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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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Ford Think: Top speed, 55mph; 0-30, 6.5 seconds; Range, 60 miles on battery.
0-60, never. :-(
The problem isn't the top speed being less than 60 mph. The problem is that as vehicles get close to top speed they tend to be less responsive to the accelerator.
With a top speed of 55 mph, this is relegated to situations where you know you will never end up on a highway... Heck, most cities have some highways in them (I know that Manhattan, New York, has a couple where you can legally go 50mph and sometimes see people hit 75mph).
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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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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.
I've seen simple steam boiler engines that are more efficient and more versatile than a stirling engine.
You mean like this one?
The higher the technology, the sharper that two-edged sword.
But here is the deal... this is a START. Better things are coming. There are other ways to hybridize a power train. Several really good ideas for recovering energy that is typically wasted in current vehicles will help, _more_ efficient engines help, better battery technology helps, more efficient solar cell technology helps, more efficient electric motors helps, and most of all a populace willing to accept smaller more efficient vehicles will help. It will take time to put it altogether and make it usable.
You should not be expecting a revolutionary vehicle or power train technology to come along next Tuesday at 2:37 p.m. It will take time. If instant success at the end goal of technology were possible we would not be following Moore's Law at all. We would simply have leap-frogged to the end-game technology. Let's not even go to that thought that alien technology would help if the government would release the information from Area 51. I'm quite happy that there are folk working diffidently to create things that will help us arrive at the end goal - very efficient modes of travel. Note that automobiles are not the only place that improvements can be made.
Safe and ridiculously cheap is what you will not have for a while yet. They will get there. There are private groups working on electric and hybrid cars as well as very cheap cars. The no one you speak of are the same people that think driving a hummer or huge pickup is ok since it only costs a few dollars more. Not everyone has those 'few dollars more' to waste.
Safety? Are motorcycles safe? If there were far fewer SUV's and other big vehicles on the road, safety issues change a bit. No vehicle is safe enough to drive head first into a concrete bridge upright at 70 MPH. Safety is a subjective word and ideal. If you want to drive around in a tank, I'm pretty sure that more than 50% of the populace is okay with you having to pay quite a bit extra for the privilege. Good luck with that.
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But the engine in a truck or bus is not fixed speed. It varies according to driving conditions, and there is a loss in efficiency due to the need to allow for the flexible load. If you use an engine merely for charging the battery then it can be a fixed speed, fixed load engine - I.e. it can run at peak efficiency whenever it is running, and the efficiency can be higher than a more flexible engine.
Does anyone remember this solid state engine from the super soaker guy?
That might be a better method to turn heat to electricity.
Also there are some blanket claims in the article that really need some more detail:
"...It can use any fuel, from biodiesel to natural gas; it burns clean; it can even be programmed to turn on so the battery and car are all warmed up by the time you get in."
I assume that the fuel is being burned as a method used to heat the stirling engine. How can this be claimed to be burning clean? The methods used would need to be explained in detail to be convincing of any major innovation here.
People who need to drive 150 mph can get a powerfull sportscar - maybe even one that'll only do 2 mpg flat out.
Nobody wants a sports/race car that only gets 2 mpg.
Gasoline is heavy. And energetic. Better fuel efficiency means you can carry less of it, and get more (speed) out of it.
Admittedly, sports cars are relatively wasteful, since they are tuned for maximizing speed. But this necessarily involves maximizing the amount of energy extracted from fuel, which is the SAME goal econo-car makers are trying to achieve. Econo-car makers are only getting there now because of a LOT of engineering by Honda, Toyota, Porsche, Ferrari, etc 10 years ago.
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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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Well those aren't very modern. there are far more modern designs that can reclaim heat in a closed loop system. Of course if I would love to own a Stanley Steamer, just from the pure novelty (and history!) of it.
Green Stream Engine is a newer design and with the right condensers is very practical and can be built compact enough to fit inside an electric vehicle to complement the electric drive train. One could just run the steam engine at a fixed rate to constantly recharge a battery system, so that overall the generators will produce enough power to maintain a constant charge on the system. But short bursts of power that deplete the system more quickly can be used for acceleration. I believe that is the point of a hybrid electric.
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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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The strength in Stirling's design is that it's effective at scavenging heat energy. So rather than powering it directly, why not use a traditional ICE or turbine for charging the batteries and then use the Stirling to scavenge energy like subject of this /. article:
http://science.slashdot.org/article.pl?sid=05/12/15/0037238
Maybe even take it step further and put the Stirling downstream of the steam engine?? With modern alloys and using freon or gaseous ammonia instead of water, you can greatly improve your efficiency.
Stirling engines are routinely used in marine applications for electrical generators in pleasure craft. They're quiet, make very good use of the heat sink (the ocean), and it's an application where you just want it to chug away at fairly constant revs.
So to say they're not in use everywhere, more like nowhere, is like, wrong.
5km/hr? Here (Queensland) it's "one", with the slogan "Every k over is a killer". And they put speed traps where you are going down a hill where the speed limit changes from 70 to 60 on a big wide road... *grumble*
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Why bother with a piston steam engine, when a turbine is way more efficient.
Once you have decoupled the power generation from the drive using electricity and placed some batteries or other electrical storage in between you have overcome the main limitation of turbines that they don't rev well.
You have also overcome the main limitation of steam, then need to get a head of steam up before you can move.
I'd like to add I like Aptera's approach of putting a small engine in an electrical car and letting it charge the batteries.
This is not a new idea, it's known as a "series hybrid". The approach has been used without batteries for many many years in your typical diesel locomotive, which is actually a diesel-electric system. Modern trains weigh too much to use a drivetrain. Sometimes small "pusher" engines are direct-diesel, but they just as often run on gasoline (better power to weight ratio since you can reasonably run higher RPMs on spark ignition than on compression ignition.)
The major benefit of this approach is that you can eliminate the transmission. Any design in which this is not done is stupid.
The other major benefit is that there is no reason to use an internal combustion engine! You could as easily use a turbine, which Chrysler had working for automotive purposes in the sixties. They had to let it go because their system destroyed transmissions. In a system in which a generator is integrated into the turbine and the transmission is eliminated, this problem is eliminated - and turbines have the additional advantage that they pair well with generators, which work best at high RPMs.
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I've often wondered if it would be cheaper to give every wheelchair-bound person one of Kamen's fancy IBOT stair-climbing chairs rather than install access ramps, elevators (right next to escalators), curb cuts in sidewalks, etc.
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Oh yeah? Then why do people driving "alternative fuel" vehicles get to use it without passengers?
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