Thermophotovoltaic cell converts 40 percent of heat energy to electricity

A new thermophotovoltaic cell that converts heat to electricity with over 40 percent efficiency is nearly identical to traditional steam turbine power plants. The cells have the potential to be used in grid-scale thermal batteries, generating energy with no moving parts.

The heating of semiconducting materials increases the energy of the light. The photos can kick an electron across the bandgap, generating electricity. TPV cells have a low efficiency because they operate at lower temperatures.

The new design from MIT and the NREL takes power from white-hot heat sources between 1,900 to 2,400 degree Celsius. To do that, it uses high-bandgap metal.

The high-bandgap layer captures the highest-energy photons from a heat source and converts them to electricity, while lower-energy photons pass through the first layer and add to the voltage. The two-layer gauntlet has a mirror back to the heat source that reflects any photons that run it.

This is an absolutely critical step on the path to proliferate renewable energy and get to a fully decarbonized grid.

The team found that the power varied with the temperature. Between 1,900 to 2,400 degrees Celsius, the new TPV design produced electricity with a 40 percent efficiency.

The same efficiency can be achieved with steam turbine, but they are far more complicated and restricted to lower temperatures.

In a grid-scale thermal battery, excess energy from renewable sources like the sun would be absorbed and stored in heavily insulated banks of hot graphite. The heat could be converted to electricity by the TPV cells. The technology already exists to create cells on that scale, so the team would have to ramp that up to around 10,000 square feet for grid-level power.

He said that thermal batteries are a viable concept, and that the last key step was thermophotovoltaic cells.