Few energy sources can top geothermal’s potential, with at least 42 terawatts of capacity available worldwide, according to the IEA, more than twice the world’s energy use last year. The technology is shaping up to be the energy world’s dark horse, even though investment in the tech pales in comparison to startups in advanced nuclear fission and fusion power. That makes the $19 million in seed funding raised by a startup called Critical Energy especially notable. Critical Energy hopes to fill a