Geothermie 14

Areas of Work
Geothermal Energy

The deep geothermal energy as base-load capable form of energy is an important component of the sustainable energy mix. The source of energy is hot deep groundwater which is used to generate energy. The generation raze depends on pumping rate, temperature and mineral content. However, the hot deep groundwater could also cause problems such as corrosion and scalings. It is important to understand the geothermal system in order to fine-tune it. Through several projects Hydroisotop gained significant experience with respect to analysis, monitoring, and scale inhibitation which allows us to offer a broad portfolio ensuring a smooth system operation e.g.:

  • Execution and interpretation of physical-chemical and isotope-hydrological investigations, determination of groundwater age and accompanying gases with regard to a sustainable usage

  • Consulting and proposal of concepts for a multiple geothermal usage

  • Reservoir analysis for a better risk assessment of operation

  • Quality control, long-term monitoring, technical operation control, and risk assessment (for insurance etc.)

  • Desaster prevention, technical problem solution, concepts for remedial actions

  • Treatment and filtration

  • Submission of application according to water regulations and mining laws, etc.

Near-surface geothermal energy plays an important role as a sustainable energy source for heat supply. The following types of usage can be differentiated: ground source heat pumps, geothermal heat collectors, and groundwater wells. The groundwater well is the essential part of the system. Various problems can occur at the contact of groundwater with other parts of the equipment such as: corrosion, scalings, and microbial mucous. Hydrochemical investigation of the groundwater and the evaluation of the water chemistry with regard to the design are the basis for precautionary measures and an uninterrupted operation. For all types of usage the secondary circuit which extracts the groundwater thermal energy by a recuperator is at risk of corrosion but also microbe growth (e.g. legionellae), in particular in the water heating system. Those microbes find optimal living conditions at certain temperatures and can pose a hazard to health. An increase of temperature causes the extinction of the microbes. However, this temperature increase requires a higher energy flux resulting in a performance drop of the heat pump and therefore a reduced efficiency of the device. Alternatively, the problems caused by microbiology can be solved through the use of desinfectant.

Geothermal resources

The earth serves as a resource of heat which is almost inexhaustible: 99 % is hotter than 1.000 °C, only 0.1 % is colder than 100 °C. Under the thin earth's crust which we are living on the earth's mantle follows. In the middle of the earth there is a liquid core.

At many locations on earth such as Iceland or Tuscan Larderello hot springs appear at the surface. The hot water of those springs is used to produce energy or heat, commonly known as geothermal energy.

Even in Germany geothermal energy is available for usage. Two different techniques utilise hot water for heat or power production:



  • Thermal water is pumped out of underground aquifers

  • For power generation the pumped groundwater should be hotter than 100 °C and the pumping rate should exceed 50 L/s

  • In hot groundwaters minerals are dissolved which precipitate with a change of pressure and temperature or cause corrosion



  • Under high pressure water is pumped though two boreholes (depth ca. 5000 m) into the earth's crust to widening the cracks in the rock

  • Ideally, a connection between the two boreholes - an underground heat exchanger occurs

  • This way water that is pressed into one borehole can be pumped out to the surface through the other borehole again

  • At temperatures of 150 - 200 °C and high pumping rates power is generated

Geothermie 2

Geothermal reservoirs

Geothermal energy is the energy kind of the future. The advantages are obvious: regenerative and base loadable; independent of climatic fluctuations, seasons and daytime; geothermal energy warrants a continuous power supply. Essential for a successful long-term operation is a well explored reservoir as well as the protection of the reservoir. This requires not only the determination of the basic parameters - pumping rate and temperature - but also the detailed characterisation of the geothermal water.

Hydrochemisches Profil

A long-term utilisation of a geothermal power plant demands an understanding of the thermal water system and a characterisation of the reservoir.

Thermal water assessment:

  • hydrochemical composition
  • determination of the origin
  • water-rock-gas-interactions
  • recharge conditions
  • age composition
  • cross-formation-flow
  • water flow regime

Characterisation of the reservoir:

  • reservoir size and usability
  • possible changes of the system
  • interactive impact
  • radioactivity
  • corrosion
  • precipitations
  • prevention of breakdown

The hydrochemical analysis of water based on the composition of positive and negative ions is used to assess the reservoir characteristic and the interactions between water and rocks.

Gasphysical analyses of carbondioxid, hydrogen sulphide, nitrogen, methane etc. provide a fingerprint of the individual geothermal systems.

By means of isotope hydrological analyses of the oxygen-18 and deuterium contents a characterisation of the formation conditions is possible. Also climatic information, age determination, and water-rock-gas-interactions can be derived from isotope methods.

The groundwater chemism as an origin-specific fingerprint it essential for the exploitation of a geothermal system.