A research team from MIT and the National Renewable Energy Laboratory (NREL) has successfully developed and demonstrated a thermophotovoltaic (TPV) cell capable of converting heat into electricity more efficiently than conventional steam turbines. And the cost is low. This has huge implications for future power stations and grid energy storage.
Thermophotovoltaics (TPV) mainly converts light at infrared wavelengths into electrical energy through the photovoltaic effect, and can realize methods of energy storage and conversion. The researchers plan to integrate such TPV cells into grid-scale thermal batteries. The system will absorb excess energy from renewable sources such as solar energy and store this energy in a highly insulated thermal graphite reservoir. When energy is needed, such as on cloudy days, the TPV battery converts the heat into electricity and distributes the energy to the grid.
It is well known that most of human electricity comes from thermal energy, i.e. burning coal or natural gas, nuclear fission, concentrated solar energy, which is used to boil water and spin steam turbines to produce electricity. Over the past century and a half, it has become ubiquitous around the world as a mature, well-optimized technology with known strengths and limitations.
One of the limitations is efficiency. While some turbines have successfully converted 60% of the energy of a heat source into electricity, the average turbine operates at only 35% efficiency. Another limitation is heat, and steam turbines rely on components that must operate at certain temperature thresholds.
The new design aims to capture higher-energy photons from higher-temperature sources, thanks to the use of higher-bandgap materials and multiple junctions. In tests between 1900 degrees Celsius and 2400 degrees Celsius, the new TPV cells maintained about 40 percent efficiency. The average efficiency of early TPV cells was around 20%, and the previous record for the highest efficiency was 32%.
The 40% efficiency of TPV is notable because it now makes TPV a heat engine technology that can compete with turbines. 40% efficiency is already higher than the average efficiency of turbine-based heat engines in the United States, but TPVs are more attractive than turbines for their potential for lower cost, faster response times, simple maintenance, ease of integration with external heat sources, and fuel flexibility .
Operating in a temperature range "suitable for natural gas or hydrogen combustion," the new heat engine technology is understood to hold promise for the next generation of low-emission power plants that can operate at lower cost from combustion sources Extract more power. In the case of green hydrogen, such a plant could emit no carbon.
"Thermal photovoltaic cells are the final critical step in proving that thermal batteries are a viable concept," said MIT professor of mechanical engineering and a researcher on the project. "This is an absolutely critical step on the road to promoting renewable energy and achieving a zero-carbon grid. ."
