Solar power installations of the future may overcome a fundamental limitation of the current technology by continuing to supply energy even when the sun is not shining, researchers say.
A team of scientists from Harvard University and MIT says they found a solution for cloudy days or even nighttime by developing a material capable of absorbing heat from the sun and storing its energy in a chemical form, then releasing it at a later time to meet demands for either electricity or heat.
While not a particularly efficient way to create electricity, they acknowledge, the new technology could be very useful for situations where the desired form of output is heat.
By providing heat for buildings or for cooking or even powering industrial processes that require heat, the technology could create opportunities for solar power to move into new arenas.
"It could change the game, since it makes the sun's energy, in the form of heat, storable and distributable," MIT material science Professor Jeffrey Grossman says.
The technology is based on a simple molecular phenomenon and a particular class of molecules, dubbed photoswitches, which can take on one of the two shapes, displaying a kind of "hinge" in the center.
When exposed to sunlight, photoswitches absorb its energy and in so doing transform from one shape to the other, remaining stable in the new configuration for an extended period of time.
However, they can be made to trigger and "flop" back to their other configuration with a small input of heat, electricity or light, and during the "flop" will emit heat.
Taking in the sun's energy, storing it for extended periods of time and liberating it to meet demand, they behave as a sort of rechargeable thermal battery.
The findings suggest a range of different photoswitch materials could be used for heat storage.
"Now we're looking at whole new classes of solar thermal materials where you can enhance this interactivity," says Grossman, co-author of the paper describing the research in the journal Nature Chemistry.
Although most solar power research has been directed toward the production of electricity, there are a number of situations were heat could be the more desirable benefit of solar farms or facilities.
In many regions of the globe the primary fuel used for cooking is either dung or wood, both of which can produce indoor pollution that can be a health risk and in the case of wood also leads to deforestation.
Heat from solar power could be a cleaner cooking aid, especially when people wish to cook when the sun isn't out, making the heat-storing nature of the new technology particularly significant.
Heat from solar power, as opposed to burning a fuel, consumes nothing and creates no polluting emissions.