President Larry Millstein called the 2,259th meeting to order at 8:15 PM October 30, 2009 in the Powell Auditorium of the Cosmos Club. The minutes of the 2,258st meeting were read and approved.
Mr. Millstein introduced the speaker of the evening, Mr. John W. Fairbanks of the U.S. Department of Energy. Mr. Fairbanks spoke on “Vehicular Applications of Thermoelectrics.”
Mr. Fairbanks started by reminding us of the recent progress in transportation. He showed a picture of a typical stagecoach in the early 20th century. A big coach that could take eight passengers, it required four-horse power. It featured drive-by-line control. The fare was 25¢ for four miles. It used biomass fuel and there was a stable fuel cost. The emissions were equine methane and an agglomeration of macro particles which were minimally airborne and easily recyclable. Things are different today, and the difference involves a great amount of energy. Pictures of roads about 1900 illustrated the difference starkly. There were very few of those four-horse coaches.
It is also instructive to compare expectations to actualities, or journalism to engineering. The October 9, 1903 New York Times said, “The flying machine which will really fly might be evolved by the combined and continuous efforts of mathematicians and mechanicians in from one million to ten million years.” That same day, Orville Wright noted in his diary, “We started assembly today.”
Hydrocarbon engines waste much of the energy they burn. Take, for example, a typical car engine, which Mr. Fairbanks calls a “spark assisted gasoline internal combustion engine.” Of the energy that goes into the system:
Joseph Henry, founder of the Philosophical Society, did pioneering work in electricity that led to the telegraph, electric motor, and telephone. Johan Seebeck, Henry’s contemporary, did related work; he made a device of copper and bismuth. He heated one end of the bismuth and cooled the other and produced a current in the copper. This was actually the first thermocouple, and with these materials, Seebeck could have made a thermoelectric generator (TEG) that was 3% efficient, as good as the best steam engines at the time.
U.S. spacecraft use radioisotope thermoelecric power generators. They are small but very constant and reliable.
Thermocouples can work either way, take in heat and put out electricity or take in electricity and put out heat. The heat transfer can be used either to cool something or to warm something.
He described the figure of merit for TE materials. Positive contributors are electrical conductivity and the Seebeck coefficient or thermopower, and negatives are two types of thermal conductivity. The best material combinations available today produce electrical generation efficiencies of about 12 per cent.
Big-engine companies like Cummins and Caterpillar are interested in TEG’s, and they are also interested in turbine engines powered by the exhaust stream, which they are already using. It is possible to run the two types of devices in a series in the exhaust stream.
Mr. Fairbanks hopes to use a thermoelectric generator to replace or reduce the belt-driven generator. With the extra available electricity, devices such as the water pump may also be electrically driven, and a beltless engine may be possible. BMW has an electric water pump. This, alone, is said to improve fuel economy 1.5 - 2%.
Electrical power demand in automobiles is going up, too. Drive-by-wire, collision avoidance, electric power steering, electronic braking, all those things take electricity. Between 2000 and 2005, the average power needed in a midsize car went from about 1 kw to over 3 kw.
Thermocouple efficiency is the effective limitation of TEG’s at present. They are working on the material structure to improve that. Many of the newer ideas for modifying the material structure are nanoscale modifications. He spoke of skutterudites, crystal lattice structures of cobalt and antimony atoms arranged as square planar rings. The structures have voids that can be filled with atoms which lowers the thermal conductivity and raises the figure of merit.
The thermoelectric modules go into the exhaust system downstream from the catalytic converter, where the temperature is highest. A heat exchanger, or radiator, will be connected to them to keep the thermal differential up. It is possible that eventually, heat will be used from the engine coolant, too, but present designs call for much higher temperature, in the neighborhood of 500°C to drive the TEG.
One of the benefits will be reduced carbon emissions. More than 80% of cars today do not meet the 2012 standards.
Mr. Fairbanks showed pictures of the devices installed in working vehicles. A BMW auto had a TEG built into the exhaust system. A gauge on a Chevrolet Suburban showed the TEG generating over 500 watts at 45 miles an hour.
They are also working on cooling using TEG’s. The cooling would be built into the seats. Such systems would work faster and eliminate the need to cool the whole cabin. There are about 220 million personal vehicles in the U.S. Cooling with TEG’s would save 4.5 billion gallons of fuel a year and reduce greenhouse gases by 69.5 million metric tons of CO2.
There is also a program to use TEG’s on boats. The engine on a boat is normally working pretty hard and there is a ready supply of cooling water. People are also experimenting with TEG cooling of a submarine, of fruit for storage, and in clothing for military troops.
Looking forward, they hope to see, in three to six years, TEG’s producing a 10% fuel economy gain, beltless engines, and thermoelectric air conditioning in cars. In seven to 15 years, they hope to see thermoelectric generators and replacement of the air conditioning with thermoelectric devices. Beyond that, they hope to have 35% efficient thermoelectrics which would replace the engine with combustors that will burn any fuel.
He concluded by saying that thermoelectrics are not just for space any more.
After the talk, one person recalled a thermoelectric project he’d done as a child and asked about the role of amateurs in thermoelectrics. There hasn’t been much activity by amateurs, Mr. Fairbanks said, but there was one interesting one. Many decades ago, in Russia, a device was developed that was attached to the base of oil lamps and produced enough power to run radios, and many radios in Russia were run that way before electrification was widespread.
A question was asked about the temperatures needed. Auto engines provide temperatures of about 800°C to 240°C. NASA uses higher temperatures, about 1,200°C. Diesel engines provide somewhat lower temperatures. The efficiency is higher with greater temperature differentials.
Someone asked, why couldn’t you replace the engine with an electric one? Automobile engines are about 35% efficient, thermoelectric generators are only about 12% efficient. TEG’s will equal piston engines when they reach 30% efficiency and replace them when the efficiency gets above that. (I believe the reason TEG’s will be competitive at slightly lower efficiency is because they are lighter.)
Another questioner asked, since hybrid auto engines increase efficiency by about 10%, what is the reason for TEG’s. Mr. Fairbanks said, in effect, that both can be used at the same time.
After the talk, Mr. Millstein presented to Mr. Fairbanks a plaque commemorating the occasion. He made the usual housekeeping announcements, including the parking announcement, and encouraged people to join our Society and members to participate actively.
Finally, at 9:18 pm, he adjourned the 2,259th meeting to the social hour.
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Ronald O. Hietala,
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