Nuclear fusion has been getting all the headlines lately. It’s understandable, as it works just like stars, including our sun, meaning it can produce a lot of energy with a tiny amount of fuel. Still, commercial viability is decades away — if it ever happens. Still, there is another promising energy source — superhot geothermal. It’s the frontier of clean energy few talk about, but it might just be one of the most powerful tools in the transition away from fossil fuels. And according to Quaise Energy’s Daniel W. Dichter, we’re now a step closer to making it work.
In two recent papers, Dichter lays out new thinking around how to build geothermal plants that can harness energy from rock hotter than 375°C (700°F) — the point at which water becomes supercritical, a phase that carries up to 10 times more energy than typical geothermal sources. One paper was published by Geothermal Rising, and the other was presented at the Stanford Geothermal Workshop.
You must now be thinking that water won’t be super critical once it reaches the surface. Still, according to Dichter, it doesn’t need to be. Yes, water becomes super-dense at extreme depths, but forcing it to remain that way on the journey up through narrow, eight-inch pipes cancels out much of the performance gain due to reduced flow rates. Dichter’s conclusion: maintaining surface temperatures closer to 350°C (660°F) still delivers output up to 10x greater than conventional geothermal systems.
And here’s the other big insight — you don’t need exotic hydrocarbons to convert that heat into power. Most geothermal plants today use expensive organic Rankine cycle (ORC) systems, where hydrocarbons like isobutane serve as the working fluid. Quaise Energy found that plain water works better at higher temperatures. Oh, and it’s cheaper, cleaner, and compatible with common steam turbines, which have a much more robust supply chain than ORC systems.
Still, there is one very big obstacle for geothermal power — digging deep enough. This seems simple enough to the regular person. Still, going 10-12 miles (16-20 km) below the surface means dealing with temperatures that could melt the drill. Quaise Energy works on a solution that doesn’t even utilize drills, though. Instead, the company is developing a novel solution using millimeter-wave energy — think microwaves, but stronger — to literally vaporize rock and reach the heat below. If successful, the technology could unlock enormous, power-dense geothermal resources virtually anywhere on Earth.
