Researchers Make Breakthrough in Capturing, Storing Solar Energy

Anders Bo Skov, a master’s student in chemistry at the University of Copenhagen, is working with photochromic molecules -- specifically, Dihydroazulene (DHA) and Vinylheptafulvene (VHF). What’s interesting about these types of molecules is that they store energy by changing shape and then release that energy by changing their shape back after a period of time and losing some of the energy.

During the early stages of his research, the molecules would change shape after an hour or two. However, Skov has developed a system based on these molecules that can store energy for more than 100 hours before releasing the energy, with only a small amount of energy loss, he told Design News in an email.

Anders Bo Skov is a master’s student in chemistry at the University of Copenhagen. He’s made a significant breakthrough in how to store solar energy, developing molecules that can take energy from the sun, store it, and then release it for later use.
(University of Copenhagen)

“When we irradiate DHA it stores some of the energy as VHF, which releases the energy and returns to the DHA structure after a period of time,” Skov wrote. “If we hope to use the system for solar energy storage, the time scale of storage (114 years) is so long, that the background loss of energy with time is negligible.”

Skov has co-written a paper, “Towards Solar Energy Storage in the Photochromic Dihydroazulene-Vinylheptafulvene System,” with his research supervisor Mogens Brøndsted Nielsen that will be published in Chemistry – A European Journal.”

He described to us the ins and outs of how the DHA-VHF system -- what is called a “closed-cycle storage of solar energy” would work in a real-world application:

In the second application of the system, which removes the catalyst, the liquid with material will instead be charged completely and will stay as the VHF for as long as needed before returning and gradually releasing the energy, Skov wrote. “Once the catalyst is returned to the tubing system, the energy will be released, and heat can be released, even after standing for years,” he told us. “It is in the latter application that our system excels.”

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There are a number of advantages to this type of solar energy storage to the types of water- and hydrogen-based storage methods being used and developed today, Skov told us.

“Modern solar cell applications works (to my knowledge) by creating electricity to be sent straight to the electricity grid, or it is stored by heating a water tank, and using the hot water later,” he wrote. “Future alternatives could include electrolysis of water and storage of the energy as hydrogen gas. However, all of these storage forms have drawbacks in that the water loses the heat too fast to store for more than a few hours, and hydrogen gas is very dangerous to store. So the advantage of our material is that the energy is stored over a significantly longer period without any losses to speak of, while being completely safe to store.”

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Another benefit to Skov’s system is that it’s made from organic materials, which makes it less expensive to manufacture than current solar cells typically used. However, one obstacle to refining and manufacturing the system is that there remains the lack of a proper catalyst for releasing the energy on demand, “so we are not looking at the final form of the material yet,” he wrote.

The system also has a challenge to implementation in that it still lacks the type of energy storage capacity desired in a modern solar energy system, Skov told us. “In the energy-perspective the system does not excel, as we have only reached around 25% of the optimal amount,” he wrote. The research team is working on building the material to improve on storage capacity, as well as trying to find a suitable catalyst that is material as well as environmentally friendly.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She has lived and worked as a professional journalist in Phoenix, San Francisco, and New York City. In her free time she enjoys surfing, traveling, music, yoga, and cooking. She currently resides in a village on the southwest coast of Portugal.

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