• The Bill Gates-backed startup Heliogen has generated solar heat topping 1,000 degrees Celsius using mirrors.
  • Concentrated solar power isn’t new, but high heat can be used to manufacture cement and steel.
  • Heliogen says it plans to split hydrogen and offer a hydrogen fuel source next.

CNN Business reports that scientists working in “stealth mode” have announced a way to turn solar energy into extreme heat that could be used by industry. Startup company Heliogen, funded by Bill Gates and other high-profile environmental investors, has built a solar plant where large mirror panels point the sunlight toward each other to harness and multiply heat, a phenomenon called concentrated solar power.

The overall principle is the same reason a magnifying glass can start a fire. Concentrated solar power is popular around the world, like when Morocco built the largest plant to date in 2016. This new application of age-old technology has concentrated solar heat to above 1000 degrees Celsius, which is hot enough to enable industries that rely on chemical reactions at extreme temperatures, like ceramics, cement, or even steelmaking.

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Like the recent nanocollector “sunflowers,” most concentrated solar power plants use the heat to boil water into steam that turns a generating turbine. Solar panels can overheat, and for most panels, the overheat threshold is surprisingly low. Heliogen’s mirror panels act together as a single magnifying lens within a system designed to withstand temperatures up to 1500 degrees Celsius. Most consumer glass melts at or below that temperature, but pure silica glass doesn’t melt until 2000 degrees Celsius. Solar mirrors can also hypothetically be made with materials other than glass.

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Heliogen’s special angle in the market is the direct transmission of extremely high heat that can power kilns, furnaces, and other industrial processes. A typical nuclear power plant contains temperatures of 300 degrees Celsius, and that’s only safe and contained because of careful construction and the continuous flush of cold water or other coolants through the reactor.

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Heliogen
How Heliogen works.

The company has purposely flown under the radar as it built and tested its plant; news coverage and tweets about its breakthrough quickly swamped the company’s own tiny online profile to date. Gates’s investment in the project has catapulted its landmark test into media around the world, and the billionaire’s serious interest in solar is part of his overall belief, first published in 2016, that the world will make a “clean energy breakthrough” by 2031.

The name “Heliogen” is a play on helio- (sun) and generator, and Heliogen isn’t the first to try to use it. A dye named heliogen, first made in 1937 and now owned by international chemical conglomerate BASF, still has an active trademark. In 2006 and 2009, a prolific inventor named Stephen Yencho tried to file a trademark on the name, each time involving solar cells.

Heliogen founder Bill Gross calls his company’s first commercial service HelioHeat, and the Heliogen website cites applications like cement and steel. Just as exciting, Heliogen says its heat can be used to help plentifully split water into pure hydrogen, solving a tough energy supply chain problem and potentially opening up the already-working clean hydrogen blast furnace demonstrated in Germany this month.

Today, Heliogen is still testing its heat technology. The company says it has plans to develop ways to store energy for later use (solar’s favorite pun, “save it for a rainy day”). Thermal solar has a huge advantage over photo solar in that heat energy can easily be stored and distributed on demand. But to store such extreme heat will require some special planning.

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Caroline Delbert

Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.