Our Geologists Map Geothermal Resources

Map of Belgium with geothermal potential (medium to very deep) and the (natural) geothermal wells. (RBINS, Estelle Petitclerc)
Our Geologists Map Geothermal Resources
post by
Reinout Verbeke

The internal heat of the Earth can be used to heat houses and to generate electricity. Countries such as Italy, Iceland and Turkey use thermal energy for quite some time, and Greece and Germany are experimenting on a large scale. What is Belgium waiting for? In the municipalities of Mol (Antwerp province) and Mons (Hainaut province) engineers extract hot water from the Earth’s interior with heat pumps as part of pilot projects. In the meantime, our geologists are mapping  the further potential. “Geothermal energy can become an important sustainable energy resource”, says geologist Estelle Petitclerc (Royal Belgian Institute of Natural Sciences - RBINS).

A specialised team has drilled to a depth of more than 3.8 kilometres at the Balmatt site in Mol, into layers of up to 350 million years old. The first results indicate that the water pumped has a temperature of about 138 degrees Celsius. Later on, this water can be used to heat the buildings of the Flemish Institute for Technological Research (VITO), organising this pilot project. Geothermal energy is also a hot topic at the RBINS. Using drill cores and (hydro)geological data, our geologists map the potential of the Earth’s superficial and deep geothermal energy for the entire country.

A Gift from Mother Earth

Geothermal energy is stored as heat inside the Earth. A small part stems from the formation of our planet. The kinetic energy released at the moment of the formation of the Earth was stored inside the terrestrial rock formations. Part of it is still present today and accounts for about 30 percent of earth’s geothermal energy. The remaining 70 percent is produced  by radioactive decay of elements such as uranium and thorium. This decay process generates a continuous supply of heat, stored in different geological layers.  The temperature rises about 3 degrees Celsius every 100 metres meaning that the deepest rock formations have the highest temperature.

The use of geothermal heat is nothing new: our ancestors already took advantage of hot springs as a heat source. In the light of the current global warming, research initiatives investigating the application of this ubiquitous and constant heat as sustainable energy resource, are now more topical than ever.

Deep geothermal energy

The first natural hot springs in Belgium were drilled around the city of Mons at the end of the nineteenth century. About 70 years later, the Geological Survey of Belgium carried out a test drill in the area. Nearby the town Saint-Ghislain a hole was drilled to a depth of 2.5 kilometres, reaching a layer of limestone containing water of 73 degrees Celsius. The well is the first geothermal well in Belgium, and the hot water is used to heat houses and the city infrastructure. When the water cools down to a lower temperature, it is used to heat greenhouses and before it ends up in the river, it passes through a water treatment plant. New drillings in this limestone reservoir have the potential to expand the geothermal network in the region.

In Flanders, scientists are investigating the geothermal potential since the 1980s. The most promising area for deep geothermal extraction is the Kempen area in the north-east of Flanders where a deep bluestone layer (Lower Carboniferous limestone) is located. In September 2015, VITO initiated a pilot project at the Balmatt site in Mol. They installed a drilling tower of 60 metres high equipped with specialized drilling material. As predicted by geologists, engineers found hot water at a depth of 3.5 kilometres. Drilling until this depth is quite challenging, considering that the drilling material needs to be adjusted continuously according to the changing pressure and temperature conditions.

After the heat extraction, the cooled water will be re-injected into the reservoir, creating a closed water loop. In a second stage, there are plans to gain sustainable energy from the pumped water by means of a steam turbine. Recent seismic measurements show that the Lower Carboniferous limestone of the Limburg province (from 2.9 km onwards) has the potential to exploit deep geothermal activity at a large scale. The objective of VITO is to build 80 geothermal plants in the provinces of Antwerp and Limburg by 2050. This would provide heat and electricity for 800.000 households.

At the surface

It is not necessary to drill kilometres deep in order to use our planet’s internal energy. The so-called superficial geothermal energy (with a very low enthalpy: < 30°C), situated close to the earth’s surface, can also be used to heat houses, city and agricultural infrastructure. For these applications, heat pumps are used.

Estelle Petitclerc and Pierre-Yves Declercq, both geologists at the RBINS, examined the potential of superficial geothermal energy, up to 10 metres deep, in Belgium. The project ThermoMap is part of a European research initiative that involves 9 European countries. Researchers collected different data sources on geothermal energy to construct a single database. Based on the data, the researchers developed a calculation model estimating the potential of superficial geothermal energy. This potential is mainly depending on the humidity and the mineral composition of the soil. By investigating soil samples of fourteen locations throughout Europe, the results of the calculations were successfully verified. Today, citizens, governments and the industry in Belgium are able to calculate the potential of superficial geothermal energy for a specific location through an online software application.

The success of ThermoMap led to another European research project: BeTemper (financed by BELSPO). In the context of this project, researchers have determined the geothermal potential of the top 150 metres, the necessary depth to install vertical ground heat exchangers, the most common geothermal heat pumps in Belgium. The geologists mapped the mineralogical composition and thermal conductivity of 400 rock samples. To perform these measurements, the geological lab was equipped with a thermal conductivity scanner.

Soon in Brussels?

It is only recently that new building projects in Brussels are equipped with geothermal systems. The new government building of the Brussels environment and energy administration has four geothermal wells of 80 metres deep, heating the building during winter and cooling it in summer. As the research prior to the construction and the installation of the technology is expensive, geothermal systems are often installed for large construction projects. The idea is to provide basic heat from geothermal energy, and to provide additional heat through other sustainable energy resources such as solar panels.

Together with their partners of the University of Brussels (VUB and ULB), the Université Catholique de Louvain (UCL) and the Brussels environment and energy administration, geologists of our Institute are mapping the geothermal potential in Brussels. They will examine the drill cores from the capital that are stored in our collections, to measure the thermal conductivity at various locations in the city, as well as evaluate the presence of aquifers. These data should be used to produce a detailed map of the geothermal potential in Brussels, covering a depth of 200 metres. The project BruGeoTherMap should be completed in 2020 and the citizens of Brussels should then get access to all information, thanks to the support of Brussels Capital-Region and the resources of the European FEDER project. This should facilitate the investments of geothermal systems in projects for new constructions and renovations. The project aims at stimulating the use of these systems both for companies and individuals, by organizing awareness briefings, conferences and trainings.

“Belgium is a long way behind compared to our neighbouring countries when it comes to geothermal energy”, says Estelle Petitclerc. “All eyes are now on the pilot project in Mol. Its success will be of great importance for the further development of geothermal energy in our country.”


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Text: Nadia Van Roosbroek

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