MIT Reveals a Battery That Stores Solar Energy to Make Heat for Later

Researchers have developed a battery-like system can store solar energy and release heat when needed. The technology could provide a new energy source for communities in the developing world that don’t depend on the grid, or create a power system for people who live in cities who want to limit the amount of electricity they use.
The MIT scientists have developed a chemical composite that only releases stored energy when it reacts to light, a system that could take wasted energy from heavy machinery and use it later for cooking or heating a room.
“There are so many applications where it would be useful to store thermal energy in a way lets you trigger it when needed,” says professor Jeffrey Grossman, who worked on the project with MIT postdocs Grace Han and Huashan Li. The team’s findings have been published in this week’s Nature Communications.
The research comes at a point when decentralized renewable energy is growing as an alternative to the grid-based model of old. More and more people are exploring ways to sever ties from the energy grid, particularly in the wake of recent hurricanes that have hit local infrastructure.
Advancements in battery technology are helping to store up locally-generated energy.
MIT’s development uses a phase change material as its starting point. These store up energy when exposed to heat and turn into liquid, but they need a lot of insulation to avoid losing that energy. They’re also not that dependable, with a habit of unexpectedly turning back to solids and releasing their energy due to temperature changes.
With this new “battery,” the fatty acids that act as a phase change material are paired with an organic compound that responds to light. The arrangement melts when heated like normal, but when exposed to ultraviolet light it stays melted even after it’s taken away from the heat. A second light pulse activates the compound and causes the acids to return to their pre-heated solid state, releasing the thermal energy as they change back.