New method enhances solar energy storage and utilization

New method enhances solar energy storage and utilization

by Robert Schreiber

Berlin, Germany (SPX) Oct 30, 2024

As reported by the International Energy Agency (IEA), about 50 percent of global energy consumption is attributed to heating, yet solar power’s contribution to this sector remains minimal compared to fossil fuels. One reason is the sporadic availability of solar energy. A promising alternative is molecular solar energy storage systems. Unlike conventional thermal storage, which retains energy in short-lived forms like hot water, molecular systems can store energy within chemical bonds for weeks or even months. These systems use photoswitch molecules to absorb solar energy and release it as heat on demand. However, current photoswitches face a trade-off between energy storage capacity and solar light absorption efficiency.

Researchers at Johannes Gutenberg University Mainz (JGU) and the University of Siegen have developed a new class of photoswitches with high energy storage potential, initially pioneered by Professor Heiko Ihmels’ team at Siegen. Originally, these photoswitches relied on UV light activation, a small segment of the solar spectrum. Now, the Mainz and Siegen teams have integrated an indirect light harvesting approach that functions similarly to photosynthesis. This method includes a secondary compound, or “sensitizer,” which effectively absorbs visible light. “The sensitizer absorbs light and subsequently transfers energy to the photoswitch, which cannot be directly excited under these conditions,” explained Professor Christoph Kerzig from the JGU Department of Chemistry.

This approach has increased storage efficiency by more than tenfold, marking an important advancement for solar energy research. The potential applications of this technology range from residential heating to large-scale energy storage, paving a promising route toward sustainable energy solutions.

Under the guidance of Professor Kerzig and PhD student Till Zahringer, the Mainz research team carried out detailed spectroscopic analysis to decode the system’s mechanics. Till Zahringer, the study’s lead author, examined each reaction stage to build a clear understanding of the system’s functionality. “This process not only expanded the light-harvesting capacity but also boosted the efficiency of converting light to stored chemical energy,” explained Zahringer. Through repeated cycling between storage and release states using solar light, the researchers validated the system’s robustness and suitability for practical applications.

The study was published in *Angewandte Chemie*, earning classification as a “Hot Paper” due to high praise from scientific reviewers.

Funding for this project was provided by the German Research Foundation (DFG) and the German Federal Environment Foundation, with a project grant awarded to Christoph Kerzig and a fellowship to Till Zahringer. Additional support came from the University of Siegen’s House of Young Talents and the Stiftung Nagelschneider.

Research Report:Triplet-Sensitized Switching of High-Energy-Density Norbornadienes for Molecular Solar Thermal Energy Storage with Visible Light