Future Energy Sources 1.10.1 Stirling Engines

It is ok I consider that on such a blog we have to be open so that I reacted but no bad feelings. Hydraulics are not fading away since for some MOBILE applications they offer a very broad range of torque and speed. What you are not accustomed with are the servo combinations variable pump + variable motor offering rection times of a few miliseconds to a few hundredth of seconds. The brakes and other equipments in cars were developped in hydrailics because of the very high force (torque) density. With respect to accumulators there are new developpments with carbon reinforced plastics which have a high working pressure range + a low weight. In fact accumulators are in hydraulics not used as a source of power for long working periods but for (as I mentionned) a "rush" i.e. for a short supply of flow energy as in accelerations or other required situations.

Of course we speek about electric power and stirling engines and I highly appreciate the very broad knowledge manifested by participants but as every good engineer knows thecnique in other branches do evoluate and it is always good to discuss of "other" crazy ideas it brings us further.

With respect to linear actuators. In the small and medium range electric systems won a lot of the market in coarse applications and in some high servo applications. Even in a direction where years ago ony hydraulics could bring a solution electric systems did a lot ( for instance in the turret stabilization cylinders in tanks the hydraulic ram was replaced by an electric cylinder). But lately in machine tools hydraulics come again to be used for their adaptability speed and power density. As you see there is a pendulum which goes in one direction and then copmes back. In some windmills hydraulics are used to maintain generator speed constant,aso.

Since every body agrees that the stirling motor is to be used at constant speed every solution could be taken into consideration.

Let's implement the idea of an alternative accumulator and think of compressed air.

It is a bit easier to handle and as it is compressible it will contain more energy just by filling a tank without special counterforce equipment.

You could also use the frame of the car as storage volume.

For small distance cars you can drive on the air contained in the frame, filling it up with windmill driven compressors. (or stirling driven in case you have a heat source which is acceptable (sun/geothermal/...))

What do you think of this?

The big pro on compressed air is the fact that itself is not so heavy and not polluting after a crash.

There is in France a guy who works since several yraes on a pneumatic car. It seems he got some interesting reults. I do not know more. The idea to use air is good since it has alow stiffness

HI ! Scapolie !

SO you did ! I checked back, your wright! You did say that, do you plan to put it in a car? and test it? IF SO, What were the results? I'me shure there better than direct connect sterlings.

goldrushnugget999

Hi GOLDRUSHNUGGET999. No as yet I have not put it into a motor car, but maybe when the right time comes i shall. Here is a photo of one of my first stirling engines.

HI ! Scapoie !

Have you gotten out any more of your engines ? have you brought out their ideas on powering them ? THERE are lots of needs for your engins and the fuel they could save. what plans do you have for the engins?

THANKS FOR YOUR INTEREST

GOLDRUSHNUGGET999

Hi,

I'm thinking about modifying a junk front wheel drive vehicle by utilizing the waste heat from the exhaust system to drive a stirling engine that will in turn drive an alternator. The alternator will charge the battery pack.

I will remove the rear wheels assembly and install the drive assembly from a rear wheel drive vehicle and install it in the vehicle. The drive shaft will be modified and assembled to an electric motor. This should provide me with a cheap home made hybrid. What do you think?

Hermit4

Just joined the group today 12/23/07

Hi, Hermit, and welcome to the gang!

The Sterling idea sounds exciting, but since you're modifying your rear wheel assembly to a drive unit, why not drive the second alternator from the rear wheels as they are wheeled along by your original front wheel drive unit? Power the batteries from the motion of the rear wheels. Save the cost of a Sterling.

Mark

Mark,

You missed the point: the free energy in the exhaust which only consists of heat can easely be used by a stirling to generate some power.

The only problem you will face is that the extra energy you can gain is neglectible to the added weigth and thus enlarged power consumption.

It could all change if you engine would have no own alternator and the stirling would do all of the electric generation. The cool down of the exhaust gasses would also be benificial for the motor/turbo counter pressure as you will try to cool down the gasses when they are as hot as possible (direct behind the catalisator)

The automotive attention for Stirling is going up again: the high energy gain can do nice things in hybrid vehicles as the immediate power needs are dealt through the battery system.

Why Hermit want's to change its rear train is also a question for me.

Your second idea is not directly cool and has been discussed before.

Hi, Gwen.Stouthuysen!

I agree that lots of heat can be garnered from the exhaust system (also agree with GM1964 that there is much lost due to efficiency losses) and utilized by a Sterling. The idea about using the Sterling instead of the primary alternator is interesting as well, although of course the weight of the Sterling is a consideration, and the bridging and/or cutout relay system would have to be a specially designed component so it could create a fairly constant rectified variation at the source (capacitance?).

I think, however, that compared to the cost of installing a Sterling, a separate dedicated alternator is preferable to the purpose of charging a battery bank; and the rear wheels, because they are postulated by Hermit4 as being driven by a separate battery-supplied power source, is indirect enough to qualify as a separate motive source for it. Suck it up from the rear wheels, store it, and when the capacity is full, pump it back through a motor to the rear wheels. Even with efficiency losses, you'd have a fairly useful hybrid.

An engine-supplied Sterling-driven generator might be used for a third power source to other battery-driven draws like a reefer system or a mainly electricity-run travel trailer/motor home maybe.

I dunno. Just throwing out ideas. What do you think?

Mark

Mark,

Here are originating ideas to improve the basic efficacy of a car.

A Stirling can work with the ultimate high temperature that is created by the full burning process of hydrocarbon based fuel. with this a high efficacy energy conversion unit can be build. The speed of the wind while driving can make the cooling easy. A small battery pack of super-capacitor saves the energy to be available within the power producing intervals.

I'm sure that some producers are working on units that will hit the market within some years.

The idea of direct burning will make the conversion of vegetable oil to biodiesel unnecessary. The controlled burning will enable to control the exhaust on NOx and the ultra fine dust as exhausted by the actual Diesel engines (it has been reduced enormously over the last decades but even invisible now still exists)

Gwen

Dear Gwen...In all the comments I've read so far I understand how great the stirling concept is but, not one solid engineering drawing or idea has been offered where one could acquire one. I do not wish to waste time reinventing the automobile since I'm sure the electrics are well on their way. You seem to be well informed on the subject matter so that is why I'm addressing this to you. I have a working drawing for a 3/4 hp stirling which would be sufficient to drive a pool pump however, I would like to develop a 6 to 8 hp unit to drive an air conditioner and preferably a household system. Air Conditioners are required when the sun is the hottest and likewise Stirlings work best in the same time frame. If one could remove the demand off the power grid the savings to the whole world in oil and pollution would be emense. By the same token, if enough units were made everyone could afford one. What would be requird to create this phenomnea. Js

Jsindorf@juno.com

I think that the amount of energy obtained will be insufficient to offset the extra forces required to pull the electric system.

While an IC engine is only ~30% efficient, taking only the heat from the exhaust will collect a small fraction of the heat dissipated by the block, cooling system, manifold......

This will also lose energy in each conversion: to mechanical, then electrical, then storage in battery, then back to electrical, and finally mechanical.

It IS utilising energy which would otherwise be wasted, but the amounts harvested may be much smaller than you anticipate.

I must apologize to all for my lack of response but the response to the existing threads can be somewhat overwhelming of late. Rather than posting a host of responses that end up getting lost I will post them all here with links back to the original posts.

I must admit that before I looked at Stirling engines in detail I was somewhat skeptical about their use but I have definitely reversed my initial uninformed position. I firmly believe that there is a definite place for them in the future of energy and power generation.

· A low grade nuclear device could generate heat for long periods of time in the back woods and taking advantage of the temperature extremes could lead to a vast power source in the cold areas like north + south pole or Alaska Greenland ETC.

I am always somewhat skeptical about trying to use spent nuclear fuels and the cores from nuclear weapons. This stuff is hyper dangerous and needs to be monitored on a continual basis. On top of that you have the problem of security and the chance of it falling into the hands of somebody that has other than peaceful uses for it. There is also a minefield of international laws, treaties, regulations and sanctions that make moving it around not to mention the danger of transporting it. For example you would have about as much chance of suffering from heat stroke while wearing bathers in Antarctica of getting permission to take any sort of high level radioactive material down there. Just getting the amount that is necessary for the operation of scientific instruments is hard enough and whatever goes to Antarctica must return and that includes food that has been eaten and passed through the digestive trace.

On somewhat of an aside to date the only realistic way of handling spent nuclear fuel and disused nuclear weapons is to use them as part of the fuel for Thorium Fission Reactors. This can dramatically accelerate the rate of decomposition and render spent reactor fuel and plutonium cores safe in decades rather than hundreds of millennia. Having said that I also believe that using Stirling engines in conjunction with thorium reactors is probably a very cost effective, efficient and safe way to generate electricity.

Something that I discovered the other day that while not directly on track is relevant to sustainable energy production. With the exception of nuclear and geothermal energy all the energy we currently consume initially came from the sun. The fossil fuels are just store houses for solar energy that fell on earth and was utilized by plants to grow millions of years in the past. The idea is rather than using the sun's energy indirectly to use it directly and to do this you need to know how much solar energy reaches the ground.

Most engineers and scientists you ask will tell you that on average you get about 1 kWm-2 but when I stumbled across the Australian Bureau of Meteorology's solar energy monitoring system I found that this wasn't even close.

The chart above shows the amount of solar energy that reached the ground over the Australian continental land mass. As you can see the maximum is about 30 MJm^-2 while on average it is around 26 MJm^-2. The summer solstice was on the 21^st December so we are pretty close to the maximum time of exposure and the sun is directly overhead at noon for the entire continent.

So, what does this all mean? Well at 26 MJm^-2 over some 16 hours gives a maximum power generating capacity of about 450 Wm^-2. That's less than half the suggested 1 Kw level many including myself have quoted and that's when the Sun is for all intense and purposes directly overhead. When you then take into account the efficiencies of most solar collecting and converting systems you would be lucky to end up with more than about 200 Wm^-2.

Considering in 2004 the average energy consumption was around 15 TW (15 x 10¹² watts) we would need to have at least 75,000,000,000 m2 bathed in sunlight. Realistically when you take into account the seasons, night, cloud cover, increased demand for energy you would end up with an area of around four times this. That's an area roughly 550 km by 550 km completely dedicated to collecting solar energy in some way which given our current technology and manufacturing capacity is completely out of the question.

While for isolated regions direct collection and use of solar energy is a realistic answer for the majority of our future power we must find some other way of either harnessing the Sun's energy or another source of energy altogether.

In post 168 hermit4 presented the following idea.

· I'm thinking about modifying a junk front wheel drive vehicle by utilizing the waste heat from the exhaust system to drive a stirling engine that will in turn drive an alternator. The alternator will charge the battery pack.

Your system is way to complex and adding all the extra equipment and associated mass is going to totally destroy any gains you get from the exhaust. With motor vehicles the place you can make the biggest gains is to find some way of utilize the energy that is lost when braking. In all but the most sophisticated hybrids and pure electric vehicles all this energy is turned into heat and lost to the atmosphere every time you need to apply the brakes. Electric vehicles use what is referred to as regenerative breaking which is really turning the motors that drive the vehicle into generators and using the power to charge the batteries. Currently you can only get back less than half of the energy in city driving where you are starting and stopping on an all to frequent basis you can produce considerable gains. Of course that means the vehicle needs to be either a hybrid or all electric vehicle. We have discussed this at length in the Battery Electric Vehicles and Hybrid Vehicles threads. There have also been some recent developments on the battery front so I will be revisiting the electric and hybrid vehicle threads in the near future.

Unfortunately that's about all I have time for at the moment, but I am pleased that the blog has achieve its primary goal of getting people to see that the answers are already there, we just need to put the ideas into practice.

"Stirling Engines ", by Graham Walker--ISBN 0-19-856209-8"

Walker's book is out of print and the only source of reprints may or may not have any left as he no longer has a web site.

You might get a copy through a large public library on interlibrary loan or place a contingency order through Amazon.

Also try to contact "Ross" at <stirmach@juno.com> for possible availability.

HI Sterling Stan !

Maybe you could give me a best sterling engine fit for this following description for the plant that i now work at ? I work in a power plant that is 1200 feet long & 400 feet wide with 6 stories high of future open space. There are 4 one million gallon fuel tanks and dock facilities for 6 200 foot barges and rail area for 26 rail cars to fill storage tanks or barges can fill storage tanks, both have piping and valves for that task. the Property is over 100 acres with two entry points by truck, one by rail & one by barge.

The brick building is being striped out and suggestions are being looked at to generate the most power from the facilities with the least investment.

Sterling Stan is it possible to load the main floor up with the new G.E. 100 megawatt turbines (40) to (60) and use the upper floors to use the heat to run sterling engines ? The Sterling engines would use the 2000 degree heat given off by the jet engines to generate at least half the jet engine power output. The jets run on biofuels to reduce cost & pollution. The use of river power (watermills) plus windmills and solar would complete the 15,000 megawatt project.

Thanks in advance for your suggestions.

Goldrushnugget999

Hi, GOLDRUSHNUGGET999!

Hope everything's enjoyable and interesting for you at the new job.

My Multi-generation bioreactor uses the gas turbines as its original generating source, then uses exchangers to take off the excess heat from the cooling system to drive a two or three stage steam turbine set.

The station's multiple Sterlings are not expected to supply much power beyond supplementing the needs of the generating station itself. The utilization of more than two power supplies (by adding in the Sterlings after the normal compound arrangement) from the same fuel source, as well as potential for the future addition of cold fusion reactors moves the system from the "compound" category to the "multi" category.

The Sterlings are supplied by Venturi tubes connected across the exhaust line of the gas turbines and the condensate line of the steam turbines. 'Across' so that they do not hamper the exhaust heat with the cold end of the Venturi tubes, and these exhaust line heat sources act in place of (or along with, depending upon whether the Sterlings are mounted vertically or horizontally to the temperature-supply differential) a driven-air source through the Venturis.

Excess heat from the generating station after all this is used as a neighbourhood HVAC source with multiple applications via more exchangers.

Mark

hi ! phill

there has been a lot of talk about cold fusion, if you could get a small cold fusion reaction going and back a sterling engine up to it there could be a lot of power or work done from one small setup i could run many things. is that what you are looking for ?

goldrushnugget999

"if you could get a small cold fusion reaction going and back a sterling engine up to it...."

What temperature would you expect from a COLD FUSION reactor and how would you use that to run a Stirling engine?

HI ! GUEST !

A cold fusion reaction can reach 4,000 to 6,000 degrees and there should be no problem with a temp difference with cold water a cold fusion reaction reactor should run the toughest running sterling engine. now the problem is to get the cold fusion reaction running for a long time to produce the power.

i did some resurch on the web and there is a man who had one going for three minnutes but then he had the power go out and he lost the reaction. the hydrogen did not build up enough to sustain the heat in the reaction. I think he should reconfigure the setup to feed the hydrogen into the reaction under preasure to make a complete closed cycle, that way the reaction will be sustained for a long time.

what do you think guest ?

goldrushnugget999

As long as an experiment can not be reproduced by different persons at different locations I do not have a very good feeling.

Hi GOLDRUSHNUGGET999. I do not beleive that anyone has proven that Cold Fusion is possible!!! If Cold Fusion was possible then why hasn't any government or serious scientist jumped on this as the answer to our prayers? I remember way back in 1985 when two Canadian science students said that they had created Cold Fusion, this was quickly put down as nobdy else could replecate their experiment! Cold Fusion is impossilble because the temperatures at which Hydrogen fuses are in the thousands of degees centigrade, this what is happening in the Sun. Spencer.

Hi, Spencer!

It's obvious that GOLDRUSHNUGGET999 is referring to hot fusion, not cold fusion, because cold fusion isn't hot and doesn't exactly take place in a bottle; at least not in the same way as hot fusion.

Pursuing your comments on cold fusion, however...

There have been departments set up in several reputable universities for pursuing the technology of cold fusion; and the US Navy spending a great deal of time and money working toward perfecting the cold fusion process, which has been around and operating for several years now. Feel free to verify this and the following information for yourself.

The process takes place at room temperature and is electromagnetically induced. Basically it unites an adsorptive material into its catalyst, which causes micro reactions on the surface of the catalyst that release energy. The (almost completely free of short-duration radiation) energy thus produced is captured and utilized as electrical current. Some reputable scientists have had one going in their own basements for a couple of years, and pictures are available on the internet. Problems with the process include, amongst other things, the ability to procure catalysts that are pure enough to encourage the reactions to occur until they are spent.

The two USA (reputable, university-based, and unfortunately for Canada not Canadian) research scientists who invented the process have now received worldwide acclaim for it. (Naturally, they were trying to determine something completely different and unrelated at the time of discovery.)

There are a number of international forums in the technology of cold fusion every year attended by leading science researchers and representatives of various government agencies for the purpose of reviewing advances and sharing information in that area.

And the science reporter who originally discredited the discoverers when he instigated the rumour that since the inventors did not first publish their findings in a scientific journal they could not have really discovered any process, has spent the past few years trying to justify why it was that in actual fact he was a horse's ass at the time.

Meanwhile, attempts at maintaining hot fusion continue to be stymied by the ability to maintain its suspension positioning (excuse my lack of terminology here...it's late and I'm too tired to pursue words) in the bottle for extended periods of time. And the universities are working on that, too.

Duration seems to be the next hurdle for both processes.

Mark

The subject is shifting a bit but.

The cold fusion I know of, and which has been proven is pressure induced, a fluid is forced through a hole and due the speed cavitation takes place, the collapsing of these bubbles creates a very high pressure on the atoms that evaporated into the cavitation bubble. The fusion can be witnessed due the flashes of radiation that come of.

In fact what happens is that the temperature is going up above any imaginable level and due the fact that it originates in water the real radiation peak can't even be measured.

They could prove that an atomic reaction took place thru radiometric film that was placed next to the reaction zone, on the film it was clear that radiation, else than normal background radiation in the fluid has taken place.

I have no info on the amount of energy that has been used to induce the reactions and the amount that was released.

Hi, Gwen!

Intersting. I hadn't heard about this one before. If you are able to give me some information on it (e.g. what's the process called so I can look it up on the internet?), I'd appreciate it. I'd like to discover:

Where is the fusion process taking place? i.e. What fuses into what? Is the cavitation produced in the fluid by the high pressure or on the hole through high resultant heat on the hole's composition materials? Can this process be used to produce useful energy; and if so, how? etc. etc.

Thanks for any additional info you can provide.

Mark

The basic effect of radiation busts when cavitation bubbles collapse is called sonoluminescence: http://en.wikipedia.org/wiki/Sonoluminescence and the source of the light burst is only recently pinpointed as the bubble the collapses. It all happened that fast that it was impossible to see from where the light came.

The fusion claims are called Bubble Fusion http://en.wikipedia.org/wiki/Bubble_fusion

As explained earlier it is a quite strange phenomenon, the light/radiation pinpoints very high temperatures, the water is assumed to filter the real peak out. What really happens in the bubble is unknown and again it is some labs that claim that they can do it and other that claim that the results are to be explained differently. but they also can't prove the contrary.

Hi, Gwen!

This is phenomenal stuff, and as I recall part of it might have been understated in school when we studied applications of surface tensions, Rayleigh's research and Stokes laws. I'm sending along the references to my former professor of marine power systems.

The cavitation method of uniting hydrogen with elements in the liquid where the cavitation is being induced depends upon reaching high temps in the collapsing bubbles. Wouldn't that qualify as hot fusion? There are hints in the wikipedia write-ups that the process might be useful for producing a contollable hot fusion reaction; and the invention depends upon utilizing the heat thus released as its energy source.

Mark

Hi Gwen & Mark,

Sonoluminescence came up in one of the other threads in this series and if I remember correctly there is a lot of discussion abut whether or not there is actually fusion taking place. The problem is the total and complete lack of high energy photons that would need to be there if nuclear fusion were actually taking place.

The idea about them being stopped by the water is a bit of a red herring as the photons that are normally produced during fusion can travel through a not insignificant amount of water and even if they used heavy water, which has a greater ability to stop them, there would still be some getting through and to date nobody has seen any.

Masu,

High energy photons or gamma radiation, what is the difference?

Something happens and as the whole picture of this process is not really understood, the conditions might be that local density is so high nothing escapes before being slowed to a decent level. When it is fusion it has to be, the real radiation from what happens in the sun does also never reach us.

This prof managed to prove that there is radiation, different from normal background radiation, but the latter is under discussion.

The whole story/discussion is quite funny: the researchers could not publish through normal channels so they used a less important channel, which proves for the main channel that it is not true/a fraud. But the main channel is getting very cautious on publishing stuff from this domain, they prefer to watch from the sideline till something really nice stands up and gets accepted. For the small publishers it was a golden luck to be able to publish this, so they jumped on board.

I am certainly not an expert on this topic, but I have a strong interest in the potential of cold fusion. The thermodynamics of possible cold fusion would probably involve ionic isotopes of hydrogen (H1/1 + H3/1 -> He4/2) not the hydrogen (plasma hydrogen) indicated by your statement. Low concentrations of the isotopes and their kinetic energy would probably limit random collisions and possible reactions thus repeatability...chain reactions would also so be limited further. Catalysts (Pt etc.) have been used with no repeatable success. I feel strongly that the advancement of this hypothesis (it has not yet reached the scientific theoretical stage) will happen in the future.

G'day gals, guys & gurus,

I agree that any workable fusion process is likely to utilize a ²H + ²H » ⁴He or ¹H + ²H » ⁴He but ³He is also a stable isotope of helium so ¹H + ²H » ³He is also possible but I don't know if the energy required for this reaction is greater than the energy released. However, to date there is absolutely no scientific evidence that the cold fusion process has been demonstrated or for that matter is even possible.

The problem is overcoming the electromagnetic repulsive forces created by the protons in the nuclei and the amount of kinetic energy that is needed to achieve this.

However, temperature is a measure of the median kinetic energy that the atoms which make up a given material possess. While this is a median value rather than a statement of the energy of individual nuclei you can state that the KE of individual nuclei resides within a statistical range and this is where the problem lies.

For cold fusion to work it means that at least some of the nuclei of a sample must be greater then that required to overcome the repulsive force and unfortunately the probability of this happening is so small that one can for all intense and purposes state that it will never happen.

Unfortunately that also means that cold fusion is also so statistically improbable which in the real universe it is more than likely impossible.

No matter how you go about it, for fusion to take place you need to overcome the repulsive force that the positively charged nuclei exert on each other by giving them sufficient kinetic energy which is in effect related to the temperature of the material you are trying to fuse.

Now don't get me wrong, nuclear fusion will probably be the long term answer to our energy needs. Unfortunately we can't even get back the amount of energy used to trigger the fusion let alone create a stable and sustainable reaction. It's going to be decades before the technology is even developed let alone technically viable. We need to reduce our reliance of fossil fuels now not in forty or fifty years time when much the damage to the world's environment and climate is a it fait accompli.

Regards, masu

I think GOLDRUSHNUGGET was writing about pairing the two, not running one off the other.

However, if a small fan was run off some of the power created by the CFR, it could be used to create the heat differences necessary to power the SE through takeoffs at the hot & cold points along a Venturi Tube by blowing air in at the narrow end.

Mark

Mark HI !

thank you for the complement, i like the reassurance of some one else saying i may be right once and a while.

I've been off the air for a while, between work and family demands, it's been a rough couple of months but i hope all is now straitened out for the holidays.

i am going over the blogs to catch up, talk again later.

goldrushnugget999

Hi, GOLDRUSHNUGGET999!

Happy holidays. We get to eat our Thanksgiving turkey in October in Canada; but the exercise is so enjoyable we usually eat a few more until Christmas, when we nationally come to the conclusion that we've had enough turkey to last us for the year.

How do we come to that conclusion?

The practice of turkey consumption --because, as every Canadian knows, 'you are what you eat!'; and turkeys (not being the brightest of birds) are "gobble-able" on so many different levels-- usually leads to a large moment when our senses leave us at the mercy of marketers who understand that turkey is a soporific food. The then inveigle us to go on a large Christmas/Hannuka/Duvali/Ramadan/Moon Festival gift-shopping spree.

When the bills come in, the turkey eating stops.

Mark

HI Mark

we all are stuffed by turkey now, i"me looking for a large steak by this time, turkey dose get to be old a few days after thanksgiving, there are some wild ones running around in the back yard.

I used to Drule over them but now they really turn me off.

thanks

goldrushnugget999

The following was posted on the HAES, Hot Air Engineering Society forum. Eslsewhere on this thread is comment regarding a 35 KW Stirling generator to be manufactured by STM Corp. It would interesting to know who made the 40-5o KW machine for Ford.

http://tinyurl.com/2xdufg

7. Paint Fumes Become Fuel at Michigan Truck Plant â€" Ford’s innovative Fumes-to-Fuel system burns paint fumes in a process that produces electricity at the Michigan Truck Plant in Wayne, Mich., home of the Ford Expedition and Lincoln Navigator. The patent-pending Ford system uses a Stirling cycle engine to burn the fumes from solvent-based paint used to paint cars and trucks. Not only does the process virtually destroy the volatile organic compounds (VOCs) in the fumes,
it also produces electricity for the plant. The program burns one-third of the fumes in one paint booth, yet 45 to 50 kilowatts of electricity are produced â€" enough to meet the typical demand of an average suburban block of houses. Currently, Ford’s North American assembly plants incinerate the VOCs in solvent-based paint fumes, but the process requires a significant amount of energy, substantial floor space and produces some carbon dioxide (CO 2). The only by-products of Ford’s Fumes-to-Fuel system are small amounts of water vapor, CO2 and nitrogen oxides."

45 to 50 KW is more than the 35 KW machine STM hasn't produced to date. A truck plant would have a lot of waste solvent fumes to dispose of but would have to collect and possibly condense same.

I've been interested in renewables for quite some time, and I was wondering about a couple of fixed stirling applications.

Dish Stiling hybrids have been developed for Solar capture technology, as a way of improving the efficiency of soalr power generators. Silicon is expensive to produce and I understand that one complex hit 40.7% efficiency at one point.

The principal apps have suggested deserts, due to the quality of infrared falling there, but I was wondering about areas of the tundra.

If Stirling works best when there are large temperature differentials, and it seems to me that in the tundra, while one might well get less intense light, one would have wonderful access to low ambient temperatures.

Moreover, inevitably, where heat-producing human activities were at play -- industrial plants, or even power plants, a Stirling engine that took advantage of near or subzero temps could entirely compensate for lack of heat input at the other part of the cycle. Surely it's a lot more expensive to lower ambient temperature effectively than it is to increase heat locally? Accordingly, if nature doing the harder task for you, you can break even with far less heat input, and thus far less new energy use. Even low grade process heat might net good CHP returns, no?

Fran

Fran

The principle is sound, and the thinking excellent, as far as it goes.

My next question is what are you going to do with the energy you produce? Transmit it throughout Canada or from sub-arctic locations to Australia/South America?

The technical challenge lies in the details.

Details, gentlemen??? What is CR4thcoming from the experts on this one?

However, if you decide that the energy produced might be used for a manufacturing concern, may I suggest you begin with a line of warm clothing?

Mark

The much trumpeted Solar Dish Stirling Generator arrays to be installed in the south western desert of the US. have been and on and off project for several years. So. Cal Edison is now raising their rates as the prospect of solar power is yet to be in the future.

Stirling generated power is still an elusive wil-o-the-wisp. Only a few working systems in niche applications and those are NOT inexpensive. CHP, Combined Heat and Power for domestic dwellings has been promoted and subsidized. A unit comparable to a household refrigerator burns natural gas to run Stirling Generator, waste heat from the Stirling heats the dwelling and excess electric power is fed into the grid. Initial cost is high but payout is expected in about 10 years or so.

A refridgeration unit usually uses much less power than a heater, but that is based on temperate climate, so I don't know how this would work at the extremes.

HI GUEST !

A low grade nuclear device could generate heat for long periods of time in the back woods and taking advantage of the temperature extremes could lead to a vast power source in the cold areas like north + south pole or Alaska Greenland ETC.

the pollution would be very low and controllable the power could be large. There are also gas wells there in Alaska and other cold Clement areas that could be taken advantage of. Greenland has geysers of hot steam possibly that could be used also.

think about the suggestions maby one will work!

goldrushnugget999

let us put together a couple of aspects:

- a Stirling engine works as all thermo machines according to a Carnot cycle and its efficiency depends on the temperature difference between the source and the sink. The higher the difference the higher the efficiency. Thus it can be used at low differences only if efficiency is not a major concern. Since every investment must have a correct ROI only if the summ of investment and energy cost leads to an acceptable ROI the solution will be accepted.

- the problem of the Stirling engine is that the incoming energy (heat) is not generated in the working medium as in internal combustion engines but outside and has to be introduced via convection and conduction which represents a supplementary efficiency reduction.

- the heat transfer being limited as flow density the surfaces to obtain a given power transfer are important and not neglect able as volume, area weight and cost.

- the advantage of the Sterling engine is that nonpolluting power sources can be used (as geothermic heat or solar energy).

- if prices are still high it is because the lack of true interest and series production, this is also related to the low cost of other types of energy (oil, gas, wood, hydro, eolian, a.s.o.).

- if the problem of environmental protection will become acute and if the oil prices go high there can be a real interest for the Stirling approach but the problem is also a scale problem since the bigger the unit power will be the bigger the heat transfer equipments.

Does it appear as a logical comment or do you have an other opinion? I would like to have comments.

Much of what you note down is true.

The ROI is not really the bottleneck for Stirling, sometimes quite heavy investments are done to go from 30 to 31% efficiency. It is a game of high volumes.

As the engine is typically for stationary use, the size is not really an issue. A steam based coal fired generation station is also not to be called small.

It will work on really low temperature differences, as you mentioned the efficiency goes down. but it can work with waste heat (exhaust pipig of stationary diesel engines.

Decent high power systems are made in cascade, gaining as much power as available.

The real issue is that series production is lacking and it is unknown by the investors. They rather like to invest in proven technology than to go for a system that in theory has a better efficiency but only small firms can supply.

I appreciate your quick reaction. I totally agree, the problem is also that the lower the temperature difference the more important the heat transfer areas and corelated weight and cost.

"It will work on really low temperature differences, as you mentioned the efficiency goes down. but it can work with waste heat (exhaust pipig of stationary diesel engines."

Is anyone building Stirling engine generators to work on diesel exhaust waste heat or is that merely a theoretical assertion??

Realistic Stirling engine generators of any real value are going to have to have more thermal energy input than waste heat from a diesel as far as I have been able to determine.

Your experience is probably much greater than mine, but would it not make sense to use the exhaust heat from a ship's engines to run the electric generator?

GM1964

It might; and in the case of modern shipbuilding that uses turbines and electric props, it does. Certainly the generator take off from steam vessels via small accessory turbines as well as atomic and fossil-fuel-fired power stations goes directly from the e.c. motive engines. However, ship builders of conventional diesel driven vessels have in their wisdom decided that redundancy is more important than availability; and so the electricity is taken from dedicated separate diesels; as is the emergency power for steam vessels.

This is because if/when a ship break-down of some sort occurs at sea, there is no local garage to drive the ship to for repairs. It has to have enough redundancy to survive while it is repairing itself.

Mark

Hi GM1964. The Russians have been doing this for a long time! They install a turbine in the diesel exaust system similar to a turbo-charger to produce electricity. Spencer.

Stan

I haven't built them yet,(as the project is only in the development stage,) but the biofuel generating station calls for several Sterlings to be employed on both the turbine and steam exhaust lines, using a Venturi tube that travels in part along those lines to generate the hot and cold supplies. They will be used to generate electricity for the station's lighting and control systems.

Mark

The exhaust line from a diesel engine contains quite some energy, approx 40 to 50% of what has gone in. Some of it is recuperated through the turbo, but still you have a gas of more than 200°C.

In big installations one could use the diesel for fluctuating power needs (eg point welding in car assembly factories) and the exhaust goes to a Stirling engine which drives a compressor. All energy that could be converted to pressurised air would be gained, it's a gain in both directions and as you do something to reduce the energy bill you could get money from the government to do the project (at least here in Europe).

Several companies have these fluctuating load generators as the power companies don't like to have these variations on their grid. Steam turbines also don't like it, only a fast reactive controllable machine can serve this. Also a Stirling engine can't handle the variations you seen on grids serving spot welding robots.

Another application would be the generators you see more and more on construction sites. regulations for temporary grid connections are getting stringent and it takes quite some administrative work to realise it. So construction firms bring in their own power. the engine runs the whole day, generating a lot of waste heat. One could use the heat to supply hot water for the showers but using it through a Stirling engine that drives a compressor (again but it's output can easily be stored) the set would deliver electricity and compressed air. Both are needed on a construction site.

I don't know whether it has been used, but it would be interesting to know about.

Stirling fanatics are so proud that the engine has proven that efficiencies above 40% are possible (I don't know the exact record) but the engine is really handy in the zone where heat is available in vast amounts and no other process can really do something usefully with it.

nick,

A couple of slight modifications/comments are suggested:

On your first point, Stirlings indeed have a Carnot efficiency, which limits their efficiency. However, other factors impact the overall engine efficiency; you have pointed out the efficiency of heat transfer as one. These affect the degree to which one can APPROACH the Carnot efficiency. Hence, an engine having a Carnot efficiency of 45% may perform better than one with a Carnot of 55% if its design more effectively addresses these other factors. (i.e., an engine that achieves 60% of its 45% Carnot efficiency is more efficient than one that achieves only 40% of its 55% Carnot.)

Further, overall efficiency is generally measured including the cost of fuel one uses. If the fuel is "free" (e.g., waste heat), efficiency can be as low as 10% and still produce acceptable ROIs.

On the issue of the high cost of Stirlings, more specificity is needed to make this assertion - i.e., high relative to what? A Stirling designed to replace a gasoline engine is high cost, even in production, partly because millions have not yet been produced. A U.S. project in the late 80's produced an automobile Stirling at a projected cost of around $70/Kw. Gasoline engines are around $55/Kw. Guess what they still put in U.S. cars? However, if you can build a Stirling for stationary power for $400/Kw while large scale power plants don't cost any more, you should be able to sell them all day long. (Assume that each technology presents an INSTALLED cost of around $1,000/Kw.)

It may be more useful to consider cost as a function of power output for power generation systems. In this comparison, smaller engines struggle to make economic sense, in large part because the costs of generator and switchgear are not as sensitive as the price of steel. A bigger genset will almost always make better economics than a smaller one, but one has to consider the technology one is competing against.

"Further, overall efficiency is generally measured including the cost of fuel one uses. If the fuel is "free" (e.g., waste heat), efficiency can be as low as 10% and still produce acceptable ROIs."

Is anyone manufacturing such a waste heat driven Stirling?

Is there any prospect of such an engine being available on the open or limited access market withing the near term?

Or are Stirling engines in general as a panacea for the energy solution an academic 'solution' with no prospect of real implementation for general uses?

SS,

Please see my Post #7 above. We are at the proof of concept demonstration phase and have garnered lots of interest from around the world.

"Please see my Post #7 above. We are at the proof of concept demonstration phase"

Keep us all posted regarding the demonstration.

Hi Stirling Stan. I have been interested in the use of stirling engines to recover the lost heat during industrial production for 25 years. I had designed and constructed a stirling engine to be used using bio-gas from a landfill site in Norway. This project was written and talked about in the local media, so a local cement producing factory got in touch with me to ask if I could help them recover their waste heat to produce electricity. I done a lot of research for them to see if this was possible, I found that their cement producing plant was throwing out vast amounts of waste heat, so I designed a stirling engine to suite their needs. Guess what, the project was terminated by them because their heating needs were covered by oil firing. I late found that their oil was supplied by BP. I hate oil companies because of their interference with our future energy technology, and I have never driven a car since as a protest. Spencer.

HI Scapolie !

I know the project was canceled, but the cement company some how needs the extra energy that the oil is not giving them at no or little recovery cost! They are all ready spending the money on producing the heat WHY NOT GET THE FREE PART NOW !

Can you convince them that they are throwing away 40% of there energy without any payback ? Most companies will jump at the chance to get that much return for no or little investment. DO THEY HAVE STOCK HOLDERS ? Maby there is a company paper ? Even waste oil heat could be put to good use! If not power maby hot water,

steam heat, exhaust scrubber power to clean the oil fumes so others can breathe better. Can you contact the town where they operate & do they have zoning laws to restrict air pollutants and are they over polluting the air ? Check the local pollution groups could they help you convince them to use that heat productively ?

There are many things that you could do to nudge them into reconsidering there decision it is a matter of breath for all around you.

THANKS

goldrushnugget999

First of all I would like to ask everyone on this site some questions; Have they ever designed and built a stirling engine? Have they ever run experiments with a stirling engine? As has been pointed out by several of you, a stirling engine would not replace an ic or diesel engine in an automobile, but for remote areas it is ideal as it has the advantage of using bio-waste or solar energy! United Stirling have been experimenting with this for the last 25 years, and finally they have come up with the solution which will one day be put into production. Spencer.

Hi, All!

When I read the blogs about Sterlings, hydraulics, pneumatic, and automobiles, and things in the way of making them work efficiently, I had a great chuckle.

The lesson is that this is the LAST place anyone should say, "It can't be done"!

First of all, when one says that to an engineer, the automatic response is to think of a way (ways) it CAN be done, or at least MIGHT be done...

And secondly, the huge variety of engineers in here will, in response, absolutely come up with solutions or reports on current technology showing that either it HAS been done or there are existing methods that can be put together to form a gestalt that might just do it!

Now I know some of you, in this exact same polar response mechanism that makes an engineer an engineer, will after reading this think that I'm saying everything CAN be done, and blog me to give all kinds of examples where it really CANT be done! Rest assured that if you do, I will be ROFLMAO (Rolling On The Floor Laughing My Ass Off).

One of the delightful things about being an engineer is to spot "problems" and come up with solutions that resolve or eliminate them.

None of this is to say that the experts in any field in here should stop telling the rest of us it can't be done. No no no. Please continue. One of the amazing things about this site is the variety of expertise it brings together under one roof, so to speak. If somebody in mechanical has an opinion on limitations re Sterlings applications, and somebody in chemical or (as was mentioned, atomic physics) or some other area of mechanical like hydraulics or pneuatics has an update, solution, or an alternative; then either saying it can't be done or at least asking if it can, as we have seen over and over in here, brings great responses one can just not get anywhere else!

All the best,

Mark

Hi Mark, I agree with you, there are so many forms of alternative power sources, wind, solar and wave power that I beleive we engineers should put our predjucies behind us and start to work together to produce real results in this field of engineering! As you said, "It can't be done" is to give up or provoke someone to prove it can be done! Newcommen, Watt, Tesla, Brunnel, Benz, and many others were told that it can't be done, but they did it and won! The problems we face today are no different to what our ancestors faced, but we have one advantage over them, "Instant Global communication", so lets pull together for a better world? Spencer.

Would it be a feasable idea to set up a web community design team and generate a wood fueled stirling setup which drives a simple linear generator, to produce electricity.

This setup can than be used by third world organisations to be able to generate electricity in rural areas. this electricity can be used to pump water, drive a refrigerator, etc. Simple modern equipment which can make the difference for rural communities.

I feel that there is quite some expertise on design and Stirling/Ericsson cycles. The vast mass of the knowledge is old and public domain.

Hi Gwen,

It sounds like an interesting proposal that would definitely be worthwhile doing. Mind you, I can see it causing a never ending string of headaches trying to keep the project on track but I for one would be willing to help whenever I could.

I do however have a couple of questions:

1. Why try and couple it to a linear generator. A Stirling engine works on rotating principal so it would make more sense to just connect it to an ordinary generator.
2. Fueling things with would is something that worries me greatly. Currently we are chopping trees down much, much faster than we are replacing them. Any additional use of timber is just going to make things even worse and add to the deforestation problems. It would make more sense to power it using hot and cold water. It would be fairly easy to heat water using a solar collector and the cold side could be any stream, river, ocean, sea that was suitably close to the location of the generator. That way you could build a system that required little input from humans leaving them free to worry about important things like food etcetera.

Just my thoughts, what do you think?

Why linear?

I've seen some very nice designs of linear Stirling generators requiring no bearings, only suspended on a spring system.

Making such a system is much easier than having to make spindles and bearings.

A linear generator is also quite easy as it does not require a commutator.

Why wood? Wood is used as fuel everywhere and locals can make it themselves, sun and cold water are not always available. In fact you can use everything as fuel as you mention: a dT between solar heated plate and a water is sufficient.

The modular idea is not so bad ad all, but is must be feasible make with easy equipment.

Gwen

Hi, Gwen!

"Why wood? Wood is used as fuel everywhere and locals can make it themselves, sun and cold water are not always available."

I used to pal around with a pulp & paper engineer who was working with the Chinese government to help plant fast growth forests for paper manufacture because in general, the population had burned up all their forests for fuel. Dunno how accurate that is, but there you are!

Perhaps heat energy (which is what we mean when we speak of sun and wood) is able to be stored in hot rocks kept in insulated tanks of water, and then used while the sun is not shining. Similarly, cold water can be stored in cisterns and water towers for later use after some is found for the purpose. (Although in deserts, this task could be a bit difficult.)

Then there is the difficulty of the heat differential required to get the Stirlings going.

I'd be very interested in seeing a schematic of the linear Stirling engine. Do you have one?

Mark

Hi Gwen & Mark,

Like Mark I too would be interested in seeing the specifications of the linear generators. Keep in mind though trying to get something that moves back and forth is many times more difficult that something that goes round and round. There are a myriad of low maintenance bearing using sealed ball races, teflon, magnetic repulsion etcetera that would not only be easier to maintain but would be far more efficient and less prone to failure than a linear system. Linear bearings have a whole stack of problems like:

1. Alignment: Alignment is a serious problem and unless it is done properly and kept properly aligned the wear goes up and the efficiency down at an alarming rate.
2. Seals: Keeping dust, dirt, contaminants etcetera out of linear bearings is a hell of a lot more difficult, less reliable and maintenance intensive than using sealed rotational bearings.
3. Efficiency: Linear bearings are notoriously inefficient. This is because of the large area and speed over which the system needs to operate. With a circular bearing you only have a relatively small speed differential between the two surfaces. On the other hand with a linear bearing you have a considerable speed differential.
4. Uneven Wear & Friction: The wear and opposing force generated by the friction with a linear bearing remains fairly constant. This is because the speed and therefore opposing force created by the friction remains fairly constant over the entire rotation of the bearing. Linear bearings are a completely different beast as the speed differential varies over the length of travel. As a result you end up with the greatest friction and wear at the middle of travel when the velocity is the greatest and less at either end where the velocity is less. This complicates any regulation and means you need a far more complex feedback loop to control the output.
5. Reliability: The increased wear, friction, difficulty in sealing, etcetera means devices that operate in a linear rather than circular motion are far less reliable and require considerably more maintenance that things that go round. Just look at the difference in reliability between piston driven aircraft engines and gas turbines. The gas turbines are considerably more reliable, require far less maintenance, have drastically higher power to weight rations, require far less monitoring and control during operation, have a considerably higher mean time between failures, are more efficient, etcetera, etcetera, than piston engines.

You also need to convert the rotational energy produced by the stirling engine to linear motion and this is going to effect the overall efficiency and viability of the system.

• I've seen some very nice designs of linear Stirling generators requiring no bearings, only suspended on a spring system.
• Making such a system is much easier than having to make spindles and bearings.

The problem with such systems is keeping the whole thing properly aligned and in doing so you always end up with some sort of system that is in reality a linear bearing and therefore subject to the problems associated with linear bearings. The end result nearly always ends up being more complex, more prone to failure, less efficient as well as costing more and requiring more maintenance than a system that primarily rotates.

The regulation of the speed is also a really big problem. With a rotational system all you need to do is keep the speed constant and the output of any attached generator will be constant and in the case of AC sinusoidal. With a linear system you need to regulate the speed so that it is sinusoidal in nature otherwise the output will vary and not be sinusoidal. It is many times more complex to regulate a system so that its output is sinusoidal than a system that has a constant speed.

• A linear generator is also quite easy as it does not require a commutator.

Nor does a generator that utilizes a permanent magnet rotor. Permanent magnet rotor generators are not as efficient as ones with active rotors but they require little maintenance and are more reliable as the number of moving parts is minimal. Regulating the output of a rotational generator is also considerably easier as all you need to worry about is keeping the rotational speed constant and within a set range. By doing so you keep the output frequency and sinusoidal wave form constant. Linear systems on the other hand need to look at both the position and speed to correctly control the output.

One important factor to keep in mind is nearly every electrical appliance and piece of equipment currently manufactured throughout the world utilizes a constant voltage AC power source and doesn't take kindly to fluctuations in the frequency or voltage.

Whatever system you design the most important factor is the size of your marked, even if you are talking about helping out third world countries. There are a couple of factors to consider here:

1. If you set up your system to generate mains type frequencies and voltages you can utilize it with the myriad of electrical appliances that are already produced throughout the world. By doing so you will maximize the usefulness and versatility of your system.
2. If you make the system so it can be used by people in industrialized and developed countries you can utilize the income stream from the sales to subsidize the systems for third world and underdeveloped countries. For a system to be useful in developed countries it is going to need to be compatible with the power grids so regulation and control of the output is an important factor. Therefore, for the reasons I have espoused to earlier it is far easier, more efficient and reliable to stick with a rotational system that generates a constant sinusoidal output

All up I think it would be far easier, more reliable and more efficient to stick with a rotary generating system. Linear motion is always tricky and not only fraught with complexity but usually considerably less reliable and more maintenance intensive.

As Mark stated,

• I used to pal around with a pulp & paper engineer who was working with the Chinese government to help plant fast growth forests for paper manufacture because in general, the population had burned up all their forests for fuel. Dunno how accurate that is, but there you are!

Deforestation is an extremely serious global problem and even in developed countries like Australia where there is a concerted effort to plant new trees, the rate at which trees are being cut down exceeds the planting rate. The situation is already critical and getting worse day by day with third world and impoverished countries being the worst offenders.

Anything that increases the use of wood and the rate of deforestation is something that must be seriously avoided and burning wood for fuel is in my opinion not only extremely wasteful.

My personal view is the only justifiable use of trees is the managed harvesting of mature trees for the production of lumber and wood products that are used to construct and build things like houses, furniture etcetera. Once a tree reaches maturity it becomes fairly CO₂ neutral, so by utilizing the mature trees you maximize the ability of forests to absorb atmospheric CO2. It is also important to utilize the wood in a way that does not release the stored carbon back into the atmosphere. By burning wood you are undoing all the good the tree had on the environment over its entire life which can be anything from 50 years to a millennia. You can also utilize nearly all of the tree by constructing manufactured products like particle board from the off cuts and sawdust generated in the milling process.

To me cutting down of trees and clear felling of old growth forests only to burn them, produce single use paper, create farm land etcetera is totally unjustifiable, grotesquely wasteful and something than needs to cease forthwith. Fuel and fiber can be easily obtained from numerous faster growing crops like hemp and sustainable management of agriculture and horticulture can dramatically if not completely negate the need for the continued clearing of forests.

I think the whole thing can be summed up with IBM's motto "THINK"! We need to look at all our practices and by applying lateral thinking reduce waste, our impact on the environment and the detrimental effect the continually growing population is having on our beautiful blue planet.

Getting back to the modular concept for the Stirling engine. What you would have would be a system that consisted of a pair of cylinders (hot and cold), a crank case that contained the flywheel, a casing system that can be stacked along the axis of the shaft and a clutch mechanism that can be utilized to engage or disengage the module. By doing so it would be fairly easy to just bole on extra modules so the system was suitably sized to suit the specific situation. The clutch mechanism then enables you to start up and connect or shut down and disconnect modules according to the conditions at any given time. The concept has been used in marine engines for a long time and with a little bit of thinking it could easily be applied to a Stirling engine bank.

Because Stirling engines are primarily external combustion engines it doesn't matter how you create the heat, all they need is a sufficient difference in temperatures to operate. The modular approach would also be extended to the source of heat with the heat modules being matched to the Stirling engine modules. For example:

• With a single module Stirling engine you would have a single module solar collector to gather the energy and supply the hot water needed to make the system go.
• If you have a dual module Stirling engine then you would need two solar collectors to supply the appropriate amount of hot water.

There could be a myriad of different modules that used numerous sources of heat. By designing the system along modular lines the final design is a simple matter of calculating how many Stirling modules you would need to supply you energy needs and then selecting the same number of appropriate heat generating modules. There is also no reason you couldn't mix multiple heat generating technologies like solar and combustion of plant waste, so you have a constant supply of electrical energy from the system.

A slight variation would be a module that was stand alone and had the generator built in. You can then just use multiple units to generate the amount of electricity required. As the load varies you then start up or shut down system as required. It's the same concept but instead of physically connecting the units using a clutch mechanism you do it using an electronic control system.

Ok, that's my rant for today over, it's safe to come out from behind the furniture. I must apologize for waffling on for so long and getting completely off track.

Phew! Some writing Masu!

I think that you may have missed the original point Gwen made, as Stirling engines have linear pistons to change the volume of the heating/cooling components, thus the rotary action is secondary, and a new design which did not go through this transform may be more efficient, especially where the linear electrical producer is encased within the unit - Could the piston itself be used as the magnet?

Hi, GM1964!

Love it when people think outside the box!!!!!!!

You might have just created an entirely new industry with solenoid coils encased in engine blocks!

Congratulations.

Mark

Thanks - It's amazing what a week's holiday does for the grey matter!

If the engine is like the one here, then the electrics are at the cold end, so can benefit from that. Who says the output must be taken from the flywheel?

Hi. GM1964!

Now, that's wild! I enjoyed the explanation, having seen the one Masu illustrated in the opening of this blogset. Closest thing I've ever seen to a PM without actually being one.

Is it employed anywhere that you are aware of?

It looks much more efficient than the two cylinder variety, and extending the cold end to be longer than the hot one might have a positive impact on its viability.

Mark

Not only GM1964, (what's in a name?) has been thinking.

Sorry to come back so lately but I had priorities to set last week.

The system I refer to is the isotope decay driven Stirling generator as build by NASA. This unit uses the heat of radioactive decay and is designed and build to work for +20 years.

It has no linear bearing and the displacement piston is oscillating.

This is the main idea, I copied the GIF from the NASA Glenn Research Center website.

On this I would add some changes to get rid of the seals.

The main idea behind the final version is the Free Piston Engine.

As discussed earlier the crank-piston is not the ideal way to get power out of a combustion system, but Stirling generators work as a result of this linear movement, without they simply would not exist. The gas needs to be transported between the hot and cold side and it is the cycle that makes the unit work.

Hi, Gwen!

All that banging and bending of internal parts has me wondering whether electromagnetoelasticity (e.g. piezoelectric, nanocrystal, etc.) components might be added/substituted to increase the machine's output value without altering its weight/configuration significantly, since it appears to be intended for solar system exploration. The nanotech crystal guys might have ideas here, and additional minute quantities of electrical production might be used to light LEDs, trickle-charge small batteries, charge air filter systems, etc.

Mark

This thing has been designed to generate 55W in a constant mode.

The heat source was a radioactive isotope.

I also think that the oscillating needs some electric support, you can see that there are some items drawn that needs clarification.

My idea is to make it in such a way that the power stroke of one system induces the displacement of the other, they are shifted 90°. So you need 4 systems to be working togheter, each of them having a coil that supplies electricity to a battery/condensator system.

when I find the time I will try to draw it.

Hi Gwen,

I'm a little confused by the pic. There seems to be nothing to regulate and synchronise the two halves of the engine - except their natural frequencies? - so any unexpected wear/deterioration of any component could cause the system to fail, where a connected system would just reduce in efficiency.

Unless, of course, there's something they're not telling us.

Gordon

Gidday gals, guys & gurus,

Now I see what you are talking about and must concede that it would be at least worth investigating and constructing a prototype.

I do, however, disagree that there are no linear bearings. The two images at right are taken from the animation and by my definition are linear bearings.

The other thing that I am concerned about is the membrane springs that it uses. Membrane springs have a nasty habit of having a defined life expectancy and are prone to failure at the mounting points. You should however be able to engineer them so they have a predicted life expectancy and therefore prevent unanticipated failure with proper scheduled maintenance.

I wonder if it would be worth replacing the diaphragm springs with pneumatic springs. They would require proper seals around the plungers but if constructed properly would do the job of the linear bearings on each of the shafts as well as the spring mechanisms.

One of the items you show is indeed a linear bearing, one to kick out.

The other is a seal.

The drivers are also missing, the displacement piston and power piston should be kept in the right sequence, the power piston will, however follow the displacer.

The spring suspensions the tricky part, Sunpower has some patents which cover them. (the animation is a result of a cooperation between Sunpower and NASA Glenn Research)

Stirling generators have the nice habit of reducing the seals and especially the high temp sealing is gone.

Hi, Gwen!

I see the genset being driven by the Sterling. I just don't understand how the Sterling is actually working. Can you label it for me?

Mark

Yes, it is true that the pistons do have a reciprocating motion but there is a requirement that this be converted to a rotary motion. The problem with Stirling engines is the two pistons which must be mounted so that their cycles are 90° or π/2 out of phase. It's also critical that the momentum of the pistons be conserved so there is sufficient energy within the system to move the gas between the heating and cooling cylinders.

I suppose it would be possible to create a Stirling engine that did not have a crank of flywheel but it would definitely difficult to control and get working and I have no idea how it could be done with any degree of simplicity or efficiency.

If anybody can describe how to build a Stirling engine without using a crank and flywheel or something similar I would be very interested in finding out how it works.

Hi masu.

I have just read all of the posts prior to yours, and whast everyone is describing here is a "Free-Piston" stirling engine. This engine was invented in the late 1950s by William Beale of Athens, Ohio. The first of these to be used in conjuction with a nuclear fuel was in 1984 at the Harwell AEL here in England. It was intended to use them on channel bouys around the coast of the UK, but then when someone suggested that a terrorist could simply steal several of them it was a no go.

These stirling engines are self starting, and they has to be a certain weight ratio between the power piston and the displacer before it will work properly. The power piston is usually a very heavy mass, while the displacer piston is very light, for the power piston to occilate there are two methods, one is for a spring bounce and the other is compression bounce. They have been built with 2,4 or 6 cylinders, they have also been used to pump freon in a cooling plant or to pump hydraulic oil.

A free-piston stirling was put into a satellite in 1984 to power the electrics, this engine was developed by GM but it was not very succesfull. Another application that was looked at in 1978 was as the power unit for artificial hearts, and one of these was put into a cow to try it out, but it did not work for very long. This type of engine can be bought on the free market if you are interested in one.

Spencer.

Yo, Spencer! You've done it again!!

I'm keeping this entire blog discussion set for my engineers to refer to when they are designing the first bioreactor emplacement. Your contribution to this topic is really great stuff, and a constant source of information to learn from. Thanks.

Mark

OK, Masu!

I finally gathered up the courage to read through the entire blog. Thanks.

Gwen, this is for you...Masu's blog reminded me that harvesting the cold air for the cold end of the Stirling was something that I had already figured out in my generating station design.

You already have several methods for obtaining the heat. Placing a Venturi tube partially along the heated inlet tube and using a battery-driven blower, initially at least, to blow the externally --normally lost-- heated air along it to the expanded end will give you a very significant temperature source differential that should drive the Stirlings. The Venturi tube can't be totally along the heat source inlet, since the expanded end would cool it and render it useless, so it has to come off at some point well before the expansion end.

Now you have both strong heat and cold from the same heat source. (Of course, you don't even need the heat source if you just narrow the Venturi Tube and take off the heat at the hot point, but the gathered heat will provide the external energy that prevents the system from being a zero energy miracle. )

Hopefully, the electricity you can generate will be more than enough to keep the little fan blowing that air through the Venturi. [Also, as in the old Venturi hot water heater/refrigerator days, you can use the cold end to keep your chicken sandwiches fresh before lunch. Just place at least one of the cold ends in a box with a door on it before or instead of utilizing the temp diff to supply the Stirling. Saves having to run a fridge with the electricity.]

As for the linear motor calibration problems, (and yes, a rotary engine is a simpler device to harness for this purpose) I don't think that's a worry now that GM1964 has invented a magnetic piston solenoidal generator. Even the internal turning portion of a Wankel can be magnetized. Come to think of it, so can the blades in a tubine engine, except that there the coils would have to be run logitudinally in the shell.

The problems in the piston-driven device (possibly useful for an automobile hybrid engine) now become:

1. modulating the frequency to produce a viable electricity source from an intermittent AC generator whose configuration resembles a simple linear two stroke water pump. The turnover at TDC and BDC has to be blurred/modified/assisted to smooth out the curve.

And 2. Developing/stepping up a frequency useful for operating appliances, charging batteries, etc.

Mark

HI masu !

here is an interesting idea ! a generator with a sterling wrapped around it. this would lesson energy transfer and increase power output because the heat from this generator cycle would help sustain the sterling. they would work in conjunction with each other, each helping to sustain the other. then the heat input could be cut back to a minimum saving a lot of fuel for longer duration runs.

THANKS

GOLDRUSHNUGGET

Hi, GOLDRUSHNUGGET!

How come you're not publishing under your membership? Nice to see you in here again.

The idea of conserving energy by wrapping the Sterling around a heat-releasing generator is a good one. It's similar to running the venturi tube along the hot exhaust I mentioned awhile back in 174 and 71, where the heat of the engine is taken off for Sterling use, and the open end of the Venturi tube provides the cold contrast.

What kind of wrap-around configuration do you envision? If the Sterling were to be actually wrapped around the generator, the heat sides could be supplied simply enough, but wouldn't the proximity of the hot generator to the Sterlings make the cold supply a little more difficult to obtain?

How about wrapping a Venturi tube around the heat-releasing generator with a point along its narrow section for a hot takeoff and then running it a little bit away from the generator for the cold takeoff in a similar manner to using the exhaust from the engines by running the hot portion of the Venturi along the exhaust lines?

Using a heat-releasing generator as a heat source is a very good idea because in a generating situation, it provides yet one more source of Sterling installation for an adjunct generator by utilizing the waste heat.

Mark

G'day Goldrush,

Interesting concept. It would almost certainly work but I'm not sure about the overall efficiency gain.

Personally I would be looking into generators that used superconductors as this would all but eliminate the heat created by the generator's internal resistance.

However, it's not just the internal resistance that generates the heat. The hysteresis and eddy currents in the magnetic materials is the next major culprit but I'm not that sure about how to recover it if you cold soaked the generator in order to realise the superconductors. I suppose you could use a sterling engine that ran on the increased energy content in the liquid that was used to reduce the temperature to the point that superconductivity takes place.

I'm trying to picture the concept in figures.

The generator that is mentioned is an electrical generator?

I have to disappoint you: the absolute heat level is not sufficient and only 1% of the energy losses can be tracked down to the generator losses (iron, copper resistance, air friction and bearing friction)

To keep the copper losses as low as possible the windings are kept as cool as possible, and as it is copper the temperature is kept below 120°C.

This would bring the cooling air at aprox 80°C, the environment is 35°C to count with. Carnot eficciency will thus be 12,75 %, a low temp system will work with efficiencies with regards to Carnot of .3 to .5.

Big generators have hollow windings to cool from the inside and as the current density is so high the inner section is not used. (Skin effect)

But adding a Stirling generator to the exhaust of cars and trucks is getting serious attention in the industry.

Here is a very handy calculator that will help you understand the power and weaknesses involved with the Stirling cycle.

http://www.bekkoame.ne.jp/~khirata/academic/simple/simplee.htm

Immediately you see why they go for Hydrogen as working gas.

Never forget that adding equipment to cars adds weight and thus will increase fuel consumption. but we can still improve the functionality.

Adding a Stirling as power generator would be a serious leap ahead.

Hi Gwen,

This is an addendum to my last post.

Ever since I did the research for the introduction for this thread the spark of an idea has been jumping about inside my head.

The idea is to design a modular Stirling engine similar to the way engines for ships are constructed. Basically you would have a module that consisted of the flywheel, pistons, hot & cold cylinders, casing and plumbing that makes it all work. The modules are designed so that they can easily be bolted together so the shafts can be linked together.

It gives you an easily scalable system that is easy to engineer depending on the amount of power you wish to create. All you need to do is add additional modules till you have the power you require.

What do you think?

Hi, Masu!

A flywheel on the joining shaft(s) might assist in modulating the lag in the modules.

I reconfigured a gas turbine array this way for my power station (I think the originator was Nakashima). Compound generating systems are just a variation of this concept. I think it might work.

Mark

Working on it.

HI Gwen !

there is a new interest developing in sterling engines because of the gas cost. people want a cheap power source and they are looking at all sources to get it. the biggest draw back to sterling power is the small amount of power it creates verses the weight ratio. to power a car, boat or, plane and large scale generators the sterling needs to be very large and expensive. there really needs to be a redesign of the power output part so the above mentioned devices can run cheaply.

THANKS

GOLDRUSHNUGGET

Apologies for being techno dumb but i have a slightly different perspective on this.. my field is socio-economic development - i run an NGO and work mostly in West Africa - particularly Nigeria and specifically the Niger Delta...

too many of our project ideas are limited by lack of access to reliable power supply so we are preparing a funding proposal with a UK university to design a biomass generator - sterling was suggested - primarily for safety reasons - but personally i have no preference over steam...

have read some of the early comments with interest... and maybe a combination of the problems will resolve both .... because of a number of circumstances which dont need elaborating yet... i have access to 'social' funding and a very real application but lack the information and technical knowledge...

the plan is to 'bolt' together a suitable biomass fueled engine and a simple generator and carry out 3 field trials in the Delta itself - ideally stock items would be best but as there appears to be some confusion over whether any sterling engines are produced commercially we are happy to include an element of design and build ...

initially any work on the technical inputs for the proposal would have to be voluntary but once the funding is confirmed then any further inputs would be on a paid consultancy basis

Any offers?

Hello Dai!

As a newcomer to this discussion, you may be interested in a pending US patent I have that is a new variety of biomass generator. Its triple redundancy primary power source is gas turbine with a takeoff of spare heat for a secondary set of steam turbines and HVAC neighbourhood uses, and the employment along the exhaust lines of Stirlings for self sustaining applications such as lighting, monitoring/communications, and the running of peripheral engine components such as methane and air supply/exhaust, lube oil, condensate circulation, a specialized air pollution abatement system that reduces pollution to a near-zero level, and the like.

The other innovative parts of this biomass generator are that the methane generation systems are tank-enclosed for a hands-on power station (providing local employment) as well as continuous maintenance/replenishment of feedstock and biomedia in used-up tanks; and being arranged in a tank farm along with the entire power station underground in a seismically protected enclosure. The entire delivery system is also below ground in emf and rf insulated cable corridors all the way to the end users.

The end result is the comparatively inexpensive, safe, adequate production of electricity for a pre-planned area (the planning is done so that brownouts and blackouts are prevented from ever occurring due to an end-user draw) from a genuine general delivery power source with zero down time and at a relatively low cost; tailored to be sized according to need. The power station may be duplicated in multiples for an unlimited across-area grid with a one-third excess production capability to allow for planned growth and exigencies.

At the appropriate moment in the future, it may also be used to house cold fusion generators.

Directly over the power station, and still well below ground, is a matching-sized two-storey building for neighbourhood usages such as parking, local markets and shopping, storage of useful compost supplied from used-up feedstock media, hydroponics gardens, community activities and the like; and over that is a restored or improved 10-meter-deep environmental restoration such as forest, game reserve, waterway, farm, school, playground, stadium, housing, or business development, etc.

The entire installation process is ecologically monitored and involves replacement of both below-ground strata in areas unused by the generator placement, and above ground (unless a change is desired) existing ecological components. It can be installed below any currently open space and built over at a future date if surface ecological restoration is not desired; but the installation itself is intended to be invisible from the surface.

For an executive summary, check out this website:

http://ecofriendlypower.wetpaint.com/

Perhaps this is what your NGO group is looking for. Feel free to get back to me on it.

Sterlings can't provide you (at this point in time) with a sufficient primary self-renewing energy source for general electricity production; but the solar-powered Stirlings along with battery storage could be a configuration that might provide you with a mini or temporary power source for a building such as a school or a few (two or three) North American-style-consumption homes ...as an interim stage before installing a general generating station.

Mark

And I can tell you the reason why, stirling engines are not marketed at this present time???

If I can design and construct a relatively non complicated and cheap Stirling engine to power my house, then surely it is not beyond the powers to be to do the same???

The main problem of course is the religous belief in modern technology to get us out of the mess we are in, if an ex engineer like me explains to people that we should look to 200 years previous technology to help us get out of this mess, they do not believe you!

Gas turbines create more CO2 than modern Stirling engines!

Spencer.

Dai,

This is exactly the domain of perfect use for a Stirling engine.

They require relatively low maintenance as they have relatively low moving parts. The only problem is the total quantities made: so little, even series production does not surpass 10K units per year.

This means that development needs to be paid by the selling price and not the numbers.

How sunny is the Niger delta? How mobile does your system need to be?

There are nice solar powered units in development, they consist of a parabolic dish with a Stirling generator in the center.

Another possibility is to use plain mirrors to boil water and to drive a simple turbine with it. This can be called a frenell mirror, which is a real cut in cost as the mirrors can be supplied by locals. which is a win win situation: your enable local economy and in return you offer power to drive fridges which enlarge the quality of local life (medication and food safety)

If you want peronal help from some of us you can alway's use the mail option that comes with your account.