It would be a fairly simple task to produce predictions about the future of geothermal energy based on a combination of gut feeling and an extrapolation of existing trends. Between 2015 and 2021, for example, the global generation of geothermal power was estimated to have risen from 13 gigawatts to 17 gigawatts. It would not seem unreasonable, therefore, to predict a similar rate of growth for the next five years, given that growth over this period tended to involve an increase of one gigawatt initially every two years and then, from 2019 on, every year. There are several factors which caution against taking this somewhat pessimistic view, however, not least of which is the urgency of the on-going search for renewable energy solutions. While debate still rages over whether COP 26 was an over-cautions disaster or a cause for some optimism, there is no questioning the fact that the pressure on governments and corporations to find ways of replacing our existing reliance on fossil fuel is going to become more intense with each passing month, as the impact of climate change becomes something we all have to learn to live with, rather than a set of grim predictions for the future.
According to the International Energy Agency (IEA), geothermal electricity generation grew by just 2% in 2020, a reduction on previous years. While some of this can be ascribed to the impact of COVID-19, it does leave the sector trailing massively the 13% annual growth which the IEA says is needed for geothermal energy electricity generation to meet the targets needed to hit Net Zero emissions by 2050.
Statements of this kind seem certain to introduce even more urgency into the search for new ways to take advantage of the potential offered by geothermal energy, and a survey of recent news stories emanating from the geothermal sector seems to highlight several trends which might point the direction for future travel.
Repurposing
One of these trends is undoubtedly a drive to repurpose assets, sites and technology previously linked to the exploitation of fossil fuel and utilise them to develop geothermal energy. In the simplest form, this involves build on existing drilling technology and the expertise of the workforce currently employed getting fossil fuels out of the ground. The Pivot 2021 conference, held the University of Texas at Austin, with support from the U.S. Department of Energy (DOE), saw speaker after speaker pointing out that the US had a current workforce in the oil and gas industries who, while not necessarily suited to a switch to working in solar or wind power, have the exact skillset needed for drilling down to harness the power of geothermal energy. The situation was compared to the decline of the coal industry across the US, with oil and gas extraction gradually declining and leaving workers looking for other options.
In the US the talk is all about oil and gas workers pivoting to deliver geothermal projects, but here in the UK, with a much smaller historic legacy of oil and gas production (the North Seas aside – of which more later), a project in the North East is exploring the possibility of drilling into disused coal mines in order to extract sea-water which has flooded the abandoned sites. The project, based in Hebburn, involves two boreholes, an extraction hole and a re-injection well, and the plan is for the initial drilling to be completed by the middle of December. Once this has been done, test pumping will take place, and the ultimate aim of the scheme is to produce green energy which reduces existing carbon emissions by 319 tonnes each year. Initially, the plan is for the energy to power Hebburn central council buildings and local tower blocks before eventually being rolled out further in future years.
Another promising UK based geothermal project is located at the Eden Project in Cornwall. Drilling on a borehole started in May of this year and a statement from the project released in November stated that "The well has found its target fault structure and the early signs of high temperatures and good permeability at depth are promising." The current best estimate is that the well could produce heat which would be the equivalent of that needed to heat 35,000 homes.
New Locations
Both of these projects, being UK based, are indicative of the way in which the search for means of exploiting geothermal energy is shifting beyond the established major forces in the field – countries such as Turkey, Indonesia and Kenya which have large and as yet untapped resources – and on to countries which have previously concentrated on other renewables. Another recent example of this phenomenon can be seen in Singapore, where the Energy Market Authority (EMA) announced, in October, that the country would be taking advantage of ‘new developments in technology’ in order to tap into the potential for geothermal energy in parts of the country such as the Sembawang Hot Spring Park and Pulau Tekong. The advances in technology referred to are shifts which enable bores to be drilled deeper than in the past and at lower cost, and would enable the creation of ‘closed loop’ geothermal systems in which pipes pump water deep underground to be heated by travelling through – in this case – a granite layer, before the heated water is driven to the surface and used to generate electricity. A similar scheme to enable exploitation of previously untapped geothermal energy resources has also been announced in Northern Ireland, where a project funded by Invest NI and led by Ulster University with the support of a number of industry partners is currently assessing aspects of geothermal energy in the province. These include the distribution of resources, the utilisation of geothermal energy at the surface, including conversion to electricity, and the legislative and policy framework that would best support an accelerated development of geothermal energy.
Another country which hasn’t, to date, been regarded as one of the geothermal ‘powerhouses’ of global production, but which is now ramping up development of the technology, is the Netherlands. In the year 2020 the use of geothermal energy in the country increased by 10% when compared to the year before, with this increase being driven by two technological factors. The first of these factors is the improvement in the operation and efficiency of the ‘doublets’ which are in operation. ‘Doublets’ is the Dutch term for well pairs, the geothermal technique which involves drilling two holes into the same source of underground hot water, with one pumping the water up for use and the other pumping cooled water back down to re-heat. Water of this kind is in fairly abundant supply in the Netherlands, with aquifers having been identified during past explorations looking for natural gas deposits. The second factor driving the rise of geothermal energy in the Netherlands is an increase in the number of ‘doublets’, with 3 new doublets on track to go into production during 2021 and more than 40 major projects in the pipeline, to coin a phrase.
Presently, the bulk of geothermal energy generated in the Netherlands is used for heating greenhouses across the horticultural industry, but the longer term plans of the Dutch government involve a 3% compound annual growth rate (CAGR) in the geothermal energy market within the country between 2020-2025. This will involve the development of deeper geothermal wells, with the energy being used to generate electricity as well as heat. The current goal of the Dutch government is for geothermal energy to meet 5% of the country’s energy demand for heat by 2030 and 23% by 2050.
One last example from the UK pulls together the themes of repurposing existing assets and tapping into previously ignored resources. It is a scheme, led by the Australian based Legacy Global Green Energy (LGGE), to repurpose abandoned gas and oil rigs in the North Sea as geothermal energy infrastructure. The company claims that there are currently 470 offshore platforms in the North Sea which will become obsolete in the next 30 years as the switch away from fossil fuel gains pace. The cost of decommissioning each platform is estimated to fall between £72.3m and £361.5m, and the bill would have to be picked up by the UK taxpayer. By repurposing the platforms to tap into geothermal energy beneath the sea bed the company claims that it could not only save the cost of decommissioning but also provide employment for the citizens of Aberdeen and Scotland as a whole, and turn the city into a geothermal hub for Scotland, the UK and Northern Europe.
Dealing with Waste
One question which does still crop up in objections to the idea of geothermal energy is that of the waste products the process generates. The answers to this problem vary around the world. In Cornwall, Lithium rich geothermal water is being recovered from abandoned copper and tin mines. Lithium is a key component in the kind of lightweight batteries needed for millions of mobile phones, laptops and electric cars. Harvesting the lithium from geothermal waters is infinitely less disruptive to the environment than existing methods of sourcing lithium – which tend to involve blasting and roasting solid rock – and while the focus in Cornwall may rest squarely on the lithium itself, a project in Hell’s Kitchen, Southern California combines a geothermal electricity generating capacity of 140 megawatts with the harvesting of lithium from the water which is being used.
Across many existing geothermal sites a company like Separo provides the technology needed to deal with the waste products of the process in the most efficient and least environmentally damaging way possible. By efficiently collecting drill cuttings, for example, we make it possible to re-use and recycle the material involved, while our produced water treatment technology can be installed on site to quickly filter impurities from produced water. The same applies to our slop treatment technology, which recovers valuable drilling fluids and removes contaminants in a way which makes it possible to return the treated wastewater to the environment, at the same time as reducing the overall carbon footprint of a project.
If the news stories of today are any guide, then the future of geothermal energy will be driven by innovation built on the foundation of existing technology, and the desire for more and more countries to harness the geothermal power which rests beneath the earth’s core. As the technology enabling drilling becomes more advanced, and the urgency of the switch away from fossil fuel more apparent, the status of geothermal energy as the renewable that could be a complete game-changer seems likely to grow.
