All the energy we’ll ever need is 5,000 metres below our feet. It works all day, every day. And if we can drill a deep enough hole, it’s ours for the taking. This is the promise of geothermal energy.  There are a few details. It turns out to be quite hard to drill down 5,000 metres. The drill bits melt. Getting the energy out requires a lot of horizontal drilling and fracking. Getting governments to approve these schemes is hard work. Getting capital to back enhanced geothermal (the term for the deepest drilling projects) is difficult, when the technology is…