Plenty of days, temperatures in California’s Mojave Desert climb above 120 degrees Fahrenheit. A measly figure. These 400 silvered glass panels, tucked into the western edge of that hot, hot desert, are there to generate heat 15 times that amount. And, ideally, to help cool the planet too.
Assembled by the Pasadena-based company Heliogen, each 16-square-foot freckle, a heliostat, reflects a kilowatt of sunlight to the top of a five-story tower, where it’s absorbed by a silicon carbide receiver. As the little black plate glows white, it exceeds 1,800 degrees. That’s hot enough to begin manufacturing cement and other industrial products—processes that typically rely on burning fossil fuels—and to potentially cut up to 10 percent of global greenhouse gas emissions.
Heliogen CEO Bill Gross has dreamed of harnessing the sun since the 1973 energy crisis, when he sold DIY solar panels. Those sales helped put him through college. When oil prices plummeted, he took a detour to build software—you can thank him for inventing pay-per-click ads—before he founded Heliogen in 2013, with funding from Bill Gates. Last fall, the company fired up this first array. “It was a bit like watching a lunar landing,” Gross says.
Similar arrays have been used to make electricity and tasty SunChips, and even drill for oil. But those peak around 1,000 degrees, because each heliostat has to be individually calibrated and can fall out of alignment over time. With Heliogen, cameras atop the tower scan the sky, and image analysis software computes the optimal position for each mirror, which can rotate in increments smaller than 1/160 of a degree. Gross says such efficiency can deliver heat 20 percent more cheaply than fossil fuels can.
As proof of concept, Heliogen has mounted a kiln atop the tower to directly heat limestone, a key step in making cement. This year the company plans to link with commercial partners that have the ample shadowless land required. Gross is also building a receiver that can handle temperatures above 2,700 degrees. That kind of hellfire can create synthetic hydrogen, which could replace oil-based fuels. “Civilization depends on cement and steel—our roads, travel, everything,” Gross says. “We’ve found a way to clean it up.”
Laura Mallonee (@LauraMallonee) writes about photography for WIRED.
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