Solar thermal power

MIT researchers and their collaborators have come up with an unusual, high performance and possibly less expensive way of turning the sun's heat into electricity.

Their system, described in a paper published online in the journal Nature Materials on May 1, produces power with an efficiency roughly eight times higher than ever previously reported for a solar thermoelectric device — one that produces electricity from solar heat.

It does so by generating and harnessing a temperature difference of about 200 degrees Celsius between the interior of the device and the ambient air. While solar thermal electricity systems aren’t a new idea, they typically involve vast arrays of movable mirrors that track the sun and focus its rays on a small area. The new approach uses flat, stationary panels similar to traditional solar panels, eliminating the need for tracking systems.

Like the silicon photovoltaic cells that produce electricity when struck by sunlight, the new system is a solid-state device with no moving parts. A thermoelectric generator, placed inside a vacuum chamber made of glass, is covered with a black plate of copper that absorbs sunlight but does not re-radiate it as heat. The other side of the generator is in contact with ambient temperatures. Placed in the sun, the entire unit heats up quickly, even without facing the sun directly.

The device requires much less material than conventional photovoltaic panels, and could therefore be much less expensive to produce. It can also be integrated into solar hot water systems, allowing the expenses of the structure and installation to serve two functions at once. Because it can be piggybacked onto the existing solar hot-water industry, the thermoelectric device could be a relatively inexpensive addition, with no subsidies required, says the team.