Expediting the introduction of renewable energy, smoothly phasing out fossil energy and – at the same time – saving energy, while ensuring that the energy supply remains secure, available and affordable. This was the shared aspiration that prompted ECN and TNO to join forces. ECN part of TNO has eight innovation programmes. Five questions and answers about ‘Towards sustainable use of the subsurface’.
Progress towards the energy transition must be expedited if we are to meet the Paris climate targets. This requires technical, social and policy innovations. ECN part of TNO is taking up this challenge. Together with the Dutch business community, various research institutes and the government, it is implementing eight innovation programmes. Here, Tirza van Daalen, Director of the Netherlands Geological Survey (GDN), answers five questions about one of these programmes.
1. What is the goal of the ‘Towards sustainable use of the subsurface’ programme?
“The subsurface has an important part to play in the energy transition. This involves aspects such as storage capacity for heat, gas and CO2. In an effort to expedite the energy transition, we are using geothermal energy in combination with other sources, such as wind at sea and wind on land. The properties and behaviour of the subsurface determine soil stability, its potential for underground CO2 storage or heat storage, and its vulnerability to human activity. So it is vital to understand the nature of the subsurface, which is where the Netherlands Geological Survey comes in. The GDN is the knowledge centre for the Dutch subsurface. We collect and interpret data, transforming it into useful geological information that is made available throughout the Netherlands. We also provide advice on natural gas extraction, geothermal energy, groundwater extraction, etc.”
“The subsurface has a very important part to play in the energy transition. At ECN part of TNO, we are using geothermal energy in combination with other sources, such as wind at sea and wind on land”
2. In terms of mapping the subsurface, what still remains to be done?
“The GDN has been studying the subsurface for more than a hundred years. However, the Dutch subsurface has never been mapped at the depths we are planning to investigate (four to eight kilometres). The Netherlands also has a unique geology. For example, formations that lie one and a half kilometres below ground in the Netherlands occur at the surface in Belgium. We are also taking on the task of converting two-dimensional geological profiles of the Netherlands into three- and four-dimensional formats. New monitoring techniques, strategies and computer models for identifying fluctuations are helping us improve our predictions about the shallow and deep subsurface. This helps us identify potential drilling sites where we can safely exploit renewable energy sources, such as high-temperature heat from the subsurface (see box). Thanks to ECN part of TNO, we can now combine our areas of expertise about the subsurface with a thorough understanding of energy efficiency.”
3. What unusual challenges are waiting in the wings?
“One practical challenge involves upscaling the number of active geothermal ‘doublets’. These are twin boreholes. Hot water from an underlying geological formation is pumped up through one of these boreholes. A few kilometres away, cooled water is returned down the other borehole and injected back into the same geological formation. The Netherlands currently has about fourteen active geothermal doublets. These are mainly used to heat greenhouses for the horticultural sector. Under the Energy Agreement for Sustainable Growth, the Netherlands is required to increase the number of geothermal doublets to 1,200 by 2030. The goal is to achieve an affordable and clean energy supply on a much larger scale than at present.”
“The goal of 1,200 geothermal doublets represents an enormous increase in scale, requiring us to cooperate with Energiebeheer Nederland, for example”
4. Why is it so important to join forces in this way?
“The goal of 1,200 geothermal doublets represents an enormous increase in scale. The only way to achieve this is to cooperate with other parties, such as Energiebeheer Nederland (EBN), a company that invests in the exploration, extraction and storage of gas and oil on behalf of the State. Their philosophy is to gradually shift from traditional oil and gas production to more renewable energy. Having joined forces to create ECN part of TNO, we are now operating in harmony to achieve the energy transition goals. If you take two scientists from two different domains and put them side by side, they will come up with new discoveries. This is how knowledge is created. I have high hopes for that. After all, by providing innovative energy solutions, we can help the Netherlands take a step forward.”
5. When do you expect to get results?
“The programme consists of various projects. For example, in April we signed a contract for a project in which we will be exploring the potential of ultra-deep geothermal energy (see box). This will involve drilling test boreholes. The work will be carried out by various construction and infrastructure companies (organized into seven consortiums), EBN and the GDN. Ultra-deep geothermal energy is a very sustainable option, as it involves almost no CO2 emissions. For this reason, a great deal of time and effort is being invested in this area. In the Netherlands, only one or two boreholes have been sunk to depths in excess of three kilometres. Ultra-deep geothermal energy – which involves drilling down four to eight kilometres into the Earth’s crust – is really terra incognita. But, five years from now, I expect we’ll know much more about the potential of these and other applications.”
“New monitoring techniques, strategies and computer models are helping us improve our predictions about the shallow and deep subsurface”
Ultra-deep geothermal energy
High-temperature heat from the subsurface is an important option as industry moves towards renewable heating. ECN part of TNO is developing the expertise needed to use this new energy source safely and cost-effectively. Test boreholes will be sunk four to eight kilometres below the surface. At these depths, the temperature of the groundwater is approximately 200°C, which is certainly hot enough to produce electricity. However, research is needed to determine whether reliable geothermal wells can be created to exploit this resource effectively.