Washington: Scientists from the Massachusetts Institute of Technology (MIT) have used nanotechnology to dramatically improve conversion between heat and power, paving the way for a new generation of products that are cheaper and run cleaner.

The latest breakthrough in the conversion, called the thermoelectric effect, would mean a host of more efficient and cheaper products - from semiconductors and air conditioners to car exhaust systems and solar power panels.

The team's low-cost approach, details of which have been published in the online version of the journal Science, involves building tiny alloy nanostructures that can serve as micro-coolers and power generators.

The researchers said that in addition to being cheap, their method would result in products that consume less energy or capture energy that would otherwise have been wasted.

The thermoelectric effect has been known for almost two centuries now, but there has been a hitch in trying to exploit it: most materials that conduct electricity also conduct heat, so their temperature equalises quickly.

In the latest innovation, the MIT team used bismuth antimony telluride (BAT) - a material used in thermoelectric devices since the 1950s - but in the form of nanoscopic dust, boosting its thermal efficiency by 40 percent.

Thermoelectricity is the "hot and cold" issue of physics. Heating one end of a wire, for example, causes electrons to move to the cooler end, producing an electric current. In reverse, applying a current to the same wire will carry heat away from a hot section to a cool section.

The grains and irregularities of the reconstituted nano alloy dramatically slowed the passage of heat through the material, radically transforming thermoelectric performance by blocking the heat flow while allowing electrical flow.

Thermoelectric materials have been used by NASA to generate power for spacecraft, and by speciality car seat makers to keep drivers cool during the summer.

The auto industry has been experimenting with ways to use thermoelectric materials to convert waste heat from a car exhaust systems into electric current to help power vehicles.