Stirling Engine?

[hodgepoj]

Several of the posts in this thread refer to Dean Kamen wanting to develop a Stirling engine. Where is information on this available?

Reading the various posts, it's difficult to get a clear picture of what everyone's thinking is about this engine. I used a small one 35 years ago to power a remotely piloted aircraft. Its heat source was a slug of radioactive Polonium 210.

The Stirling engine is not new or magic. It converts heat energy to mechanical energy just like other engines. Gasoline and diesel engines are internal combustion, that is, the heat is generated directly inside the cylinders by burning fuel. The Stirling is like the steam engine, it is external combustion -- the heat is generated external to the cylinders.

The heat may be obtained from any reliable source -- combustion of fuel, geothermal (including Iceland's hot sea water), solar, radioactivity, exothermic chemical reactions, friction, or whatever.

Dr. Paul O. Johnson
Senior Exhibit Developer
The Science Place
Dallas, Texas 75210

[don c.]

There have been volumes of discussion, right or wrong, about Stirling engines and Dean Kamen's Stirling patents (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2Fsearch-bool.html&r=0&f=S&l=50&TERM1=kamen&FIELD1=INZZ&co1=AND&TERM2=stirling&FIELD2=PPDB&d=ft00), on TIQ, Stirling Engine Society USA (http://groups.yahoo.com/group/sesusa/), and elsewhere. The Stirling, though a very old concept, has realized many new advancements, particularly over the past 20 years. There are several companies worldwide, in addition to Kamen's DEKA Research (http://www.dekaresearch.com/coreTech.html), that are marketing and/or developing Stirlings in one application or another. The suggestion has been, and the patents may support, that Kamen may have overcome some of the inefficiencies found in real world Stirlings (to date), and produced an engine that makes electrical power and clean water available to the rest of the world.

[GyroGo]

www.StirlingInfo.com

I've been searching for the link that compared an earlier Deka Stirling to others in US Navy tests several years ago. I'd appreciate any help.

[don c.]

quote:Originally posted by GyroGo.com

www.StirlingInfo.com

I've been searching for the link that compared an earlier Deka Stirling to others in US Navy tests several years ago. I'd appreciate any help.


http://www.onr.navy.mil/sci_tech/ocean/reports/docs/oe/99/oekady.pdf

DEKA Research and Development Corporation 340 Commercial Street Manchester, NH 03101

Navy engineers attended a demonstration of the Stirling engine produced by DEKA in Manchester, New Hampshire on January 21, 1999. Two beta units were running indoors at their facility. Each unit consisted of a Stirling engine and rotary DC generator hermetically sealed in the same housing. One unit was running in an office space and the other was in a laboratory space. Both of the units burned propane and exhausted their combustion by-products into the surrounding environment. The first unit's electrical output was attached to a load bank of light bulbs such that the load could be varied through a switch box. Indicated electrical output for the first unit was 90V at 480 watts with an average helium pressure of 320 psi. This unit did not have an hour meter. Indicated electrical output for the second unit was 90V at 100 watts with an average helium pressure of 220 psi. The second unit had an hour meter that read 180 hours. The control system for both units was at the breadboard stage of development.

[GyroGo]

Thx Don :)

www.StirlingInfo.com

[don c.]

Here are a few good Stirling links, hydrogen links to follow..


1) Stirling Engine Society USA (http://groups.yahoo.com/group/sesusa/). Yahoo Stirling discussion group.

2) STM Power, Inc. (http://www.stmpower.com/): "STM Power Inc. is a developer of on-site, electricity and cogeneration systems using a proprietary Stirling-cycle (external combustion) engine.
The Company refers to its products as PowerUnits which it believes produce electricity and heat more economically than other energy conversion technologies competing in the distributed generation market (fuel cells, microturbines and photovoltaic systems)."

3) DEKA Research (http://www.dekaresearch.com/coreTech.html), the company developing Dean Kamen's Stirling; also the company responsible for the ibot, the portable insulin pump, and in-home kidney dialysis machines.

4) Whisper Tech Ltd (http://www.whispergen.com/company.html/): About Whisper Tech - "Whisper Tech is a New Zealand registered private company which was formed in 1995. The company is based in Christchurch, New Zealand and has its research, development and manufacturing facilities there. Whisper Tech's activities are focused on the design, development, manufacture and distribution of residential sized cogeneration systems." (such as WhisperGen (http://www.whispergen.com/resident.html))

5) Sunpower (http://www.sunpower.com) Founded by William Beale, Sunpower was one of the strongest innovators of Stirling motor technology, and the basis for the book The Next Great Thing - the Sun, the Stirling Engine, and the Drive to Change the World (http://www.sunpower.com/enthusiast/tngt.html), by Mark Shelton.
I cannot recommend this book strongly enough to those who have an interest in Stirling engines, alternative energy, and a behind-the-scenes look at small hi-tech ventures. Kamen has read it (trust me).

6) American Stirling Company (http://www.stirlingengine.com/). You can purchase a stirling that runs on the heat from a cup of hot coffee here, or another that runs simply from the heat of your hand. Company president Brent Van Arsdell offered an analysis (http://www.stirlingengine.com/kamen/dean_kamen_patent.html) of Dean Kamen's stirling patent. He is also a contributor to the SESUSA discussion group mentioned in item 1 above.

7) QRMC (http://qrmc.com) (Quiet Revolution Motor Company) - "The desire to develop quiet efficient engines for lightplanes has been the driving force behind our Stirling engine "improvements. We expect these same advances to serve markets such as silent sailboat powerplants, silent motorhome generators, silent lawnmowers, and a host of other applications. "

You may remember Darryl Phillips of QRMC addressing Stirling questions from TIQ'rs some time back.

8) How Stirling Engines Work (http://www.howstuffworks.com/stirling-engine.htm), from How Stuff Works (http://www.howstuffworks.com), is a good intro to Stirling engines.

[don c.]

Here is the complete text of question and answer from Darryl Phillips and, heh, another forum...

The following article was submitted to this forum by Darryl Phillips, co-founder of the "Quiet Revolution Motor Company". The article answers questions from several forum members about his work in Stirling engines and of his thoughts on Seqway inventor Dean Kamen's Stirling patent.

First, thanks for the opportunity to add my thoughts to your discussion. I'm speaking for myself and my views are not necessarily those of Quiet Revolution Motor Co LLC.

Dean Kamen. I have the very highest regard for Dean, he has managed to successfully practice the art of invention in a age where individualism is frowned on and creativity is discouraged. My all time hero is Tom Edison and there is no modern-day equivalent closer than Dean.

Do you realize that Edison had a goal of a major invention every 90 days and a minor invention every week? And he usually met the goal! Light bulbs, movies, recorded music, and so much more. Today we see immense corporate research departments going 10 years, 20 years, and sometimes their entire corporate lives without an invention of that stature, and we see individual inventors scoffed at and shunned because they don't have Fortune 500 resources. In that climate, Dean has managed to succeed financially and to provide things which benefit humanity. I salute him.

When I reviewed Dean's stirling patent (US 06062023) I was disappointed. It is certainly as good as many other ideas being patented, but from Mr. Kamen I expected more. In my opinion that engine has a nifty crankshaft but totally fails to address the fundamental problems of practical stirling powerplants. I don't want to get into what they are....that takes too long!

Now to the questions submitted by Don ..

1) The ability to quickly reverse the direction of rotation is critical to the way Segway balances. It currently uses electric motors to do that. Can a Stirling be designed to reverse direction at any point of crankshaft rotation?

Not likely. I see the stirling as the "battery charger", with electric motors powering the wheels. Remember that each wheel has to be servo'd independently which couldn't be done with one engine.

2) The Segway's electric motors produce about 2.5 hp according to DEKA. Can a Stirling small enough to fit on that platform output that much or more power?

Easily.

3) There are such diverse possibilities for Stirling, from power tools to submarine powerplant. Are there practical lower or upper size limits for a Stirling?

"Practical" is a moving target. Suffice it to say that stirlings are appropriate for a wider range than the I.C. piston engine. I'm particularly intrigued by the power tool market and by hybrid automobiles. Those are pretty diverse.

4) Is the idea of a Stirling in every house replacing the existing power grid just wishful thinking?

Remember that the energy has to come from somewhere. Natural gas, for instance. So there still has to be a distribution system except in Arizona which has a direct pipeline to the sun!) I prefer to think of the overall system from energy source to the end use (not end user). We really don't need much electricity. TVs, computers, microwave ovens need electricity but they are small loads. The big things like home heating, home cooling, food refrigeration and water heating should either be converted directly from the energy source, or should be byproducts of electricity production. Otherwise known as co-generation.

4) What might be the cost to a new home buyer for a 5kW unit that would last 10 years or more?

One dollar per watt is common today for large coal or natural gas fired power plants. But the question is not nearly that simple. Peak power is much more expensive than base load power and the "5kW" spec seems to ignore peaks. Remember that if we move to distributed power for the base load, the electric grid is relegated to providing the peaks without receiving income for the base load. If only a few customers do it that's fine, but if the percentages grow then the entire picture is affected.

I'm not arguing against stirling-powered distributed generation, I think it has a very bright future and is more likely to succeed than fuel cells. But we have to look at the overall picture. When we learn to time-manage the cogen loads we can better manage the peaks and keep the costs reasonable. An example would be a larger water heater which has bottom priority yet supplies all the water the home needs. Today an electric water heater wastes 98% of the energy quality, but still contributes to the peak loads. We can do a lot better than that.

5) Do you believe that energy companies could or would attempt to stall the widespread introduction of such a technology?

I have two different views. On the one hand it is tempting to ask "Can you spell Enron?" On the other hand, I don't subscribe to conspiracy theories about 100 mile per gallon carburetors. Suffice it to say that every company will act in its own best interest and will lobby in that regard. Some companies will oppose new technology but other companies will see the business advantage in getting the new technology first.

We may see the emergence of a new class of business that provides all the home's energy requirements at today's level of dependability and cost, but using technology that greatly increases efficiency. This business might operated on a house-by-house basis, or block by block where efficiencies of scale are possible. A bigger piece of the home energy budget would go to this business and a smaller piece to the world energy providers. And in the process we have lower global pollution and reduced political pressures and more dollars kept at home.

6) Have you seen the Van Arsdell's analysis of Kamen's first stirling? What are your views on his analysis?

Brent and I have compared notes on the Kamen patent. I haven't seen his analysis.

7) Have you studied all of Kamen's stirling related patents? What sorts of products do you conceive might come from these patents?

The first thing to remember is that no one has seen the patent work still under wraps. That is true for my company and I'm sure it is true for Kamen too. The best stuff is always yet to come. I've not seen any stirling patent issued to Dean since #6062023.

8) Do you expect Kamen's APU to be a universal battery charger for Segways etc. or as serving some other primary function?

Battery charger, in the general sense of the term. But I'm not privy to the neat stuff Dean may be doing. It would sure be fun to be a fly on the wall in the DEKA lab.

9) Do you see your firm as being directly in competition with Kamen?

No. Some overlap maybe, but at this time we're moving in very different directions.

10) If I recall correctly, you can get more work out of a Stirling by increasing the pressure of the working gas or by increasing the volume of the cylinder. To make a micro-Stirling, you would want to increase the pressure and reduce the volume. What are the practical limits to the pressure of the working gas? What are some typical pressures, volumes, and corresponding work outputs?

First, remember that an engine is just a converter, changing the energy from thermal to mechanical. The design intent is to make the conversion as efficient as possible. In a fueled application, you can back up a step and think of the converter with fuel input and mechanical output, or go back one more step and consider it as a box with fuel in and electricity out. In each case, the goal is to get as much out as possible - per unit of input.

Golly....looking at where this answer is going, we're heading into a complete course in stirling design. I can't do that today! But in general, when considering tradeoffs between pressure and volume, look at the overall energy picture and don't focus on just the internal stirling stuff. The high quality energy has to flow in, the waste (low temperature) thermal energy has to be removed and dissipated, and the desired output has to be maximized. Don't lose sight of the big picture.

11) What are the limiting characteristics for increasing the pressure of the working gas?

One...wall thickness of the containment vessel, and the resultant thermal conduction losses between the hot and cool ends of that vessel. Heavy walls conduct better than lighter walls and that conducted energy is pure loss. Two...heat exchanger losses. If you try to get twice as much out of an engine by doubling the pressure, remember that you have to cram twice as much energy into that volume, and you have to remove twice the waste heat. With the same surface area, twice as much quantity (calories) will produce twice as much loss in quality degrees). Thus you won't get twice as much output. Gee...there goes the whole design course again!

12) What are the current directions in research for improving the heat transfer to the working fluid? Is there any room for improvement in or research on improving regenerator materials?

The current directions in research are all secret. At least I hope they are, I'm not seeing much in the open literature. We are certainly working on some interesting things here at QRMC that we cannot discuss.

The big thing to understand is that there is tremendous room for improvement. We need to see a lot more work on engines and combustors rather than on simulations of engines and combustors. I love computers and we have a high ratio of computers to people here at QRMC. But to advance the stirling state of the art we need to model less and whittle more.

13) Constant combustion is one advantage some claim for Stirlings, because that means fewer combustion byproducts. Are you aware of any research that has studied the emissions, fuel consumption, and efficiency of a constant combustor vs. an intermittent combustor combined with a heat battery such as molten salt?

I'm not sure I understand the question. Constant combustion will always be better because less time is spent heating the combustor up and cooling it down through temperature ranges that produce unwanted emissions or simply lose thermal quality.

Remember that thermal energy has two components just as different as voltage and current. And just as it takes both voltage and current to make electrical power, it takes both quality (temperature) and quantity (calories or BTUs) to make thermal. Every fuel has a maximum temperature of combustion. Anything that consumes the fuel but doesn't achieve and utilize the full temperature is throwing away a lot of the goodie.

With an intermittent combustor and a thermal battery, I see a situation where the fuel burns at a high temperature but only part of the time, and the battery averages this energy at a lower temperature. Thus, part of the usefulness is lost. Better to use a smaller burner, burn it hot all the time, and enjoy the increased engine efficiency that comes from the larger delta T. (And, once again, we're back into Stirling Design 101. Hard to avoid, isn't it?)

Thanks for giving me this chance to participate,

Darryl Phillips

[yop]

The interesting thing about Kamen's Stirling engine is the combination of small size, high efficiency, and low cost. The goal is to enable families to take control of their own water and power needs. Here's the vision: a family in a rural part of a Third World country saves up several months' salary. They send their eldest son to the nearest big city to purchase a portable Stirling, which he carts back home. This Stirling engine generates heat to purify enough water to meet the family's needs. It also generates enough electricity to power a couple of appliances, say a refrigerator and a computer with a satellite modem. Kamen envisions his Stirling engine providing- in one package- clean water, fresh food, education (via the web), and a good income (again, via the web).

Oh, and if you hook the Stirling engine up to a couple of wheels, it can also provide transportation. (And Eldest Son can ride home from the city instead of having to cart home the Stirling.)

[Seeker]

I wholeheartedly endorse Kamen's vision for providing pure water and cheap electricity for people in 3rd world countries, via the Stirling. What I'm trying to figure out,is how this vision might become a reality. So the problem is people in 3rd world countries being able to afford a Stirling or Stirling/ Segway combination.I seem to recall Kamen suggesting something about leaving it to business minded people,to find a solution.

Seeker