Dean Kamen Combines Stirling Engine With Electric Car 324
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.
Disruptive technology (Score:5, Informative)
When he mentions it being 'disruptive', he's referring to the concept of disruptive technology as written about in The Innovator's Dilemma by Christensen:
http://www.amazon.com/Innovators-Dilemma-Revolutionary-National-Bestseller/dp/0066620694 [amazon.com]
Great read, and the concepts are laid out here:
http://en.wikipedia.org/wiki/Disruptive_technology [wikipedia.org]
If you're not familiar with the concept, it's worth checking out.
Wondering what a Stirling engine is? (Score:5, Informative)
Wonder no more [wikipedia.org]
"A Stirling engine is a closed-cycle regenerative heat engine with a gaseous working fluid."
As with many of these hybrid and electric car announcements, it'd be great if I could really go buy one, and have it be inexpensive. We're always just "2-3 years" away from these things reaching market, and "eventually" being affordable by regular folks.
Perhaps some Indian or Chinese company will make these and sell them here for under $10k. That would spark a huge revolution. Hybrids at $24k don't change people's buying habits enough to cause a huge shift in demand.
For better or worse, I think we'll see an alt-energy evolution in the US, rather than a revolution.
Re:stirling engine is a no-go (Score:5, Informative)
I'm no engines expert, but I thought the good part of a stirling engine was that they often are just a few percentage points from theoretical maximum efficiency of a heat engine, about 50%???
http://en.wikipedia.org/wiki/Stirling_engine [wikipedia.org]
I thought the downside is that they take a while to get up to speed. Ford in the 1970s tested a small vehicle with such an engine and they could get it up to speed after 13 seconds. So it should be a natural fit as a battery charger in an electrical car...
At least, that's what I thought when I looked into this a few years back (just as a curiosity, nothing professional mind you).
Re:stirling engine is a no-go (Score:3, Informative)
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. Many vehicles only use a tiny fraction of their horsepower to maintain speed and the rest is for acceleration, so in an car driven by electrical motors - the gasoline recharging engines can be significantly smaller; 5-20hp (? - my civic has 140hp in comparison); probably just a little more than what's needed to maintain targetted top speed (or up-hill considerations).
And a gasoline or better, a diesel engine is plenty efficient already just for this general approach.
Air Submarines And The Hunky Men Who Love Them (Score:2, Informative)
Like 3 to 6 percent. That kinda explains why it's not in use everywhere, more like nowhere.
'cept for those submarines of the Gotland and SÃdermanland classes... Oh and it helps propel man into the depths of space... here [wikipedia.org].
Stirling not connected, not enough to power car. (Score:5, Informative)
http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/10/27/sv_deankamen.xml [telegraph.co.uk]
I read several articles on this when news first broke. The above indicates the Stirlin isn't even connected. When it is, it doesn't produce enough power to actually move the car. Kamen has a 1KW Stirling that is about the same size as what is pictured and other articles mentioned it as a "trickle charger".
In this case the Stirling is essentially a novelty, it doesn't drive the car when the battery is run down.
Re:The Uri Geller of industry (Score:5, Informative)
Well, I'd say his inventions such as the portable dialysis machine, the auto-syringe technology for people who require round the clock injections, and the wheelchair that can climb stairs made a tremendous difference. These medical inventions restored a reasonable standard of living to a great number of people, and are the foundation of his current fortune.
Re:stirling engine is a no-go (Score:4, Informative)
Stirling engines can be fairly efficient if you have the (space and weight) budget to make them big and heavy. For cars they're certainly not a very good idea.
But the main point of Stirling engines isn't efficiency but the fact that they are not only fuel-agnostic; unlike combustion engines or steam engines they don't need any kind of combustion or medium phase-change to operate. Anything that can generate a temperature differential will do. They're also quiet and very reliable (few moving parts).
That makes them well suited for things like backup generators, where you can store them for years on end, then run them on whatever fuel you can get hold of. They're used in submarines too, due to their silent operation and no need for actual combustion to generate enough heat. You could set up a Stirling engine to run on the waste heat from other processes. And they're reversible, so they're used as coolers for certain temperature ranges (overkill for a normal freezer but if you want much colder it's one way to go). Heat pumps are essentially Stirling engines.
Shameless plug ahead: a blog post of mine on Stirling engines here: Stirling Engine [blogspot.com]
Re:Thermodynamics 101 (Score:3, Informative)
Sterling engines in theory approach the Carnot limit. In practice, they do very very well compared to other engines, especially on a weight basis. However, they also have problems that normally make them inappropriate for cars. They don't do well with variable outputs, and they don't start up rapidly. Over the normal operating range of a car engine, diesels do much better. If, however, you could run it at a fixed speed and not care about startup time, then the Sterling engine starts to look good. And, of course, a series hybrid with large batteries (or an electric car with a battery charger, depending how you look at it) is exactly that.
Of course, there are other problems with Sterling engines -- unknown long-term reliability, for example -- that are likely far more relevant. But efficiency is decidedly not the reason to avoid them.
Re:Gas Turbine? (Score:3, Informative)
It's not. "Minutes" isn't a problem at all for ER-EVs. Gas turbines integrate quite nicely. They take the time that they need to to start up and can run for a dozen minutes or two, then they shut off. DesignLine busses use Capstone microturbines for this very purpose. The Capstones use an air suspension so that the shaft encounters nearly no friction. As a consequence, they have very long lifespans.
Re:stirling engine is a no-go (Score:5, Informative)
According to NASA, there was no weight change. Read it. More expensive is a matter of mass production, no auto engine is exactly simple nowadays anyway.
Re:Air Submarines And The Hunky Men Who Love Them (Score:0, Informative)
space has a cold side? what would that be - the vacuum? like what you have for a fucking brain?
Re:Thermodynamics 101 (Score:3, Informative)
The car/truck industry has attempted to make these work for decades with varying degrees of success. The fundamental issue is why you *need* a transmission at all. That tells me that there's something basically wrong with the internal combustion engine as a source of motive power. Indeed there is - it is just not really suitable because of the 'impedance mismatch' between the mechanical power it produces and that needed for a car in ordinary use. Therefore you need a clutch to overcome the fact that it cannot run at 0rpm, and gives barely any torque at all at idle speed, and it needs gears to overcome the limited speed range. It's also a one-way energy conversion system, so once it has converted to mechanical motion, it's gone - when you brake you simply throw the excess energy away (what's left after the transmission has thrown another third away before it even gets to the wheels). Looked at this way the I/C engine powered car is as wasteful as it gets. An electric motor on the other hand, has none of these problems. It gives plenty of torque at 0rpm (no clutch required) and a wide speed range (no gears required) and is a bidirectional converter (no brakes required, or at least most of the energy embodied in the moving vehicle can be recovered). Electric motors do away with the whole question of infinitely variable transmission, and all that weight saved translates into a potentially much lighter vehicle too.
I believe the short/medium term future for hybrid vehicles is an all-electric drive system using enough on-board battery (or supercapacitor) storage for a typical commute, plug-in-able, with an efficient fixed speed diesel-electric generator system to supply the power for longer trips. Current approaches such as the Prius are a joke - a mere tiptoe in the water - still far too complicated and hampered by the mechanical connection of the I/C component to the wheels. Trouble is most of the big car manufacturers are too wedded to their traditional mechanical thinking so far to make the leap, but there are signs that things are moving that way: the QED Mini, the Lightning GT and even the Chevy Volt. This car is actually thinking along the right lines, my only beef is with the Stirling-electric generator, which might look efficient on paper but I'm sceptical that it can be made to work in real life. At least a diesel is tried-and-tested, with loads of accumulated experience out there that can be tapped. If something better comes along then it could be swapped in without having to redesign the rest of the vehicle.
Re:A few questions: Stirling engine thermodynamics (Score:3, Informative)
33cc is optimal for the piston size/stroke which can be oversquare (stoke is longer than piston diameter). or undersquare (stroke is shorter than piston diameter).
Longstroke = more torque, short stroke = more power at high rmp. - Just scale it up if you need bigger.
Your problems will be the heat exchangers - very efficient at heating water btw.
Wiki has a good description and will give you a few types to consider.
There's what you want already built in Spain: Point focus parabolic dish with Stirling engine and its solar tracker at Plataforma Solar de AlmerÃa (PSA) in Spain.
http://en.wikipedia.org/wiki/Sterling_engines [wikipedia.org]
There are also other 'solid state' alternatives too.
Just google it to find a pile of hobby sterling engine sites.
There are also commercial sterling fridges, water-heaters and power generators ready to go.
Re:stirling engine is a no-go (Score:4, Informative)
A Stirling engine is an external combustion engine. It generates waste heat as a byproduct of operation just like an internal combustion engine does. That allows the heat to be used for the defroster and heater. But it's primary function is no more to generate heat than it is with the engine in your car. However, unlike an internal combustion engine that requires fuel that can undergo controlled explosion, the stirling engine just requires a source of sufficiently high heat (efficiency of the stirling cycle is related to the difference in temperature between heat source and sink).
So are small Diesels (Score:3, Informative)
Stirling engines used in military system have the advantage that cost is almost irrelevant, but Stirling for road vehicles has the chicken and egg problem - to prove the viability of the concept, you need to get up to big manufacturing volumes to get the reliability data and drive costs down. The takeover by Diesels for cars in Europe was made possible because the technologies for advanced Diesels were already in wide use in marine engnies and just had to be engineered down the size scale. This situation does not exist for Stirlings.
On the pollution front, it is true that Stirling engines will burn most fuels, but the downside is that it is very hard to produce a multi-fuel engine that does not produce a lot of soot from some of those fuels. You can drive a small Sitrling by burning wood - if you don't mind dismantling the heat exchanger periodically to get the gunk out.
Kamen's idea is, I feel, less about viable technology than pressing buttons with the US Government's priorities. It would be more economical, and more reliable, to fit a small off the shelf packaged generator of the sort that is already available to fit into boat lockers. Compare the price of one of these with a Whispergen and you will see the point very quickly.
Re:The Uri Geller of industry (Score:1, Informative)
Artery stent, too.
Re:stirling engine is a no-go (Score:3, Informative)
The reason I found that article was because I was seeking plans. What I found was that some of the major documents (like the summary I posted) have been scanned and are available online, but most of the technical documents are in their paper library. You have to buy them for something like $60 apiece (can't remember exactly the cost).
It is all there though.. for those who want to invest in the paper weight. This page will get you most of the Stirling results [nasa.gov] and this is the main document research website for NASA [nasa.gov].
Re:Waste heat (Score:3, Informative)
Then you have to convert that 23% into a useful form of work (let's say electrical energy) which incurs additional efficiency loss.
Not that there's anything wrong with that... using an extra 5 or 6 percent of the chemical energy in the fuel for useful output still counts, but there is a pretty high cost in money and weight associated with getting that extra energy out. If it's done in a vehicle you have to account for the decrease in acceleration efficiency due to the extra mass...
Re:Think CITY?? (Score:3, Informative)
First off, I can't recommend strongly enough that you view the YouTube video of Chris hitting the shell with a hammer. It has over double the required roof and door crush strength for cars. It has not just an ordinary crumple zone, but an innovative crumple/deflection zone designed to help the vehicle ride up in an accident. It has full in-seatbelt curtain airbags. This is a vehicle that should blow most cars out of the water when it comes to safety. Secondly, as for handling, you need to read more about three wheelers; here's a primer [autospeed.com]. One wheel in front and two wheels back is notoriously unsafe and unstable, but two wheels forward and one wheel in back, with the CG just behind the front wheels, handles almost identically to a four wheel car, except that it has a faster response time. Basically, when you brake or steer, the CG slides up between the two front wheels, and thus has the same amount of resistance to flipping laterally that a four wheeler has. Also, they are naturally prone to understeer (like four wheelers), not oversteer (like tadpole three wheelers). About the only thing you wouldn't want to do in a tadpole three wheeler is something like a J-turn.
There are many reasons for going with three wheels. Yes, a big one is that it has a lot less certification that has to be done. But if they're voluntarily doing crash and crush tests, who cares? The other benefits are numerous; here's just a few. The ideal aerodynamic shape to enclose as much volume as possible with as little drag as possible is a stereotypical teardrop (or truncated teardrop); this means wider in the front than in the rear (hence, two wheels forward, one backward). Three wheels means you can elimiante an entire wheel. And all of the drivetrain/braking/cabling/wiring requirements that go along with it. Which reduces weight, purchase costs, and maintenance. And cutting weight means increasing range, and so on down the line.