The main problem with most sources of renewable energy is that they’re intermittent – the wind doesn’t always blow and the sun doesn’t always shine – and storage isn’t very efficient, but for at least some applications a novel use of switching material could make it possible to use solar energy 24 hours a day.

MIT Photoswitches

A team of researchers from MIT and Harvard University have found a specific type of molecule that can efficiently absorb solar energy and then release it as heat on demand.

Photowitches could be a game changer

“It could change the game, since it makes the sun’s energy, in the form of heat, storable and distributable,” says co-author Jeffrey Grossman,

The photoswitches that Grossman and lead author Timothy Kucharski write about in their recent Nature Chemistry article change configuration when exposed to sunlight, and will then maintain that new configuration until a jolt of energy snaps them out of it, causing them to release the stored energy as heat.

For applications that need electricity or a lot of power (electronics, any type of engine) the photoswitches aren’t going to cut it. But anything that just needs heat to operate is fair game. Grossman specifically mentions solar heating, which could replace the wood and dung which are still used for cooking in many developing countries. This would save money (after the initial investment is recouped), but it could also alleviate a major environmental harm.

The photoswitches aren’t yet ready for commercial production, but now that the underlying concept has been worked out it’s just a matter of improving efficiency.

“Now we’re looking at whole new classes of solar thermal materials where you can enhance this interactivity,” says Grossman.

Photoswitches could reduce seasonal change in demands on power supply

The fact that solar energy is only available during the day, and it is most productive in the summer while energy demand is higher in the winter is a problem. The result is that every year the power supply goes up just when demand is falling, and traditional power plants become unprofitable. Since those facilities are necessary to maintain an adequate power supply year-round, nations that have invested heavily in solar have to find ways to keep unprofitable power plants in business.

That’s why photoswitches in particular are so interesting. It’s mostly heating that drives the winter increase in energy usage, which is exactly what photoswitches provide. A decentralized system of photoswitches powering central heating and water heaters could reduce the seasonality of electric demand that currently caps the amount of solar that a national can realistically use.