Soon, batteries that could store sun’s heat instead of electricity

WASHINGTON - MIT researchers have discovered how a molecule works to store and release heat on demand - a find that could form the basis of a rechargeable battery to store heat rather than electricity.

The molecule called fulvalene diruthenium into a higher-energy state after absorbing sunlight, and can remain stable indefinitely. Then, triggered by a small addition of heat or a catalyst, it snaps back to its original shape, releasing heat in the process.

However, in an intermediate step, the molecule forms a semi-stable configuration partway between the two previously known states.

The two-step process helps explain why the molecule is so stable, why the process is easily reversible and also why substituting other elements for ruthenium has not worked so far.

Jeffrey Grossman said that in effect, this process makes it possible to produce a “rechargeable heat battery” that can repeatedly store and release heat gathered from sunlight or other sources.

In principle, Grossman said, a fuel made from fulvalene diruthenium, when its stored heat is released, “can get as hot as 200 degrees C, plenty hot enough to heat your home, or even to run an engine to produce electricity.”

“It’s reversible, and it’s stable over a long term. You can use it where you want, on demand. You could put the fuel in the sun, charge it up, then use the heat, and place the same fuel back in the sun to recharge.”

The problem of ruthenium’s rarity and cost still remains as “a dealbreaker,” Grossman said, but now that the fundamental mechanism of how the molecule works is understood, it should be easier to find other materials that exhibit the same behaviour.

“It’s my firm belief that as we understand what makes this material tick, we’ll find that there will be other materials” that will work the same way,” Grossman said.

The paper was published on Oct. 20 in the journal Angewandte Chemie. (ANI)