Despite much interest, gothermal energy remains largely untapped and its current contribution to the global power mix capacity is limited to just 1%. Much of the limitation is to do with the lack of suitable sub-surface locations that can be accessed using current technology. There is also the not-insubstantial risk of seismic activity being triggered. Finally, there are the costs, which the International Renewable Energy Agency (IRENA) says can be considerable. Indeed, the Agency estimates geothermal energy to be the ‘second most expensive renewable energy source’ to install, behind concentrated solar power, although there is the caveat that once installed operation and maintenance costs tend to be very low.

Good news though is on the horizon. Enhanced geothermal technologies that can provide ‘deep geothermal’ renewable energy are now coming onstream. These will allow geothermal energy extraction to take place on a much larger scale and bypass current sub-surface restrictions.

Essentially, these technologies involve two techniques: hydraulic fracturing (fracking) and underground storage; and non-mechanical drilling. Fracking is already widely used in the US oil and gas industry to increase the permeability of rock formations. But with new and advanced drilling techniques, much further penetration of solid underground rock is now possible. This also can involve injecting water deep into the ground to create the steam to drive turbines for power generation.

Last year, US company Fervo Energy demonstrated a pilot plant in Nevada using what it calls an ‘enhanced geothermal system’ involving drilling a horizontal doublet well system consisting of an injection and production well pair within a high-temperature, hard rock geothermal formation. It now plans to continue with the construction of a 400 MW geothermal power plant in Beaver County, Utah. The plant plans to supply electricity to the grid in 2026.

Non-mechanical drilling is being developed by AltaRock Energy of the US, using techniques such as plasma or millimetre-wave methods in partnership with Quaise Energy to penetrate very hot rock at depths of up to 15–20 km. AltaRock expects superhot rock geothermal (SHR) energy to yield ‘up to 10 times more energy’ than a conventional geothermal well and to supply 30 TW of global energy demand by 2050 potentially.

EU seeks ‘deep’ geothermal energy boost
Europe also plans to develop deep geothermal energy. Since Russia’s invasion of Ukraine in 2022 some three quarters of Russian piped gas have been locked out of the European Union (EU) effectively. This has led to a redoubling of EU efforts to expand the bloc’s share of deep geothermal in its energy mix from 0.2 % of electricity currently.

The goal, says Philippe Dumas, Secretary General of the European Geothermal Energy Council (EGEC) lobby, is for geothermal to supply a quarter of Europe’s energy needs by 2030. Germany is already pivoting from its traditional reliance on Russian gas towards geothermal energy with projects such as Vulcan Energy’s geothermal plant located at Insheim in western Germany.

Horst Kreuter, Vulcan Energy’s co-founder, said his plant currently has two geothermal wells but there are plans for seven more. ‘These will supply heat to Insheim’s new district heating system in five to eight years,’ he says. By 2030, Germany’s geothermal market is projected to grow from €50mn to €750mn.

France, Italy, the Netherlands and Hungary are also turning towards geothermal. Hungarian company Szeged’s geothermal heating system is believed to be the second largest in Europe, after Iceland, and the largest in the EU.

Russia’s invasion of Ukraine in 2022… has led to a redoubling of EU efforts to expand the bloc’s share of deep geothermal in its energy mix from 0.2 % of electricity currently.

Cornwall project slated to deliver power late-2024
In the UK, plans to develop deep geothermal energy are reaching fruition. Its first deep geothermal power plant, the United Downs geothermal project is under construction in Cornwall. It is being developed by Geothermal Engineering (GEL) in collaboration with the Italian clean technology company Exergy International and is expected to begin producing power later this year, delivering around 3 MWe of base-load renewable electricity and up to 10 MWth of heat for a large housing development at Langarth Garden Village, a project being developed by Cornwall Council.

Luca Pozzoni, General Manager of Exergy, anticipates that: ‘The United Downs project will be a milestone in the development of the geothermal industry in the UK. Under a structured long-term agreement with Geothermal Engineering, we will be able to partner for the development of future geothermal initiatives.’

The geothermal site utilises the naturally heat-producing granite which underlies most of Cornwall. Two deep, directional wells have been drilled: the production well to a depth of 5,275 metres, and the injection well to 2,393 metres. ‘The naturally-heated geothermal fluid will be pumped to the surface, passed through the power plant to produce electricity, then returned underground via the injection well where it will percolate through the granite to reheat. This process means that geothermal energy produces clean, green power with no waste product,’ according to Exergy. The company is constructing a closed-loop Organic Rankine Cycle (ORC) binary power plant specifically for the project.

Iceland pioneers ‘closed loop’ geothermal economy 
Perched on the boundary of the Eurasian and North American tectonic plates, Iceland has some of the best potential for deep geothermal sourced energy in the world. It was also one of the first to begin using it around a century ago. Today, more than 70% of Iceland’s energy comes from geothermal sources.

The drive to begin using Iceland’s geothermal resources in the most circular manner started in the late-1970s by HS Orka. This led to the development of the ‘Resource Park’, a business cluster that aimed to utilise the resource from HS Orka’s geothermal power plant at Svartsengi on the Reykjanes peninsula. HS Orka is the largest privately owned power producer in Iceland, providing the country with 275 MW of electric energy and 175 MW of thermal energy capacity. At its Resource Park, 10 companies currently tap into the multiple resource streams coming from Svartsengi.

World Bank backs Indonesian and Turkish projects
Indonesia also has deep geothermal ambitions, backed by the World Bank, to replace its previous reliance on fossil fuels. According to industry sources, the country has the second-largest geothermal energy resource in the world, after the US, with a potential of 23,965 MW. However, installed geothermal power capacity was only 2,130.7 MW in 2020. Substantial support will be necessary if the government is to achieve its target of 23% renewable energy mix by 2025. The World Bank estimates that for geothermal energy to contribute ‘about 7%’, or 7,000 MW of Indonesia’s energy mix, a total investment of approximately $35bn will be required.

One project that is underway is the Gunung Galunggung geothermal power plant project in West Java. It is owned and developed by PT PLN (Persero), the state-owned electric utility, and will be brought online in multiple phases with commissioning expected in 2027.

Middle East ambitions
In the Middle East, the World Bank is also supporting Turkey’s ambitions to make the switch away from fossil fuels towards renewable geothermal energy generation. The Bank provided two loans worth $300mn in December 2021 to enable Turkey to scale-up its renewable geothermal energy generation. This was in addition to two earlier loans worth $250mn. The financing package allows the country’s Geothermal Development Project (GDP) to leverage private sector investment by reducing risks for investors through a risk sharing mechanism (RSM) and access to long-term financing through the Loan Facility for Resource Development.

The GDP is expected to finance a total of over 380 MW of new geothermal capacity and mobilise about $555mn of private capital. Exergy International is also partnering with Turkey on this project. This January it announced plans to add an 8 MW geothermal binary plant to the Emirler 1 geothermal power plant in Sarayköy, in the Denizli region. The facility is scheduled to be commissioned by the end of 2024. Turkey is also cooperating with Indonesia, which earlier this year signed a confidentiality agreement with the Indonesian state-owned company Pertamina Geothermal Energy, a subsidiary of Pertamina Oil and Gas.

A balance is sought between technology innovation and cost
Deep geothermal heat is apparently an abundant and carbon-free energy source offering a clear alternative to fossil fuels. However, success will require the adoption of some new technologies that are being trialled if its market share in the global energy mix is to grow from just 1% currently, closer to the ambitious 25% envisaged by enthusiasts for the global energy mix. For this to happen, the pilot projects now underway will not only have to be technologically successful, but also will have to demonstrate that they can operate cost- effectively at commercial scale.

• Further reading: ‘Innovative Bavarian geothermal project secures European funding’. The European Investment Bank and European Union are backing the roll-out of the Eavor-Loop geothermal heating project in the German state of Bavaria.
• Find out how Latin America’s geothermal potential is to be released with over $1bn investment in 2027.