Researchers have developed a new thermophotovoltaic cell capable of converting heat into electricity with unprecedented efficiency, allowing them to surpass traditional steam turbines.
Efficiency greater than 40%
The thermophotovoltaic cells (POS) are usually made from semiconductor materials that have a narrow bandgap, determining the energy that electrons must acquire to reach the conduction band. When such devices absorb high-energy photons, they can send electrons across the band gap and thus generate electricity.
Featured in the magazine Naturethe new cell POS developed by the MIT and the National Renewable Energy Laboratory (NREL) is able to operate at higher temperatures (up to 2,400°C), allowing it to achieve efficiency greater than 40% compared to 32% for its predecessors. This consists of three layers: a metal alloy with a high band gap placed above an alloy with a slightly lower band gap, under which there is a layer of gold acting as a mirror.
The high bandgap layer captures the most energetic photons from a heat source and converts them into electricity, while the lower energy photons passing through it are captured and converted by the second. The particles of light that manage to cross the latter are in turn returned by the mirror layer to the heat source in order to avoid any waste of energy.
Although they offer similar efficiency, steam turbines are much more complex (they have moving parts that must be regularly inspected and replaced) and also have lower operating temperatures. making cells POS advantageous alternatives, capable of producing electricity reliably.
“TPV cells were the last key step to demonstrate that thermal batteries are a viable concept”
According to the team, the large-scale use of thermal batteries exploiting this approach would allow excess energy from renewable sources to be absorbed, which would be stored on a graphite medium. When needed, the cells POS could convert this heat into electricity and feed it back into the power grid.
If it will be necessary to reach an area of about 900 m² for a system of thermal batteries on the scale of an electrical network (the cells POS experimental tubes used in the study measured only 1 cm²), the team points out that the necessary technology already exists.
” TPV cells were the last key step to demonstrate that thermal batteries are a viable concept “, valued Asegun Henry, lead author of the study. ” These pave the way for the generalization of renewable energies and a completely carbon-free network.. »
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