Saving heat until you need it
MIT researchers have demonstrated a new way to store unused heat from car engines, industrial machinery, and even sunshine until it’s needed. Central to their system is what the researchers refer to as a “phase-change” material that absorbs a large amount of heat as it melts and releases it as it resolidifies. Once melted and activated by ultraviolet light, the material stores the absorbed heat until a beam of visible light triggers solidification and heat release. Key to that control are added molecules that respond to light by changing shape from one that impedes solidification to one that permits it. In a proof-of-concept experiment, the researchers kept a sample mixture in liquid form down to room temperature — fully 10 degrees Celsius below where it should have solidified — and then, after 10 hours, used a light beam to trigger solidification and release the stored thermal energy. More than half of all the energy used to...