Thermoelectrics to replace car alternators and improve MPG

Thermoelectrics to replace car alternators and improve MPG
Prof. Rowe with the TEG equipped Volkswagen
Prof. Rowe with the TEG equipped Volkswagen
View 1 Image
Prof. Rowe with the TEG equipped Volkswagen
Prof. Rowe with the TEG equipped Volkswagen

February 9, 2009 Thermoelectrics - the phenomena in which a temperature difference creates an electric potential - have been known about for almost 200 years, but practical applications have not been widespread due to their low energy efficiency. That may all now be about to change as 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.

Thermoelectric refrigeration

Thermoelectric have been used for refrigeration utilizing the Peltier effect originally discovered in 1834. An electrical current at the junction of two different metals results in heat being absorbed by one metal and expelled by the other metal. Thermoelectrics can also be used to generate electricity using the Seebeck effect that dates back to 1770. Thermoelectric power generators convert heat energy to electricity. When a temperature gradient is created across the thermoelectric device, a DC voltage develops across the terminals.

Thermoelectric generators

Typical applications for this technology include providing power for remote telecommunications and navigation beacons. A more familiar application is a thermocouple that is a type of temperature sensor that can generate a current proportional to the amount of heat it is exposed to. Thermocouples were used in remote parts of Russian in the 1920s to power radios from a wood fireplace and they also form the basis of radioisotope thermoelectric generators (RTG) that use heat from a radioactive material to power deep space satellites. The drawback to all thermocouple based electric generation is that they are very inefficient at between 3-7%.

Automotive thermoelectric generators (ATEG) have been developed intermittently since 1988 when Porsche made a exhaust ATEG capable of 20-30 watts out of a 944 exhaust system but they have never made it past the prototype stage of development.

Paul Evans

Via: International Thermoelectric Society.

There are a lot more efficient ways to recycle waste heat.
James Doughty II
About the steam driven absorbtion of energy idea: Can you imagine what it would be like if you were followinng several cars with this kind of device? I imagine it would be at least a bit foggy. Now imagine if this really worked and caught on in a place like Los Angeles. You wouldn\'t see all those slow moving vehicles on the freeway, because of the fog they create. Then there\'s the question of what becomes of the toxic steam after the Sun heats it and the Wind carries it away? Will it create acid rain? So we need to consider mitigation with this design to account for these factors. Somehow condenste the steam right after it\'s released or even recycle it back into the system somehow.
Gregg Eshelman
It\'s 2012. Where\'s my aftermarket TEG for my exhaust pipe? I want to be able to get one at Autozone.
Andrzej Feliks
Add the Solar sunroofs and alternator no need .