Development of a Novel Energy Storage Method Inspired by Sunburn
The energy storage method using molecules that capture heat has emerged as a promising technology to help decarbonise heating. This innovative approach was inspired by the experience of chemistry professor Grace Han, who noticed how her skin reacted to the strong sun in southern California. Her observations led to exploring how molecules in human skin change shape when exposed to sunlight, a process that can be harnessed for energy storage.
How Sunburn Inspired Molecular Solar Thermal Energy Storage
When exposed to ultraviolet (UV) light, DNA molecules in the skin undergo a shape change, flexing into a strained form. This natural process, which can cause sunburn, involves molecules storing energy in their altered shape. Scientists have long sought molecules capable of twisting their shape to store energy and then releasing it on demand by reverting to their original form. This concept is known as molecular solar thermal (MOST) energy storage.
MOST systems offer a potentially cheap and emissions-free way to supply heat, with the ability to store energy for months or even years. Professor Han realized that the DNA molecules in skin, which have evolved to repair their sun-damaged shape with the help of an enzyme called photolyase, could serve as ideal candidates for MOST systems. These molecules are very small but can store a large amount of energy per mass.
Recent Advances and Performance of the Energy Storage Method
In a paper published in February, Han and her colleagues described a MOST system with an energy density of 1.65 megajoules per kilogram, surpassing that of lithium-ion batteries commonly used in phones and electric cars. The system was powerful enough to rapidly boil a small amount of water in a vial, demonstrating its practical energy release capability.
The success of this work was supported by computer analyses predicting molecular performance, conducted by collaborators at the University of California, Los Angeles. Independent experts in the field have noted the impressive energy density achieved, which exceeds previous records.
Challenges and Future Directions for the Energy Storage Method
Despite its promise, the MOST system developed by Han and her team has some limitations. The molecular shape change is triggered by harsh UV light at a wavelength of 300 nanometres, which is present in only small amounts in natural sunlight. Additionally, the energy release requires hydrochloric acid, a corrosive chemical that must be neutralized after use, making it less ideal for practical applications.
Researchers are hopeful about improving the system to respond better to natural light and to trigger energy release without toxic chemicals. The ultimate goal is to create a sustainable energy storage solution that can help reduce reliance on fossil fuels for heating, a sector that remains difficult to decarbonise.
MOST technology operates without combustion and can be deployed anywhere on Earth, unlike fossil fuels that are geographically concentrated. It also offers the potential for long-term energy storage, possibly lasting decades, which is a significant advantage over conventional thermal storage methods.
Considerations for Practical Implementation
Experts note that the light-sensitive molecules in MOST systems must be arranged in thin layers to allow light penetration, with thicknesses likely limited to a few millimetres. Using liquids to contain these molecules introduces complexity and cost due to the need for pumping and moving the fluid within the system.
Research is ongoing into solid-state versions of MOST technology, which could be applied as transparent window coatings to release heat for preventing condensation or warming rooms. While MOST may not provide all the heating needs of a building, it could be useful for warming temperature-sensitive components in satellites or aircraft.
The field of MOST energy storage remains relatively niche, with a small global research community. Continued innovation and research are expected to address current challenges and expand the technology’s applications.