Interestingly, the material can be activated with light and then release the collected energy on demand in the form of heat. Researchers began their work with organometallic structures (MOF - metal-organic framework), i.e. materials famous for their porosity and, consequently, their huge surface. This allows them to stick to a huge number of molecules, making them great at desalinating and filtering water, capturing carbon dioxide from the air, and delivering medicine to the body. In this new study, scientists from Lancaster decided to go a step further and see how MOF would handle energy storage.
The team started with a version of the material called DMOF1 and loaded its pores with azobenzene molecules, an ingredient famous for its phenomenal ability to absorb light that causes molecules to all about movies change shape. When a material is exposed to ultraviolet light, the particles bend into an unnatural shape and would normally return to their original state when the light is turned off, but this time the tiny pores of the MOF cause them to be trapped in their new form, storing their potential energy in a manner similar to a compressed one springs.
When it is time to receive this energy, the material is slightly heated, so that it quickly releases stored energy in the form of heat - importantly, the heat released is much higher than the initial temperature, so we have a profit. And since it is a mechanical process, it does not require any external power to store energy, which can be held at room temperature for a very long time. During the research, scientists kept this energy for 4 months, but they estimate that we can speak of up to 4.5 years. As for potential applications, scientists aim at capturing solar energy during the day and returning it as heat at night, or storing summer energy for winter uses, etc.
Admittedly, the material has a low energy density so far, but the team is working hard to fix it quickly: “The material acts a bit like the phase-changing materials in hand warmers. However, the heaters need to be heated to restore them to function, the MOF has the nice feature of capturing "free" energy straight from the sun. There are also no moving or electronic parts, so there is no waste involved in storing and releasing solar energy. We hope that future development will allow us to create more materials that will store more energy, the researchers explain.