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Dean Kamen Combines Stirling Engine With Electric Car
Colin Smith writes "Dean Kamen, (inventor of the Segway) has combined a Stirling engine with a battery-powered electric vehicle based on the Ford Think to provide a fully decoupled electric hybrid car which can run on any fuel which can provide enough heat to run the Stirling generator. Think are also producing a purely battery 'Think City' car which is capable of 62mph and with a range of 126miles." Some stats on the Ford Think: Top speed, 55mph; 0-30, 6.5 seconds; Range, 60 miles on battery.
I've seen simple steam boiler engines that are more efficient and more versatile than a stirling engine. And something like the Green Steam engine can be small, compact and cheap and operate in a closed loop system. (I've only seen the Green built up to 10hp, but I think theoretically it should scale to a fairly large size due to the short stroke)
I think the important thing to realize is that people are out there trying new ideas and experimenting with old ideas.
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Actually stirling engine in theory has almost perfect efficiency, unfortunately in practice this is difficult to do. A large, as in huge compared to car engine, stirling engine is easier to make efficient and there are several applications where these are used. And if you run it in reverse you have a great heat pump, often used in cryocooling etc.
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Citation Needed
20 years ago NASA had an automotive Stirling program. Read it and stuff it.
They converted a Chevy Celebrity and the results show that the highway gas mileage was increased from 40 to 58 mpg and the urban mileage from 26 to 33 mpg with no change in gross weight of the vehicle. This is NOT a hybrid - it is Stirling only.
By combining the efficiency of the Stirling with the get-up-and go of an electric this is a pretty good thing coming, and I've been waiting a while to see someone to produce it.
It is indeed the most efficient thermal engine we know of. Whoever said they're terrible in terms of efficiency is, for the most part, incorrect. They're difficult to implement because of the extremely tight tolerances needed to maintain such high efficiency, but you can achieve efficiencies at least as good as or better than a typical car engine (28% is usual for the car, 35-40% is easily achieved with a stirling engine, depending on the operating points).
The problem isn't that they're difficult to get up tospeed, but rather that they tend to operate at a constant speed. This is related to the pressure inside the engine, so the only way to vary its natural operating speed is to add or remove pressure from the chamber. It was this added system that drove the Ford's engine to failure because of the extreme complexity needed to control the speed.
This engine does make an ideal charger. I'm excited to see the results in production.
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Don't forget the water purifier. Kamen went on Colbert and showed off a system that can extract pure water out of essentially any stew, and is robust and cheap enough to use reliably and distribute throughout the the third world. His demonstration was pulling good water out of, I don't know, raw sewage or something, and he was drinking it.
When Colbert made his characteristic sarcastic remarks about not being able to see the point, Kamen responded that 50% of the deaths in the third world could be traced back to water-borne diseases. With this machine, he said, we could save the lives of millions of people per day.
Until that moment, I had thought that he was the self-promoter-yadda-yadda of the GP poster, but his concern and contemplation of the possibilities seemed genuine and sincere. I'm not going to buy a Segway any time soon, but man, but hats off to him if his inventions really do save lives.
FWIW, Colbert had a sip, too.
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