Can Ultra-deep Geothermal Contribute to a Sustainable Energy System?

May 24, 2018 | 08:00
Image: The Nesjavellir Geothermal Power Plant in Þingvellir, Iceland. Public Domain. Source: Wikimedia.
Image: The Nesjavellir Geothermal Power Plant in Þingvellir, Iceland. Public Domain. Source: Wikimedia.
The last five years, geothermal energy has seen a slow but steady rise. District heating in Germany, France and the Netherlands is a success. Due to financial and regulatory constraints growth of Ultra Deep Geothermal energy slackens, though. Can UDG serve as a renewable energy source in the Netherlands, now that it is phasing out Groninger gas?

Geothermal energy is a millennia-old technique. Traces have been found in China and during excavations at Aquae Sulis, present-day Bath in Somerset, UK, where the Romans, after 43 AD, used hot springs for public baths and underground heating for condominiums (like today). Modern geothermal started at the turn of the 19th century with District Heating (DC) in Boise, Idaho, and geysers for green houses in Tuscany, Italy, two decades later.

Nowadays, there are more than a hundred geothermal power plants producing 15 TWh of electrical power every year in the EU, according to the sixth and latest report of the European Geothermal Energy Council. Especially geothermal heat – i.e. district heating and cooling - is a success: between 2012 and 2016, 51 new plants have become operational. In Western Europe, France is taking the lead with 493 plants, followed by Germany (301), Italy (157) and the Netherlands (127). This ‘shallow’ geothermal market – largely for housing – is expected to grow at a rate of ten percent a year, experts forecast.

Ultra deep geothermal energy (UDG) is another matter, a chance for Dutch industry as well as a headache. Some forty percent of all energy demand in the Netherlands is heat; housing and process industry take an equal share. Up until now, UDG is used at two to three kilometres depth for sixteen greenhouses in Holland (Westland and Haarlemmermeer) but there are opportunities for other industries (like paper and dairy) as well. Moreover, the Dutch government recently announced that natural gas from its Groningen field has to be phased-out before 2023 (due to recent earthquakes in the Northern part of the country).

One of the few, large-scale opportunities for the process industry to switch away from natural gas is UDG. Simply said, the deeper you drill, the warmer it gets: at one kilometre below earth’ surface temperatures are 40 to 50 degrees Celsius, at four kilometres 120 to 130 degrees and below five kilometres around 160 degrees, as the new and dedicated website of EBN (Energie Beheer Nederland) points out. UDG for industrial heat processes is only technically viable below five kilometres.

R&D and exploratory drilling for UDG as a viable renewable energy source is a headache, though. After extensive research and mapping most of the seismic risks, exploratory drilling will cost around one million euro per kilometre. It’s a risky enterprise without guarantee these drilling exercises hit the right permeable layer for warm water. Moreover, contrary to district heating there’s no governmental hedge fund to alleviate those risks.

Drilling capacity isn’t the biggest hurdle: oil and gas exploration in the North Sea is at its lowest level since the 1970’s. Drilling costs may be lowered because of this. Drilling for UDG though, requires not only twice as much but also far wider pipes than drilling for fossil resources due to the transportation of water (from and to the well). Last but not least, heat from all geothermal wells needs to be utilised close to the source. That physical characteristic raises some financial challenges: no demand means absence of infrastructure and vice versa, thus hampering much needed investments.

Above all, knowledge about ultra deep underground layers is still in its infancy. Most of the earth far below the Netherlands, especially in areas with a high population density and/or industry, hasn’t been mapped yet. Therefore, the Dutch government closed a Green Deal UDG last summer. EBN and TNO research will work together with market parties to explore the possibilities of using the Dinantian play – a layer formed during the Lower Carboon, 326 to 359 million years ago - for UDG in various parts of the country (such as Friesland, Brabant and the Rotterdam Harbour).

According to an open letter of DAGO (Dutch Association Geothermal Operators) to Eric D. Wiebes, Minister of Economic Affairs and Climate, UDG has the potential to cover some five percent of total energy use in the Netherlands, three times more than Minister Wiebes expects. In order to exploit its full potential, action is needed, DAGO states. As a young energy sector – the first well was drilled in 2007 for a greenhouse in Bleiswijk, Holland – standards like safety measures have to be put in place soon, as well as regulatory mechanisms and (financial) incentives to tackle the huge investments necessary.

Image: The Nesjavellir Geothermal Power Plant in Þingvellir, Iceland. Public Domain. Source: Wikimedia.
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