Vox has an article on Icelandic efforts to develop deep geothermal energy reserves - Iceland is digging a seriously deep hole to tap a new source of clean energy.
Most geothermal projects harvest energy from hot rocks relatively near the surface, at temperatures of around 200 degrees Celsius. But the Iceland Deep Drilling Project (IDDP) is going much deeper, in search of hot magma reservoirs that generate temperatures between 400 degrees Celsius and 1,000 degrees Celsius. If that energy could be tapped, a single well could generate 10 times as much electricity as a conventional geothermal well.
There’s some precedent for this idea. In 2009, the IDDP was drilling a conventional geothermal well and accidentally struck upon a magma reservoir 1.2 miles below the surface. When they poured water into it, they were able to draw out superheated steam at temperatures higher than 400 degrees Celsius — an extremely potent source of energy. So now they’re trying to see if they can replicate the concept.