You played a key role in the construction of the first two geothermal power plants in Germany – in Neustadt-Glewe and later in Landau. Neustadt-Glewe was a real pioneering project at the time and paved the way for larger plants such as those in Insheim and Unterhaching. How did you get involved in these projects back then – and what fascinated you about geothermal energy?

Dr. Heiner Menzel: That’s an exciting question. I’m originally a marine engineer – so I was actually made for the sea. But due to my seasickness, I quickly realized that it wasn’t for me in the long term. Coincidentally, geothermal energy was being developed at the time and I thought to myself: seawater is salty, so is thermal water – that somehow fits. So I changed my career direction and went into geothermal energy in Schwerin. That was my first step into this new field – exciting, challenging and just the right thing at the right time. In the course of reunification, East German expertise in the field of geothermal heat utilization was to be further developed. This gave rise to the project in Neustadt-Glewe, which went into operation in 1996. In 1998, the idea of also generating electricity was added – inspired by a conversation with a representative of Ormat and by the EEG, which was being planned at the time. In addition to Erdwärme Neustadt-Glewe GmbH, which was responsible for supplying heat to Neustadt-Glewe, this later gave rise to Erdwärme Kraft GbR, of which I was the technical managing director. This company built and operated the first geothermal power generation plant in Germany, which went into operation in 2003.

And then you came to the Palatinate…

Dr. Heiner Menzel: The next big step came in 2003: I was brought to Landau to set up another geothermal project there. Together with Pfalzwerke and EnergieSüdwest AG (ESW), we founded geoX and realized the geothermal power plant in Landau.

You have been part of the Vulcan family since 2023 – what has been your greatest success at the Karlsruhe-based company so far?

Dr. Heiner Menzel: There are three personal highlights. The biggest for me was the move to Vulcan – because it turned a vision that I had had since my early days in Neustadt-Glewe into reality: to use geothermal energy not only for energy but also for materials. There are many valuable substances in thermal water, and Vulcan has taken the decisive step towards tapping into this potential. That was also the main reason for my move – and a real milestone. My second highlight was the takeover of the power plants in Landau and Insheim – that closed a circle for me. And the project I am currently working on with great dedication is the geothermal heat supply for Landau. This project is particularly close to my heart because we are not only reliably supplying the city with climate-friendly heat, but also showing how the decarbonization of the heat supply can succeed with the resources of our own region. This is exactly the path we need to take as a society – local, sustainable and future-oriented.

In the context of the energy transition, geothermal energy is increasingly seen as a key technology. What developments are currently shaping the industry – and where do you see the greatest potential for the future?

Dr. Heiner Menzel: The biggest challenge in geothermal energy is still the discovery rate. You have to drill several kilometers deep to be able to say for sure whether and how much usable thermal water is available. This means that before you can even start building a plant, you have to invest 10 to 15 million euros – a different entrepreneurial risk to wind power, photovoltaics or hydropower. But once the source has been tapped, you have a reliable, local and base load-capable source of energy – which makes you independent of the time of day and season. This is what makes geothermal energy fundamentally different from other renewable energies. In recent years, there has been a rethink, particularly as a result of the energy crisis caused by the war in Ukraine. Geothermal energy offers stable, calculable heat prices – in contrast to gas, whose price development is almost impossible to plan. The material use of thermal water is also becoming increasingly important. In addition to lithium, the focus is also shifting to elements such as strontium and magnesium, which – depending on the geological composition – have sometimes been detected in higher concentrations in thermal water. Its use is considered technically feasible and the first pilot projects have already been launched. Although economic processing is still in its infancy, this is precisely where new prospects are opening up: Because anyone who sees geothermal energy not only as a source of energy, but also as a potential source of raw materials, is thinking an important step ahead.

Geothermal energy is regarded as an environmentally friendly and reliable source of energy. Nevertheless, some projects are slower than expected or require particularly intensive support. Why do you think this is the case?

Dr. Heiner Menzel: Geothermal energy is used successfully in over 40 countries worldwide – for both electricity and heat generation. This illustrates the great potential of this natural resource. There is also growing interest in Germany. At the same time, geothermal energy is a technology that is barely visible in everyday life – it works underground. This distinguishes it from wind or solar plants, for example, which we perceive directly. It is precisely because geothermal energy cannot be experienced directly that many questions sometimes arise: How does the technology work? What happens underground? Such topics offer a good opportunity to provide factual information and make the interrelationships understandable. In regions such as the Upper Rhine Graben, geological activity has been a natural part of the earth’s history for millions of years – and with modern processes, this energy source can now be used in a targeted and responsible manner. It is crucial to communicate openly and transparently. The better people understand how geothermal energy works and what contribution it can make to a sustainable energy supply, the more trust is created – and therefore the greater the willingness to move such projects forward together.

What do you think is particularly important to promote acceptance of geothermal energy – especially in local communities?

Dr. Heiner Menzel: Transparency and an open dialog are crucial. It is about making the technology tangible and showing local people how responsible and forward-looking the work is. Continuous monitoring of all relevant geological and technical processes plays a central role in this. Modern systems enable us to gain precise insights at all times and to fine-tune the systems accordingly. A particularly effective way of arousing interest and strengthening trust is to visit geothermal plants directly on site. For schools, clubs or interested groups of citizens in particular, such visits offer very good access: you can see how the technology works, get to know the people behind the projects and understand the benefits for the region. At a municipal level, the main aim is to get people involved at an early stage and develop viable solutions together. The more people are involved in processes, the greater their willingness to follow this forward-looking path.

Is there an experience in your career that has particularly influenced or inspired you?

Dr. Heiner Menzel: Definitely the move from northern Germany to Landau and the associated establishment of geoX – that was a decisive turning point. With this step, I not only broke new ground professionally, but also laid the foundation for my future career.

What do you do when you’re not working on the energy and raw materials supply of the future?

Dr. Heiner Menzel: In my free time, I enjoy hiking and going to the gym. I particularly enjoy being out in nature – for example in Bad Herrenalb, where I live, or in the Allgäu region. And, of course, I’m always drawn to the sea – that’s probably because I used to work at sea.

Thank you very much for the exciting insights and the openness with which you shared your personal experiences with us, especially during the pilot projects in Neustadt-Glewe and Landau!

The interview was conducted by: Patrizia Bär – Public Affairs I Regional Management