New method improves the storage and use of solar energy
As reported by the International Energy Agency (IEA), around 50 percent of global energy consumption is attributed to heating, but solar energy’s contribution to this sector remains minimal compared to that of 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 holds energy in short-lived forms such as warm water, molecular systems can store energy in 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 sunlight absorption efficiency.
Researchers from the Johannes Gutenberg University Mainz (JGU) and the University of Siegen have developed a new class of photoswitches with high energy storage potential, initially developed by Professor Heiko Ihmels’ team in Siegen. Originally, these photoswitches relied on activation of UV light, a small segment of the solar spectrum. Now the teams from Mainz and Siegen have integrated an indirect light harvesting approach that functions similarly to photosynthesis. This method involves a secondary compound, or ‘sensitizer’, that effectively absorbs visible light. “The sensitizer absorbs light and then transfers energy to the photoswitch, which cannot be directly excited under these conditions,” explains Professor Christoph Kerzig from the JGU Department of Chemistry.
This approach has increased storage efficiency more than tenfold, which represents an important advance for solar energy research. The potential applications of this technology range from home heating to large-scale energy storage, paving a promising route to sustainable energy solutions.
Led by Professor Kerzig and PhD student Till Zahringer, the research team from Mainz carried out detailed spectroscopic analyzes to decode the mechanics of the system. Till Zahringer, the lead author of the study, examined each reaction phase to gain a clear understanding of the system’s functionality. “This process not only expanded the light-collecting capacity, but also increased the efficiency of converting light into stored chemical energy,” Zahringer explains. Through repeated cycling between storage and release states using sunlight, the researchers validated the robustness and suitability of the system for practical applications.
The research was published in *Angewandte Chemie* and was classified as a “Hot Paper” thanks to the rave reviews from scientific reviewers.
Funding for this project was provided by the German Research Foundation (DFG) and the German Federal Environmental Foundation, with a project grant to Christoph Kerzig and a grant to Till Zahringer. Additional support came from the House of Young Talents of the University of Siegen and the Stiftung Nagelschneider.
Research report:Triplet-sensitized switching of high energy density norbornadienes for molecular storage of visible light solar thermal energy
