Dean Kamens Sterling Generator
 

Hi Guys,

Does anyone here know the current (2011) status of Dean Kamens Sterling generator?? The last I remember hearing around 4 or 5 years ago was that Dean had licensed some group to produce & market them with profits going towards giving many away to impoverished regions of the world where there is absolutely no clean water for people to drink. (In some areas folks will walk 30 miles a day to carry clean drinking water home to their villages).

For those who haven't heard of Deans' Sterling generator, one of Dean Kamens neatest inventions is a self-contained, portable electric generator. You start a fire under one end of it with wood, coal, propane....whatever and the "Sterling generator" (after its original inventor) which is an enclosed pressured gas system that when heated turns a turbine, which in turn Dean Kamen hooked an electrical generator to provide power to impoverished areas of the world. A totelly unforseen by-product of the heated turbine was the fact that as it cooled & ran & cooled & ran it produced distilled water which drained out of the machine. This invention of Deans' makes FRESH water!!
The whole unit is about the size of a normal portable generater that many of us have in our garages and shops at home, VERY KOOL and is a world changing proposition.

Close, but not quite right. Actually, Dean is developing a generator based on the Stirling Engine, which he did NOT invent, does NOT have a turbine, and does not produce distilled water. That generator will produce energy to run a different product that he DID invent -- the "Slingshot" water purifier which produces clean water from very polluted sources including urine, sewage, sludge, or polluted river & stream water. The two devices complement each other for field usage, but the Slingshot can be used by itself wherever there is an adequate source of electricity.

Here is an article that summarizes the information, but it is a few years old.
http://www.newsweek.com/2008/04/04/b...-solution.html

Also, see this video: http://www.evtv1.com/player.aspx?itemnum=17636




:)

Dean's a very, very smart guy. I am apparently missing a critical part of the big picture.

You burn something, make electricity, use the electricity to run a machine that makes fresh water. but there are fundamental inefficiencies in conversion of heat to electricity, even in a Stirling engine, and there will presumably be losses in the electricity to water machine too.

Why not just make a "still" (distillation apparatus) that is directly heat-fired. It can be made from relatively cheap stuff and needs no real maintenance. You could probably make 20+ stills for the cost of the two machines. You could even skip the step of trying to make and contain methane from cow dung. Dried cow dung is used for fuel all over the world.

Can you get the same volume of water from a given amount of fuel? I don't know. Perhaps that's the genius of Dean's approach, but it seems terribly complex.

I don't know the answers, but I can point out a couple things from your message.

First, a Sterling engine is more efficient (theoretically), and you'd like to get electricity out of it, not just water.

Second, distillation is not efficient. It takes 2260 J/g to vaporize water. That heat then comes out the other side of the process. You can recover a little of it to preheat the incoming water, to bring it up to the boiling point, but you can't make it boil.

You could drive a Sterling engine with that heat, though, with a working fluid at a lower boiling point. Or probably more efficiently, you could run a Sterling engine at a higher temperature, and run the still with the waste heat, which would also help the Sterling engine's efficiency. If I recall correctly, practical Sterling engines work more efficiently at higher temperatures.

While a Stirling engine (yes, I was mistyping it earlier, following the topic title; I thought it looked wrong but failed to check) is generally considered an "external combustion engine", that's somewhat misleading, in that it doesn't depend on combustion at all. More accurately, it's a heat engine.

It's not a steam engine. The working fluid is generally a gas, although I'm sure you could have a mixed phase system. It's generally recirculated, so generally, you don't get any distillation going on as part of the engine itself.

That doesn't mean Dean's thing doesn't do it differently -- but then it wouldn't really be following the Stirling Cycle exactly.

Still, I suspect the distillation (if any) is not directly a result of the engine's operation, but rather the engine's cooling. A Stirling Engine is dependent on the temperature difference, so cooling the cool end by boiling water, while heating the hot end by burning fuel fits the picture pretty well.

There is a great deal of information about Stirling engines here.
http://en.wikipedia.org/wiki/Sterling_engine

By definition, Stirling engines use only gases for working fluids, and then only gases that remain in the gaseous state throughout the entire cycle. Helium is a good choice. Good old air is not too bad. Stirlings are not turbines, and unless you are burning hydrogen as a fuel, Stirling engines do not produce water.

Kamen's Stirling engine drives a generator (or more likely alternator), and because it is a Stirling engine, it does so efficiently. This can be a very efficient way to produce electricity from non-conventional or renewable fuels.

The Kamen invention (Kamen did not invent Stirling engines or alternators) is the "Slingshot" water purifier. Apparently, it is heat driven and it's claim to fame is that is very efficient,it recovering most of what would otherwise be waste heat. There didn't seem to be any claim that waste heat from the distillation process is used by the Stirling engine, so the two units could be looked at as semi-related. The Stirling generator makes electrical power from almost anything that burns. The Slingshot can use that electrical power efficiently to make potable water.

If you've got a Stirling generator, then the Slingshot might be a good addition, but if all you want is potable water, then a still might be the way to go. Yeah, you've got to boil the water, but apparently that's what the Slingshot does. I would wager that a maxi-efficient still could be devised, driven directly by burning cow chips, needing no Stirling generator, and costing much less.

(Sorry Bob! You posted just after I checked for new posts)

Kamen didn't invent the Stirling engine, but he's been working on making it more practical. A counterflow heat exchanger that also serves as the boiler of a still makes so much sense I find it hard to believe it's not a part of the package.

There's a downside here. Burning fuel has environmental consequences. Deforestation, air pollution, toxic waste. That can all be offset by replacing traditional fuel uses with more efficient ones, but there's always unintended consequences to consider.

While you could use, say, thermite as a fuel, all traditional fuels except charcoal and coal produce water when they burn, as they do contain hydrogen. (And if you heat coal or charcoal, and pass steam through it, you get coal gas -- which then burns and produces water again).

If you bring down the cool side of the Stirling engine down to near the inlet temperature of the water, you could then, on the hot side, heat it with heat from the condensation side of the still. But that doesn't make any sense, because you'd need a lot of water flow to bring it down that much.

It would make more sense to me to preheat the combustion air, thus raising the hot side temperature, and making the combustion more efficient (and cleaner). At the same time, you're making the distillation more efficient (or making the cooling you're already doing more efficient -- for example, you could drive that airflow via convection with a tall chimney).

I have no idea what Dean's doing, I'm just being an engineer. But I'd love to see. I'll have to check for patents when I get a chance.

Dean's pretty clever with names. I wonder if there is a clue to function in the name 'Slingshot'.

It runs on rubber bands?