Washington: Scientists are working on generating energy from heat without using sunlight at all.
While the principle involved is not new, engineering the surface of a material to convert heat into specific wavelengths of light, to match the wavelengths that photovoltaic cells can best convert to electricity, makes the new system much more efficient than previous versions.
The key to this fine-tuned emission lies in a material with billions of nanoscale pits etched on its surface, the journal Physical Review A reports.
When the material absorbs heat, whether from the sun, a hydrocarbon fuel, a decaying radioisotope or any other source, the pitted surface radiates energy primarily at these carefully chosen wavelengths.
Based on that technology, MIT researchers have made a button-sized power generator fueled by butane that can run three times longer than a lithium-ion battery of the same weight; the device can then be recharged instantly, just by snapping in a tiny cartridge of fresh fuel, according to an MIT statement.
"Being able to convert heat from various sources into electricity without moving parts would bring huge benefits," says Ivan Celanovic, research engineer in MIT`s Institute for Soldier Nanotechnologies (ISN), "especially if we could do it efficiently, relatively inexpensively and on a small scale".
According to the US Energy Information Administration, 92 percent of all the energy we use involves converting heat into mechanical energy, and then often into electricity -- such as using fuel to boil water to turn a turbine, which is attached to a generator.
But today`s mechanical systems have relatively low efficiency, and can`t be scaled down to the small sizes needed for devices such as sensors, smartphones or medical monitors.