Thermoelectric generators to recover waste heat?

According to an online source (Wikipedia), auto makers have Thermoelectric generators to recover waste heat from engines and provide electric power. Can anybody verify this?


Germany automakers Volkswagen and BMW have developed thermoelectric generators (TEG) that recover waste heat from a combustion engine.

According to a report by Prof. Rowe of the University of Wales in the International Thermoelectric Society, Volkswagen claims 600W output from the TEG under highway driving condition. The TEG-produced electricity meets around 30% of the car?s electrical requirements, resulting in a reduced mechanical load (alternator) and a reduction in fuel consumption of more than 5%.

BMW and DLR (German Aerospace) have also developed an exhaust powered thermoelectric generator that achieves 200 W maximum and has been used successfully for more than 12,000-km road use.


I hadn’t heard, but sounds reasonable. 600W is about 0.8 hp, a small fraction of the car’s needs, so a 5% mpg bump sounds ok. Of course, it all comes down to cost, how much $$ for that 5%…

At least this is a move in the right direction…Wasted heat is wasted energy that we pay dearly for…

Here is my dream solution. Raise the engines operating temperature to 250-280 degrees and generate steam. Generate more steam from liquid-cooled exhaust systems. Use this steam to drive a small steam turbine alternator. In a hybrid electric drive system, the electricity could be used to power the car. The condensed coolant is pumped back into the engine in a closed loop. Once the technology is perfected and the system mass produced, the cost / benefit ratio should be favorable…Lets face it, todays ICE motors make a better furnace than a producer of torque…They waste 70% of the fuel they burn…We should be able to get that down to 40%

I like the idea. For years, aircraft and cars alike, have been using the 70% of wasted heat energy, in the form of turbo chargers and power recovery turbines. But these are used to increase the power of the engine. I like the idea of using it to power other devices (ie: electrical), and I believe they could find other uses for it as well.

Actually there is a 6-cycle engine that uses the extra cycles to inject water into the cylinder, cooling it and making steam for a power cycle. But it didn’t seem to catch on, perhaps the gain in power is offset by the extra losses.

In the first approach, the engine captures the heat lost from the four-stroke Otto cycle or Diesel cycle and uses it to power an additional power and exhaust stroke of the piston in the same cylinder. Designs use either steam or air as the working fluid for the additional power stroke. The pistons in this type of six-stroke engine go up and down three times for each injection of fuel. There are two power strokes: one with fuel, the other with steam or air. The currently notable designs in this class are the Crower six-stroke engine, invented by Bruce Crower of the U.S. ; the Bajulaz engine by the Bajulaz S.A. company of Switzerland; and the Velozeta Six-stroke engine built by the College of Engineering, at Trivandrum in India.

The second approach to the six-stroke engine uses a second opposed piston in each cylinder that moves at half the cyclical rate of the main piston, thus giving six piston movements per cycle. Functionally, the second piston replaces the valve mechanism of a conventional engine but also increases the compression ratio. The currently notable designs in this class include two designs developed independently: the Beare Head engine, invented by Australian Malcolm Beare, and the German Charge pump, invented by Helmut Kottmann.

It sounds like an interesting way to try to recover a bit of the energy lost out the tailpipe. I’ll be interested in seeing how thiis idea evolves.

IIRC, their generator is actually a steam turbine.

That’s awesome.

BMW is already working on that combining steam and a 4 cylinder engine. They call it the turbosteamer.

I think steam is too complicated. A free piston Stirling engine powered by exhaust heat and generating electricity would be simpler. Cooling system should be a stand alone steam system. Not only does its draw on engine power, but taking away energy from coolant using a turbine reduces radiator requirement and, in turn, aerodynamic drag.

I read something about this. I think they originally labeled it a 5-cycle engine, which made my head spin.

I can remember efforts to reduce waste heat back in the 1970’s. If they can come up with a system that is reliable enough, cheap enough and saves enough energy, great. Maybe they can. I wish them the best of luck, but the technology is not ready for prime time yet.

Seems like I mentioned this in a post(it was generally ignored)but yes!.I’m a fan of turbo compounded and any practical way to recover the energy in the waste heat and a thermogenerator should be considered for the mix.
Ever see the proposal for the “Gnome-Fairy” Horizontally opposed 12 cylinder Diesel aircraft engine,that was turbo compounded?Very interesting,but I think the advent of the turbine knocked it out of contention,the turbine wasnt very fuel efficient but for the application was better.We always come back to the cost,performance and reliability of a system vs. the savings in one area or the other.Case in point-Steam powered vs. Diesel-Electric locomotive,Diesel wasn’t cheaper,but for the application,better.-Kevin