a high-stage thermophotovoltaic cell converts 40% of thermal energy into electricity

a high-stage thermophotovoltaic cell converts 40% of thermal energy into electricity

TPV cells could enable “dispatchable” renewable energy

A team of engineers from MIT and the National Renewable Energy Laboratory (NREL) approached a fully carbon-free network with the design of a highly efficient thermophotovoltaic (TPV) cell that converts heat into electricity with over 40% efficiency.

For over 100 years, steam turbines have been used to obtain electricity from heat sources such as coal, natural gas, nuclear power and concentrated solar power. However, steam turbines rely on moving parts that cannot operate after a certain temperature. While they can convert around 35% of a heat source into electricity, the machines get too hot after 2,000°C (3,600°F).

Unlike a steam turbine, this revolutionary TPV cell has no moving parts and can convert approximately 40% of a heat source into electricity. It also operates from 1900°C to 2400°C (4300°F).

“One of the advantages of solid-state power converters is that they can operate at higher temperatures with lower maintenance costs because they have no moving parts. Jhey, just sit there and reliably generate electricity, ‘ says Asegun Henry, Robert N. Noyce Professor of Career Development in MIT’s Department of Mechanical Engineering.

Thermophotovoltaics works by converting heat into electricity via photons. “Like solar cells, TPV cells could be made from semiconductor materials with a particular band gap, the gap between a material’s valence band and its conduction band. If a photon with high enough energy is absorbed by the material, it can send an electron across the band gap, where the electron can then conduct, and thus generate electricity. explains the MIT news desk.

Previous TPV cells used relatively low bandgap materials, which convert photons at low temperature and low energy, and therefore convert energy less efficiently. What makes this design more efficient is the use of higher band gap materials and a higher temperature heat source to capture higher energy photons.

a high-stage thermophotovoltaic cell converts 40% of thermal energy into electricity
diagram showing how thermal energy could be stored, converted and distributed

Researchers want to turn the thermophotovoltaic cell into a grid-scale thermal battery that would be used in conjunction with renewable energy sources such as solar. Excess energy on a sunny day would be stored in heavily insulated hot graphite banks. The TPV cells would then convert the stored thermal energy into electricity on days when there is no sun, thus enabling “dispatchable” renewable energy.

“Thermophotovoltaic cells were the last key step in demonstrating that thermal batteries are a viable concept,” Henry continues. “This is an absolutely critical step on the path to proliferating renewables and achieving a fully carbon-free grid.”

To achieve this, the experimental TPV cell would have to be massively enlarged by one square centimeter to 930 m². However, Henry notes that the infrastructure to build cells on this scale already exists to make large-scale photovoltaic cells.

“There is definitely a huge net benefit here in terms of sustainability,” adds Henry. “The technology is safe, environmentally friendly in its life cycle and can have a significant impact in reducing carbon dioxide emissions from power generation.”

The research has been published in the online journal Nature.

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