About geothermal energy
Geothermal energy refers to energy gained from heat stored in the earth's crust. This heat source is constant and permanent, unchanged by weather conditions or the time of day. The use of the earth’s heat can enable emission free energy generation.
The HotRock concept
The general area and characteristics of potential sites are evaluated on the basis of data from prior hydrocarbon drillings and from our own geophysical and seismic explorations. Reservoirs are tapped into by deviated wells with the goal of penetrating as long a section as possible of the reservoir horizon in order to attain a maximum flow rate.
The established Organic-Rankine-Cycle (ORC) and Kalina-Cycle are two processes that can be used for reservoir temperatures over 80°C. Both processes do not use steam from the reservoir directly to operate turbines, but rather transfer the heat through one or more heat exchangers to a secondary fluid. By the use of closed systems for both the production and transmission through the heat exchangers as well as the re-injection of the cooled water, negative effects on the environment, for example from emissions of saline mineral water, are avoided.
In accordance with the German Renewable Energies Act (Erneuerbare Energiengesetz – EEG), the electric power produced is fed into the grid of the closest net provider, who is under a legal obligation to accept the entire volume of electricity. Such provider is also responsible for paying the remuneration for geothermal power.
Geothermal systems
There are two basic types of geothermal systems: deep and close-to-surface (up to a maximum depth of 400 m, also referred to as ground source heat pumps).
Deep geothermal systems
A) Hydrothermal Systems…
… use hot water reservoirs deep under the earth’s surface at drilling depths between 2,000m und 4,000m. These include high enthalpy systems for example in the circum Pacific region and low enthalpy systems for example in Europe.
Low enthalpy hydrothermal systems use deep hot water reservoirs. By means of a production well, hot water is brought to the surface, where the heat is extracted via a heat exchanger. The cooled water is then re-injected into the ground through a second well (doublet). Main targets are natural aquifers or fault zones which can serve as natural pathways for thermal water.
B) Petrothermal Systems…
… use the heat energy stored in the rock masses beneath the earth’s surface, but function mostly independently of water bearing structures. The hot rock mass itself is used as a heat exchanger. Both HDR systems and deep geothermal probes are considered petrothermal systems.
One of the oldest and best-known concepts of using geothermal heat is the hot dry rock system (HDR), also referred to as deep heat mining (DHM), hot fractured rock (HFR) or stimulated geothermal system (SGS). The collective term used to describe all of these systems is enhanced geothermal system (EGS). The concept is that the rock from which heat is to be derived is dry, but contains faults and fracture zones capable of carrying water. If not enough natural fractures are found, they can be artificially created by hydraulically cracking the rock (massive hydraulic fracturing) to reach the desired flow rates. The network of cracks and faults is then connected into the production and reinjection well. HDR systems are usually used in crystalline rocks such as granite (Soultz sous Forets, Basel) and gneiss (Bad Urach). The HDR concept has the advantage that it can be used practically everywhere. Disadvantages include the still very high cost.
Geothermal energy refers to energy gained from heat stored in the earth's crust. This heat source is constant and permanent, unchanged by weather conditions or the time of day. The use of the earth’s heat can enable emission free energy generation.
The HotRock concept
The general area and characteristics of potential sites are evaluated on the basis of data from prior hydrocarbon drillings and from our own geophysical and seismic explorations. Reservoirs are tapped into by deviated wells with the goal of penetrating as long a section as possible of the reservoir horizon in order to attain a maximum flow rate.
The established Organic-Rankine-Cycle (ORC) and Kalina-Cycle are two processes that can be used for reservoir temperatures over 80°C. Both processes do not use steam from the reservoir directly to operate turbines, but rather transfer the heat through one or more heat exchangers to a secondary fluid. By the use of closed systems for both the production and transmission through the heat exchangers as well as the re-injection of the cooled water, negative effects on the environment, for example from emissions of saline mineral water, are avoided.
In accordance with the German Renewable Energies Act (Erneuerbare Energiengesetz – EEG), the electric power produced is fed into the grid of the closest net provider, who is under a legal obligation to accept the entire volume of electricity. Such provider is also responsible for paying the remuneration for geothermal power.
Geothermal systems
There are two basic types of geothermal systems: deep and close-to-surface (up to a maximum depth of 400 m, also referred to as ground source heat pumps).
Deep geothermal systems
A) Hydrothermal Systems…
… use hot water reservoirs deep under the earth’s surface at drilling depths between 2,000m und 4,000m. These include high enthalpy systems for example in the circum Pacific region and low enthalpy systems for example in Europe.
Low enthalpy hydrothermal systems use deep hot water reservoirs. By means of a production well, hot water is brought to the surface, where the heat is extracted via a heat exchanger. The cooled water is then re-injected into the ground through a second well (doublet). Main targets are natural aquifers or fault zones which can serve as natural pathways for thermal water.
B) Petrothermal Systems…
… use the heat energy stored in the rock masses beneath the earth’s surface, but function mostly independently of water bearing structures. The hot rock mass itself is used as a heat exchanger. Both HDR systems and deep geothermal probes are considered petrothermal systems.
One of the oldest and best-known concepts of using geothermal heat is the hot dry rock system (HDR), also referred to as deep heat mining (DHM), hot fractured rock (HFR) or stimulated geothermal system (SGS). The collective term used to describe all of these systems is enhanced geothermal system (EGS). The concept is that the rock from which heat is to be derived is dry, but contains faults and fracture zones capable of carrying water. If not enough natural fractures are found, they can be artificially created by hydraulically cracking the rock (massive hydraulic fracturing) to reach the desired flow rates. The network of cracks and faults is then connected into the production and reinjection well. HDR systems are usually used in crystalline rocks such as granite (Soultz sous Forets, Basel) and gneiss (Bad Urach). The HDR concept has the advantage that it can be used practically everywhere. Disadvantages include the still very high cost.