Future Energy Sources 1.10.1 Stirling Engines

I just witnessed some Sterling engines being tested at a national laboratory in my home town with concentrating sun tracking mirrors super heating the engine. So I suppose there is a focused effort by at least the US government to develop this into a real solution. I have no technical details as to the success / failure of the project. I only report that I saw about 6 or more big engines running suspended above a dish full of mirrors.

About 15 years ago I was involved in a conceptual design for a sterling engine powered by the sun and thought as a power source for African countries for the water pumping. It seems the project was too early and the development was not further funded so that it stopped. I think it is a real solution for isolated spots with limited energy requirements as water supply from deep sources in desert countries.

The concept was a combination of direct mechanical transmission coupled with a generator for the periods when the power was not needed fro the water supply.

Hi nick name. I believe you are right, it was not the time for Stirling Engines. In 1978 to 1986 I ran a small engineering workshop where among other things I designed and constructed several Stirling Engines. These engines ranged from 1/4 hp to 6 hp, one problem that has been stated is heat transfer through the heater head to the gas medium in the engine, but this is quite easy to overcome. The other problem is much more difficult to acheive, ie. getting the heat through the cooler. We all agree that water is the best heat sink medium, so my first engine of 4 hp was put into a small boat, after all the sea is an unlimited heat sink, at us in the UK at least. This engine ran for 3 years without any problems. My last engine was of 6 hp and was coupled to an alternator. The idea for this motor was to produce electricity in remote area's anywhere where it was needed. I even ran it on landfill gas for a while using the hot water outlet to heat a hot water tank via a heat transfer coil. But the sad thing was that nobody wanted it so I gave it all up. I still have two of my Stirling Engines at home and I run them for demonstration at the local technical college every year. Spencer.

Hi, you should start again to test the market since now the interest for harvesting energy from everywhere is a lot higher. And with your experience it could lead to some positive bussiness.

I am interested in cooperating with you for promoting stirling engine in INdia. You know INdia has excellent radition and performance of stirling engine with solar energy can be peaked during summer.

Please do write to me at : jinshui@vsnl.net

Regards

Paul

Spencer: how economical is it to produce. I have a couple of ideas I'd like to run by you. Jsindorf@juno.com Joe Sindorf 408-265-3641

How soon can this be ready for production. What are your est costs

jsindorf@juno.com

I still cannot make out your response as to availability for production. I'm actually looking for a 10/12 hp sterling for another purpose however a 5hp should work well for project I have in mind. Do you have working drawings. Please contact me @ jsindorf@juno .com or 408-265-3641

Hi. I am sorry I have not contacted you before now, but a death in the family threw me off. I do have a complete set of working drawings for a 4-5hp alfa stirling engine, these drawings can be scaled up if need be to suit the size of engine you want. I have not tried to put it into production since 1988 as at the time nobody was interested in stirling engines, now that I am retired and do not have the workshop facilities I find that I cannot do it. If you want to take over then you are more than welcome to as far as I am concerned. Also, I will help you as far as I can with technical support. I am awaiting your instruction to go further with this project. Spencer.

Hello, I too am retired but have been in manufacturing for several yrs. Currently spend most time teaching. As you must be aware, the time has arrived for an economical product to produce mechanical power for pumps as well as electrical generation. I would like nothing more than to pull PG&E off the grid. They have been taking ad-vantage of Californians for a long time. Most generators I have investigated require 10 to 15 hp to turn out 8-10k output. most houses can operate on 4-6000 amp. A 5 hp can run a pool pump forever and free. I have checked into solar collectors which can be produced for less than $200. Con ed in Los Angles is currently constructing a solar sterling to be on line in a couple of years. That means it's coming...a family unit, and, sterling is much more reliable than solarcell panels. I started research on a half/assed basis a short while ago and I am convinced it can be done. every family should have a free generator in their back yard that doesn't cost their first child. It has to be gas/solar operated and put out 8000 amps. and be affordable. I know there are production models in Europe but only at 50hz. Do you feel that you or we could pull it off? Joe Sindorf 5368 Ayrshire Dr. San Jose, CA 95118 jsindorf@juno.com pleas post to my address......

When you run you own house and only your own (not grid connected) the frequency is no problem, your engines will be a bit slower.

Hi Guest

• Most generators I have investigated require 10 to 15 hp to turn out 8-10k output.

If you can get 8 kW out of 10 hp then you are breaking the first and most fundamental law of thermodynamics and have built yourself an impossible perpetual motion machine.

Watts and horsepower are both measurements of the rate you are consuming and producing energy and have a direct linear relationship.

1 Horse Power = 745.7 Watts

Now, no system is ever 100% efficient so if you have an engine that can produce a mechanical output of 1 Hp driving a generator the maximum possible output you can ever get from the generator is 0.7457 kW. In reality generators are usually about 80% efficient so you will more than likely end up with an output of around 600 watts per horse power.

The next thing you need to consider is the efficiency of the engine that you are using to drive the generator and any mechanical heat engine is going to be pretty inefficient. Stirling engines do have the potential to be more efficient than most but even so you are not going to get anything like 100% of the heat energy being converted into mechanical energy. Another factor you need to look at is peak demand. If you have no way of storing energy your system will need to be capable of generating enough to cover the peak demand. That also effects the overall efficiency and it is pretty much impossible to get a system to operate efficiently over a wide range of loads.

• That means it's coming...a family unit, and, sterling is much more reliable than solarcell panels. I started research on a half/assed basis a short while ago and I am convinced it can be done.

I seriously doubt that you will ever get any mechanical system of generating electrical energy to be as reliable as a panel of solar cells. Any mechanical system is going to need regular servicing and sooner or later you will need to replace parts as they wear out. Solar cells on the other hand are solid state devices and as such do not suffer from degradation due to use or mechanical wear.

Put simply, if you have sufficient light falling on your solar panels then they will work and the only regular maintenance needed is to keep them clean so there is nothing obstructing the light.

Trying to be completely autonomous and disconnecting yourself from the grid is a bad idea and makes generating your own power considerably more expensive and less efficient. The problem is, you need to be able to generate enough electrical energy to cover your peak demand and have a backup system that can cover you in the event of a failure. On the other hand if you stay connected to the grid you can use it to distribute any surplus generating capacity to others on the grid who have a generating deficit. It also means you can draw power from the grid to cover the short periods of peak demand and in the event of equipment failure. Doing this also means that you can dramatically reduce the size of your system as you no longer need to be able to cover peak demand but rather only need to be able to generate the same as your median rate of consumption. It also means that you don't need to use multiple technologies to ensure supply and can rather concentrate on using a technology that is suited to your location. For example in a desert area solar cells would be the way to go while in a windy area near the cost can use wind turbines.

The great thing is all the technology and infrastructure of a cooperative system already exists an is available off the shelf already in may places already. There is no "it's coming", it's all hear and available now, all that is required is the willingness to invest in the technology.

Our entire sociopolitical structure and economic systems are based on a cooperative basis with individuals that specialize. We have long since moved on from a subsistence life stile and it only makes sense that the generating and consumption of energy be done the same way. To become completely energy self sufficient is a step backwards to a sociopolitical structure we found too oppressive and limiting several millennia and have since moved on. So, becoming completely self sufficient in power generation is a backwards step and makes no sense whatsoever.

I really appreciate your input since I tend to think in logics rather than liniar so I do miss a lot of details. If Con Ed in Southern Cal is ganging 20000 sterlings, each with its own solar disk to generate 500,000 meg, then each has to generate 25meg. It also seems logical to me that if I go to home depot and purchase a home generator that will put out 10000 watts and requires a 10hp engine and I replace the gasoline engine with a sterling engine that is solar powered, I can run my airconditioner all day long using no energy. Now est cost of solar array,$250; Sterling engine, $2500?; generator, $1000...<$4000. Compared to Solar panels on your roof...$25,000 less rebates. Please don't tell me it can't be done ....just do it. Sterlings' "ST5" puts out 25,000watts but it's a little pricy. And, there is a company in europe...Denmark?, making 800000 gas driven generator/heater combo's for England...they don't have time to mess with US market at this time.

Hi jsindorf,

There a whole stack of things you can do and I would be glad to help you in any way I can. However, the first I would suggest becoming familiar with the metric or SI system of units and measurers.

Here are some links to sites that will help you get round the metric or SI system of units and measures:

• Basics of SI Units & Measurement
• SI Base Units
• SI Derived Units
• SI Prefixes

I gather you live in the USA and are not used to using SI units. However I have worked as an engineer using both Imperial and SI units and I can guarantee that any engineering work is fare simpler, easier and less prone to contain errors when you use the SI system. Also the USA is the only developed country left in the world that doesn't use the SI system, so since you will more than likely need to deal with companies and engineers from outside the USA you are going to need to supply SI figures. Converting back and forth becomes very tiresome and is prone to error so it makes sense to stick with SI units from start to finish. The other thing is that even in the USA electrical energy is measured using SI units so trying to design or build something using imperial units is fraught with problems and makes no sense what so ever.

If you would like I can help you come to grips with the SI system and any project you take on but it is easier if we communicate directly rather than via the CR4 system as it dramatically limits the format of information that can be exchanged. If you wish to contact me directly don't publish your email address here but rather follow this link to the CR4 personal message system and tell me how I can get in contact with you directly.

HI jsindorf !

can you give me the company name and address on the ST5 Sterling engine ? I May have a use for a few of them.

THANKS

goldrushnugget999

Look up ST-5 or Sterling Engines...theyre located in Ohio. While the patent is held by Sterling Engines, they have indicated to me that the unit is currently being mfg in Japan.

HI Guest !

Thanks for the info on the sterling ST-5 engine i hope i can get something going with it thanks again !

goldrushnugget999

HI Guest

A solar & Sterling Pool pump what a good idea it may be a saleable item you should look into it !

thanks

goldrushnugget999

HI Guest !

Have you two contacted each other & started working on that sterling engine ? can you keep me informed on your progress ? I am interested in the colabration and how it turns out.

thanks

goldrushnugget999

Sorry Its taken 5 months to reply. If this unit can be produced for less than $1000 I believe I can make us some money however, I need some sort of working drawings.

Jsindorf@juno.com 5368 Ayrshire dr. San Jose, CA 95118

Scapolie....how much energy were you able to get from your alternator on 6hp. Let's build something. If it's cost effective California has a lot of desert that could benifit from airconditioners. Do you have a cost breakdown...or, if you've lost interest I could use some general detail dwg's. my e-m is jsindorf@juno,com add: 5368 Ayrshire dr. San Jose, CA 95118 408-265-3641

Spenser: I was extremly interested in your 4 and 6 hp engine...I realize the time lapse since you wrote was quite long so I'm not sure if I originally contacted you. Would you consider a joint venture in development, assuming they work as you say, or could I acquire a working drawing. Joe Sindorf, 5368 Ayrshire dr. San Jose, CA 95118,

jsindorf@juno.com 408.265.3641

I am extremely interested in your Stirling work. We would be willing to take on your old designs and projects. May we please open a conversation? Please email me at: anthonykwelch@me.com

Hi,

I've just registered. I'm based in UK I'm retired (ex aeronautical engineer and until retirement ex university lecturer for 8 years). My interest in Stirling Engines is to a degree focused on their use in developing nations and in engineering for fun. At university I introduced students to the Stirling engine and had them taking engines apart, measuring and evaluating, analysing and predicting performance, reassembling and then testing andmeasuring performance. The students loved it. I also got them to develop associated CAD drawings to help them get to grips with solid modelling software.

In retirement I'm looking at powering a bicycle using a Stirling engine (Andy Ross's book "Making Stirling Engines" shows two such installations). This is partly a fun thing but could lead to use in developing nations.

There is a superb book called "Striling Engines" engines by G.Walker, published in 1980 by Clarendon Press, Oxford. It's now out of print but if you can get hold of copy it's worth its weight in gold.

If anyone has plans and drawings for a Stirling engine that will produce about 1 hp (approx 750 W) I would be interested in buying them. If not I will resort to designing one. I aim to write a book on designing and building a bicycle powered by a Stirling engine. I'm also interested in fitting one to a samll boat - again partly for fun but also with a developing nation focus.

I've only come across about three Stirling engine powered bikes, the two bulit by Andy Ross and one built by Nathanael Greene Herreshoff in 1872 in the USA.

If anyone wants to communicate my email address is robert.knotts@btinternet.com

Hi

Do you have plans of a 1 hp engine that I could buy?

RobK

Hi,

Are you still interested in Stirling engine based water pumping solution for rural areas.

At present I am involved in project of developing and building Stirling engine up to 5 HP, in India.

Regards

Madhav Chowdhary

SWEE Technologies

Pune (India)

Yes

sterling engines are an untapped potential energy source!

Things that were stupid & crazy when oil was $20/barrel, seem alots more practical @ $60/barrel.

HI Garthh !

How will it look at $80/barrel, that's what it will be soon, you better start getting those ideas going we all are crying for ways to save dollars while powering, heating & cooling a factory or home, as low cost as possible. sterlings could be an important part of that setup.

thanks

goldrushnugget999

Would sterling engines be useable with geothermal hot water such as exists in Yellowstone and the San Luis valley of Colorado and of course other locations

Hi Dr.Tom. Yes it would work with a small model Stirlig Engine but it would not produce any usable power. For a Stirling engine to work efficently you have to have a high Delta T. Most modern stirling engines work at about 1000K, ie. heater temperature of about 700C and the cooler at about 20-25C. Spencer.

HI Scapolie !

A LITTLE LATE BUT COLARADO IN WINTER WOULD SUPPORT sterling engines in Yellowstone, with temps below zero (f) the temp difference is sufficient to run a low power sterling that is geared up for constant power all winter long. so get out your slide rule and start designing that system. with power costs the way they are you may have a hit on your hands.

GOOD LUCK

goldrushnugget999

Stirling engines operate wherever there is a temperature difference to be found.

Hi PWSlack. Yes you are right, but to get any sort of energy efficiancy you have to have a large temperature difference between the hot end of the engine and the cool part. There is a type of stirling engine called a "Fluidyne", this engine uses water instead of pistons and has to be finely tuned to work. It has only two moving parts, an inlet valve and an outlet valve and are excellant for pumping water. There is an excellant book by Collin West called "Liquid Piston Stirling Engines" which explains how you can build one yourself. Here in the UK there has recently been built a number of new houses that have a stirling engine built into the gas water heater, so supplying electricity to the house. Otherwise, it has to be noted that modern Stirling Engines have been in use for the past 20 years in many applications. Spencer.

Quite. There is a difference between 'efficiency' and 'effectiveness', and a moderate risk of confusing the two terms. The Stirling_cycle has high thermodynamic efficiency. One might not use the Stirling cycle where an equivalent Otto_cycle machine would work, for example, as the Otto would be much smaller, being 'more effective' for most applications.

The energy sources the Stirling machine has been applied to historically have generally been quite dilute, and installed-equipment-volume-per-shaft-watt for the equipment is usually large, tilting many investment decisions away from the Stirling machine save for the niche applications as correctly indicated. As the value of energy rises over time, the investment balance will tip more towards the Stirling machine.

Educational construction kits for Stirling machines are available, though the investment decision is also a matter of much concern...

"Stirling engines operate wherever there is a temperature fifference to be found."

How about a slight correction?

"Stirling engines operate wherever there is a SUFFICIENT temperature Difference to be found." An LTD has been run on the difference in temperature between a small body of water and the evaporative cooling of some of that same water wicked up onto the upper cold plate of the displacer chamber. Everything being in a very nearly constant temperature basement room. Of course the LTD had barely enough output to run itself.

Dear Guest,

As you properly point out, the real issue for low temperature differential Stirlings is how to get real power out? Stirlings can, indeed, run on very small differentials - the well-known "coffee cup" Stirling will run on the difference between the heat of your hand and room temperature. But try putting a load on it and see what happens - it stops. In fact, you need a significant heat differential (at least a couple of hundred degrees F) AND many hundred psi in pressure. You won't get any power at atmospheric pressure with low temp differentials as far as I know.

sterling engines seems fascinating

can such engine be put on windows air conditioner where there is sufficient temperature difference between inner blower and heat radiator outside ,atleast some energy can be created to drive little generator that any how would have been wasted

how about putting such engines on colder regions of the planet and driving the heat source from sun with concentrators and intesifiers , are we aproching perpetuality motion

Vikas,

I'll stick with my earlier comment relative to your first question. The temperature differentials are not nearly big enough to create any useful power.

On the second point, one needn't be in cold air to get power from solar heat. Any colder air helps, of course, but most solar thermal applications are located in warm weather because that's where you get the most sunlight. We think solar thermal has alot of potential as long as you have another fuel to keep the engine running 24 hours a day.

"as long as you have another fuel to keep the engine running 24 hours a day."

Or only work when there is enough power being produced,

Or find a way to store excess energy from high temperature times for use when the sun don't shine.........

Or even better have a distributed system that uses multiple technologies all interconnected so the shortfall in one location can be covered by the surplus in another.

It requires no energy storage, can be introduced piece by piece, can use any technology and the interconnection is already there with the power grids we are currently using.

masu !

This is the best that I've herd from you, I agree most of the time using the grid as a backup but it is expensive to do as a last resort. Can't you go wind and solar and a third part is hydro or sterling or some other night generating part. The sterling could be used from a excess heat source that is not currently being used like excess heat from some jet turbines.

I Just got a new job at a power generating station in Devon Connecticut owned by N.R.G. companies. they took it over from a utility in the area by a state mandated sell off. This Plant was a coal generator that was poorly used and was retired but there are a lot of possibilities for the plant uses. It's on a river with 3000 feet of frontage that could be used for watermills. they have six jet turbines that is replacing the power generation on an on call basis. they also have 4 gas & oil generators that are in a holding closed area that can be restarted as needed. The possibilities are endless for the 100 acre site at this time, but they are only updating the electric output equipment at this time, hopefully there will be more later.

Goldrushnugget999

Hi Goldrush,

• This is the best that I've herd from you, I agree most of the time using the grid as a backup but it is expensive to do as a last resort. Can't you go wind and solar and a third part is hydro or sterling or some other night generating part..

The problem with going completely off the grid and utilizing multiple technologies is the added cost. If you stick to the one technology that is best suited to your particular location you maximize the efficiency and provide you generate over any period the same amount of electricity you consume the whole system will remain stable. The other point is the grid is already there and can just as easily take power from existing consumers and distribute it to others as supply the consumers alone.

If you were to add other generating technologies that were not as well suited to you location you will end up increasing the total cost dramatically. To be totally energy independent 100% of the time would likely cost somewhere between twice and five times as much as sticking to one technology and that's what makes the distributed multi technology system more cost effective than an isolated system.

HI masu !

Say you load up your yard & roof with solar, than the clouds come in with a lot of storms. The solar only puts out one 6th what the original solar generated. Wind in this situation would generate the difference to cover the problem in a storm. the wind would generate excess power in good weather, and your excess solar power could pay to gradually build the wind power over a few years. now you have a base to start working on night power replacement weather it's hydro or biofuel and sterling generators or another type of generator the costs are covered by the solar and wind. Doesn't this seem the way to go, just use the grid to sell the excess power and as a last resort backup. even if there is a greater initial expense the system will pay for it self over time & because the grid is not used to provide power the savings will surpass the expense over time.

THANKS

goldrushnugget999

You're sort of pretty close to what I believe is the answer. The grid already exists and works both ways. It is perfectly capable of taking power from any of what are currently only consumers and distributing to anywhere on the grid where there is a demand.

Now, if you stick to one technology at any individual point of consumption you can maximize the generating capacity while minimizing the costs. For example, if you live in a sunny area so the most efficient way to generate electricity is to utilizes solar panels to generate electricity. However, you cant generate electricity at night but you can add extra cells so the amount of energy generated during the daylight hours is sufficient to cover your total energy consumption over the entire day. The advantage of doing it this way it that it does not cost twice as much to add the extra solar panels to double the generating capacity during daylight hours.

On the other hand if you were to add additional technologies to cover the shortfall at night the cost instantly increased by two fold or even more and you end up having technology that is not ideally suited for your location.

The more diverse the technology base and wider spread the area of coverage the more reliable the system becomes and the smaller the backup generating capacity that is needed to cover periods when demand is greater than generating capacity.

If you stick to one technology at each site you reduce to overall cost while increasing efficiency. The other plus is that this can all be achieved using existing technology and can be implemented on a piecemeal basis house by house, building by building and business by business.

It is already starting to happen and in Australia Origin energy offers a highly subsidized system that utilizes solar cells to generate 1 Kw during daylight hours. Any electricity that you return to the grid reduces your electricity bill at the same rate as you purchase electricity. The system utilizes a solid state control system to generate grid compatible power and there is no reason it can't be modified to utilize power coming from wind turbines, hydroelectric generators, geothermal or even hamsters in treadmills if you so desire. It however makes more sense to stick with a single generating technology at individual sites as by doing so you can maximize the efficiency of the system. If you try and use multiple technologies you end up with a compromise that cost more per unit of energy than a single technology system.

PS I forgot to add that you current work with the power station sounds like a great step in the right direction so pleas keep us informed with the progress. If you would like me to start a special thread under my expanded blog to follow the development drop me a line and I will set it up.

"If you stick to one technology at each site you reduce to overall cost while increasing efficiency."

I don't entirely accept your premise here, Masu.

There are off-shore wind turbines being erected around our coast, which would be able to produce so much more electricity if they also included some wave/current/tidal elements all within the same footprint, and using the same cables to send the power ashore.

Likewise, large areas of solar panels could have windmills at intervals throughout the array.

Could the water in Del the Cat's panel be pumped by a Stirling engine, using the differential between front and back of the panel?

Hi GM1964,

I'm thinking more along the lines of each individual house, building etcetera that is currently at the final consumption point of the existing grid using some sort of generating technology that is most suited to their particular location. At such a small scale duplication becomes a really expensive option.

The problem is the base instillation costs and the base functionality that needs to be duplicated if you install a second generating technology. Here's and example;

If you wish to install photovoltaic cells to generate grid compatible electrical energy in Australia it costs about AU$12,000 for the first kW of generating capacity and then about AU$3,000 for each subsequent kW of capacity. So, if you consume 24 kWH of electricity a day and have roughly 12 hours daylight a day you will need to spend around AU$15,000 to cover your needs using solar alone.

Ok if you wanted to do it with wind the first kW of capacity cost around AU$20,000 and about AU$1,000 for each additional kW of capacity. So if you had around 15 hours per day that could generate electricity you would need to spend around AU$21,000 to cover you energy needs.

If , however, uou used a mix of solar and wind you would need the AU$12,000 which is the smallest installation you can get plus an AU$20,000 wind installation as well with a total cost of AU$32,000 to cover you energy consumption.

As you can see both the single technology systems are far less expensive than the multi technology system of a similar capacity.

The figures I have given are only an educated guess but they are not that far from the truth. The problem lies with the base technology that is used to control and regulate the equipment that is actually generating the electricity. With two technologies you will often need to duplicate this technology and on an individual building scale this can really kill the concept with the cost of the duplicated regulating system.

On the off shore wind farms yes, one of the major costs is the transmitting of the power back to the land based grid and the more power you can generate at a given point the less it costs be unit of energy to get it to where it's needed.

They are both legitimate solutions and I can see them both being an important factor in the future generating of electrical energy.

HI masu !

I am glad that you can see that large scale power production could economically use multi sources of power as long as parts of the combined components can be used by the different generating sources to cut the over all cost and return on investment.

I have stated this all a long but i did not differentiate between small scale and large scale installations. Thanks for breaking it down into a more simplified explanation of the costs and benefits derived.

Thanks again

goldrushnugget999

HI masu !

A Special blog sounds like a good idea, all the step by step developments could be tracked by all. Let me Know it"s name so i can post all the updates that are going on at the generating station. a lot of things are happening presently to update the power sources.

thanks for all your help

goldrushnugget999

HI GM1964 !

a sterling that runs 24 hours would have many various uses, sounds like a winner for many stores to sell, for many uses.

thanks

goldrushnugget999

hi mrdick !

how about a sterling gass pump, there is little resistance & a sterling engine would move a gass from one chamber to another, or move air in a cooling room etc,etc.

I hope this will stir your thoughts about new uses for sterling engines.

thanks

goldrushnugget999

I think that's pretty well the thrust of my blog #19.

However, in theory, as your Limited Temp engine illustrated, the size and delicacy of the working parts can, to a degree, have an effect on the amount of differential required.

Mark

Yes. Higher efficiencies happen with higher temperature differences. There are also low delta T (low temperature difference) Stirling engine designs, but the efficiencies are also low.

Rather than forcing a higher temperature differencial, some designs use presurized engines where the engine pressurizes the crank case/cylinders as it runs. Other designs have used different working fluids (hydrogen or helium, or other gasses) that have higher specific heat retention abilities. Basically you want the fluid (gas) to be compressable and to gain/loose heat quickly, and carry as much heat as possible. The more heat that can be exchanged between the hot and cold sides the better it works.

'Heat engines' have always worked this way. Rev. Stirlings real addition to efficency was to put a 'regenerator' that would help keep so much heat from going from the hot to cool sides, but store the heat temporarially. As the working fluid (air) leaves the hot end going toward the cold end, it would pass through and heat the regenerator. Once cool and the air goes back to the hot end, it would pass through the regenerator and pick up the heat it left there, going back to the hot end a bit warmer than it would have been without the regenerator.

I am guessing that the regenerator does reduce the pressure in the cold end a little (with the resultant loss of pressure on the power piston), but it is made up by heat savings on the hot end in not needing to add the 'regenerated' heat back to the hot end. (someone please correct me if I am wrong).

Making 'high quality' heat (so there can be a high temperature difference) is the holy grail of any heat engine (steam, stirling, etc). The real challenge is using LOW or MEDIUM quality heat.

Personally I would like to see something that works well with a 75 to 150 degree temperature difference, hot end to cold end.

Steam engines work with this, but add pressure to make it work efficently.

The real challenge is to make a Stirling engine work with a under 100 degree F temp differential (55C?) with out presurization and low tolerances and exotic materials. It needs to generate enough power to be 'useful'. Keeping it simple, few moving parts and 'buildable' with mainly off the shelf components are also part of the holy grail to keep things inexpensive to manufacture, repair, and use. Just my 2 cents worth.

The ultmate low cost would use mason jars in a rows and a sealed solor oven designe. Air conditioning out flow could help the heat side and water baths the cool side. Low efficiencies are better than none. For example an after market sterling cycle generator ran off the heat of a car, charges a fly wheel and when you get home just plugs in to the grid. To intergrate this in to air conditioning for the car would be nice.

several attempts to add stirlings to car exhausts have been made, revealing that the added wheight had much more influence than the recovered energy.

But you are right on the solar application, it exsists as demonstration and is in full development for large scale applications in the tropics.

Hi, servant74!

You stated "Steam engines work with this [lower temperature/pressure differential], but add pressure to make it work efficiently"

Now, this gets more and more interesting. The old "triple banger" (triple expansion, and even quadruple expansion!) steam engines were called that because they worked by cool steam expansion into a second larger and third larger-still (etc.) chambers used to drive increased surface-size pistons with steam at a lowered pressure in each chamber.

The hot steam from the boiler was (they're no longer in use, having been replaced by turbines) injected into the first chamber and expanded to push the first small-ish piston, and as it moved, a passage opened to the second chamber to admit the slightly cooler steam with less pressure, which forced down a second piston with a larger surface, and thence through another aperture into the third chamber for the largest piston before being returned to the boiler via the condensation chamber. The hottest steam from the boiler was also used to operate several small single-cylinder steam engines simultaneously with the first cylinder of the prop-driving triple banger. An animated version may be seen in Wikipedia.

Now, you are proposing a Stirling running under a smaller temperature difference, which alludes to a smaller pressure differential and therefore at least potentially larger piston surfaces.

So my question is, why not a design multiple-cylindered Stirling operating on a short chain of reduced pressures on the hot side to take as full advantage as possible of the cooling down initial heat before exhausting it; matched by slightly increased pressures on the cold side as it heats up in parallel?

[All shown in phase, although they propbably should be shown in stepped opposition for timing purposes. Although I used a balanced (uniflow) steam engine for the diagram, I thought the similitude might be OK for display of the thought. Please forgive the illustrative license.]

Have there been any developments in Stirlings along these lines of multiplicity? And in parallel with the advancement of the steam engine, have there been any developments in Stirling turbines because after all, a turbine is driven by the pressure differential past its blades? The main obstacle in the latter would be in containment of the source of pressure differential before and after the turbine(s).

Mark

I suspect there is indeed a future for Stirling technology, but inventors need to focus on a market where it can add value. Many seem to focus on the technology itself, then look for a place to sell it. Our company, ReGen Power Systems (www.rgpsystems.com) is developing a series of low temperature differential engines to be used to convert industrial waste heat into power. One engine will act as a steam condenser, operating at 100C and extracting the latent heat from condensing steam to operate the engine; another will operate at 250C for higher temperature gaseous waste heat. The engines are sized to produce power in the range of 250kW to 2MW. Obviously, some significant design modifications had to be made to accomplish this, which will be the subject of patent applications yet to be filed.

The demand for this engine could be enormous due to the relative inefficiency of so many industrial (and power production) activities. It will operate at 13% efficiency for steam condensing and 24% for higher temperature applications. The entire system can be produced at a price of $600/kW. With "free" fuel, it will pay back in 2-3 years in the U.S. and less in many European markets.

In this case, the inventor looked at the market for stationary power and determined that an engine must have a much longer life than existing Stirlings, lower operating costs and lower capital costs. With these constraints he set about to design the engine. A proof of concept is under construction and several companies stand ready to fund full scale prototypes. With luck, it will be in the market within 2 years.

HI mrdick !

Would it be possible to change the heat transfer medium from water to a sealed nitrogen system? there are numerous advantages of using a sealed system & maby lower temps would work the engine, which would give you more uses for your engine

and widen your customer base. i know myself that i am interested in a small engine for home power that can be used in a multi heat system, say a water heater, furnace, fire place, cooking range, oven, clothes drier and generator. All the excess heat could be routed to a sterling engine to generate power for the house.

A house generates a lot of excess heat, we should be able to use it for other needs also. there is no law against reusing the heat again for extra power.

I HOPE I HELPED with my comments !

goldrushnugget999

Hi mr goldrush,

Yes, we are examining many sources and forms of heat transfer. Stirlings are simple in many regards, and heat transfer is one of those. Thanks for the suggestion.

As to a home system, WhisperTech from New Zealand is offering them in Europe and elsewhere. The farther north you are, the better, because if you don't produce enough home heat, the economics are not so good.

Cheers.

Hi mrdick. I believe that the stirling engines in use at home heating plants here in the UK are free piston stirling engines, so I presume that Whisper Tec stirling engines of the same type. Spencer.

Spencer,

Not sure. I know that WhisperTec is selling in the U.K. There is another model by Honda, but sold only in Japan, I think. These units cost around $7500 and produce 1kW. Looks like a 10-year payback at least, but depends alot on your cost of power.

hi ! mrdick !

THANKS FOR THE SUGESTION I will look them up !

goldrushnugget999

Mr. Dick,

You are a leading person in this ReGen Power Systems company. Do you see a possibility in the development of Stirling driven compressors?

I live in an area with lot's of agricultural activities, mostly fruit like apples. Those farmers have cooling rooms that need to preserve the apples till the price goes up.

My idea was to build a system based on Stirling Engines that cool the rooms with the waste (wood chips and logs) from the orchards. Now this is simply burned on a big pile.

If you could gain energy from a temperature difference of only 80 to 100K the systems might even work from collected sun heat without complex concentrators.

The compressor could even be used in the application that has been asked for by zooinahat in the compressed air as utility blog.

How real is you business model? Are you ready for the real world.

Gwen

Hi Gwen,

Yes, we could directly drive a compressor. Simply leave the generator out of the picture. And we expect the engines to be used in solar applications, though we will need some sort of collectors - we are considering parabolic troughs - to give us enough heat.

One thing to consider is that the system is meant to be operated as close to 24 hours/day as possible. The fewer hours it is operated, the more expensive it becomes on a per kW basis. The 2-3 year payback quoted assumes 8,000 hours per year operation.

Also, the lower temperature engine - acting as a steam condenser - can only be operated with steam, since it is the latent heat of condensation that is the major source of energy. Burning biomass will require the 250C engine to be used. This will operate at 24% efficiency, so the smallest engine we will make - 250kW - will require about 3.5 million Btu's of heat per hour.

Thanks for your query. Hope this helps.

Dick,

At witch power level will the smallest condensing steam engine run?

With 100°C, you intend to work with atmospheric steam.

Interesting setup to be used as energy gainer in desalination plants: in some applications the water is simply coocked out and the fresh water condenses in a cooler, replace the cooler with the unit and you have the possibility to make electricity from the energy that is normally lost.

gwen

Gwen !

This looks good for a large candy company in the area, they use a lot of heat that is just vented out after initial use they don't reuse that heat for multi purposes like generating power or drying coconuts or other reasons. The building is heated with steam heat & is venting off the leftover heat & not reusing it.

Good idea i will send off a e-mail to them tomorrow.

Thanks

goldrushnugget999

Gwen !

I Sent several e-mails to filks at the candy company and there going to move to the south east in november this year so that idea is not to be utilized. maby some other company will use it.

goldrushnugget999

I find the Stirling Engines fascinating, but to me it's like reinventing the wheel. Been there dune that sort of thing. Most of the top minds in the future energy hunt and I say with respect are hobbled by combustion or the fact that they must heat something up or burn it to make power, or to drive around the block. After all why are they changing the light bulbs? HEAT right. Lets say we use the Stirling engine. I don't want to be sitting in traffic or live in a big city with engines running at high heat like that, if you know what I mean. This is the very reason we need to get the combustion engines band for good. The Stirling engine had it's place, open doors to the gas burner we know and love. today it's a novelty, Any real time spent on this toy to make a future energy source, is a waste of good time. So now what? Well if you are an inventor I set before you a test with some rules.

no fuel ...... no having to recharge battries.....no harmfully liquids(antifreeze)....and no solar panels. All on this list don't exist gone for ever. Could you make an engine that would give you say 20 or 30.000 RPM and not pollute the earth?

Stirling versatility and temperature differential:

No point in using a Stirling to run your car. It would be a secondary energy consumption engine in a car. Unless you ran it from the differential between say, ambient air temp and the glass of iced tea you were drinking as you drove along, you would probably need a primary source of energy to provide the required differential. That being the case, you might as well run the vehicle directly from the primary.

But as far as having a source of high heat in the Stirlings, that's not exactly accurate. Theoretically, Stirlings can be run at any temperature. The temp is not relevant. Just the temp differential in the pistons.

Adjust the temperature differential between the pistons. It's all relative. The lack of heat in one cylinder is just as important as the surplus of heat in the other from the point of mechanical advantage. Both sides contribute to the Stirling's motion, not just the heated side.

Closed cycle is one configuration, not the only one capable of powering a Stirling. Because of its simple operating concept (heated air expands, pushes; cooled air contracts, pulls), a wide variety of configurations is theoretically possible. Open cycle on both cylinders is possible with each having its own intake and exhaust ports, so long as there is a steady source of both heated and cooled air; and so is a semi-open cycle with only one side receiving the supply of heated/cooled air flow and the other side having the exhaust port, with one or more heat sources/heat sinks between the two to create the differential.

The temperature differential may be felt below both pistons or above both pistons, may be switched from piston 1 to piston 2 either above or below alternatively, or may be switched from piston 1 upper to lower as piston 2 is switched from lower to upper, and even crossed to share the heated and cooled air between the heated sides/ends and the cooled sides/ends. Valving determines the flows.

With the exception of new configurations that contain provision for a dedicated supply of heated and cooled air, Stirlings are used as a secondary energy device because they depend upon an external heat source (hence their classification as an ec engine) and because they do not develop much torque. Might as well put the heat source to a primary use first, then use up the leftover energy running something like a Stirling. But temperature differences exist all over nature. Wherever a significant heat differential exists, there is a possibility for Stirling engine implementation. We already implement Sizes/types of engines that vary depending upon the burn and/or the expansion in the cylinder. There are big ol' slow ones, with geared up applications, and little fast ones with geared down applications, as well as "just right" ones (usually owned by Baby Bear, and stolen by Goldilocks).

Mark

Hi MarkThehandyman. The open cycle stirling engine has been invented before by Ericsson nearly 200 years ago. Ericssson was a Swedish engineer who was the first man to devise the ships propeller, and in a tug of war between a paddle ship and a screw driven ship the latter won, thus the paddles were detined for the scrap heap. His open cycle stirling engines were used to great effect for many years, even powering a large vessel. On this vessels maiden yoyage it sunk in New York harbour. Spencer.

Every time I hear about a good implimentation of a Stirling engine, it fails in some weird way and is forgotten about. Makes me very suspicious.

not all secondary sources are bad! there is that old tale you learn early in Thermodynamics classes of using one engine to pump heat from a huge low temp source to a huge high temp source then usining the high temp energy to drive the heat pump and provide leftover fenergy or the output....looks good on paper but according to the books the figures don't add up.... just like they don't add up for the jet engine (fortunately Frank Whittle didn't know it wouldn't work.....)

one source of long term heat which is very suitable is high frequency radiation, like microwaves and gamma rays from radioactive waste. the british atomic energy people designed a small sterling generator with a cap of 'waste' isotope supplying the heat source. teh concept opens up all sorts of possibilities; such as Gas turbine sterling engines for long term low maintenance power systems.

Another factor which hasn't been considred yet; is building engines with a phase change, cold end liquid, hot end Gas. Such an arrangement improves cold end thermal conductivity and regeneration.

just some thoughts from the future for you to consider!

HI GUEST !

YES SOME GOOD THOUGHTS !, can you test them out? they might just work!

Maby you can get a government grant to afford a test of your ideas.

i have an idea and i am looking for a investment angle to help me to build an operating demo model are there any takers?

goldrushnugget999

Hi Guest. You are wrong, stirling engines using a phase change from liquid to a gas and back have been built experimenally in the UK many years ago. This type of stirling engine was designed and constructed by the UK Stirling Engine Consortium in the 1980s. The problem with this type of stirling engine is that water condences in the lower part of the regenerator and impedes the passage of the working medium,ie water. Spencer.

"looks good on paper but according to the books the figures don't add up.... just like they don't add up for the jet engine (fortunately Frank Whittle didn't know it wouldn't work.....)"

If you read Frank Whittle's biography you will find that he found that the calculations that had been used on all the turbines up till that point were actually incorrect and he redesigned the turbine. The end result was that the figures for the jet engine did actually add up it was all the previous turbines that didn't.

What you describe is a standard electricity generation system: boil water, drive a turbine with the steam, use a low pressure condensor to generate the low pressure end of the turbine.

The regained water can be pumped back into the boiler. (and it is reused as the quality of the supply water is a huge problem in these installations)

Ford motors back in '76, during last gas snaffoo, created a sterling experimental. it's biggest fault...you had to wait for it to heat up...no instant key and run. when the gas fuss was over...they stopped improvements and it went into limbo. They could have solved this problem with a remote ignitor. most new technology is a combination of old with new jazz......

HI jsindorf !

Ford also could have used a plug in preheater like the heated oil stick for truck drivers in the winter this would keep the fluid at a hot temp for instant starts.

thanks

goldrushnugget999

Hi Goldrush & others,

Something I forgot to mention in relation to Stirling engines was Kockums. Evidently they have been manufacturing fairly large Stirling engines for use in their submarines for several decades now so it might be worth getting in contact with them. I don't know how much they can help as much of their expertise may come under the category of Top Secret Military Technology but it might be worth a try.

The other thing I would like to do is extend the offer of a thread to anybody that has a technology that is worth discussing. As is evident from the new introduction at the beginning of this thread, reaching the end of the future energy technology list has given me the opportunity to expand the theme of the blog. However, I do not intend to drop the future of energy theme completely so if anybody is working on a project or has come across something they feel is worth discussing pleas use the link in the introduction to send me a message and I will start up a thread to cover it.

Regards,

MaSu

It is so strange: as soon as people hear the name engine they start building it in a car.

Why the hell would we want to replace a nice piece of equipment with perfect caracteristics to something that has less flexibility.

The Stirling cycle EC engines are perfect when running at a certain speed giving a certain power. At this point they are way better than the automotive ICE's. But they have a bad reaction to power changes, you need to start burning more fuel and slowly the engine will start running at a higher speed. Speed control is also not logical.

Stirling engines are great for burning stuff that should burn at a certain temperature to be sure that the rest products are safe. Medium and low level energy level heat is also nice to be used by the stirling cycle, which can work in a zone where steam turbines can't really be effective anymore.

It is not because it is called an engine that is can be fitted in a car.

Hi Gwen.Stouthuysen. Yes, I agree with you, but this happens to be an American thing puting anything into a car if it is called an engine. I have studied, designed and constructed stirling engines for many years, and not once have I ever thought about putting it into a car, because I know its limitations. You will find that most other countries who have dabbled in stirling engine technology do so for use as a stationary engine or a marine use. As for controlling the speed of the engine it is not only turning up the heat to accelerate it. We do this by increasing the pressure of the working fluid or gas inside the engine, the speed increase is instantanious. As for the combustion products, these are only 5% to 10% of an internal combustion engines. This is because inside a stiling engine combustor the temperatures are a lot higher than inside a combustion chamber of an I.C. engine, thus burning all the fuel completely, plus the fact that a lot more air is pumped into the combustor of a stirling engine. I have a 4hp stirling engine at home which I use for generating electricity which I use whenever we have a power cut. I suggest you read the book called," Stirling Engines ", by Graham Walker--ISBN 0-19-856209-8 This book is easy to read and understand. Spencer.

Not only over there, here in Holland they once made a car with a Stirling engine. Superb fuel consumption caracteristics but to slow in reaction.

Hi Gwen.Stouthuysen. Yes you are right, they were produced by Philips of Eindhoven. As a regular visitor to The Netherlands I remember that they had two buses in Holland driven by Philips type 4.235 stirling motors as a feasability test, the problem was the cooling, so each bus had four radiators to cope with this. They also used stirling engine propulsion in a motor yacht called," Johan de Witt ", which was very successfull because it floated in the worlds largest heat absorbing medium, Water. The car engine was a Philips type 4.215 D.A. stirling engine and was fitted in a ford Torino car. I remember this very much as I saw test runs of this vehicle in Eindhoven while I was on a visit to the Philips plant in 1975. The best designs I have ever seen for a stirling engine driven car is by General Motors. As Stiling engines are best run at a constant speed General Motors in 1969 decided to design the "Stir-Lec" vehicle. This would have a stirling engine running at a constant speed coupled to an elternator which would feed the batteries, they in turn would power an electric motor as the main drive. An elecric motor is much more flexible than a stirling engine to power the car. I hope that this idea catches on as not only is a stirling engine omnivourus but it is also clean. Spencer.

Spencer, you may call me Gwen,

Then you must have visited the Greenhouse, the Stirling lab. the period I was working for Philips it was our flexible PCB modelshop.

The idea to mount a Stirling in a car as main electric power supply is still in the back of the designers, but as Stirling enegines are so dammed old and never made it to real commercial applications it is not fancy to do this, it is better to invest in hydrogen fuel cell technology.

Nasa has made some nice evolutions in the Stirling technology, driving them from radioactive decay.

The main problem for transportation use for me is the wheight: we do the utmost to reduce the cars dead wheight as this is the key to low power usage in city traffic, the next step of mounting a Stirling generator would be the vice versa.

Gwen

Hi Gwen. Thankyou very much, it is nice to be able to converse with someone who remembers the good old day's of stirling engine development. Yes, I remember the greenhouse, and you must remember Mr van Beukering and the man who saw the potential of using radioisotopes as a heat scource, Mr van Witteveen. I agree with you that using stirling engines in cars is not viable, but i do beleive that stirling engines have their use as stationary power supplies in remote areas. If you want to continue conversing with me then I will be only to happy to oblige, you can contact me on: garnets@blueyonder.co.uk With regards. Spencer.

HI Scapolie !

NOW wait a minute there are several engines referenced that use sterling's to run a electric motor which runs the car, sterling generating power used in electric motors should do better than direct drive sterlings, easier to control and regulate starts and stops & speed without large delays.

goldrushnugget999

Hi GOLDRUSHNUGGET999. As I said in my first post, I powered my boat (21ft) with a stirling engine. But it was not directly driving the propeller, the stiling engine was coupled to an alternator which in turn loaded 12v batteries. These batteries (3) were connected to an electric motor which turned the propeller. As you said it is much easier to control the speed of an electric moter than a stirling engine. The stirling engine ran at a constant speed, which has many advantages, the first being less wear, the second being better fuel economy. I designed this configuration in 1977 before I had even heard about stirling engines in motor cars. I didn't get round to doing it before 1982 as In the meantime I had been running around the world doing my job. So yes, you could say that I know a lot about this type of drive. Spencer.

It is clear to every body that the electrical solution has the advantage of an "energy accumulator". But there is an other solution which could compensate the weight of this stirling-electric motor match. A very fast reaction could also be obtained with hydrostataic transmissions and for a "rush" a hydraulic accumulator can be used.

The very high power density of hydraulics would compensate the weight of the stirling motor and avoid the much more important weight of the electric motor + transmission.

The power density of hydraulics is poor. (compared with electricity, do compare not only the pump or motor but compare the complete systems)

Especially the accumulator power density is very poor.

Several have tried it before: gain the braking power back through hydrostatic accumulation (cilinder - spring combinations) The weight of such a system is enormous.

These units are used to overcome static friciton in hydraulic driven vehicles: the accumulator can organise the high fluid flow to have that extra bit of power for some seconds. When the unit is rolling the motor can cope with the power demand.

You are a bit off the issue: this is more something for this weeks discussion: Future Energy Sources 2.1 Battery Electric Vehicles

I am very sorry to notice akind of agressivity which is on my modest oppinion not the way engineers should behave. I agree that you know EVERYTHINK and even a bit more but I have the personnal feeling that with respect to hydraulics your knowledge is a bit out of range. Sorry but I use the same way to answer as you did I hope you will appreciate as I did. And if you would be correct you will notice that I mentionned the advantage of electricity for accumulating energy.

Sorry if it came over rude.

You are right on my hydraulic knowledge: it is primarily scholar (which means stuck in the previous century)

But: Hydraulic accumulators keep on being heavy: you need a pump, a storage, a cylinder with spring (or something similar) and hydraulic motors for the wheels. (the pipework and coolers not counted in)

I don't know how versatile these motors are in terms of speed, but can they give high torque in the low speed range and reach high RPM's up to 1300 RPM?

I may have a silly modernistic view on technical road maps but hydraulics are an old style solution to cope with the fact that electronics could not cope with the demanded power in and stable way. Now that solid state can easily switch 100's of amps hydraulics are fading out.

I admit that there will be technical regions where the hydraulics will never easily be replaced (eg. linear actuators)

Regards, Gwen

Hi Gwen,

Hydraulics have been used in the past for the suspension/steering/braking on Citroen cars, the accumulators being green spheres, with compressed nitrogen rather than a spring.

Several new initiatives are around, some using hydraulics to supplement the engine during acceleration, and saving more energy from regenerative braking than motors can, and at least one other - used in refuse vehicles - which allows the use of a much smaller engine to provide constant input to an accumulator. This method gives better fuel economy, and greater acceleration rates in a truck of similar weight.

http://www.epa.gov/otaq/technology/

http://technocrat.net/d/2006/6/22/4774

Hydraulics are still used for steering assistance and braking in almost every car.

The accumulator being green is new for me, it must make a difference. (kidding) The amount of energy stored in the suspension system is low.

Can you explain: refuse vehicles

I'm trying to build a picture. I know that the accumulator system is used in some multi start-stop vehicles like garbage trucks and town busses. But it is not a common practice as the extra wheight added was a serious disadvantage. And a garbage truck has the hydraulics already there as it's mechanics are hydraulic driven.

On stationary systems the hydraulic accumulator is a wide spread technique.

We are a bit drifting away: this blog is on Stirling engines and I'm not in favour to put them in cars.

The green is to signify that they use LHM (Light Hydraulic Mineral) fluid, as opposed to the early DS, which used black synthetic fluid. I thought that you may have seen in the engine compartment of one - the spheres stand out as unusual and are often a talking point when the bonnet is up.

My understanding of pneumatics is that they work at significantly lower pressures - several (11-15) bar, whereas hydraulics use up to many hundred bar.

The accumulator in a hydraulic system ensures that the pressure stays nearly constant over the cycle, while an air system will have considerable pressure fluctuations.

Would it be possible to run a hydraulic pump from a Stirling Engine? (I had to get back on thread somehow)

The answer is yes but it should be a variable pump/motor combination for regulation.

Gwen,

A "refuse" vehicle IS a garbage truck. Refuse is one of those words that means different things if pronounced differently. To decline an invitation, it is pronounced "ree fuze". To refer to garbage, it is pronounced "ref uce". Cheers.

Thanks, From time to time I don't exactly understand the full meaning of the english, I learned that it is better to ask.