California Sunburn Inspiration Leads to Advanced Molecular Solar Thermal Energy Storage System
A chemistry professor at the University of California, Santa Barbara, has unveiled a new molecular solar thermal (MOST) energy storage system, drawing inspiration from the way DNA molecules in human skin react to ultraviolet light. The system, detailed in a paper published in February, demonstrates an energy density of 1.65 megajoules per kilogram, exceeding that of conventional lithium-ion batteries.
Professor Grace Han, noting her own experience with California's intense sun, realised that the shape-shifting property of DNA molecules upon UV exposure, and their subsequent repair mechanism involving the photolyase enzyme, could be adapted for energy storage. Scientists have long sought molecules capable of storing energy by changing shape and releasing it on demand, a process analogous to setting and triggering a mousetrap for heat generation.
Energy Density Achievement and Operational Challenges
Han and her team achieved a significant leap in energy density, a factor that impressed fellow MOST experimenter Kasper Moth-Poulsen, who confirmed the 1.6 MJ/kg figure as “really amazing” compared to previous systems. The new system proved powerful enough to rapidly boil a small amount of water in a vial during testing.
However, the current iteration presents operational limitations. The system requires a specific 300-nanometre wavelength of UV light for activation, a harsh form only present in small quantities from the sun. Furthermore, the release of stored energy is currently triggered by hydrochloric acid, a corrosive substance necessitating neutralisation after use. Han acknowledges this is “not the most ideal choice” but expresses optimism regarding future improvements in light responsiveness and the development of non-toxic release mechanisms.
Future Prospects for Decarbonising Heating
The ultimate objective of MOST technology is to decarbonise heating, a sector heavily reliant on fossil fuels. Moth-Poulsen highlights that MOST systems operate without combustion and can be deployed globally, unlike fossil fuels, which are concentrated geographically. He also noted the potential for multi-decade energy storage, far exceeding the lifespan of conventional thermal storage.
Despite the scientific achievement, scepticism persists regarding MOST's broad applicability. Harry Hoster, from the University of Duisberg-Essen, points out that the light-sensitive molecules require thin layering, limiting the system's thickness to an estimated 5mm in an optimistic scenario. The reliance on liquid-based systems also introduces complexity and potential points of failure through pumping requirements. While Hoster doubts MOST could heat an entire building, he suggests niche applications such as warming temperature-sensitive components in satellites or aircraft. Researchers, including Han, are exploring solid-state versions, potentially as transparent window coatings, to address these challenges. The field remains niche, as evidenced by a recent conference attracting only around 70 attendees globally, yet the scientific promise is clear.