Engineers at Massachusetts Institute of Technology and the United States National Renewable Energy Lab designed a heat engine with no moving parts. Their new demonstrations show that it converts heat to electricity with over 40 percent efficiency a performance better than that of traditional steam turbines. The researchers plan to incorporate the thermophotovoltaic cell (TPV) into a grid-scale thermal battery. The system would absorb excess energy from renewable sources such as the sun and store that energy in heavily insulated banks of hot graphite. When energy is needed, like on overcast days, TPV cells can convert the heat into electricity, and dispatch the energy to a power grid. The hope is that this innovation will be scaled up and allow this system to replace fossil fuel-driven powerplants and enable a fully decarbonized power grid, supplied entirely by renewable energy.