What are the main geothermal energy technologies, and which of these technologies has the greatest potential on the European market?
E.H.: Geothermal energy technologies depend on the specific geological setting. We have hot water bearing horizons in many parts of Europe. We call them hydrothermal reservoirs. In addition, the ground all across Europe has increasing temperature with depths. The horizons which do not bear water are called petrothermal systems. A general technology to economically exploit these reservoirs is to follow the so called concept of Enhanced (or Engineered) Geothermal Systems (EGS). The EGS concept includes artificial improvement of the hydraulic performance of a reservoir with the goal of using it as a source for the economic supply of heat or electric energy. The enhancement challenge involves the use of several non-conventional methods for exploring, developing and exploiting geothermal resources that are not considered economically viable with the use of conventional methods.
What is the current contribution of geothermal to the EU energy mix and how is this share expected to change in the medium to long term?
E.H.:The current contribution is still very small compared to the huge existing potential. In the medium term a significant increase in geothermal heat supply can be expected, with a significant increase in geothermal power production in the long term. In the past we observed an increase in capacity of one order of magnitude in 20 years. With investment in research and development we have the chance to accelerate the deployment of geothermal technologies. However, it is important to note that a project with deep drill holes takes several years to implement and therefore the learning curve cannot be as steep as with other technologies, such as solar and wind, for example.