Home/Test drilling on the Rebstockbad site to research geothermal energy as a climate-neutral energy source

Test drilling on the Rebstockbad site to research geothermal energy as a climate-neutral energy source

Press release from April 22.11.2021rd, XNUMX

Geothermal energy as part of the energy transition in Hesse

Test drilling on the Rebstockbad site provides important data / A total of 17 test drillings in Hesse

The use of geothermal energy to heat or cool buildings can make an important contribution to the energy and heating transition. In order to bring this technology for heating and cooling supply closer to municipalities and citizens and at the same time provide them with well-founded planning data, the Hessian Ministry for Economic Affairs, Energy, Transport and Housing has commissioned the LEA LandesEnergieAgentur Hessen GmbH (LEA Hessen) to carry out geothermal test drilling and investigations to be carried out in Hessian towns and communities. The Hessian State Agency for Nature Conservation, Environment and Geology (HLNUG) evaluates and processes the knowledge gained in this way. A total of 17 test bores are being carried out in Hessian municipalities, which are being expanded into geothermal probes. If a location is suitable, geothermal energy can not only provide energy and heat for homeowners, but also for municipalities that want to develop building areas or for commercial real estate.

Knowledge of the local geological and geothermal situation is also being gathered on the Rebstockbad site in Frankfurt by means of a 100 meter deep test bore.

The Hessian Economics and Energy Minister Tarek Al-Wazir said on the occasion of the test drilling in Frankfurt: "A large part of our energy consumption flows into the heating of our apartments or industrial process heat. You could also say: In many places we heat out the window. The result: the CO2-Emissions in the building sector are too high. This has to change, which is why we are pursuing different paths at the same time in the energy and heating transition: on the one hand energy saving and energy efficiency, on the other hand alternatives to fossil fuels. This also includes near-surface geothermal energy. That is why the State of Hesse, together with the State Energy Agency of Hesse and the State Office for Nature Conservation, Environment and Geology, is supporting test drilling in municipalities to determine geothermal potential on site.” The state is investing a total of 500.000 euros in the project.

"The new construction of the Rebstockbad is an important milestone for the Frankfurt baths and we want to focus more on new energy and resource-saving technologies," says the city council Mike Joseph, Chairman of the Supervisory Board of BäderBetriebe Frankfurt GmbH. "In particular, the use of energy sources that are as climate-neutral as possible is important for the new Rebstockbad, along with many other means of optimizing energy consumption - such as a highly thermally insulating building envelope and very efficient technical systems."

"The scientific investigations of the Hessian State Agency for Nature Conservation, Environment and Geology (HLNUG) provide the public with important data for the site-related planning of efficient geothermal systems. In this way, we support potential users in their decision to use near-surface geothermal energy,” says dr Gabrielle Aderhold, head of geology department at HLNUG. "We also ensure that the installation of a geothermal probe does not affect the groundwater."

Geothermal heat is given to a heat pump via a geothermal probe. In this way, geothermal energy can be used to heat and cool buildings. dr Karsten McGovern, Managing Director of LEA Hessen, explains: "Geothermal energy is so attractive for businesses and property owners: It is available all year round and regardless of the weather and does not cause any CO2 still fine dust. In addition, there are low operating costs and high subsidies for investing in heat pumps.”

How is the drilling going?

A drilling rig is delivered and positioned on a low-loader. A drill bit at the tip of the drill pipe then works its way down to a depth of 100 meters. In miners' language, this is called "sinking". The rock material that is loosened in this way is transported upwards out of the borehole with water. Rock samples are continuously taken for geological description.

After the planned drilling depth has been reached, the drill rods are removed. A geothermal probe is then lowered into the borehole. It consists of two U-shaped plastic tubes. The borehole is then filled with a cement-bentonite suspension. This is necessary to firmly connect the geothermal probe to the surrounding rock. This achieves a high heat exchange between the probe and the ground. In addition, the borehole is sealed against groundwater-bearing layers.

What comes next?

The Hessian State Agency for Nature Conservation, Environment and Geology (HLNUG) examines the rock samples. A specialist company carries out a so-called "Thermal Response Test" (TRT) one to two weeks after installing the geothermal probe and determines the thermal conductivity of the subsoil. In addition, the temperature of the subsoil is determined in the geothermal probe.

In einem Characteristics the HLNUG summarizes the results and publishes them on its website (www.hlnug.de) available to the public. On the basis of the profile, those who want to build in Frankfurt, property owners and energy suppliers can plan the correct dimensioning of geothermal probes as well as the drilling and expansion work on a large area around the test bore on the basis of well-founded data.

Drilling on the Rebstockbad construction site

The data obtained during the drilling are therefore also of interest in the planning process for the new Rebstockbad. The Rebstockbad is currently being redesigned with an innovative concept. Construction will start in early 2023. The opening of the new Rebstockbad is scheduled for the end of 2025. An important part of the new pool is the energy and resource-saving, ecological and economical construction and operation. The new energy concept provides for an energy mix. Geothermal energy could also contribute to the heat requirements of the new Rebstockbad. “Further modules for the energy supply are being developed in close cooperation with the Mainova specialists. These include a photovoltaic system on a roof area of ​​more than 2.000 square meters, a combined heat and power plant and a connection to the district heating system," reports Mike Josef, Chairman of the Supervisory Board.

What is geothermal energy?

The heat stored in the earth's interior, also known as geothermal energy, can be used to heat and cool buildings, heat water and generate electricity. The heat comes from the earth's core. According to current knowledge, it is hotter than 5.000 degrees Celsius there. The temperature in the ground increases with increasing depth: in Germany by about three degrees Celsius per 100 meters.

The warmth of the earth's interior is practically inexhaustible. Geothermal energy is therefore one of the renewable energies. The use of geothermal energy for heating and cooling buildings is possible all year round, sustainably and efficiently. The state government is therefore promoting knowledge about their use.

Background to the project

The LEA State Energy Agency Hesse commissioned by the Hessian Ministry for Economic Affairs, Energy, Transport and Housing (HMWEVW) perform test drilling by a specialized company. In the years 2021 to 2022, near-surface test drillings will be and were carried out in a total of 17 Hessian municipalities. The Hessian State Agency for Nature Conservation, Environment and Geology (HLNUG) carries out investigations into the geology and geothermal properties of the subsurface as part of the geological survey of these boreholes and makes the results available to the public.

Test drillings are and have already been carried out in some of these communities: Alsfeld, Büdingen-Düdelsheim, Frankenberg (Eder), Frankfurt (Rebstockbad), Groß-Gerau, Habichtswald, Hofheim-Wallau, Homberg (Efze), Langgöns-Dornholzhausen, Offenbach, Pohlheim, Riedstadt-Goddelau, Solms, Stockstadt am Rhein, Twistetal, Vellmar and Waldeck.