The future of clean energy is unfolding on a desert plateau about four hours north-east of Las Vegas. Dotted around the spectacular sands near Milford, Utah, are nearly two dozen wells, each one reaching deep into the Earth where the rocks are permanently hot. Standing atop one of the electrified rigs responsible for digging those wells, Jack Norbeck has to shout to make himself heard over the fierce winds. “Ten rigs that are identical to the one that you see sitting here in front of us,” he say...