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German researchers are testing laboratory molecules designed to absorb, store and release solar energy on demand, acting as “thermal batteries.” The researchers say their method is more effective at storing solar energy than conventional thermal heat storage systems.
Scientists at Goethe University in Germany are investigating the potential of molecular solar thermal energy storage, a high-capacity method for storing solar energy.
Molecular solar thermal energy storage consists of a large number of synthetically created molecules that together store the suns energy and function as a "heat battery."
The molecules contain mainly carbon, oxygen, nitrogen and hydrogen. They do not require rare earth elements, heavy metals or plastic.
Although still in the early stages of development, scientists believe the method could be more effective than conventional thermal heat storage systems, which have used materials such as volcanic rock, sand, molten salt and aluminium. Initial direct comparison tests with these materials have yielded positive results.
According to Josef Wachtveitl, one of the Goethe University scientists involved in the research group, "all steps - conversion, storage and release of energy - are combined in a single molecule," making the process quite simple.
When molecules come into contact with sunlight, their structure changes. This is called a photoinduced reaction. The light causes the molecules to absorb energy, which they later release when they return to their original state away from sunlight.
Currently, researchers are studying three different molecules, which they call photoswitches. They are norbornadienes, azaborines and azobenzenes, all of which were created in the laboratory. When exposed to light, all three change from their basic state to a higher energy storage state, which changes their molecular structure and, in some cases, their colour.
Since heat is stored directly, there are no conversion processes, such as converting electricity into heat. This means that losses that would otherwise occur during any energy conversion are absent, making the process more efficient than the average solar thermal system, the scientists say.
The new method allows “much more flexibility in storing solar heat,” Wachtveitl said. He highlighted its ability to store heat for longer periods and release it on demand – like a switch – compared to normal thermal systems.
Scientists are still fine-tuning some of the molecules features, and several German universities are involved in fine-tuning the process so that it can eventually yield more quantifiable results. The project has a few years left in development. It started in 2023 and will end in 2027, and is receiving total funding of around 4.8 million euros ($5 million) from the German Research Foundation.
Now, however, the method is just beginning to be tested in a real-world setting. For example, molecules are placed on glass surfaces that are later intended to become windows. The glass molecules can store energy during the day and release it again at night. Molecules that can be pumped in a closed loop are also being developed. They could be installed as panels on roofs, where the sun would induce them to switch to their storage state.
According to the scientists, storage systems using molecules can be used in cars, houses, factories and even animal sheds. Because they only use molecules, the systems are decentralized and do not require large production plants. |
