German scientists investigate molecular storage of solar energy – pv International magazine

November 27, 2024
Patrick Jowett

A German research group led by Goethe University in Frankfurt is conducting research on MOST energy storage.

Still in its infancy, MOST energy storage is described as a method of storing solar energy similar to a thermal battery but incorporating a large number of synthetically produced molecules.

The Formost research project, implemented in 2023–2027, investigates the molecular mechanisms of energy storage and release in MOST molecules.

MORE molecules undergo structural changes when exposed to sunlight in a process known as a photoinduced reaction. The structural change is where the molecules absorb energy when exposed to light, which can be released again later because the molecules have an on-off function, leading to them being referred to as photoswitches.

As part of the Formost project, scientists are investigating three types of photoswitches: norbornadienes, azaborines and azobenzenes.

“Under the influence of light, all three transform from their ground state to a higher energy storage state, thus changing their molecular structure and, in some cases, also their color,” Goethe University said in a press note.

Research has already shown that MOST molecules, which are composed mainly of carbon, oxygen, nitrogen and hydrogen, have several advantages.

“All stages – energy conversion, storage and release – are united in one molecule,” explained Josef Wachtveitl, head of the Wachtveitl group involved in the project.

Researchers from Goethe University found that in side-by-side comparisons, MOST energy storage outperforms conventional solar heat storage. Molecules that must be activated to release heat enable energy to be delivered on demand. The system, completely carbon neutral through storage, conversion and release, allows heat to be stored for weeks or months, depending on needs.

“MOST gives us much more flexibility in storing solar heat,” Wachtveitl said. He added that because all processes occur inside a single molecule, MOST heat storage systems can be placed anywhere, eliminating the need for a large manufacturing facility.

Work on the Formost project will continue, with researchers looking at modifying the molecules to obtain the best MOST storage properties. This will include trying to modify the photoswitches so that they can absorb visible light, as they currently tend to only absorb in the UV range where it borders on visible light, and assessing the charging processes in the photoswitches.

The Formost project is a collaboration between Goethe University and the universities of Tübingen, Giessen, Heidelberg and Erlangen in Germany.

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