In the 2000s, geologists in Iceland were hunting for a mythical form of water—supercritical water—a state of matter that’s unlike the three familiar versions. They hypothesized that it lurked in the intense heat and pressure deep in the Earth’s crust, a naturally-occurring counterpart to the laboratory and industrial conditions under which it was known to exist. So down they drilled, searching for what could be a copious and carbon-free source of energy.
Alas, they never hit supercritical water. Instead, in 2009, they hit magma—which sounds exciting, but was a failure compared to their goal of tapping supercritical water. Unlike water, magma by itself isn’t a usable source of energy. (Current geothermal power stations simply rely on the heat of the crust deep down—their pipes don’t run through magma.) Or at least it wasn’t until the research team discovered that groundwater had seeped into their super-deep well. What resulted was superheated, 450 ˚C (842 ˚F) water. That’s the hottest anyone has ever retrieved water from underground.
Christopher Mims, writing for Quartz:
While 450°C is not hot enough at atmospheric pressure to be supercritical, it still contains an enormous amount of usable energy. As a result, engineers estimated they could use the well to create a power plant capable of generating 36 megawatts of electricity. That’s 20 times less than what a typical coal-fired power plant can generate, but it’s often the case that a geothermal power plant will have more than one well. Plus, geothermal power doesn’t come with any fuel costs or appreciable carbon emissions.
For now, it’s still a technology in the early phases. But if Iceland and other tectonic hotspots can tap into veins of magma, it has the potential to unleash a renewable, practically unlimited power source.