A new technology closer to superhot geothermal energy sources

Conventional geothermal power plants reach temperatures of around 230 degrees Celsius through holes about two kilometers deep. Super hot rock can be found near the surface in a few areas like Iceland and near volcanoes, but for most of the world it is between seven and 20 kilometers below the surface.

According to conference panelists, things get particularly interesting at around 374 degrees Celsius, where water pumped to the rock becomes supercritical, in a vapor-like phase. This supercritical water can carry about 5 to 10 times more energy than regular hot water, making it an extremely efficient source of energy if it could be pumped above ground to turbines that could convert it to electricity.

Super hot rock can be found near the surface in a few areas like Iceland and near volcanoes, but for most of the world it is between seven and 20 kilometers deep.

But the drilling techniques are not there yet.

During a session titled “Chasing the Holy Grail: Deep, Super-Hot Geothermal,” presenters said conventional drill bits used in the oil and gas industry fail under the extreme temperatures and pressures involved in reaching the geothermal springs.

Modern drill rigs also include electronic components that cannot withstand extreme conditions, while other elements, such as borehole liners and backing materials, must also survive repeated thermal cycling or large changes. of temperature.

Yet steps are being taken to address these issues. Experts mentioned self-healing cement that recrystallizes to repair fractures and the use of more precise data to characterize subterranean rock conditions and better calibrate devices penetrating very deep systems.

“Open access to the data and models that underpin these pilot projects is essential,” Mark Ireland, senior lecturer in energy geosciences at Newcastle University, said during the session. “Then we can open the lid of the box and explore all the different parameters within it, and compare and contrast how we characterize the potential resource. The more we are able to share, the better our decision making.

To that end, Ireland and others highlighted the need for collaboration between groups around the world exploring super-hot geothermal energy.

The future of geothermal energy

An example of such a group is Quaise Energywhose representatives presented their gyrotron during the conference’s “The Future of Drilling for Deep Geothermal” session.

Quaise’s machine works by creating millimeter wave energy, a cousin of microwaves for cooking, which is directed to deep, hot rock via waveguides. A gas that accompanies the millimeter waves brings the vaporized rock to the surface.

According to company CEO Carlos Araque, conventional drilling techniques are used in the shallower rock for which they were optimized, and then replaced by millimeter wave technology for harder, hotter and deeper rock. deep.

Geothermal drilling anywhere, on the other hand, uses plasma, an energized gas, to break deep, hard rock into tiny pieces. Their technology is integrated into conventional drilling systems and is currently being tested in a state-of-the-art facility near Bratislava, Slovakia, which can replicate the high pressures and temperatures far underground.

Another approach presented was that of Hypersciences, whose hypersonic projectiles fired past a rotating drill bit allow it to drill about 10 times faster through hard, deep, high-temperature rock. This technology – like the others – is tested in field trials, and it is also applied to tunneling, mining and aerospace.

A final project, titled ORCHID and supported by the European Union, was presented by researchers from ARMINES/MINES-ParisTech in France. Still in development, their technique consists of combining high-pressure water jets with percussion drilling.

“I see a number of very high potential drilling methods coming up,” Susan Petty, chief technology officer at Cyrq Energy and president and founder of AltaRock Energy, told the conference.

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