Superhot rock geothermal – the holy grail for geothermal?

Superhot rock geothermal – the holy grail for geothermal? Graphical overview of hdyrothermal vs superhot rock geothermal (source: CATF)
Alexander Richter 4 Nov 2021

Could superhot rock be the holy-grail of geothermal? A report by Clean Air Task Force describes why and what would be needed to make it a reality.

As part of exploring advanced energy technology and tapping the “next-generation” technologies, superhot rock is often described as the “holy grail” of geothermal energy. So-called “moonthots” aim to take aim at a calculated strategy taking existing research to a new level. How superhot rock is seen as such as a moonshot approach for the geothermal sector, as described in a recent report by the Cean Air Task Force (CATF).

While in its 2020 report – “A Year of Global Impact (pdf)”, CATF gives a short intro into why it thinks targeting superhot rock at deep levels can “radically upgrade the economics of the overlooked source of energy” [geothermal].

In the more detailed report on “Superhot Rock Geothermal – a Vision for Zero-Carbon Energy “Everywhere” (pdf)”,  CATF describes in detail the value of superhot rock geothermal.

The report looks at the overall energy potential provided by superhot rock geothermal, the status of the approach both in the past and today, and gives an overview over the path forward.

It points to the high energy density provided, how competitive it is in providing clean and efficient power, as well how the environmental footprint is manageable.

Looking at past projects, CATF points to the over two dozen wells drilled in superhot rock conditions, among them the Japan Beyond Brittle Project back in 1994-1995 which targeted a zone with temperatures above 500 degrees Celsius at a depth of 3.7 km. It also describes the Iceland Deep Drilling Project which reached conditions of 426 degrees Celsius at a second well drilled in 2017. Other projects mentioned the Descramble project at Larderello, Italy, the GEMex research project at Acoculco and Los Humeros, Mexico, as well as the Hotter an dDeeper Exploration Science project in New Zealand.

Clearly there are innovations needed to commercialize superhot rock geothermal, among them are drilling technologies that not only can target the required depths economically but also handle the superhot resources. The creation of the heat reservoir is another aspect and so are well construction, downhole power and remote sensing tools and an adapted approach to surface power production, given the high-pressure and high-temperature of the resource.

What is needed now are pilot demonstrations that will be key in attracting the large-scale investment needed to make “geothermal everywhere” a reality. Projects like the Krafla Magma Testbed in Iceland, or the planned targeted project at Newberry in Oregon, U.S. will be crucial in this regard.

Some have called superhot rock (SHR) the “holy grail” of geothermal energy, so a recent report published by . This is because, in most of the world, SHR could provide competitive, zero-carbon, dispatchable power and could support zero-carbon hydrogen fuel production. It is one of the very few high-energy-density, zero-carbon resources that could replace fossil energy around the globe.

CATF concludes that “Commercial superhot rock geothermal energy could make a transformational contribution to global energy system decarbonization.”, and describes the required resources and collaboration by the geothermal industry, government laboratories,
academic institutions and the oil and gas industry.

Check out the report here (pdf).