An illustration of a heat trapping device.
Engineers are cooking up a new clean energy solution: charging up crystals with solar energy to temperatures of 1,832 degrees Fahrenheit (1,000 degrees Celsius), potentially making them a greener substitute for the carbon-intensive processes that smelt steel and cook cement.
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The new technology—described in a proof-of-concept study published today in Device—makes use of a property of quartz that allows it to trap sunlight. Attaching a rod of synthetic quartz to a silicon disk used to absorb energy, the team tested whether the apparatus could retain heat. They blasted it with energy equivalent to sunlight from 136 Suns; the rod warmed to about 1,112 degrees F (600 degrees C) but the absorber plate reached a temperature of 1,922 degrees F (1,050 degrees C).
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“People tend to only think about electricity as energy, but in fact, about half of the energy is used in the form of heat,” said Emiliano Casati, an engineer at ETH Zurich and the corresponding author of the study, in a Cell release. “To tackle climate change, we need to decarbonize energy in general.”
To date, solar receivers—devices that concentrate heat from mirrors reflecting sunlight—have not been able to efficiently handle solar energy at temperatures above 1,832 degrees F (1,000 degrees C). Some of the most widespread carbon-intensive processes, like glass, steel, and cement manufacturing, require temperatures at and exceeding that limit, which companies achieve by burning fossil fuels. Cement manufacturing alone was responsible for about 8 percent of CO2 emissions in 2023, according to CBS News, and glass melting is responsible for about 95 million tons of anthropogenic carbon, according to research published earlier this year in the journal of the American Ceramic Society.
Cement factories along China’s Yangtze River.
Adding quartz into the manufacturing mix could make it possible for manufacturers to achieve the necessary temperatures to work with steel, glass, and cement using sunlight, instead of relying purely on processes that are warming our planet.
“Energy issue is a cornerstone to the survival of our society,” Casati said. “Solar energy is readily available, and the technology is already here. To really motivate industry adoption, we need to demonstrate the economic viability and advantages of this technology at scale.”
Besides their experimental tests, the researchers modeled the setup’s efficacy and found that quartz boosts the the receiver’s efficiency. In their model, an unshielded receiver was 40 percent efficient at a temperature of 2,192 degrees F (1,200 degrees C) but was 70 percent efficient at the same temperature when the receiver was shielded with 11.8 inches (300 millimeters) of quartz.
The team is now testing other materials, including fluids and gases, that can act as thermal traps. Through their heat-retaining abilities, these materials could boost the efficacy of renewable energy solutions that have a long way to go if they’re ever going to supplant the longstanding primacy of fossil fuels.
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