The big role for medium-depth geothermal in Switzerland

In a recent interview with Swiss publication Aqua et Gas, Nathalie Andematten, President of Géothermie-Suisse, and responsible for the canton of Geneva for the GEothermies program provided a strong and optimistic outlook for geothermal energy in Switzerland. A geologist, she is enthusiastically committed to the development of geothermal energy within the framework of the energy transition underway.

With a 2050 goal by Switzerland to not emit greenhouse gases anymore, geothermal will have an important role to play and the geothermal association of Stizerland,  Géothermie-Suisse is committed to ensuring that geothermal energy becomes an essential pillar in the supply of heat and electricity as well as for cooling in Switzerland.

What are the objectives of the association Géothermie-Suisse?

Geothermal-Switzerland aims to implement and accelerate the use of different forms of geothermal energy in Switzerland, in order to provide as many people as possible and quickly with a source of local, renewable and carbon-free energy. Today, the Geothermie Schweiz association is driven by the need to accelerate the development of geothermal energy. The priority is to increase the visibility of geothermal energy, to facilitate the start-up of projects and to develop sectors – particularly at medium depth – in order to provide Switzerland with a genuine geothermal market. To meet its challenges, the association has initiated partnerships with complementary associations and has strengthened and professionalized its structure.

What are the different types of geothermal energy and what are the classification criteria?

Depending on the depth, we speak of shallow, medium or deep geothermal energy. There are different ways of exploiting the heat of the subsoil, either by so-called “closed” systems – for example geothermal probes – which recover calories directly in the subsoil by installing heat exchangers within boreholes cemented, or so-called “open” systems which allow the pumping and reinjection of underground water by two boreholes (called doublet), with recovery of calories from the underground water on the surface. In the case of systems that exploit the calories of underground water, we also speak of hydrothermal geothermal energy.

The temperature of the water drawn from the depth depends essentially on the depth from which it is pumped. Generally speaking, what temperatures are found at what depth?

At a depth of about ten meters, the terrestrial temperature remains practically constant throughout the year and is around 12°C on the Swiss Plateau. As it deepens, this temperature increases by about 3°C ??every 100 meters, thus being able to reach about 100°C at 3,000 meters depth.

The type of use depends on the temperature level. What are the typical applications according to the type of geothermal energy and in which situations does distance heat come into play?

Depending on the depth levels, and therefore the temperature of the resource, the exchange of calories with the subsoil or the recovery of calories from groundwater will therefore make it possible to provide either cooling, heating (by heat pumps or by direct exchange) or underground thermal storage solutions. When the temperature level exceeds approximately 100°C, it is also possible to co-generate electricity with the recovered heat.

Medium and deep hydrothermal geothermal installations are connected to a remote heating network because the power delivered by a single well generally provides energy for several thousand households.

Each year, Geothermal-Switzerland draws up statistics on the production of geothermal energy in Switzerland on behalf of SuisseEnergie. How much heat is currently produced by geothermal installations in Switzerland? How is this heat production distributed between the different technologies and the different types of use?

Today geothermal energy is already an important contributor of local renewable energy. Indeed, more than 4 TWh/year of geothermal energy is recovered, which covers approximately 5% of Swiss thermal needs. Over the past ten years, the heating power and heating energy produced by geothermal energy have doubled. About 80% of geothermal energy is produced today by geothermal probes and probe fields, which are highly developed in Switzerland, and 10% by the use of shallow groundwater. The rest of the geothermal production in Switzerland comes in particular from thermal baths, the recovery of heat from tunnels or the recovery of medium-depth aquifers (realization of Riehen).

Several pilot installations have already been carried out abroad, in which geothermal energy is used to produce electricity. In your opinion, what is the potential in this area in Switzerland and can such projects be expected in our country in the years to come?

The interest in generating geothermal electricity lies in the fact that it is a ribbon energy source, available 7 days a week and 24 hours a day. As we are not in a volcanic country where the subsoil is warmer than in Switzerland, the potential for electricity production is lower there. However, we see it in the Munich basin where such facilities exist while the geological context is similar to ours, from about 3 kilometers deep the temperature would be sufficient to produce electricity. This electricity production potential is estimated by the Federal Office of Energy at 2 TWh/year, but it could be revised upwards if profound and ubiquitous technological developments occur as a result of the pilot projects in progress.

When we talk about geothermal energy in Switzerland, many people think of the tremors caused by the projects in St. Gallen and Basel a few years ago. What lessons has the sector learned from these incidents?

As mentioned above, there is not a single type of geothermal energy but a multitude of more or less complex possibilities with very different levels of technical maturity and therefore related risks. With the projects in St. Gallen and especially Basel, we immediately wanted to develop projects of the greatest complexity in Switzerland, even though knowledge of the Swiss subsoil was not good. The difficulties encountered by these projects have had the merit of highlighting structured exploratory approaches and other geothermal solutions, particularly at medium depth, which are now being developed in large numbers. These experiences make it possible to gradually improve local know-how and therefore to have more mature sectors capable of carrying out efficient and low-risk projects.

“The difficulties encountered by these projects have had the merit of highlighting structured exploratory approaches and other geothermal solutions, particularly at medium depths.”

How do you assess the risks that current geothermal projects, such as those in Haute-Sorne or Lavey-les-Bains, will again cause tremors of this type?

The Haute-Sorne project is a pilot which aims to develop innovative and reproducible deep solutions in terms of electricity supply. As it involves hydraulic fracturing, it will be carried out under close supervision, based on lessons learned from Basel, so that the operations are controlled in terms of induced seismicity. The Lavey-les-Bains project is a hydrothermal project that does not require hydraulic fracturing and therefore presents a low risk of induced seismicity. In general, the prevailing rules for the management of induced seismicity and the monitoring methods have been greatly strengthened since the Basel project.

In October 2020, Geothermal Switzerland published the position paper “Thermal potential of geothermal energy”. Which 2050 goal is there and where is the greatest potential?

In the position paper, the objective is formulated: In future, geothermal energy will provide at least 17 TWh/year of heat for the Swiss building stock and for industrial processes. The shallow geothermal potential will be able to more than double and reach a production of around 9 TWh/year, while that at medium depth will take off and should cover at least 8 TWh/year. With at least 17 TWh/year, geothermal energy would thus cover more than 25% of the estimated thermal demand in 2050.

Since 2018, the law on CO ₂provides subsidies for projects involving the direct use of geothermal energy for heat production. These support measures for medium-depth geothermal energy are bearing fruit since many projects have since started. With the reinforcement of these measures and a dynamic of sharing and feedback of structured information such as set up by Géothermie-Suisse thanks to the Transfer platform, the medium-depth sector will be able to take off.

Where is medium-depth geothermal energy already used in Switzerland for heat production?

A medium-depth geothermal operation has existed in Riehen in the Canton of Basel for decades. Building on this success, new developments are underway to increase geothermal production on the already supplied district heating network.

What projects are currently being planned, particularly with regard to district heating networks?

Projects are underway in Geneva where two exploratory drillings have already been carried out with encouraging results. In addition, exploratory drilling work has just started in Lavey-les-Bains and an equivalent project should start immediately on the Vaud coast in Vinzel. In addition, prospecting is in progress or planned on many sites such as Lausanne, in the Yverdon region, Fribourg, Macolin or Basel. On all of these sites, discussions are being carried out to develop heating networks that will make it possible to recover the large quantity of energy produced. The Lavey-les-Bains project plans to produce electricity in addition to heat.

We note that the projects are mainly located in the west of the country. One of the reasons could be that the weight of St. Gallen and Basel weighed more heavily on the German-Swiss part than on the western part. In addition, we always need pioneering projects. Thus, the Geneva project plays an important role in relation to the visibility of geothermal energy and in relation to all the communication that is made around it. Such pioneering projects trigger a certain dynamic, as can currently be observed in western Switzerland.

You mentioned earlier the possibility of thermal storage in the basement. What are the possible solutions in this area? What thermal storage projects have already been completed or are in the planning stage?

Geothermal storage takes advantage of the thermal storage capacity of the subsoil to store heat when not in use. Storage is possible with geothermal probes, just like with groundwater: the heat that no one needs in summer will warm the groundwater by a few degrees. In winter, the natural resource will then be preheated and the calories will be available. There are many shallow geothermal storage projects in Switzerland. Most provide for storage in the form of geothermal probe fields or in aquifers, with integration into anergy networks. Examples can be cited in Zurich, Lucerne and Zug. But storage in deeper aquifers also offers very promising prospects.

“Storage in deeper aquifers offers very promising prospects. The Forsthaus storage project in Bern serves as an example.”

The GEothermies program of the canton of Geneva acts as a precursor program. What are the objectives of this program and how do we proceed?

The Geneva program aims to massively and sustainably develop all types of geothermal energy in the Canton of Geneva. Various transversal actions are carried out jointly by the State of Geneva and by SIG in order to develop all the geothermal sectors. More concretely, geological exploration and subsoil mapping at shallow, medium and great depths are being carried out to clarify geothermal potential and identify favorable targets: Exploratory drilling was done, then, in autumn 2021, a campaign 3D seismic survey was carried out in the Geneva conurbation, including in neighboring France. The vibratory waves sent into the subsoil and their returns measured by sensors allow precise mapping of the subsoil.
At the same time, more institutional and organizational works are being set up in order to have a favorable framework for the development of geothermal energy. The axes on which it was decided to intervene are in particular the legal aspects, data management, energy planning, communication, the development of professional sectors or even cross-border and inter-cantonal coordination. The framework is thus today much more adapted and favorable to the development of geothermal energy with in particular new legal bases and the frank integration of geothermal energy in territorial and energy planning.
After an exploratory phase conducted between 2015 and 2021, the program is now in a stabilization and transition phase towards industrialization which will take place by 2026.

In the middle of 2020, Géothermie-Suisse launched the Transfer program, which you have already briefly mentioned. What is the purpose of this approach and what projects are currently underway?

The Transfer platform was set up to encourage feedback and shared experience sharing between geothermal players. The goal is to accelerate joint know-how and thus promote quality projects, notably with substantial immediate returns on investment. The platform has already dealt with several essential themes and benefits from governance representative of the branch as a whole, making it possible to identify high-stakes themes and thus prioritize them. Here are some examples of completed and ongoing projects:

• Identification of the main obstacles to the start of medium-depth hydrothermal projects with the various stakeholders (project leaders, authorities, planners, implementers), accompanied by the identification of solutions to facilitate and accelerate such projects. A corresponding guide will soon be available.
• Creation and first successful use of a targeted networking platform, with profiles of expertise and service offers from the various players:
  www.connect4geothermal.ch
• Promotion of the experiences of the 3D seismic campaign in Geneva in autumn 2021. Never had such a campaign been carried out in such a vast urban area. In one of the Transfer projects, the accumulated experiences, good and less good, have been systematically collected and are now shared and supplemented with the experiences of other project promoters in other cantons. By the end of the year, a guide to good practices for seismic surveys will thus be made available to industrial services, municipalities and cantons, enabling them to improve efficiency and quality.
• Development of a recommendation, or even a standard, for the data to be collected during exploratory drilling. As Switzerland is not yet very active in this area, we lack experience. The standard for minimum data will also allow a gain in efficiency and quality, as well as an optimization of costs. This project is in progress and the recommendation should be available at the end of the year.
• Identification of factors inhibiting the integration of geothermal energy in the early phases of development of neighborhood plans, in order to propose improvement measures.

Finally, we create and animate communities of practice for geothermal energy, in order to allow the various key players – project leaders and authorities in particular – to share their experiences in an appropriate framework.

Source: Aqua and Gas