If solar energy is truly going to take over from fossil fuels, it needs to be hot enough for not only generating power, but replacing industrial processes outright -- and even the 1,049F of the best solar concentrator systems wouldn't cut it. Heliogen, however, may have finally cracked that barrier. The Bill Gates-backed startup has successfully concentrated solar energy at "breakthrough" temperatures above 1,832F, making it toasty enough to replace fossil fuels for industrial tasks like producing cement or steel.