September 29, 2023

New Heat Engine With No Moving Parts Could Fully Decarbonize the Power Grid

A thermophotovoltaic (TPV) cell (size 1 cm x 1 cm) mounted on a heat sink created to measure the TPV cell performance. When the energy is needed, such as on overcast days, TPV cells would transform the heat into electrical energy, and dispatch the energy to a power grid.
Much like solar cells, TPV cells might be made from semiconducting products with a particular bandgap– the space in between a materials valence band and its conduction band. The group evaluated the cells effectiveness by putting it over a heat flux sensor– a gadget that straight measures the heat taken in from the cell. They exposed the cell to a high-temperature light and focused the light onto the cell.

The scientists plan to integrate the TPV cell into a grid-scale thermal battery. The system would take in excess energy from sustainable sources such as the sun and shop that energy in heavily insulated banks of hot graphite. When the energy is needed, such as on overcast days, TPV cells would transform the heat into electricity, and dispatch the energy to a power grid.
With the new TPV cell, the team has now successfully showed the primary parts of the system in separate, small experiments. They are working to integrate the parts to show a totally operational system. From there, they intend to scale up the system to change fossil-fuel-driven power plants and enable a totally decarbonized power grid, supplied completely by renewable resource.
” Thermophotovoltaic cells were the last crucial action toward demonstrating that thermal batteries are a practical concept,” says Asegun Henry, the Robert N. Noyce Career Development Professor in MITs Department of Mechanical Engineering. “This is an absolutely critical action on the course to proliferate eco-friendly energy and get to a totally decarbonized grid.”
Henry and his collaborators have actually published their outcomes on April 13, 2022, in the journal Nature. Co-authors at MIT include Alina LaPotin, Kyle Buznitsky, Colin Kelsall, Andrew Rohskopf, and Evelyn Wang, the Ford Professor of Engineering and head of the Department of Mechanical Engineering, together with Kevin Schulte and collaborators at NREL in Golden, Colorado.
Jumping the gap
More than 90 percent of the worlds electrical energy originates from sources of heat such as coal, gas, atomic energy, and focused solar energy. For a century, steam turbines have actually been the industrial standard for transforming such heat sources into electrical energy.
On average, steam turbines reliably transform about 35 percent of a heat source into electrical energy, with about 60 percent representing the greatest effectiveness of any heat engine to date. However the machinery depends upon moving parts that are temperature- limited. Heat sources greater than 2,000 degrees Celsius, such as Henrys proposed thermal battery system, would be too hot for turbines.
Over the last few years, scientists have actually looked into solid-state options– heat engines with no moving parts, that could possibly work effectively at higher temperature levels.
” One of the advantages of solid-state energy converters are that they can run at higher temperatures with lower upkeep expenses because they have no moving parts,” Henry says. “They just sit there and reliably create electricity.”
Thermophotovoltaic cells used one exploratory path towards solid-state heat engines. Just like solar cells, TPV cells might be made from semiconducting materials with a particular bandgap– the gap between a materials valence band and its conduction band. If a photon with a high enough energy is soaked up by the product, it can kick an electron throughout the bandgap, where the electron can then conduct, and therefore create electrical power– doing so without moving blades or rotors.
To date, many TPV cells have only reached performances of around 20 percent, with the record at 32 percent, as they have been made of reasonably low-bandgap materials that convert lower-temperature, low-energy photons, and therefore convert energy less effectively.
Capturing light
In their brand-new TPV design, Henry and his colleagues sought to catch higher-energy photons from a higher-temperature heat source, thereby converting energy more effectively. The teams brand-new cell does so with multiple junctions and higher-bandgap materials, or product layers, compared to existing TPV styles.
The cell is produced from 3 main regions: a high-bandgap alloy, which sits over a somewhat lower-bandgap alloy, underneath which is a mirror-like layer of gold. The first layer records a heat sources highest-energy photons and converts them into electricity, while lower-energy photons that pass through the first layer are caught by the 2nd and transformed to add to the created voltage. Any photons that pass through this 2nd layer are then shown by the mirror, back to the heat source, rather than being soaked up as lost heat.
The group evaluated the cells efficiency by putting it over a heat flux sensing unit– a gadget that directly measures the heat soaked up from the cell. They exposed the cell to a high-temperature light and concentrated the light onto the cell.
” We can get a high performance over a broad range of temperature levels pertinent for thermal batteries,” Henry states.
The cell in the experiments has to do with a square centimeter. For a grid-scale thermal battery system, Henry pictures the TPV cells would need to scale approximately about 10,000 square feet (about a quarter of a football field), and would operate in climate-controlled storage facilities to draw power from substantial banks of kept solar power. He explains that an infrastructure exists for making large-scale solar batteries, which might also be adapted to manufacture TPVs.
Recommendation: “Thermophotovoltaic effectiveness of 40%” by Alina LaPotin, Kevin L. Schulte, Myles A. Steiner, Kyle Buznitsky, Colin C. Kelsall, Daniel J. Friedman, Eric J. Tervo, Ryan M. France, Michelle R. Young, Andrew Rohskopf, Shomik Verma, Evelyn N. Wang and Asegun Henry, 13 April 2022, Nature.DOI: 10.1038/ s41586-022-04473-y.
This research was supported, in part, by the U.S. Department of Energy.

A thermophotovoltaic (TPV) cell (size 1 cm x 1 cm) mounted on a heat sink created to determine the TPV cell effectiveness. To determine the performance, the cell is exposed to an emitter and synchronised measurements of electric power and heat circulation through the device are taken. Credit: Felice Frankel
A New Heat Engine With No Moving Parts Is As Efficient as a Steam Turbine
The design might someday enable a fully decarbonized power grid, scientists say.
Engineers at MIT and the National Renewable Energy Laboratory (NREL) have actually designed a heat engine without any moving parts. Their brand-new presentations show that it converts heat to electricity with over 40 percent performance– a performance much better than that of standard steam turbines.
The heat engine is a thermophotovoltaic (TPV) cell, comparable to a solar panels solar batteries, that passively catches high-energy photons from a white-hot heat source and converts them into electrical power. The teams style can create electrical power from a heat source of in between 1,900 to 2,400 degrees Celsius, or approximately about 4,300 degrees Fahrenheit.