Clean technology series: geothermal energy – a revolution beneath our feet

As the global transition to net-zero accelerates, the search for scalable, reliable, and weather-independent clean energy has intensified. While solar and wind power have seen massive adoption across the world, as discussed in our previous articles, their inherent intermittency presents an ongoing challenge to grid stability.

Stability is where geothermal energy comes into its own. Conventional geothermal energy (hydrothermal) production requires a rare geological combination: naturally occurring heat, water, and permeable rock near the surface. This has restricted its use to tectonically active regions like Iceland or parts of the Western United States, meaning that geothermal energy currently provides less than 1% of global electricity^[1]. However, this is set to change, with the International Energy Agency estimating that geothermal technologies could theoretically supply up to 15% of global energy demand by 2050^[1].

In this latest instalment of the clean technology series, we discuss some of the “next-generation” geothermal technologies — spanning commercial, pilot, and experimental stages — that are moving the sector from a geographically localized niche to a mainstream source of clean energy.

Unlocking the core: the enhanced geothermal system (EGS) breakthrough

Traditional geothermal power plants operate on a relatively straightforward principle: capturing energy from naturally heated hydrothermal reservoirs. In some locations, hot springs bring the heat to the surface.  In others, engineers tap into the hydrothermal reservoirs using conventional oilfield equipment. In both cases, the hot fluid is brought to the surface, where it is used to turn turbines and generate electricity.

However, in locations with impermeable rock or inadequate water supply (often referred to as hot dry rock), these conditions can be emulated by pumping water into artificial fractures created using techniques similar to those developed by the shale industry (such as horizontal drilling and hydraulic fracturing, or fracking). Parallel wells are drilled, with artificial fractures created in the solid rock between the two wells to create a subsurface loop. Water is pumped down the first well, migrates through the newly fractured hot rock, and returns to the surface via the second well to drive a turbine. This is known as an enhanced geothermal system, or EGS.

Although there have been EGS projects around since the 1970s, with several pilot and early commercial-scale projects already operating in Europe, the transfer of knowledge from the shale industry is estimated to have shortened EGS drilling times by 50-70% over the last few years^[2]. As a result of these developments, new EGS projects in the United States are expected to produce electricity at competitive market prices by 2027^[2].

Closed-loop geothermal systems (CLGS): the underground radiator

While EGS opens up vast new territories to geothermal energy extraction, the technology still requires both water injection and hydraulic stimulation. In regions where fracking faces regulatory bans or where water is scarce, closed-loop geothermal systems (CLGS) provide an alternative approach. As with EGS, CLGS technology is advancing rapidly, with the first commercial-scale demonstration of a fully closed loop geothermal system starting to provide power to the grid in Germany in December 2025^[3].

Closed-loop systems do not rely on permeable rock or fractures; instead, they operate like a giant underground radiator. In CLGS, a sealed loop is constructed underground. A specialized working fluid circulates inside the sealed loop, acting as a heat exchanger with the Earth; the working fluid flows down one side to absorb the geothermal gradient heat of the Earth through the pipe walls, and returns up the other side to deliver that thermal energy to the surface. Energy recovery can be increased through selection of a suitable working fluid, with wellbore configuration, temperature gradient and geological characteristics influencing the choice^[4].

Because CLGS requires extensive precision drilling and often a significant amount of subsurface piping to achieve adequate heat transfer, the system can be both complex and expensive to install. However, concepts described in some recent patent filings suggest companies are looking to reduce costs in future by forming interconnecting wells “without casings”^{[4], [5]}, thereby reducing the number of pipes needed; it is suggested that fluid slugs containing sealants can be circulated during geothermal energy recovery operations to maintain the integrity of the sealed wells^[5].

Superhot geothermal: the ultimate powerhouse

The International Energy Agency estimates that “the technical potential of geothermal would be more than enough to meet all electricity and heat demand in Africa, China, Europe, Southeast Asia and the United States”^[1]. However, their analysis only considers wells up to 8km below the Earth’s surface.

Even more energy is available in “superhot” geothermal conditions, where the temperatures and pressures force water into a supercritical state where it is neither a pure liquid nor a gas. Supercritical water has a lower viscosity than normal water, and so can penetrate rock fractures more readily, potentially carrying five to ten times more energy to the surface than standard hot water^[6] under favourable conditions. This is the ultimate frontier for geothermal energy generation.

Although these superhot conditions are typically found at great depths (often greater than 5-10 km below the surface), in some regions they occur shallower than that, which has enabled experimental wells to be drilled. So far, superhot conditions have been the downfall of standard engineering equipment, with the intense heat, corrosive chemistry, and brittle rock leading to severe tool degradation and stuck drill rigs.  However, a new era of drilling equipment and techniques is bringing superhot geothermal energy closer to reality.

Standard drill bits are being replaced with heavy-duty compact polycrystalline diamond bits, engineered to grind through hard basement rock. Highly insulated piping allows for more effective regulation of the temperature of drilling fluids, improving the cooling of electronics and sensors during wellbore formation. In addition, techniques to weaken the rock structure before the drill bit even makes contact can be employed, reducing mechanical wear.

One approach to weakening the rock is the use of high-pulsed-power (HPP) drilling, in which electrical discharges generated within a conductive fluid create rapid plasma-induced pressure pulses in the surrounding rock. These pressure pulses induce microscopic fractures and pre-crack the rock formation, allowing the mechanical drill to pass through the rock more quickly and with reduced wear. In some implementations, changes in pressure (due to e.g., geothermal heat) can be compensated for, preventing changes to the output power of the electrical discharges at depth^[7]. A similar weakening effect can be achieved with thermal-shock drilling, where localized temperature swings from rapid heating and cooling cycles weaken the structural integrity of the rock. Other approaches utilise kinetic forces, whether from water jets, metallic shot or percussive hammers, to break down the rock.

However, a big aim for superhot geothermal technology is non-contact techniques to melt, vaporise, or disintegrate rock without mechanical interaction. Experimental approaches under investigation include the use of plasma-based drilling torches (which use high-voltage electrical discharges to generate an ultra-hot gas plasma stream) or millimetre-wave energy beams (akin to a high-powered laser) to vaporise rock. The rock vapours generated during this “drilling” can also be analysed to monitor the composition of the rock, enabling a comprehensive and rapid survey of the subsurface chemistry in the borehole at the same time^[8].

Funding the frontier: economics, policy, and the road ahead

Due to the nature of the technology, new EGS, CLGS and superhot geothermal projects require a large amount of capital. However, knowledge transfer from the oil and gas industry has already helped reduce drilling cost and drilling time significantly, and these efficiency gains are spurring new investment in the next-generation geothermal sector to the tune of nearly USD 2.2 billion in 2025^[9]. With strong financial and political backing (including from the European Commission^[10]), we should soon see geothermal energy becoming a significant player in the renewable energy space.

Crucially, the technological renaissance rewriting the rules of geothermal energy generation may also unlock an unexpected secondary benefit. Because these engineered subsurface systems can regulate fluid flow and manage immense reservoir pressures on demand, they have the potential to double as massive, long-term energy storage systems. Non-chemical energy storage solutions, including the possible storage capabilities of geothermal reservoirs, will be considered in our next article.

For more information or advice on protecting your invention and the help that is available, please get in touch with Alexandra Collingwood-Pierce or your usual Venner Shipley adviser.