Scientists are hopeful that solid-state thermophotovoltaic cells with no moving parts can achieve higher efficiency when it comes to converting heat into electricity, and lead the way to power grids based entirely on renewable sources.
A new world record of 40 percent efficiency has been set by a TPV cell. The steam turbine used to turn heat into electricity typically maxes out at 35 percent and has upper-temperature limits too.
White-hot heat sources are converted into electricity by TPVs. When combined with thermal batteries, they could keep the Sun's energy out of sight and release electricity when needed.
One of the advantages of solid-state energy converters is that they can operate at higher temperatures with lower maintenance costs because they have no moving parts, according to mechanical engineer Asegun Henry from the Massachusetts Institute of Technology.
They just sit there and generate electricity.
The thermophotovoltaic cell involved in the record-breaking conversion can generate electricity from heat sources at temperatures of 1,900 to 2,400 degrees Celsius. The moving parts of the steam turbine make it too hot to work at.
The cells are more viable now that their efficiency is rising. The previous record was 32 percent efficiency, while most TPV cells have hovered around the 20 percent efficiency rate.
The efficiency record was measured using a heat flux sensor to measure the heat absorbed by the cell, which is around a centimeter squared in size. A high-temperature bulb was used to vary the amount of heat that the cell was exposed to, revealing that it was suitable to be fitted into a larger system.
Henry says that they can get a high efficiency over a broad range of temperatures.
The materials used have a low bandgap that allows electrons to cross for electricity to be generated. The researchers have used higher bandgap materials.
Three layers are used, a high bandgap alloy to capture high-energy photons to turn them into electricity, a low bandgap alloy to capture low-energy photons that slip through the first layer, and a gold mirror to reflect the light that has passed through.
With the TPV cell now proven to be operational, reliable, and efficient, scientists can get on with the work of scaling it up and combining it with other elements to form a full energy production system.
Henry says that the last key step toward demonstrating that thermal batteries are a viable concept was thermophotovoltaic cells.
The research has been published.
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