Wednesday, April 06, 2005

News on the supply side and the demand side.

Canadian auto manufacturers have reached a voluntary agreement with the government on a plan that would reduce annual gas emissions for Canadian vehicles by 5.3 million tons by 2010. To achieve the regulations, the Canadian automobile industry will promote a variety of fuel-saving and emerging technologies, Natural Resources Canada said in a statement. The industry will also encourage the use of alternative fuels such as ethanol, clean diesel and biodiesel.

The pact was possibly stimulated by California's adoption last year of the world's toughest vehicle-emissions standards, designed to cut exhaust emissions in cars and light trucks by 25 percent by 2016. The Alliance of Automobile Manufacturers, however, has filed a federal lawsuit, claiming the regulations are too rigid. Seven other states are adopting similar measures.

It may be that, in Canada, the auto industry is looking for the best deal it can get in the face of a growing tide of state regulation.

"The automakers will find it financially impossible to make one clean set of cars for eight states and Canada and a dirty set for the rest," said Dan Becker, director of the Sierra Club's global warming program. "Eight plus one equals 50."

On the supply side scientists from Australia and Oregon may have figured out an efficient way not only to recover that lost energy, but to at long last capture the power-producing potential of geothermal heat.

Thermoelectric materials try to recover this energy by converting it to electricity, but they don't work very well if the flow of heat is uncontrolled. The breakthrough presented by Humphrey and Linke involves controlling the motion of electrons using materials that are structured on the nanoscale.

"The idea is to play one type of non-equilibrium (the temperature difference) against another one," Linke explains.

Humphrey and Linke have shown that if an electrical voltage is applied to an electrical system in addition to a temperature difference, it is possible to harness electrons having a specific energy. This means that if a nanostructured material is designed to only allow electrons with this particular energy to flow, a novel type of equilibrium is achieved in which electrons do not spontaneously ferry heat from hot to cold.

"This delicate balance may have huge practical importance because it means that thermoelectric devices, which use electrical contact between hot and cold regions in a semiconductor to transform heat into useful electrical energy, can be operated near equilibrium," says Humphrey. "This is a key requirement for cranking up their efficiency toward the Carnot limit, the maximum efficiency possible for any heat engine."

Because the system is in a state of equilibrium, the flow of electrons is reversible, Humphrey explains, noting that reversibility allows the device to reach maximum possible efficiency.

Until now, the efficiency of such devices, which have no moving parts and can be small enough to fit on a microchip, has been too low (less than 15 percent of the Carnot limit for power generation) for use in all but a few specialized applications.

However, Linke and Humphrey say implementation of their design principle is possible by tailoring the electronic bandstructure in state-of-the-art thermoelectric materials made up of a huge number of nanowires. If all goes well, nanostructured thermoelectric devices with efficiencies close to 50 percent of the Carnot limit may be realized, Linke says.

Such materials could make possible the generation of electricity from geothermal sources -- or from the waste heat of engines in hybrid cars, he explains.

In non technical terms, we lose less to entropy and gain more in electricity.


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