient) for longer periods of time.

If your model allows you to look at small increments in a cycle like the EPA urban cycle (essentially the same as the ftp 75) you will find that even with a vehicle much more aerodynamically clean than the typical sedan (such as one I modeled for a client recently, for which the Cd was .20) the opportunities for regenerative braking are fewer than you might expect: aero drag, tire drag, and transmission losses are sufficient for many of the decelerations. As you say: I wouldn't overestimate the value of energy recuperation for a passenger car, especially not for rather tame cycles like the NEDC. You're right, and the same applies to the EPA cycle. I can't take the time right now, but I think that with regen turned off and on in our model, the difference was perhaps 15% in the cycle fuel efficiency. The vast majority of the gain in efficiency (when this plug-in hybrid was running in charge-sustaining mode) came about from running the engine only at peak efficiency, rather than running it (at times) at a specific fuel consumption 4 times as high (or infinitely worse if idling). This gain is compounded by downsizing the engine, which requires real energy storage.

My model does not know whether the motors and generators (or pumps) and controllers (98% efficient for electric, but substantially lower than that for even the most sophisticated hydraulic valving and transforming) are electric or hydraulic. All it knows is operating efficiencies at various loads and speeds. If I plug in your efficiencies rather than electric efficiencies, I cannot come up with anything close to a 366% improvement in the urban cycle.

As I said before, for a real world comparison of hydraulic vs electric, using comparable levels of technology, we could not have a better example than UPS vs Fed X, with both produced by the same company. We know the FedX generator is about 95% efficient virtually all the time. We know the motors are about 90% efficient at peak, and spend a lot of time at over 85%. We know, without a doubt, that control is more efficient electrically, and we know that wires are more efficient than tubes and pipes. We know the energy storage is far more weight-efficient electrically.

We know that the only benefit of hydraulic hybridization generally cited is in better regen. But we know two more things: 1. regen has little effect, 2. regen into big batteries (as in a plug in hybrid) is as efficient as hydraulic regen. The fact that the Fed X trucks do slightly better in MPG improvement than the UPS trucks supports all this.

Suppose we change all the 90% efficiencies to 100%. Still, a 366% improvement is hard to support.

We also know that a plug-in hybrid can use electric power, which is cheap, has the potential for being very clean, and already has a lot of support from buyers. Electric cars are all the Detroit manufacturers are talking about, now that they are suddenly getting "green" and going to spend our money on "cars we really want"... as if we didn't "want" the SUVs we bought by the millions.

So, I'd like to see a more efficient hydraulic hybrid, and wish you success, but there is nothing in the numbers than convinces me that there is any real advantage over an electric hybrid. For a project like my own (for which I roughly modeled hydraulics using real world off-the-shelf components a couple years ago) hydraulics lost in every sense: cost, performance, and weight, when looking at a simple series hybrid. (Obviously, as a plug in hybrid, the idea would be insane).

And then there are the leaks... I used to work for an underground mining equipment company called Lee-Norse. Although we made pretty good products, we managed to earn the name "Leaky Norse".

Electric components are simply too expensive and too heavy for automotive applications, even after years of development.

Does that mean that all the Toyota, Honda and Ford hybrids do not exist? Or that the Tesla is a lead sled? Or that the GM EV1 was slow and overweight? Are you saying that the 1000 lbs of fluid and accumulators used on the UPS truck, which has less than half the energy storage capacity of a Prius battery of 1/10 the weight, is magically actually cheaper and lighter? I used to be a math whiz kid, but I can't make this compute.

The fact that UPS has ordered 250 diesel-electric hybrids and just 5 diesel-hydraulic hybrids says something, does it not?

__________________
There is more to life than just eating mice.
Reply Score 1 for Good Answer
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3945
Good Answers: 182
#70
In reply to #69

Re: Hydraulic Hybrids Race Against Electrics

02/13/2009 7:42 PM

Hi Ken,

You wrote some thing which is the basis of the differences. In your analysis you considered "available of the shelf" components.

Usual components work in the range of 1000 to 3000 Psi. this make them big and heavy since for same power the flow has to be more important than at 5000 psi. Already 25 years ago it was established that if hydraulics have to be used in small cars the pressure has to be at least 5000 psi (350 bar) in order to be interesting from the weight/power ratio. The components available at that time were not very well adapted to the job, for instance Renault build a car which worked very well but used gear motors with of course a constant displacement. Evolution of the pumps allowed to avoid many losses in the valves since pump or motor are piloted only by changing their displacement. The higher pressure leads to a lower flow and thus to lower losses in the ducts. The transformer has as well a positive influence on the general behaviour. I am not sure to understand why the drag coefficient (low) will reduce the regen. The regen is based on recovery of the kinetic energy, if the drag is low less energy will be used against it in braking and more will be recovered by the system. I am not a car specialist only one who designed over many years hydraulic special components as pumps, valves and motors and I do not say how many years ago a free pistons (twins) gas generator. So that I shall not contest what you wrote on car dynamics. What should also be considered is that the transfer of energy from the engine to the hydraulic system is with very low losses since it is a direct transmission.

Several years ago I made a comparison between electric and hydraulic drives. The comparison was based on data from existing motors and on theoretical analysis. It came out that even with e-motors designed for short duties (high temperatures accepted for instance) for same volume the hydraulic drives even at medium pressures were by far lighter per kW. The e-motors could reach the same torque only with help of gear transmission and in several cases only with planetary gears since they were more compact due to multiple meshing.

As far as I know (but I do not know all) in the different solutions considered for direct wheel drives are with a gear transmission between the motor and the wheel. To day, due to stronger PM, specific torques are higher but the limited flux strength at around 1.4 T limits the force per A and unit of conductor length.

May I give a value to compare, at 350 bar a 10 cm^3 constant displacement motor has about 55 Nm output, can run easily at 5000 rpm and delivers 27,5 kW. Dimensions are about 100x100 mm for a weight of roughly 5.5 kg. Those are estimated values not exact but enough to make a comparison. May I doubt that an electric motor alone can reach same values.

I do not want to say that one has to consider only one of the technologies but hydraulics are not as bad as you think.

I may also say that the pump/motor concept with the floating cup has a lot of advantages in comparison with classical solutions and especially in the reduction of internal friction.

Now last but not least with respect to leaks. I do not know when you were confronted with the problem but there are several solutions which allow a leak free function; One of them is the redundancy of seals where leaks can occur. I build and used for several years without any leak and maintenance cylinders (servo quality thus for high speed) based on this principle. If you look at Valentin's page you see such an approach for the flanges. It has to be also mentioned that seal materials (compounds) and design methods with FEA lead to new much more wear resistant seals able to work even in abrasive environments. Most probably the equipment which gave you head aches was not the last concept from the hydraulic point of view. Hydraulics are a "speciality" and not always easy to handle especially when pressures are over 2000 Psi problems are more complex due to the deformation under load of components. Fine tuning is required to avoid at same time losses and noise since too thin walls allow a lower leak level but also a more intensive noise generation. Ok I broke a spear for the honor of hydraulics and of course I hope which ever will be the way that in a short time we will have less polluting cars.

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#74
In reply to #70

Re: Hydraulic Hybrids Race Against Electrics

02/16/2009 4:32 PM

You're quite right that available off-the-shelf components can be quite different than prototypical ones.

My own situation is unlike, to some extent, that faced by the automobile industry. Unless I what to incur what, for me, are staggering development and tooling costs, I have to work with existing technologies, and hopefully novel ways of combining existing technologies. As it happens I looked into 5000 psi hydraulics, because that sets a lower limit for practicality. But because 2000-3000 psi hydraulics are so common, 5000 psi systems are not so common -- for many applications, 3000 psi works just fine. That means that 5000 psi components and 10,000 psi components are relatively expensive.

Neither hydraulic hybrids nor electric hybrids are new ideas, and the trend has been toward electric and away from hydraulics, even in the earth-moving industry where hydraulics have been used for many decades. The norm in haul trucks is now AC drives for traction, rather than the older hydraulic wheel motors. For light hybrids (not light in mass, but light in energy storage, and thus limited in effectiveness) then hydraulics can make sense. But for more serious hybrids (where you want to be able to store the energy of going down a mountain to come up another mountain on the other side of the valley) hydraulics simply don't offer adequate energy storage at reasonable weight: The real world example of the UPS truck having only 2000 hp seconds (.4kWh) storage in 1000 lbs demonstrates the problem. Even for my tiny vehicle, .4kWh is not adequate for even simple hybridizing, and is 1/10 the energy requirement for use as a plug-in hybrid.

There are cars running around today powered only by solar cells. (In fact a friens of mine has several electric cars, and charges them (and runs his house on solar cells). Solar cells are not perfect, but now are at the point where they can return the dollar cost and manufacturing energy cost in 6 or 7 years (I think BP suggests an even lower number). That, combined with all the other ways of generating electricity, makes electric vehicles really attractive. A good step toward making electric cars viable today to people of ordinary means, is a plug-in hybrid: keep the expensive part (the batteries) small, an eliminate the range problem with an ICE w/ generator, and I think you have a vehicle that can sell in volume.

I don't think hydraulics are bad, by any means, and have considered a hydrostatic transmission to optimize the efficiency of electric motor power transmission. But despite the obvious advantages, and despite the fact that many have tried to implement hydraulic infinitely variable transmssions in cars, it has not happened. If Peter's company can produce a small hydrostatic transmission for $100 that can transmit 20 hp then I'd buy many of them, as would many motor scooter manufacturers.

Re regen and aero drag, I think we are agreeing. In modeling the EPA urban cycle, you find that there are decelerations for which active braking is not required, just as you do when driving in the real world. (The EPA cycle was generated from real world driving data.) When you look at the graph of speed vs time, it looks like closely spaced mountaind, and you can imagine that the energy used going up is recaptured coming down.) But when you actually run through the numbers, you find what you find in real driving -- that you often coast almost all the way to a stop, with tires and air sucking up your kinetic energy. If the vehicle is relatively slippery, heavy, and rolling on low-resistance tires, then you need to brake more frequently to slow down at the rates required by the cycle -- so if all braking is regenerative (as it can be with electrics -- the PML flightlink people do this with their Mini -- ditch the mechanical brakes entirely) then more energy goes back into the battery and less goes to heating tires and stirring air.

There is no question that hydraulic motors are lighter than electric. But again, the PML Flightlink wheelmotors are something like 35 lbs for 160 hp, which is not 10 times as heavy as a 160 hp hydraulic motor.

I think Peter's system will work; I just think his numbers are optimistic: we have real world examples which indicate that there is little difference, even under the ideal condition for hydraulics: heavy vehicles in stop and go traffic. The Fed X trucks do slighly better than the UPS ones, and UPS has ordered many more electric hybrids than hydraulic.

Oops, gotta go.

__________________
There is more to life than just eating mice.
Reply
Member

Join Date: Feb 2009
Posts: 8
Good Answers: 1
#71
In reply to #69

Re: Hydraulic Hybrids Race Against Electrics

02/14/2009 11:12 AM

Hi Ken,

I don't want to convince you. I support any activity trying to substantially change the inefficiency of road vehicles. I doubt whether the efficiencies of Eaton or Artemis system are very close to ours.

There are several differences between batteries and accumulators. One of the most important aspects is energy and power density. Batteries can store much more energy than accumulators but they suck as power management devices. The power transients in a passenger car are enormous and the battery is really not a good device for handling these transients. In my philosophy a hybrid drive train of a passenger car doesn't need a large energy storage, but it does need a robust capacity that can handle power transients of up to 50 kW for many charge and decharge cycles. Accumulators are a much better match for these demands. They are simple, robust, efficient and low cost. You are right concerning the pressure drop (much like the voltage drop of a capacitor). But this is why we introduced the hydraulic transformer.

I don't want to downsize the engine. The peak performance requirements of a vehicle can only be met with the internal combustion engine. If you want to cross the mountain passes of the Alps in Europe, climbing for half an hour or more, having a fully loaded car and trailer, then there is no way you can achieve this with the help of a battery, nor is there sufficient capacity for handling the power and energy while going downhill for half an hour. My question to you would be why you would like to have a smaller engine? Your argument that "it spends more time running at lower relative loads" is exactly what we avoid. If the vehicle requires a high traction power then the engine can perfectly run constantly without stop-and-go operation. It is only at low traction requirements that the engine will be driven start-stop, at low rpm.

"My model does not know whether the motors and generators (or pumps) and controllers (98% efficient for electric, but substantially lower than that for even the most sophisticated hydraulic valving and transforming) are electric or hydraulic. All it knows is operating efficiencies at various loads and speeds. If I plug in your efficiencies rather than electric efficiencies, I cannot come up with anything close to a 366% improvement in the urban cycle."

Maybe I should give you a simple version of our model. Let's look at it from the energy need perspective. A mid sized sedan needs 0.47 MJ for performing the NEDC. This is the sum of the rolling resistance and the aerodynamic drag. Again, I didn't include the kinetic energy since this is not a real loss. If we would now assume a transmission which would be 100% efficient and an engine having a 40% efficiency than this mid sized sedan would require 1.16 MJ for performing the city part of the NEDC. Having a distance of a little more than 4 km and assuming diesel oil as the fuel than 1.16 MJ corresponds to 0.8 litres per 100 km or a fuel mileage of 293 MPG. We claim to have 126 MPG for the HYDRID, so we are far from perfect. This simple calculation shows how bad current cars are designed from an energy consumption point of view. I don't know about your model but my guess would be the difference could be caused by the starting points. Again, we have a regular vehicle, with a regular engine performing a standardized cycle. You also need detailed information about the engine map of the vehicle clearly showing the engine efficiency at very low loads.

"As I said before, for a real world comparison of hydraulic vs electric, using comparable levels of technology, we could not have a better example than UPS vs Fed X, with both produced by the same company. We know the FedX generator is about 95% efficient virtually all the time. We know the motors are about 90% efficient at peak, and spend a lot of time at over 85%. We know, without a doubt, that control is more efficient electrically, and we know that wires are more efficient than tubes and pipes. We know the energy storage is far more weight-efficient electrically."

You must have different efficient numbers than I have. I think everybody agrees that the energy density of electric batteries is superior.

"Electric cars are all the Detroit manufacturers are talking about, now that they are suddenly getting "green" and going to spend our money on "cars we really want"... as if we didn't "want" the SUVs we bought by the millions."

Ken, I don't oppose the electric battery. I would certainly agree that the battery opens the road towards sustainable energy in vehicles. But why not combine the hydraulic hybrid with batteries? We have hydraulic motor/pumps that have more than 95% efficiency and can easily fit in the core of an electric motor/generator. The hydraulic system would simply replace the mechanical transmission and create a new transmission which would handle all power transients in the vehicle. The electric motor would not need more than 5 kW to start with (again the power transients are handled with the hydraulic system), which is about the average power you would need while driving in the city. If the electric components get improved then the battery capacity and the size of the electric drive can be increased.

"Does that mean that all the Toyota, Honda and Ford hybrids do not exist? Or that the Tesla is a lead sled? Or that the GM EV1 was slow and overweight? Are you saying that the 1000 lbs of fluid and accumulators used on the UPS truck, which has less than half the energy storage capacity of a Prius battery of 1/10 the weight, is magically actually cheaper and lighter? I used to be a math whiz kid, but I can't make this compute. The fact that UPS has ordered 250 diesel-electric hybrids and just 5 diesel-hydraulic hybrids says something, does it not?"

We work with the automotive industry. We learnt from their analysis and reports that the hybrid electric vehicle is a dead end. I agree with you, HEV's are on the market. But this doesn't mean they are cost effective and offer a solution for the future.

Peter

Reply
Power-User

Join Date: Feb 2007
Location: Nebraska
Posts: 104
Good Answers: 2
#72
In reply to #71

Re: Hydraulic Hybrids Race Against Electrics

02/16/2009 1:07 PM

Hi Peter,

You say that you don't want to downsize a cars engine. And I agree that there are times when you need all the power that that engine can supply. But couldn't you down size the engine and supplement that power with and electric motor or motors and batteries? My thought, and others on this discussion don't think much of it, is to use a super hybrid if you will. A small gas/diesel engine - to be used to charge your batteries, electric motors and a small battery pack - to power the hydraulic pumps, and hydraulics as your transmission / high energy storage. Wouldn't you be able to use the best of all worlds? You could size your gas engine and electric motors to your maximum power load. But as your load goes down you can shut down each system to maintain maximum efficiency. Maybe I'm crazy but it seems to me that you can get your best power usage out of a system like this.

I have really enjoyed reading your comments and you have added a lot to this discussion. I have never heard of a hydraulic transformer and wish I could get my hands on one. You also say how cheap accumulators are. I sure haven't found them to be cheap. I've thought of building my own but I'm kind of stumped as to what kind of membrane to use. Can you not use any membrane at all and just use a membrane-less storage chamber, I've thought of a 10" sch 40 pipe? Or does the nitrogen diffuse into the oil?

I would like to hear your comments.

Fishpipes

Reply
Member

Join Date: Feb 2009
Posts: 8
Good Answers: 1
#73
In reply to #72

Re: Hydraulic Hybrids Race Against Electrics

02/16/2009 3:40 PM

Hi Fishpipes,

You are touching an important but also difficult point. First of all downsizing an engine is not the same as choosing a smaller engine. A downsized engine is a small engine that can deliver the same power as a larger engine (by means of extreme super charging). The advantage is that the downsized engine has its peak efficiency at lower loads, without compromising the performance in terms of power or maximum torque. There are many disadvantages to this strategy and I won't go into details, but one important disadvantage is that it doesn't bring enough efficiency advantage. The ratio between maximum performance and average driving conditions is just too big for a downsized engine to cover.

What you seem to refer to is not a downsized engine, but simply a smaller engine with a reduced power output. The system you describe is the Toyota Prius, which indeed has a smaller engine. The Prius compensates the reduced engine performance by means of adding an electric propulsion system, which is also in line with your philosophy. But this compensation is only partial. Your are for instance not allowed to tow a trailer with the Prius. The electric system would simply overheat (which is caused by the relatively high internal losses of these components).

The other point is the cost factor. For the automotive industry, the manufacturing cost of a drive train is the most important decision factor. In the previous decades, the cost pressure has already been enormous, but will become much more important and unprecedented in the years to come. It is extremely different to get (reliable) cost information. We are privileged that we work together with the industry and we have (to some extent) excess to this information, but we can't share this information or make it public. There is however also a simple and straightforward approach to have a feeling for costs. The cost of any product can be estimated by looking at the weight of the product and the specific costs in $/lbs or €/kg. This can also be done for subassemblies, like an engine, or a transmission. Electric hybrids are expensive because an extra system is added to the old drive train. The smaller engine hardly compensates for the extra weight of the electric motor/generator, the converters and inverters, the battery and the extra cooling. The added weight would as such result in a higher fuel consumption, but Toyota has designed an extremely light chassis to compensate for the extra weight. The low weight chassis is however much more expensive than a normal chassis. Finally, the electric system is not only heavy, but it also has higher specific cost (in $/lbs) than engines or gear transmissions.

The hydraulic components have a power density which is the same as mechanical gear transmissions. Hydraulic components are also very comparable from a manufacturing point of view, having the same materials, the same fundamental loads, and the same tolerances as gear transmissions or CVT's. Only hydraulic components have the potential to replace the mechanical transmission without increasing the weight or cost. But hydraulic systems offer power management and energy recuperation, to an extent that mechanical transmissions can never do. Our goal is not to oppose the electric system. Our goal is to eliminate the mechanical transmission and introduce a new 'backbone' which allows a new, modern vehicle drive train which enables the choice for the best power plant or power plants. This could well be a strong powerful internal combustion engine (for peak performance) in combination with a small electric (base load) power plant for city operation and commuting.

Finally some words about the accumulators. Don't try to develop your own. I know they are expensive if you just want to buy one single piece. Try to get one at one from a scrapyard, although that might be difficult because they are extremely durable and are often recycled. Good luck! Peter

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#75
In reply to #71

Re: Hydraulic Hybrids Race Against Electrics

02/17/2009 4:42 PM

Hi Peter,

You wrote: We learnt from their analysis and reports that the hybrid electric vehicle is a dead end.

Perhaps you are talking to the wrong people. Many concept cars and prototypes from all the manufacturers are plug-in hybrids, petrol-electric hybrids, and diesel-electric hybrids. The models here in the US which are introduced with the most fanfare are the various forms of electric hybrids (including plug-ins) and pure electric vehicles. This interest in electric hybrids extends to the truck world, as seen by the large purchases of electric hybrids versus the rather small purchases of hydraulic hybrids.

There is a very strong tendency in the automotive industry to continue doing the same thing -- namely creating heavy gas guzzlers because they are profitiable. For this reason, and despite remarkable improvements in engine technology, the US fleet average has gone from 27 mpg in 1985 to just over 20 today, but the engines are substantially more efficient in terms of bsfc when fully loaded. So some people are probably thinking that things will not change. They may be right.

But Lutz says electric cars are the future, Toyota (the world's largest car manufacturer) is focusing on electrics, hybrid electrics and plug-in hybrid electrics, the Peugot concept cars at Geneva were all electric hybrids, and Ford has just brought out their hybrid electric Fusion to critical acclaim. (It just won a recent comparison test of electric hybrid models from Ford, Toyota, Nissan, and GM). So I think electric hybrids and especially plug-in hybrids are hear to stay, and will be the stepping stone that drives up volume on batteries, reducing future battery cost, which will permit more pure electrics.

I agree with you, HEV's are on the market. But this doesn't mean they are cost effective and offer a solution for the future.

The fact that Toyota has sold over a million Priuses suggests that they are indeed cost-effective. There is no better measure of cost-effectiveness than the marketplace. Even a Bentley is cost-effective if it delivers perceived value to its owner. (For me they have negative value -- I'd be embarrassed to be seen in one.)

I don't want to downsize the engine. The peak performance requirements of a vehicle can only be met with the internal combustion engine.

Of course, this is is entirely dependent upon design. In a hydraulic hybrid, where you have so little energy storage capability (and in which is is nearly impossible to have meaningful storage because of low gravimetric storage density) then, of course, you need to rely on the ICE for almost everything other that initial acceleration away from a stop light. (This is one reason hydraulic hybrids are proposed mainly for garbage trucks and delivery trucks.) A hybridized version of a Tesla, with a small range extender generator, would rely on the electric motor for peak performance requirements, just as the Chevy Volt* will. So yes, you would not want to downsize the engine for an automotive hydraulic hybrid that you intended to drive up mountains, but in an electric hybrid, this downsizing is both practical and desirable. (I use the term downsizing in the sense generally used in the US in connection with hybrids, not as you have used it in this thread to mean an engine that is smaller than might otherwise be used, but brought back up to competitive output via turbocharging. The selection of a smaller engine in the interests of lower weight and higher relative loading is almost always applied as a hybridizing technique -- in fact, I don't think there is a successful automotive hybrid in which this technique has not been exploited. Having the weight of a full-sized engine plus the weight of accumulators or batteries erodes efficiency advantages of hybridizing.)

I think Lutz said that he expects that by 2020 or 2025, half the cars will be powered by electricity much of the time. I would not be too surprised it that is the case. In the US, diesel fuel is too expensive to be attractive for automotive use, so I'd expect that our long-range trip cars will be similar to today's, in which all the energy comes from gasoline, and with a significant number of those being Prius-style hybrids. (Hydraulic hybrids like those you propose would be a good fit here too.) For non-trip use, I'd expect to see a lot of vehicles like the Volt, and a few pure electrics.

But why not combine the hydraulic hybrid with batteries? We have hydraulic motor/pumps that have more than 95% efficiency and can easily fit in the core of an electric motor/generator.

Personally, I'd like to see something exactly like this. For a vehicle like mine, there are readily available PM motors that are cheap and 90% efficient or expensive and 94% efficient. Small AC induction traction motors are either not adequately efficient, or they are slightly larger than I need and quite expensive. The AC motors can have an advantage in that they can do without a multiple ratio (or CVT) transmission. The PM motors, on the other hand, cannot operate optimally with a single ratio. (If you are after really impressive performance, even the AC motors need more than one ratio. The Tesla, for example has a very low top speed, by today's standards -- about 10 mph lower than my plane-Jane 4-cylinder Honda Accord -- about as average as average can be in performance. For good acceleration and high top speed the Tesla would need at least two ratios.) So an electric motor with a pump built into its core would be perfect. Three tiny wheel motors and we've eliminated a lot of parts.

*As you probably know, GM wants the Volt to be viewed as an electric car, rather than as a hybrid, because then it would appear to be more efficient, with a rating well over 100 MPGe (rather than the 45 mpg or so it will get as a hybrid running on gasoline.) Of course, it is a classic series hybrid, and the only way GM could reasonably make their case would be, I suppose, to have it written into the owner's manual that when the batteries die, you must park the car with the generator engine running and wait for the batteries to charge before driving -- pretty silly.

__________________
There is more to life than just eating mice.
Reply
Member

Join Date: Feb 2009
Posts: 8
Good Answers: 1
#76
In reply to #75

Re: Hydraulic Hybrids Race Against Electrics

02/18/2009 4:02 AM

Hi Ken,

I am quite aware of all the hybrid developments around the world. I see the magazines, read the articles, marvel the prototypes displayed at auto shows, but at the same time I have to agree with Vinod Kostla who compared the Toyota Prius to a Gucci bag (http://www.khoslaventures.com/presentations/Hybrids.pdf): they both sell, but only to the happy few. The electric hybrid is not only expensive, it is also not very efficient, at least not compared to efficient diesel vehicles (in Europe more than 50% of the cars is driven by a diesel engine).

We both agree that the weight of the vehicle should be kept low, although I believe we have a different intention. Your argument is that a weight increase erodes the efficiency advantage. My argument is that a heavy transmission costs more. The manufacturing costs of automotive engines and transmissions is around $15 per kg (for electric batteries, power electronics and PM motors these specific costs are higher!). If we would add an extra transmission system with the same specific manufacturing cost having a weight of 100 kg than the manufacturing cost of the vehicle would be increased by $1500 (aside form additional costs for a heavier vehicle structure etc.). The concept of the HYDRID is weight neutral, including the accumulators (that is one reason why we have small accumulators). Having the same specific manufacturing cost as of current engines and transmissions, the HYDRID also doesn't increase the manufacturing cost.

I don't believe that a weight increase always must result in a reduction of the specific fuel consumption. Of course it does with current vehicles. A higher weight increases the rolling resistance, but that is a rather small part of the vehicle load. A heavy vehicle is often also larger, having a larger frontal area, which increases the aerodynamic drag. But provided you have the same chassis, then a heavier transmission does not have an influence on the fuel consumption as such. A heavy vehicle also needs more energy to accelerate. But if you have an efficient energy recuperation system, than this energy is not lost. The most important reason why a weight increase results in a higher fuel consumption in current vehicles is that a heavy vehicle needs a stronger engine to accelerate the car fast enough for todays customer demands or to have sufficient gradability. The larger engine will however also be used for driving in the city or cruising on the highway, at which point the engine load is strongly reduced. With a large engine the ratio between peak performance and average performance demands is larger, which results in a stronger part load operation and consequently in a reduced engine efficiency. Only if you can completely avoid strong part load operation of the engine (and that is what we do in the HYDRID), then you can rid of the strong relationship between vehicle weight and fuel consumption.

In the end we are all looking for a system which is not just efficient, or durable, or safe, or powerful, but for a system which is efficient and durable and safe and powerful and offers the industry a way to survive the current cost pressure. I think we are both working on that.

Peter

Reply Score 1 for Good Answer
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#77
In reply to #76

Re: Hydraulic Hybrids Race Against Electrics

02/18/2009 3:34 PM

Hi Peter,

The Prius has been a cultural icon here, which carries both positives and negatives. But now, with so many other hybrids already on the market, it is purchased more frequently by people who just want good fuel efficiency and great utility: you see them everywhere here for that reason: last I heard, they were number 11 on the bestseller chart. (But still at number one for the full year 2008 figures: the Ford F150.)

The Jetta TDI, its closest non-hybrid competition, has less interior volume and less cargo volume, but only gets 29 mpg city, 40 mpg hwy, yet costs about $2000 more than the Prius, for the auto trans version. The Prius gets 48 mpg in the city, a 65% improvement over the Jetta, and 45 on the highway, a 12.5% improvement over the Jetta. Today, the Jetta's fuel is $1.99 per gallon here, and the Prius fuel is $1.69, so the Jetta is far more costly to operate. (This is the smallest price differential I've seen for a long while -- usually diesel is substantially higher in price.)

In Europe the situation is much different, of course, with a wider range of diesel cars available, and with greater acceptance of diesel as a fuel for cars. But even in Europe, it is hard to find a car with the Prius's interior volume that gets better mileage, even if you don't balance the fuels for energy content.

In the end we are all looking for a system which is not just efficient, or durable, or safe, or powerful, but for a system which is efficient and durable and safe and powerful and offers the industry a way to survive the current cost pressure. I think we are both working on that.

I commend your efforts. As it happens, I am not focused so much on offering the industry alternatives (my current project is a clean sheet design which fills a niche currently not served at all by the industry) but I think your system could work well as an alterative to existing transmission and hybridizing schemes. The transmission end of it could be very appealing for my project as well. I'll have to email you with some details.

Regards, Ken

__________________
There is more to life than just eating mice.
Reply
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#62
In reply to #58

Re: Hydraulic Hybrids Race Against Electrics

02/11/2009 10:19 PM

Mr. Achten,

Thank you for the post. I have read most of your patents, and received your CD just recently. My opinion is that your system is the most advanced in public view, and way beyond what Eaton has to offer, showing a much better understanding of the critical details needed. I applaud you for your work and creativity.

My question is: How would you or could you address the problem of dropping efficiency with dropping power output?

The variable transformer concept you propose, in my view, has a central problem of dropping efficiency with dripping power output. This is caused by the constant volumetric and frictional losses having to be accounted for with less and less power. Herein is the central problem, which you approach does NOT address.

For example, if your wheel motors are 50 hp (I forget your figures off the top of my head) each (total 200 hp) at 70 mph and normal pressure, the actual power required for a 3500 lb car with 7 square feet flat plate drag is approximately (based on a program I have) 22 hp. A Prius would need 19 hp. 19/200 is 0.095, or 9.5%, or less than 10% of rated power.

The Innas graphs, as I remember, show your efficiency is very poor at that low rated power which is what would be considered a highway cruise.

At 35 mph city, the power required is only 2.6 hp or 1.3% of peak. At this point, the volumetric and mechanical losses become dominate therefore your efficiency would be very low. Based on the free piston to accumulator efficiency of 38% as you claim, you get then .38 x something very low which equals something that is very very low. I believe you might be able to do better than a standard stick transmission diesel drive, just like UPS does, but there is a lot of improvement, perhaps 2x's that is being lost with your approach.

To solve this problem you would have to redesign the transformer(s) and motor(s) and several other things of your system. What say ye?

I agree with the need for a constant torque, which most engineers cannot or refuse to see as a major issue. This sets you apart, in my opinion, as few have made such a comment.

It would seem that your claims are possible, but most people will not believe it until they see it...

I would suggest you build a trailer with an engine and push a car with the old drive disconnected. You could then prove your claims on many cars without the need of a custom, and costly, specific installation.

seaplaneguy@msn.com

Seaplaneguy

Reply
Member

Join Date: Feb 2009
Posts: 8
Good Answers: 1
#64
In reply to #62

Re: Hydraulic Hybrids Race Against Electrics

02/12/2009 7:17 AM

Seaplaneguy:

There are three components to consider: the pump, the transformer and the wheel drive units (which can act as motor as well as a pump). To start with the pump, we have chosen a constant displacement pump which is directly connected to the internal combustion engine. The pump only supplies energy to the high pressure accumulator and is therefore always operated at relatively high loads. Since the internal combustion engine can only be operated above its minimum speed, the pump is operated at favourable operating conditions. You could also say that the engine-pump combination is always operated above a certain minimum power level, thereby avoiding extreme part load operations. Never use a variable displacement pump for a hydraulic hybrid. The efficiency of a variable displacement pump decreases if you swash down the unit to small displacements (basically the ratio between dissipative losses, like compressibility effects, and power output becomes worse if you reduce the pump displacement). But the most important reason not to apply a variable displacement pump is that a reduction of the pump displacement forces the engine to be operated at a lower torque output, which is exactly what you need to avoid.

The wheel motor/pumps are also constant displacement units. The operating speed is chosen to be equal to the wheel speed (i.e. between 0 at 0 mph and about 1700 rpm at 124 mph). For most conditions the operating speed is below 1000 rpm. As for the main pump, we have chosen constant displacement units. Compared to variable displacement machines they have a higher efficiency (as mentioned before), are more robust, small and light, and quieter. In a series hydraulic hybrid the wheel units have to fulfil all operating conditions. Moreover if you want to brake on the wheel motors then the hydraulic motors have to be operated in 4 quadrants: forward propulsion, forward braking, reverse propulsion and reverse braking. The design of a 4-quadrant motor/pump is however extremely complicated. Many designers have therefore chosen to have a two-quadrant operation and create the other quadrants by means of valves.

To understand the high efficiency of the wheel units you will need a good understanding of the floating cup principle. Since you have studied the literature you will have noticed that the losses are not constant but vary with pressure and speed. The principle offers a high efficiency in an extremely wide range of operating conditions. The efficiency is highest at low to medium operating speeds. The other thing you have to understand is the fundamental difference in varying the torque by means of the displacement or by means of the pressure. Almost all hydraulic hybrid developers opt for displacement control. The size of the unit is chosen for extreme torque requirements. This is for instance the brake away torque while driving uphill (i.e. you have a stand still at a 12% slope with a fully loaded trailer on the hook and you need to start driving uphill). This is where most hydraulic motors suffer from stick-slip effects. The resulting torque loss has to be compensated by choosing a bigger motor. Moreover the capacity of wheel units has to be increased because the peak torque demand should be delivered under all conditions, also if the pressure level in the high pressure accumulator is at a minimum value. The oversized unit is subsequently operated at strong part load conditions during most of the time.

The floating cup principle has the advantage that stick slip effects are almost completely avoided. This means that the unit does not need to be oversized. The next step is to include the hydraulic transformers into the equation. Different from displacement control, the transformer changes the wheel torque by changing the pressure offered to the high pressure port of the wheel units. The great thing about the transformer is that you can amplify pressures. If for instance the accumulator is 'empty' having a minimum pressure of 3000 psi, then the transformer allows you to amplify this pressure to 6000 psi, thereby creating a boost torque at the wheels, even when having a small displacement. Both the transformer and the wheel motors will not have their best efficiency point at these conditions (they are designed for average, rather low load and low speed operating conditions) but since a peak torque demand is seldom requested this doesn't hurt the day-to-day fuel consumption (just consider how often you are standing still at the hill with a fully loaded vehicle and trailer behind your car?).

I read about your concern of the constant volumetric and frictional losses. But your assumption is wrong. The losses vary with the operating conditions of the transformer. I'm sorry for the short answer, but another answer would take much more time (I could write a book about it). Maybe the best thing would be to send some efficiency plots of the units together with the operating points. We will have a peer reviewed publication in the German magazine ATZ later in May this year which will show these plots.

Of course you are completely right that experimental evidence is always much more convincing. We already build a fork lifttruck and are working on a passenger car. The concern of the automotive industry is however not anymore the efficiency of the HYDRID. They are already pretty much convinced about the reduction of fuel consumption. The costs demands are however harder to prove and just one demonstrator won't do. Finally we are proposing the automotive industry to abandon a drive train concept which has been around since the first days of the car history: an engine, a transmission, a differential and wheel shafts.

Peter

Reply Score 1 for Good Answer
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#65
In reply to #64

Re: Hydraulic Hybrids Race Against Electrics

02/12/2009 3:36 PM

Achten:

Thank you for the reply.

I agree that I am 'wrong"... Why? Other hydraulic equipment agrees with me, but your equipment has unique features.

The shuttle between pistons (part of your patent) would eliminate the compression/decompression. Ok. I can see a 3% increase in efficiency by this at peak pressure, but not when the transformer lowers the pressure to 100 psi or so.

The cups must be pressure dependent, correct? Your piston expands with the cylinder, which is better than Eaton, but it still give a level friction relation that become dominate as power goes down. No?

How do you lower the bearing on other losses as a function of power?

Could you send me some of those efficiency graphs to: seaplaneguy@msn.com ?

Do you sell your transformer to the open market?

Costs?

I might like to buy your transformer and motor for a system I am working on.

Seaplaneguy

Reply
Member

Join Date: Feb 2009
Posts: 8
Good Answers: 1
#66
In reply to #65

Re: Hydraulic Hybrids Race Against Electrics

02/13/2009 2:24 AM

Seaplaneguy,

The principle of the floating cups is rather simple. Each piston has its own cylinder which is able to move on a rotating plate. The cylinders are hydrostatically balanced, in the axial and in the radial direction. They are more or less floating (hence the name floating cups). If the oil content of the cup is pressurized then the cup will expand. The pistons have a cavity in the piston crown that is made as such that the expansion is the same as the expansion of the cup. This keeps the gap closed. Important is that there are almost no contact forces between the piston and the cylinder/cup. This is different from ordinary axial piston pumps and explains why we have low contact (Coulomb) friction. Furthermore we introduced a double, mirrored configuration. This strongly reduces the bearing load and hence the bearing losses.

The main loss of the floating cup principle is the (viscous) friction between the barrels and the port plates. This loss is (linear) dependent of the rotational speed, but almost completely independent of the pressure level. But yes, the efficiency is influenced by the power of the hydrostatic machine (which is true for any machine, even for a gear transmission), but much less than in an ordinary pump or motor. I will sent you the efficiency plots.

Peter

Reply
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3945
Good Answers: 182
#67
In reply to #66

Re: Hydraulic Hybrids Race Against Electrics

02/13/2009 5:35 AM

Can you give an address where I can find more about the floating cup?

I looked in my OP collection but I found not the old mags.

Thanks

Nick name

Reply
Member

Join Date: Feb 2009
Posts: 8
Good Answers: 1
#68
In reply to #67

Re: Hydraulic Hybrids Race Against Electrics

02/13/2009 5:50 AM

Nick,

go to www.innas.com

Peter

Reply
Associate

Join Date: Nov 2008
Posts: 25
#86
In reply to #66

Re: Hydraulic Hybrids Race Against Electrics

03/28/2009 7:34 AM

Peter,

I maybe an unknown but really likes hydraulics(hydrostatic)...(its a passion to me). I have never read, meet or seen a person who talked about hydraulics better than you... so far.

I have read only topics about HHV and also about electric... just recently. I have been posting a lot in hydraulicspneumatics forum and the recent was on the "control of the secondary units" to which I am trying to think about combination of electric-hydraulic hybrid.

I am not a typical nerdy guy(i am more of a college of hard knocks) who can respond to numbers easily and just trying to use simple mathematical computations/formula and estimates so as not to mess up my passion to just learning/expressing my hydraulics opinion.

I have read about UPS trucks and Rexroth regenerative braking. I had a quite debate with someone who has invented DHT(digital hydraulic transformer) about how the variable displacement motor system can operate bi-directional in an open loop without using in between change-over valves(fast response) as well as the the energy recovery efficiency(at an accumulator size). Later I thought that (from my humble analysis/guess of the pdf) a close-loop system was used (although reverse direction was not illustarted) using a fix displacement bent-axis motor(I wont go into some details because of my limited english and typing speed) which could back up my argument in the other forum.

Now as "fish" would like to do this combination of electric-hydraulic hybrid to which it is possible but my limited scientific knowlede about efficiency of transforming energy, then recover, and then another transformation as not a good process... (I cant agree or disagree)some people said.

As you said "management" is really the best advantage of hydraulics system(controllability and simplicity) over the pure electric one. I was illustrating also in the other forum(but deleted mostly...disappointment) about the possibility of using a variable pump(proportional-electronic piloted) and a variable disp motor(CSU) instead of a constant pressure/flow to avoid heating due to higher pressure drop(my name...i hate it).

Now, if I could really know the actual circuitry used then I could explain some more common sense thought about HHV. I am a proponent of energy savings(efficient hydraulic system applications) and IMO probably by using a closed-loop with variable displacement motor, a hydraulic transformer(i have no idea of this...DHT?!) and very efficient controls management HHV will become a very interesting efficient vehicle in the coming years.

BTW hydraulics is not that complicated as some people say... IMO it is the simplest among the engineering fields as well as the most exciting one.

Reply
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#88
In reply to #86

Re: Hydraulic Hybrids Race Against Electrics

03/28/2009 12:52 PM

Pressure drop,

What do you mean by a "digital hydraulic transformer" ? Can you explain what that is? The Innas transformer is not digital.

Reply
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3945
Good Answers: 182
#90
In reply to #88

Re: Hydraulic Hybrids Race Against Electrics

03/29/2009 4:44 PM

If you try with google you find a US patent describing the device.

I consider it as theoretical interesting solution and for some very limited applications as well of interest but not for general use due especially to its complexity.

I made a down load of the patent which is in PDF and can send it to you if neede if you send me on the PM channel your e-mail address.

Reply
Associate

Join Date: Nov 2008
Posts: 25
#91
In reply to #88

Re: Hydraulic Hybrids Race Against Electrics

03/29/2009 6:30 PM

Someone invented a DHT(just recently patented) or digital hydraulic transformer. I think the company is Digital Hydraulic LLC or something. I used to argue with the inventor(elton bishop) regarding the CSU(control of the secondary units... variable displacement hydraulic motor... rexroth A4VSO) as to how the system can be used in automotive(especially the reverse motion(without any reversing valve)... and he mentionedd the patent for DHT. I think the principle is the same as IHT.

Then I came across this post of Mr. Peter Achten and visited "innas site" and slowly trying to understand what a hydraulic transformer is. And I am still guessing as if it is kind of a flow divider(but bleeding[bleed off system of flow controlling without much power losses] some flow to tank).

I cant figure out still based on the simple illustration that innas had in the site and it seem that the hydrid(series/parrallel) is nice not that I am a true blooded hydraulic person(i am an EE), but because I can see the simple way of using hydraulics in another efficient application.

Maybe one of this days, if I can get hold of some detailed circuitry or facts about innas revolutionary floating cups systems, then I probably could share some simple annalysis/opinion(BTW i am not an expert). I have quite a good sense of understanding of hydraulics but not too much on calculating to higher degree to express my opinion... but I can... maybe.

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#92
In reply to #91

Re: Hydraulic Hybrids Race Against Electrics

03/30/2009 2:32 AM

Then I came across this post of Mr. Peter Achten and visited "innas site" and slowly trying to understand what a hydraulic transformer is.

Their hydraulic transformer trades volume for pressure and vice versa. It is a near perfect analog for an electrical transformer, in which the product VA is the same at input and output, but the voltage and amperage values are different on each side (ignoring losses).

It is very similar to a hydrostatic transmission (which is typically a variable displacement pump and a fixed displacement motor) but instead of having a mechanical output, its output is fluid. You could make one: put a fixed displacement pump on a prime mover, like an engine. Pump its output to a [fixed displacement motor which turns a variable displacement pump.] The stuff in the brackets works as a transformer. Then feed the output of the vd pump to fixed displacement wheel motors (etc.) The transformer then works like an infinitely variable gearbox.

__________________
There is more to life than just eating mice.
Reply
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#93
In reply to #92

Re: Hydraulic Hybrids Race Against Electrics

03/30/2009 11:33 AM

Ken,

One of Innas's innovations, if you read their patents and the evolution of thought, starts and centers around the ability to switch ports while the volume is changing. See patent 7,090, 472. By enabling port switching during volume change, as opposed to Top/bottom dead center, the disk can be rotated to allow volume change at any point around the circle, thus allowing one port to power another, depending on where it is on the circle. See 6,116,138.

If you look at 6,887,045, Rexroth does a similar "tranformer" combination, as does catepiller in 6,460,333. The notion of a transformer is NOT new. Innas is not the only company doing transformers. That said, nobody really has a transformer for sale, and neither does Innas. You cannot buy a transformer from Innas, Rexroth, Danfoss or any other company, unless you want to fund their R&D and pay hundreds of thousands for that opportunity...not to mention pay for their production line...

The Innas transformer varies pressure to the wheel motors and thereby changes "gears" as it were. This requires that the wheel motor must operate efficiently at <20-100 psi, where most of the city driving would occur. Hydraulics want to run at high pressure to overcome fixed losses, and by doing what Innas advocates, you violate well held notions in hydraulics.... Innas claims they have losses that go down with pressure, so you be the judge...

Now that I have looked at Innas's stuff long and hard, I cannot see that I can reach my goals with the Innas system and strategy. They won't license it either... I asked...

There is a better way... Onward and upward!


Seaplaneguy

Reply
Associate

Join Date: Nov 2008
Posts: 25
#94
In reply to #93

Re: Hydraulic Hybrids Race Against Electrics

03/30/2009 7:07 PM

Could it be possible that Innas want to utilize the higher pressure capability of a hydraulic system/component?! (hydraulics in small packages). I am surprise too that the average operating pressure is around 200 bars at average speed to which IMO would require around minimum of 180(+-) bars of accumulator nitrogen charge(quite high)...

Regarding the hydraulic transformer... I cant really imagine Innas thought about using this component, then the fix displacement drive motor/s?! While some other company like rexroth could use a variable displacement over-center motor/pump(A4VSO). Somehow Peter said that it is best to use a fix displacement pump!? No doubt, I like Innas floating cup design... and will like it more if it can be over-center type.

My simple thought and question (coz I am not an expert) is why cant they use a variable displacement or close-loop overcenter pump(with fast response pilots) and an overcenter variable displacement motor(control of the secondary unit)?! I am not saying that a constant pressure rail is not a good idea... it is IMO, in an average/highway speed and fast response(do we need precise/fast response for cars?!). I am not sure but if we we use a close loop circuit or a variable disp. pump, a constant pressure/flow is also possible at average speed. Some how it is possible to swivel the swashplate/positioning piston to lower pump displacements(low flow in idle and traffic... at any pressure) and can manipulate the VDM(variable disp. motor) positioning pistons to vary the displacements(varrying the torque or speed).

For close loop, we can have only pump, motor and accessories. For CPR, we have pump, transformer, motor and accessories... Cost?

just asking...

Reply
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#95
In reply to #92

Re: Hydraulic Hybrids Race Against Electrics

03/31/2009 12:34 AM

Ken,

Guess what?

I hear Innas got around $50 million for the rights to their "transformer" from a major earth mover company, and, from what I hear, it does NOT work, and this company is, shall we say...not happy. I would be...livid...ticked...nuclear...

No wonder Peter did not want to license it to me... It seems like the big guys cannot solve this problem and are willing to shell out boat loads of cash...

The transformer (gold rush) race is on! This area is worth... maybe... billions... serious...but only if it works...which Innas seems to not be able to make it work...

The Innas transformer becomes unstable at different times (system pressure fluctuation resonances, amoung other problems) and the real performance is at best 83%, and much lower when off the "sweet" spot. It can only transform 1.2 times input (2000 psi to 2400 psi, for example), and is therefore only a "de-intensifier" at best.

The thing is, I think I could actually make his system work, with some major changes, but Peter thinks he knows it all... I guess when you get paid $50 million for an idea that does not work, you start acting like people in Washington DC....but I digress...

I wrote Peter off line and I could sense there was something up with this...now I realize there are many more bugs in the ointment... Needless to say, I don't want a license...even if it were free...because it won't get me from here to there. I feel sorry for the guys who paid $50 mil for the rights...sounds like GM and bailouts....

"Another one's gone, another one's gone, another one bites the dust..."

One in 1000 patents are worth something. The Innas patents moves to the 999 columm on my list...Next...

There is a better way... Onward and upward!

Seaplaneguy

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#38
In reply to #27

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 5:34 PM

The valentine concept is not new and has many "devils" that they do not disclose, and this is why, in part, the auto companies do not accept it.

True. And much of what they do disclose is simply wrong. For example, they claim that a solar cell on the roof of the car will recharge the hydraulic accumulator to provide 10-15 miles of range. (Just above that claim, they say the range with full accumulator is 4-6 miles). A pair of panels just slightly larger than the roof of this car will supply about 1 kWh over the course of a day. Even if this energy were stored without the losses incurred in pumping up an accumulator, 1kWh of power is not sufficient to power a car of this size and weight for 10 - 15 miles. The Aptera, which is substantially more streamlined, of smaller frontal area, and lighter can barely eke out 10 miles on 1 kWh. I'd estimate the they are off by a factor of 2, even given good sunlight and positioning of the car.

They say that the consumption at a constant 60mph is 110 mpg. The original Honda Insight was lighter, had less aero drag and had a real engine specific fuel consumption just slightly higher than the theoretical value quoted by Valentin. The Honda had a direct mechanical link to the wheels, which is substantially more efficient than a pump/motor/piping combination. The Honda could get 70mpg at a constant 60mph. The Valentin, if they could produce it at the advertised weight, would be expected to get perhaps 65 mpg, if the hydraulic system were extraordinarily efficient. Again, it looks like they are off by a factor of 2.

The UPS system, which only stores .4 kWh, (2000 hp-seconds) (and which was built under government contract at high cost) weighs about 1000 lb in accumulators and hydraulic fluid alone. The Prius battery, with more than three times the energy storage capacity, weighs 90 lb. Valentin's claim of 30% weight reduction seems very suspect, and I would expect that the weight of accumulators and fluid alone to get 4-6 miles (or 10-15?) would be almost the entire advertised weight of the car, leaving nothing for niceties such as wheels, a body, steering gear, engine, hydraulic pumps, hydraulic motors, etc.

Apparently, they've been working on this since 1988. A working prototype would certainly help their case (if it is legit), and 20 years seems like enough time to come up with something to prove the concept, even if it is not pretty.

__________________
There is more to life than just eating mice.
Reply Score 1 for Good Answer
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#39
In reply to #38

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 6:14 PM

Ken,

I don't think that the UPS/EPA concept would have gotten UPS to buy in unless they had an actual inprovement in a real vehicle.

There is nothing like a real working prototype.

Reply
Guru

Join Date: Aug 2006
Posts: 4485
Good Answers: 245
#42
In reply to #39

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 6:57 PM

UPS has 1600 vehicles in its "green" fleet, which includes all-electric, hybrid electric, propane, natural gas, etc. By 2010, they will have 7 hydraulic hybrids. In their kind of driving for the local delivery trucks the hydraulic system works OK, although Fed X's electric hybrid system claims to be a little more efficient. If production volumes increase, then the hybrid system could cost as little as $7000, with a three year payback in fuel savings possible. But now, the system is far more expensive than than which explains UPS's small order, supported, I am sure, by my tax dollars. Garbage trucks would be a better bet yet for hydraulics... again, if production volumes could get to the point where the systems are affordable.

I think the other issue that will leave hydraulics in an oily pile beside the road, is the range issue. Today, I can plug in and go 30 or 40 miles without using any gas, and then have the engine fire up to keep the batteries charged. That is a compelling feature for many commuters (and if implemented on a large scale would thrill coal producers, too).

__________________
There is more to life than just eating mice.
Reply
Power-User

Join Date: Jun 2006
Posts: 306
Good Answers: 15
#43
In reply to #42

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 7:20 PM

Ken,

My system won't have oil... Water...eco nuts love it... Make distilled water to drink on board... No need to stop for a drink... Change the water...no problem... Change oil...call the EPA and bend over...

Like I have been saying...if you have 10 steps to engine heaven, with one being IC piston crank, 2 being hybrid, 3 plug in hybrids and hydraulic hybrids, what are the next steps? I think water hydraulics will be at the 10th step and electrics will be confined to control and information and not power...

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#32
In reply to #25

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 11:58 AM

I couldn't help but note that the Valentin operation is pretty top heavy with phD's. When it comes to competition for the XPRIZE I'd hope for their sake that winning or placing high isn't an absolute "must do".

After a read of the XPRIZE rule book (which looks like it was written by a lawyer) I'd rate the "event" as an automotive competition. It's been my experience that entrants in such contests do poorly if the team is thin when it comes to good experienced race car mechanics and pit crew leadership. It's also been my experience that phD types all too often do not play well with "lesser beings" especially when the heat is on.

I think I'd put my money on the experienced car guys in the XPRIZE competition.

Ed Weldon

Reply Off Topic (Score 5)
Anonymous Poster
#35
In reply to #32

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 1:57 PM

Weldon,

I looked at the xprize and found it is driven by a lot of PC types who think they know what a customer will want. I think the premise is false, or at best distorting. I find contests like these end up distorting development and setting false goals. People don't buy what some elite guy thinks they want to buy.

There is are many reasons people cannot get into the market, even as a supplier. When a supplier cannot deliver a part, it shuts the factory down. That supplier has to have insurance (read deep pockets) to compensate if they shut down a line.

A guy in a garage is a massive risk, not a sure test bet. Would you invest $10-20 billion on an xprize car with a new untested engine "concept" that may crap out in who knows how many years, if not months?

Hence, only large Hydraulic suppliers will be allowed to supply any hydraulic system, or they will force the garage guy to license it to the big guys.

Then there is the fact that if the car company hollows out their production, what is to stop the hydraulics/engine guy from flipping the game and having someone make a nice pretty body...

Control is at the center of all this. Who makes the profit? The OEM squeezes the supplier once they get going (read Wal-mart effect) and the OEM has the end customer. The OEM is in control of the design and serves as control of what they (we) get for a design. A supplier is just an employee outsourced, that can be discarded.

Selling any system, like you ask me off line, is not part of auto culture reality. Any patent can be circumvented or designed around, and most patents can be contested by saying it is common sense to one in the art.

To play this game, which the xprize deceptively promotes, requires a lot more than a $10 mill drop in the bucket! Oh, if I understand it, the "winner" has to share most of that 10 mill with others...

Then, what do you have after you have won the xprize? Not much...

The way into this market is not by the front door...sorry, you and I are NOT wanted. The OEM has a job and they are not interest in any cool hydraulic/eletro/wizzbang eco anything. They want control and power. It is about ego...

You have to be able to go directly to the customer like Apple did. You need volume BEFORE you try to build a car as a start up, unlike Apple, because the market is mature. None...no not even one...of the xprize guys has volume BEFORE they build the car for the general market.

This is what I want to do...have volume before volume... A new engine must be tested and in volume production before you build the car. The engine and systems must be running and doing something good, like generating electrical power at $0.36/kw-hr (what a gold mine!), BEFORE they are even mentioned as possible car power systems... Or they can be used in experimental airplanes...seaplanes preferablly...but wasting time on the xprize that leads to sub optimum solutions is not the way to go...and neither is hoping to find true love with ANY auto company.

The entrance point is after the power system is flowing loads of cash, and when one of these Big 3 goes belly up and nobody wants all their rather good looking car bodies. There is so much work making a good looking car, all ripe for the picking, just in time for a new engine...a proven engine with real performance. I like GM style myself...but Chrysler will do... Timing is key.

SPG

Reply Off Topic (Score 5)
Guru
United States - Member - USA! Hobbies - Musician - Sound Man Engineering Fields - Mechanical Engineering - More than a Hobby Technical Fields - Technical Writing - New Member

Join Date: Oct 2008
Location: City of Roses.
Posts: 2056
Good Answers: 99
#30

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 11:27 AM

Hydraulic motors are VERY inefficient at low speeds due to leaks.

-I'm not sure i agree with your statement. Are you talking specifically of internal leakage? I have hydraulic fluid cursing through my veins, and have many motors in the shop. I can assure you, that if you have properly designed your system, and selected the right components, you should see some decent efficiencies. It all depends on the overall system design.

In regards to the general topic, I personally don't think Hydraulic Hybrids will ever be mainstream (even though i would like to see it) But i do see some promising potential in the regenerative braking, and launch assist.

The Valentine car is fun to look at and think about, we'll see what happens in 2010 for the X-prize. It will be great to see all the home tinkerers bring new technologies to the market.

__________________
Don't believe everything you read on the Internet!
Reply
Anonymous Poster
#34
In reply to #30

Re: Hydraulic Hybrids Race Against Electrics

01/27/2009 12:41 PM

RVZ717,

Low speed comment is based on performance graphs of motors listed by the manufacturer. This is my interpretation of the graphs. As the variable volume pump/motor comes from full volume to zero volume, the numerous and various frictional sources and valve losses continue.

For example, if a motor is 95% at full volume and optimum RPM (usually around 1000-1500 RPM depending on design), and it produces 10 hp at design pressure (3000 psi, or whatever), when the volume drops to 1/10th of peak, the produced power potential is 1/10, yet the original 5% loss remains (yes there are non linears, but for discussion sakes...) 5% of 10 hp is 0.5 hp. When the pump is 1/10th the volume or 1 hp, you still have .5 hp of loss, netting out 1-.5=.5, or 50% efficient. In the actual graphs they a MUCH worse than 50% at 10% of power.... This is no secret and is on the graphs for all to read. Anybody, expert in hydraulics or not, can read this, and the Auto guys know this.

So, by using variable volume pumps you are shooting yourself in the foot, because the main issue is duty cycle. Valentine claims 720 hp in the four wheels at peak pressure of 7000 psi (to be fair to them) and the average would be around 3500, or say half that, or 360 hp or 90 per wheel...

OK...lets see...to push a 2200 lb low drag car (use Prius 6.3 flat plate drag) down the road at 35 mph and 70 mph takes, respectively, takes 1.55 hp and 16.85 hp. 1.55/360=.004 or 0.4% of peak, and 16.85/360=.0468 or 4.7% of peak. If they shut off the rear wheels you can double those figures, IF(!) you isolate those wheels of the losses...which is not being done...and would require a clutch to STOP the rear motor with a valve upstream to stop flow.

Valentine is usually operating a variable volume motor at LESS than 5% on the highway, and below 0.5% around town. Now go look at the manufacturer's efficiency graph...and see for yourself...NOT good...

The question is...how do you overcome this fatal flaw?

That is what I am working on...because that is where the problem is...

Reply
Guru

Join Date: Mar 2007
Location: City of Light
Posts: 3945
Good Answers: 182
#51

Re: Hydraulic Hybrids Race Against Electrics

01/29/2009 7:44 PM

I would like to put a very simple question and I would very much like to have answers:

Who from the participants designed and build hydraulic pumps and motors not only used them in circuits ?

Some of the comments seem to be done on a user basis and not designer basis.

I apologize but hydraulics being a quite special domain it is good to know on which personal designer experience were based the opinions.

Reply
Guru
United States - Member - USA! Hobbies - Musician - Sound Man Engineering Fields - Mechanical Engineering - More than a Hobby Technical Fields - Technical Writing - New Member

Join Date: Oct 2008
Location: City of Roses.
Posts: 2056
Good Answers: 99
#52
In reply to #51

Re: Hydraulic Hybrids Race Against Electrics

02/02/2009 11:20 AM

Nick Name-

-I'm a Hydraulic Systems Designer, but get into pneumatics, motion control, and automation as well. Unfortunately I seem to spend 90% of my time on industrial, and a mere 10% (or less) on Mobile applications.

__________________
Don't believe everything you read on the Internet!
Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#53
In reply to #51

Re: Hydraulic Hybrids Race Against Electrics

02/02/2009 1:59 PM

nick name -- To answer your question I have designed real production gear pumps for pressures up to 500 psi and a prototypes up to 1000 psi. Also I have some experience with screw pumps and other rotary pump types. I've had no design experience with high pressure piston pumps; but many of the basic principles of fluid flow and bearing design that apply to rotary pumps also apply to piston pumps. An important example of this is the laminar flow of viscous liquids through small clearances and its effect on pump efficiency and hydrodynamic film development. That's where I come from......

Ed Weldon

Reply
Guru

Join Date: Oct 2008
Location: I'm outa here
Posts: 1924
Good Answers: 196
#59

Re: Hydraulic Hybrids Race Against Electrics

02/11/2009 4:01 PM

The subject of the electric drive conversion of the F150 pickup maybe already known to a lot of contributors to this thread; but the following link is a nice writeup on the story:

http://www.hipadrive.com/sema.html

Ed Weldon

Reply
Associate

Join Date: Feb 2009
Location: Songjiang District, Shanghai, China
Posts: 41
Good Answers: 4
#80

Re: Hydraulic Hybrids Race Against Electrics

03/02/2009 7:07 PM

A quick comment and question:

Lots of working ROVs (Remotely Operated Vehicles - used in sub-sea work) use hydraulic propulsion systems. An electric motor drives a hydraulic pump, and the pump supplies the thrusters for moving the vehicle as well as for any special hydraulic tools that were placed on the vehicle package.

One of the challenges was the incredibly fast heat build-up in the hydraulics when the vehicle was operated out of the water (for test and repair purposes). Even when we circulated the fluid through a 55 gallon cooling tank, we could only operate the system for a few minutes at at time, and that was with little 20 HP and 40 HP systems. I don't know how to effectively cool a constantly loaded hydraulic system in air without massive heat exchangers. Please let me know your thoughts / insights on this problem.

My question is: How do you run the vehicle with the engine off?

Cheers !

Reply
Guru
United States - Member - USA! Hobbies - Musician - Sound Man Engineering Fields - Mechanical Engineering - More than a Hobby Technical Fields - Technical Writing - New Member

Join Date: Oct 2008
Location: City of Roses.
Posts: 2056
Good Answers: 99
#81
In reply to #80

Re: Hydraulic Hybrids Race Against Electrics

03/02/2009 7:45 PM

Sounds like some design changes could be made... Heat is definitely a bi-product of a working hydraulic system, but only being able to run a system for a minute or two makes me question how the system was designed to begin with. I've seen ruby red glowing orifices, and smoking relief valves in poorly designed systems. You might try to find a competent hydraulic guru in your area to come and inspect the system that has no ties to the job other than giving it a thorough once over.

__________________
Don't believe everything you read on the Internet!
Reply
Associate

Join Date: Feb 2009
Location: Songjiang District, Shanghai, China
Posts: 41
Good Answers: 4
#82
In reply to #81

Re: Hydraulic Hybrids Race Against Electrics

03/02/2009 8:51 PM

The systems were designed to be operated underwater, where all that nice cool water acted as a coolant. Up on deck out of the water was where we did our maintenance and repair work. That's where heat became a problem.

How did the systems you're familiar with handle the heat problem?

Top o' the day !

Reply
Associate

Join Date: Nov 2008
Posts: 25
#96
In reply to #82

Re: Hydraulic Hybrids Race Against Electrics

04/02/2009 9:05 PM

I will give 1 basic heat source on hydraulic system... my name... "pressure drop". Most conventional hydraulic system should avoid higher pressure drops in any point. But in most precise applications that involves servo and proportional valving system heat loss due to pressure drops are being sacrificed to get the desired work.

Pressure drop is actually a difference of pressure from one point to another. This is one of the deepest aspect of hydraulics system. It occurs mostly in:

1. Relief valves(when setting is overcame)...system pressure- tank pressure

2. Throttling(on flow controls, orifices and proportional/servo) ... Inlet pressure- outlet pressure(may include the load pressure)

In most mobile application where precision is not being emphasized, variable displacement pumps are used to prevent heavy pressure drops. To do this, most pump controls(constant pressure, load sensing, etc) are set in such a manner that the relief valve is not relieving unless emergency. Relief is higher setting than pump pressure control(to varry the flow).

Reply Off Topic (Score 5)
Member

Join Date: Jun 2008
Location: dubai
Posts: 8
#85

Re: Hydraulic Hybrids Race Against Electrics

03/21/2009 1:56 AM

A hydraulic drive in any transmission arrangement will always insert an in efficiency into the drive. You will lose at least 20% efficiency due to the inefficienty of the hydraulic pump and hydraulic motor. So if you save 20% with a hydraulic drive you will lose by way of its inefficiencies bringing us back to square.

Reply
Associate

Join Date: Nov 2008
Posts: 25
#87

Re: Hydraulic Hybrids Race Against Electrics

03/28/2009 11:38 AM

Peter,

I am wondering why it is not nice to use a variable displacement pump(especially a close-loop circuit ) instead of a hydraulic transformer. The possible application on passenger cars requires a frequent turning on and off(short distance drive... staying longer).

This will just be an assumption: I dont really know the design(am not expert too)... correct me if I am wrong and shallow(im assuming on hydraulic transformer too)...

If you use a fix displacement pump, the possibility is to use an open loop with hydraulic transformers, (correct me if I am wrong) a "reversing" and recovery (energy)valve(bi-directional rotation) and a variable displacement motor(secondary unit). At start-up(low/zero torque with mechanical brake... if pressure is not ported to all motor pistons)), even if you use a "digital" hydraulic transformer, a bigger reservoir or a very good cooling system if possible(depending on which area you are into) are needed (idle times, but engine running), as compared to variable type?

Now when you are running(average), the required pressure set at the relief valve/s are commencing to provide pilot pressure, preload the accumulator and a constant pressure to the motor for better response ability. Whether we use a "digital" hydraulic transformer(with various flow transformation) and any pressure control valves, the possibility of creating heat losses due to pressure control valve's pressure drops is significantly less than variable type?

Reply Off Topic (Score 5)
Associate

Join Date: Nov 2008
Posts: 25
#89

Re: Hydraulic Hybrids Race Against Electrics

03/29/2009 12:22 AM

Peter,

I just visited "innas site" and although had a little understanding/education of your product/s which were really new(to me), but really very impressive/simple/innovative technology!!!

Maybe after a few more visits and reading/understanding(though quite hard without more details...) more of the component concepts/applications, I could slowly help in promoting HHV. Never heard about hydraulic transformers and floating cups(I was absent from hydraulics for 5 years since 2003) and was pondering about it for 2 weeks already(since it was brought out in some other forum... about digital hydraulic transformer).

Reply Off Topic (Score 5)
Reply to Blog Entry 96 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Age > IQ (1); Anonymous Poster (11); Blink (17); capblanc (1); Del the cat (3); Ed Weldon (13); Emjay4119 (1); fishpipes (5); Happy Fish (2); Laughing Jaguar (1); micahd02 (1); nick name (4); Peter Achten (8); PhysicsProf (2); Pressure Drop (6); RVZ717 (6); seaplaneguy (13); uathavia (1)

Previous in Blog: Government Bankrolled Power Projects?   Next in Blog: Buy Local or Buy Best?

Advertisement