Converting Heat to Mechanical Motion

Probably me being thick...I'm on a run at the moment!... But.

If you power something from an expanding gas ...won't the exhaust be cold? So there won't be any spare heat to extract from it.

It's certainly a valid (and currently used) idea, called cogeneration. I recall a recent article about a major car maker adding a small heat engine to run off the energy in exhaust gases. It usually comes down to economics though, it may not be worth the extra cost/weight for a mobile device (say a car), but can make perfect sense for a large stationary engine (say a power station). As always, the efficiency of such devices is highly dependant on the temp difference available (check out the Carnot cycle for more info). So the idea's a good one. What do you mean by Tesla type devices? As I understand it, they are well understood but not practical. Jeff

It's easier to run an auxiliary turbine off the exhaust system to power a generator and options to do that existed 20 years ago. The later genrations of turbochargers are now so efficient that there is still some useful exhaust heat after the turbo. Mostly used on marine and industrial diesel engines where the average load factor is a lot higher than in automotive applications. Combined heat and power (CHP) is a similar method to this and gives copious amounts of steam and hot water from the exhaust, thermal efficiencies up to 80% are not uncommon. Remember that any system that increases the exhaust back pressure means the engine has to do more work to push out the exhaust against the higher resistance. Turbo chargers do have to do this but the overall gain of the turbocharger, and CHP is positive.

Georgee

Hi. I think you are looking for " Organic Rankine Cycle" where ammonia plus water, R-134, butanne, or another one gas could be "working fluid" instead super pressure and heat water. Please refer geothermal electric systems in all world. Only for example: http://www.geothermie.de/gte/gte36-37/altheim_gaia.htm

Could you be more specific? What kind of mechanical motion do you have in mind?

Dear Guest,

SKIPPER said: "releasing it to a hydraulic motor which turns a generator".

That seems to be quite specific.

I mean rotational motion, as you can see in website point out. The "ORC" turbine can drive a mass, instead a electric generator. Of course, "low enthalpy" cycles has low engine performance! I don´t want to change any usual mechanic motors!
In the other hand, in electric power plants at least, natural geothermics heat sources, or even solar heat, about 7% system performance, over "zero cost" is high better, than 30% over "fine adjust thermodynamics cycles" (maximum theorical = 33%) over charcoal, diesel, or any other fuel input with their higher prices plus logistics and environmental costs. Please, if you want to go on this chat please e-mail: acquaway@acquaway.ind.br

Turbo SuperChargers in Diesel Engines do Just that.

If You have a very large flow of " Waste-d Heat" ,you can go for:

• Expander Turbogenerators--Standard Equipment with Hi -Top-Pressure Blast Furnaces
• Run a Large Bakery Oven or similar food Processing (Tea /Grain Drying say)

Your picture:

with converting heat to mechanical motion by storing pressure in an accumulator via a refrigerant gas such as r-134 or ammonia instead of nitrogen,then releasing it to a hydraulic motor which turns a generator to charge the batteries on a hybrid vehicle--looks difficult to organize.

But a fresh look is needed-if you can supply:Gas Type.MassFlow rate.Temp.Pressure.

I think this is worth pursuing. People have been thinking along these lines, with BMW for instance, having a turbocharger-powered alternator.

Recently, I had what I though was an original idea, that being to generate electricity for a house with a fairly standard small generator, and to capture virtually all the waste heat to heat the house. Assuming the generator is located in such a way that radiated heat warms the house, and with an efficient heat exchanger on the exhaust (furnaces are about 95% efficient now) and the cooling water routed to a hot water tank, the total system efficiency could be very near 100%. Just a few days later, I came across a the Honda Power Products site which shows exactly such a unit, of which they've sold 50,000 in Japan, I think. I was a little disappointed to see "my" idea already on the market, but it illustrates that people are really just starting to think more seriously about efficiency: there is nothing in "my" idea that I couldn't have thought up in 1968 when I was a teen with some physics background. It's anything but rocket science. But consider that electricity arrives at your wall outlet with 38% efficiency in the US. If you could get heat and electricity at nearly 100% efficiency, that is a huge difference. And all it takes is thinking about it and doing it.

66% waste heat is a big deal. We can't continue to throw away our resources, willy nilly.

You will find more about ORC developments on www.heat2power.net (look in the benchmark section). You will also find some links on that page to the DEER conference where this subject is treated.

The truck and automotive industries show increasing interest in WHR (Waste Heat Regeneration) to improve engine efficiency.

Everything has already been invented. Well , almost everything then....

Randolph Toom

Everything has already been invented. Well , almost everything then....

I'm really happy now with some intellegent response to my probably rediculous idea,..but my problem is a lack of schooling in mathematical ability to express this idea...you have all been kind in knowing that fact.. but, you might want to kick my butt a little and the rest of us.. I know there's probaly an "X" point where this won't work, sort of like an EMD engine's turbo goes into gear drive mode, EG.(@300RPM), and, up to where exhaust pressure overruns the gear train mechanism but I do know.... there's a happy medium to where all this random energy I've been concerned with can be utilized in some practical way..I'm someone that for the last 35 years has frustatingly watched this litterly go up in smoke!! I'm sick of it! any ideas?If not I'll guess i'll get over it.....thanks again guys,Skipper