Thermoelectrics are attractive for heating because they’re more efficient than ordinary electric heaters, which generate heat by running a current through a material that has high electrical resistance. What’s more, thermoelectrics make it possible to completely redesign the cooling and heating system. In most of today’s vehicles, the heating and cooling systems are designed to heat the entire passenger compartment. Thermoelectrics are compact devices that can be installed at points throughout the car–in the headrest, the seat, at a person’s feet, and so on. So, instead of heating and cooling the whole cabin, they can heat or cool individual passengers.
The savings of electrical energy such a system could provide to a plug-in hybrid car could be enormous. Where a conventional electric heating and cooling system requires up to 4,500 watts to maintain the desired temperature inside a car, a thermoelectric system would use 3,000 watts if the car is full of passengers or less than 700 watts if the driver is alone, according to estimates from the Department of Energy. Future generations of thermoelectric materials that rely on nanotechnology now being demonstrated in academic labs could improve these savings even more. (See “Cheap, Efficient Thermoelectrics” and “Turning Waste Heat into Power.”)
Both Maranville and Jihui Yang, a staff scientist at GM, say thermoelectrics are likely to be incorporated gradually as different components become available. One of the first ways it can help is in downsizing conventional air conditioning to make it more efficient. Yang says GM’s cars use oversized air conditioners to meet a requirement that they cool the passenger compartment in two minutes, even on very hot days. Well-placed thermoelectrics could make passengers feel cooler immediately by cooling their necks or face while a small, conventional air conditioner gradually lowers the temperature everywhere else.
In general, automakers have worried that most consumers won’t be willing to put up with inconveniences to drive more-efficient cars. Thermoelectric heating and cooling could help. “Our big challenge in research is to make the technology transparent to the customer, so that when they get into a vehicle, it doesn’t matter whether they’re in a conventional vehicle or in an advanced technology vehicle,” Maranville says.