Geothermal anywhere: Advanced drilling technology for CO2-free energy could be widespread

Geothermal energy aims to do what solar panels and wind turbines cannot: provide renewable energy around the clock. Until now, CO2-free electricity has been generated by harnessing the heat stored in accessible areas of the Earth's crust. The problem with conventional methods is that geothermal plants can only be built in certain locations with permeable rock and water resources. This limits the availability of clean energy locally.

However, new and enhanced methods of geothermal energy extraction could make it possible to use this source of energy on a large scale - but not without potentially significant risks. The use of geothermal energy is not a new invention and has been used to produce climate-friendly electricity for several decades in countries with favourable geothermal conditions, such as Iceland and Italy, and for over 100 years in Tuscany.

In total, around 88 countries worldwide are using this renewable energy source, albeit with a global renewable energy capacity of only one percent to date. However, recent progress by individual companies shows that the potential is much greater, as Fervo Energy demonstrated last year with its plant in Nevada and now plans to continue with the construction of another plant in Utah.

Hydraulic fracturing and underground storage

One of the new techniques - hydraulic fracturing, or fracking for short - is used in the oil and gas industry to increase the permeability of rock formations. With the help of advanced drilling techniques, it is now possible to penetrate much further into the solid underground rock. Water is then injected deep into the ground to create steam, which is much lighter than liquid water and rises through the pores to drive turbines for power generation.

Fervo Energy also plans to build huge underground batteries, as the pressurised hot water or steam essentially acts as a storage device for the thermal energy in the soil. For example, when electricity demand is low, more water can be pumped into the fractured rock formations, increasing the pressure in the system.

Conversely, when electricity demand is high, the amount of water pumped can be reduced or even some of the existing hot water can be extracted. This reduces the pressure, allowing the remaining high-temperature water to flow more easily and provide more steam for power generation.

Non-mechanical drilling

It is becoming increasingly clear that geothermal energy is a topic with great potential for accelerating the energy transition, and research and pilot projects on geothermal energy are increasing worldwide. AltaRock Energy, for example, under the motto "Geothermal everywhere", has developed special non-mechanical drilling techniques such as plasma or millimetre-wave methods to penetrate very hot rock at depths of up to 15-20km.

Utah Forge is an underground field laboratory sponsored by the US Department of Energy (DOE) that is currently drilling a hole that can serve as a test bed for improved geothermal technologies by providing a detailed picture of what happens deep underground.

Danger of earthquakes?

However, scientists are divided on the safety of hydraulic fracturing, and there are concerns that the process could increase seismic activity and trigger earthquakes, which has been linked to an incident in South Korea in 2017. As a result, it remains to be seen just how safe the new methods really are.