The sun is always hanging in space, blasting out more energy than we could even use here on Earth. However, sunlight is much less consistent at ground level. You have to contend with nighttime, clouds, and inclement weather to use solar energy, and that means storing it. Researchers from MIT have developed a material that might make it feasible to store energy from the sun as heat that can be released on-demand.
Most methods for storing solar energy are based on batteries, which have been notoriously slow to improve. This new material could make the process more efficient by storing energy via a chemical reaction for later release as heat. At that time, you could use the heat for anything you want. It’s an incredibly adaptive material as well, in the form of a transparent polymer film. It could be built into car windshields to remove ice, or as a layer in your favorite sweater to keep you warm on a chilly day.
Researchers were able to create this material with the aid of a molecule that exists in two states, one of which can store significant energy. The material is what’s known as a solar thermal fuel (STF), which have been developed in the past. However, this one is different (and more useful) in that it’s actually functional in a solid material. Past STF molecules were only active in a liquid phase suspension.
When exposed to sunlight, an STF flips to a charged state. It can remain “charged” for several days. The molecules can then be triggered on demand with a small temperature increase or some other stimulus to release that energy as heat. You won’t be boiling water with this system right now, but it’s still impressive for an early design. The polymer film designed at MIT can currently release a burst of heat about 10 degrees Celsius warmer than the surrounding environment (about 18 degrees F).
The researchers are using a car windshield application as a way to test viability of the material. It would consist of a single layer of STF film sandwiched between two layers of glass. It’s a straightforward, but potentially quite useful application of the technology. It’s illegal to embed opaque heating wires in front windshields as many cars have in the rear, but the transparent STF film could be even more effective anyway. Testing shows that the burst of heat from a “charged” STF film is enough to melt the ice from a car windshield.
The team believes that it can raise the heat output of the material to as much as 20 degrees C above room temperature with some more fine tuning. They’ll also work to improve its transparency. Right now it has a slight yellowish tint. At that point, it could make a significant impact on electric cars, which use a large amount of their battery power to de-ice windows with electric heaters — and that’s only the start.
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