An updated device offering record-high thermal-to-power conversion efficiency could lead to thermal batteries for power grids. This “heat engine,” developed by engineers at MIT and the National Renewable Energy Laboratory, is a solid-state device with a thermophotovoltaic (TPV) cell. It is optimized to absorb photons from high-temperature sources, converting them into electricity with 40% efficiency. TPVs have minimal environmental impact and could generate affordable power, because they are inexpensive to make and have no moving parts, and require little maintenance. Absorbing surplus renewable energy, the system would work by dramatically heating up insulated banks of materials such as graphite. That stored heat would be released according to power demand and converted into electricity. A large-scale system would need TPV cells the size of a quarter of a football field, but current ones are about a square centimeter.
Next Generation Batteries