Answers to questions on geothermal energy

An innovative form of energy extraction stimulates a lot of questions – so does geothermal energy. Here you find answers to the most frequently asked questions.


How are such large-scale projects financed?

The financing in FG is composed as follows::

  • Phase 1 and 2:

    The financing of the design, project preplanning, creation of seismic data, provision of all the expert opinions required, as well as the costs for acquisition of the plot of land and the creation of a land development plan is carried out with the financial means of FG group as well as financing from Here more than 2500 investors have already placed their trust in us. In this way they allow us to develop the Amerang, Gars, Kirchweidach, Seebruck and Schnaitsee projects.
  • Phase 2:

    This phase includes drilling at the developed site, and is financed both by private investors and by large-scale institutional investors.
  • Phase 3:

    The third phase of the implementation of a geothermal project includes the development of the geothermal power plant. Here “classic” bank-based financing is used. 


What is the geological risk?

In the whole of Germany there is a very low geological risk. The entire Bavarian Molasse Basin is even in a preferential situation with respect to this, and on the basis of geological findings and experiences to date, the risk can be estimated as being very low. 

In order to determine the underground target fields, we were able to use the results of a 3D seismic study carried out for the projects of FG. Since the late 1960s, the oil and gas industry has carried out 30,000 drillings in Germany. For geothermal projects, to date 73 drillings have been carried out. 

Geologische Verhältnisse

The geological conditions for geothermal projects can be considered to be particularly favourable in Bavaria. The greatest potential for hydrothermal energy extraction is in the area to the south of the Danube, in the Malm Karst of the South German Molasse Basin. 


What is the ecological risk?

In comparison with the technical standards for drillings in the oil and gas industry, in geothermal drillings higher ecological norms are adhered to, as borehole cleaners are always used which are compatible with groundwater. For this reason, when these standards are adhered to there are no physiological problems (e.g. for drinking water supply). Moreover, the geological results of the drillings from the Molasse Basin are available. 

The geological conditions for geothermal projects can be considered to be particularly favourable in Bavaria. 

The greatest potential for hydrothermal energy extraction is in the area to the south of the Danube, in the Malm Karst of the South German Molasse Basin. 


What advantages does it bring for the community?

We are currently developing a model which involves allowing both the communities and their citizens to share the economic successes of our projects. Unfortunately, diversion of heat can currently only be implemented in Gars, due to the structure of the settlements and the situation of the available plots of land for the settlement of industrial customers.

However, should it prove possible to find appropriate plots of land which would be acceptable for the citizens, and should the construction of remote heat diversion make economic sense, this would by all means be a desirable goal. Here we would like to make reference to our successful model in Kirchweidach, in which 12 hectares of greenhouses are heated in an emission-free manner. Here an extension is being considered to make a total greenhouse plant area of 25 hectares. 


Which disadvantages would the project have for the community?

The locations being considered are selected for “minimal perception” of the plant by neighbours and inhabitants of the locality. Both during the drilling and during the operational phase, the goal is to keep interferences through noise and construction activity as low as possible. We make an effort to remain significantly below all of the legal limit values on noise production. 


What is the difference between hydraulic fracking and the stimulation process in deep geothermal projects? What is used here?

In hydraulic fracking, stone layers are blasted open artificially with high fluid pressure and held open with propping agents. The Bavarian Molasse Basin has a highly permeable limestone layer as a reservoir, for which fracking is not a suitable stimulation method, as high pressures cannot be built up. 

In order to clean the borehole and carry out stimulation at the same time, after approval by the authorities of the special operating plans submitted, fluids are used which clean the dolomite and the limestone in the area of the borehole of drilling cuttings and impurities, and hence make the area close to the borehole more accessible. In principle the process is comparable with decalcification in the kitchen and bathroom.


Which consumption structures are provided for heat consumption?

According to the current status of plans, the Schnaitsee project is to be used to transform the energy extracted into electricity. Unfortunately in the immediate vicinity of the potential plant sites no suitable areas are available for the placement of industrial remote heat consumers.


How many employees would be necessary for operation? Is remote maintenance planned? How many jobs would there be in total?

A geothermal plant can largely be operated free of supervision. For its operation 1-2 qualified jobs would be created, and in addition there would be a series of accompanying activities (cleaning services, small repairs, care of the external installations, etc.).


Would the locality receive business tax when the construction has been paid for?

It is planned here to transfer the registered office of the company into the corresponding community, in order to enable earnings through business tax. In addition, we are currently developing a participation model for the relevant communities in order to secure earnings from the first year of energy extraction. Since the investment costs of this kind of project are of the order of two-digit millions of Euros, earnings through business tax would only have effect after a few years.


Will an Environmental Impact Assessment be carried out before the beginning of construction?

The mining authority or the district office will decide on the necessity of an Environmental Impact Assessment. The emphasis is on an investigation of the fauna of the planned site (special species investigation).


Is a HAZOP to be carried out? (Hazard and operability study: a process management for damage to property and the environment, security controls and security measures)

This has not yet been decided. Generally, in the preliminary phase, during construction, drilling and operation, all applicable laws and specifications of the approving authorities are fulfilled as a minimum. 


  1. Is continuous groundwater monitoring to be carried out?

    If this is required by the approving authority, then it is self-evident. So far we are not sure if in the Molasse Basin such demands have been made based on the hazard evaluation made by the authorities.
  2. Which volumes of water are used for cleaning and testing during drilling, and where does this water come from?

    The water is taken from the normal drinking water supply, which can supply the water volumes required during drilling and testing without any problems.
  3. How is waste water management carried out?

    During operation there is only a small amount of waste water for filter backwashing; this can be introduced into the normal channel. Here too, the concerns of the community are fully taken into consideration, and all legal requirements are taken into account. 
  4. What happens with the drilling cuttings (special waste)? Are the employees trained for this? 

    Drilling cuttings, in accordance with their respective composition, are disposed of by a specialised, certified waste disposal company.
  5. Is the floor plate sealed and is this checked in order to exclude the ground water damage? 

    The floor plate (the base for the drilling plant), the three drilling cellars and the rod bearings / casing are situated in the inner drilling area. The floor plate and the drilling cellar are designed in concrete on the basis of the results of the soil mechanical foundation soil examination, and according to the static and foundation engineering requirements. The remainder of the inner area is asphalted.


The inner fully asphalted/concreted over drilling area, and the bypass, which is also secured, are limited by a surrounding upturn. The water which accumulates is collected and disposed of in accordance with regulations.
  6. Is a weather station planned? 

    No. If necessary, data from regional weather recordings are used.
  7. Is noise measurement carried out before beginning construction in a particular area? 

    Noise measurement is carried out in order to investigate the prior noise level.
  8. Are there continuous noise measurements with plans to adhere to the noise limit values? Will it be switched off if the values become too high?

    Of course the plant must fulfil all the specifications of the Technical Instructions on Noise (TA Lärm), otherwise it would not and could not be operated.
  9. Will there be prior wind measurements to determine the main direction of the wind, with respect to the carrying of noise?

    These measurements will also be carried out in order to be able to adhere to all limit values at all times.
  10. Are there glare protection devices for the closest neighbours if drilling is carried out day and night? 

    No glare is expected during drilling.
  11. Are there detectors on the houses in order to be able to document tears, raising and lowering?

    This kind of measure would have to be stipulated by the mining authority. Currently such measures are not planned.
  12. Are continuous radon measurements planned?

    No cases of radon exposure are known from the Malm aquifer in the South German and Upper Austrian Molasse Basin, which is the drilling target. 
  13. Are measuring devices installed to monitor earthquakes close to the construction site before the project begins? 

    Earthquake monitoring through measuring sites assigned to the projects is stipulated by the authorities for operation. For drilling and test operation, as far as we know, no dedicated stations were stipulated by the authorities for projects in the South German Molasse Basin. We also point out that measuring stations exist for the Kirchweidach and Waldkraiburg projects.


If nothing is found, is removal of the plant planned?

If a drilling site is later not used for its planned purpose, it must be dismantled. Here appropriate safeguards are to be used in order to guarantee the dismantlement independently of the economic development of the companies. 


How many lorries will be driving day and night during the drilling phases?

The main lorry traffic is to be expected during construction and dismantling of the drilling sites. During the drilling phase there will only be occasional traffic (disposal of drilling cuttings, delivery of pipes, special tools, and measuring devices). This only represents a marginal encumbrance.


Is REACH taken into account? Are safety data sheets planned for the stimulation materials?

REACH is taken into account. Safety data sheets are required by the mining authority.


Are there emergency plans?

The mining authority requires and examines emergency plans. During the drilling, breakout practices (so-called “kick practices”) regularly take place which must be reported in the drilling report and are regularly examined by the authorities. The local fire services are involved. 


Could there be changes in the microclimate? Would there be heat emission in the surroundings? 

The heat of condensation produced during electricity generation is emitted via air coolers. No change in the microclimate is to be expected.


Is the power plant only used to generate electricity? What happens with the remaining heat? 

The plant is initially designed as an electricity generation plant. However, later diversion of the heat can be realised simply, so that appropriate consumer structures may be realised. 


What does a geothermal plant look like?

The supplier has not been decided yet. Comparable plants are to be found for instance in Kirchstockach, Dürrnhaar or Innsheim. In the following you find a model of how we conceive that the geothermal plant should look later. 

According to the current plan status, the ventilators are to be embedded so deeply in the lowering of the ground that they should be made entirely inconspicuous through the forest cover. 


Modell einer Geothermieanlage
Model of a geothermal plant 


Which noise protection measures are planned with respect to the ventilators, pumps, assemblies, etc.?

The Technical Instructions on Noise (TA Lärm) must be adhered to. This may be accomplished by a number of different measures, e.g. through low-noise ventilators, encapsulated drives, insulated steam pipes, etc.


What is the difference between a hybrid cooling tower and the stand-like construction of the ventilators?

A hybrid cooling tower is a combination of air cooling and wet cooling. This solution is not planned. 

We favour air condensers. An air condenser consists of ventilators which are mounted above the condenser tube bundle in order to transport cooling air through the condensers.

The air condensers are executed in such a way that adherence to the technical instructions on noise (TA Lärm), for instance low-noise ventilators are used. 


Is a dedicated noise evaluation created, or are “foreign” values used for the calculation?

A noise certificate is created in advance, which is to be the basis of the service specifications of the plant builder.


Where are the measuring points for the noise evaluation? Where is the emission point?

Generally the critical immission points are stipulated by the authorities.


Is there a Risk Matrix?

All works for the installation of deep boreholes in the context of the geothermal project are carried out in accordance with the current state of technology, occupational health and hygiene. A safety and health protection document is created and maintained by the general drilling contractor; as well as the fire brigade and fire protection plan, this also contains an alarm plan. 


How long do the drillings last?

Generally a drilling lasts around three months.


Please explain the ORC process:

  1. What is it?

    The ORC (Organic Rankine Cycle) process is in principle the same closed work process as in a conventional power plant using a water-steam cycle. However, in the ORC process instead of water an organic working fluid is used. The particular significance of the ORC process is in low-temperature electricity generation, in which water is thermodynamically no longer appropriate for use as a working fluid. 

  2. Which combinations are possible? 

    There are a great number of potential working fluids which may be used according to the temperature range and preferences of the plant installer.

  3. Which toxic substances are used? How are the citizens protected?

    The working fluids which may be used show low toxicity.

  4. What is the risk level?

    This can only be specified after the choice of the working fluid, but all of the working fluids which may be used can be technically controlled safely.

The plant is a closed circuit in which all of the legal limit values on pressures and leakage rates are adhered to. In ecological precariousness, the systems are comparable with refrigerators and air conditioning systems. 


How many ventilators are planned?

This depends on the individual plant supplier. In the plant size planned, around 50 individual ventilators could be assumed.


  1. If there is a greater number of ventilators, does the noise increase exponentially?

    What is important is the overall emission of the plant. Here all necessary measures are taken to keep the noise creation as low as possible and to stay below the legal limit values. 

  2. How densely distributed are the ventilators? Do they give off emissions? If so, is this observed or dealt with appropriately according to radiation protection law?

    Apart from the noise we have already spoken about, the ventilators produce no additional emissions, and also produce no vapour, unlike for instance a wet cooling tower.

  3. Can leaks in the working fluid cycle be excluded?

    The plants are subjected to stipulated, regular tightness tests (so-called pressure tests) and additionally a series of leakage detectors and a fill level monitor are installed. As the working fluid is expensive to supply, the operator also has an interest in excluding leakages from the very beginning.

  4. What is the amount of this liquid? What dangers are there?

    The liquid is over ten tonnes. The materials used display only very low toxicity; however, some of the fluids are easily flammable. This is taken into account through appropriate operating installations and restrictions. For instance, plants with pentane as a working fluid have been used successfully worldwidefor many years, without any incidents being known.

  5. Do the employees receive training and emergency plans? Is the fire brigade of the site informed?

    All of the employees working in the company management are specially trained. The local fire brigade is involved even in the process of the approval procedure. Should the necessary extinguishing materials/devices not be available, these are procured at the cost of the site operator. No radiation exposure is conceivable.

  6. What explosion protection is planned? What happens in the case of a fire? 

    This depends on the authority’s requirements, which in turn depend on the working fluid. Generally the regional fire brigade is familiar with and appropriately equipped for the plant and the potential dangers it has. 


With which water pressures is reinjection carried out, and what effects could this have inside the earth and on the surface of the earth?

  1. Would it be a high continuous pressure? Would it cause flow paths to break up? Can stones be shifted so that the ground could be changed?

    It is not possible for flow paths to break up through reinjection. The pressures used are below those of fracking. This is to be demonstrated to the mining authority.

  2. What does it mean in terms of monitoring requirements?

    The mining authority requires monitoring of seismic events using highly sensitive measuring devices. 

  3. What risks are there?

    The monitoring of the projects in the heavily geothermally utilised area around the South-Eastern Munich area has shown no anomalies in the past few years. In contrast to the Upper Rhine Rift, the South German Molasse basin is one of the areas with the lowest intensity of earthquakes.

  4. Is the deep ground water which is found reservoir water? What ingredients could it contain, and how must these be dealt with in an appropriate manner?

    The thermal water of the Bavarian Molasse Basin  only has a few minerals. In Erding the thermal water is also used for the drinking water supply after processing. For this reason, the requirements are relatively low.


The deep ground water from the Malm Aquifer is not reservoir water, as otherwise broad use of it would not be possible. Accompanying gases which may appear, generally in low concentrations, are methane, carbon dioxide and hydrogen sulphide.

  5. Is it possible for methane, ammonia or sulphur deposits to form? If so, what is done to counteract this?

    The thermal water is circulated in a closed cycle and is entirely reinjected, hence deposits of the kind mentioned are not to be expected. Substances which are released from filters are to be disposed of in an appropriate manner. Long years of experience in the Molasse Basin show that this is possible without any particular requirements.


To counteract potential deposits, the closed circulation aboveground is kept under pressure. No appearances of ammonia are expected.


Which safety measures are planned for pipes and pressurised containers? Which transport safeguards are planned? 

The installations must fulfil the requirements of the pressure equipment directive, and are correspondingly tested and accepted by the authorities.


How are precautions taken to ensure soil conservation?

All surfaces must be listed on which work is carried out with substances which have a hazardous potential. 


How is the air kept pure when steam or vapours are formed?

There are virtually no emissions from the plant in operation such as steams, etc. In particular, there is no wet cooling tower. However, in backwashing of the thermal water filter, very small amounts of thermal water escape in the form of steam. However, this is scarcely perceptible even within the plant premises. 


Which mobile and stationary sources of noise are there?

There are no mobile sources of noise, as there is no vehicle traffic to speak of during operation; the stationary source of noise is the ORC plant with its side assemblies. 


Which net efficiency* is attained?

An ORC plant in the expected temperature range can transform around 11-13% of the heat energy with which it is provided into electrical current.

* The efficiency of a technical plant is defined as the usable energy output divided by the energy input. Depending on the plant, it is influenced by various parameters (e.g. solar energy: shade, hours of sunlight, material and system design; geothermal power: temperature and transportation rate of thermal water, pump power, working fluid). The efficiency of a geothermal power plant is lower than of a wind power plant or a solar power plant, but this is at least compensated for by the considerably higher number of hours at full load in the year, i.e. through the degree of utilisation of the plant.


Are there physical limits for this net efficiency?

The so-called Carnot efficiency describes the maximum theoretically attainable efficiency of a cycle process for the purpose of energy generation. The technically attainable efficiency is well under the respective Carnot efficiency for all technical plant processes.

Generally the efficiency which is possible rises along with the usable temperature drop between heat source and condensation temperature (= outside temperature).


How high is the system’s own use of the electricity it generates? 

This depends on the quality of the transportation and reinjection drillings, as well as on the technical design of the plant process. Depending on these, in the Molasse Basin the system’s own consumption could be around 20% of the gross electricity generation, but higher values are also conceivable.


Are there differences between summer and winter?

An ORC plant, due to the relatively high dependency of the usable temperature drop on the outside temperature, for thermodynamic reasons displays fluctuations of +/- 25 % of its power depending on average temperatures, from very cold to very hot weather. 


What are deep geothermal projects?

Deep geothermal projects are geothermal procedures which use geothermal energy from a depth of more than 400 metres – hence this also includes hydrothermal geothermal energy. At this depth, the temperatures are much higher than at the surface of the earth. Hence the deep geothermal projects in Bavaria can use hot thermal water which is at a temperature of up to 140°C. This heat is sufficient to generate electricity as well as heat energy. With this energy towns and villages can be supplied, while close-to-surface geothermal projects are generally used to heat or cool individual buildings.


Do dangers occur through geothermal energy?

In principle, no. A geothermal power plant brings no particular risks for the residents. It is only when the thermal water deposits are being made accessible that layers bearing natural gas may be drilled through. This risk is encountered by the mining authority with strict security regulations for every drilling. Hence two independent security systems need to be present which avoid uncontrolled escaping of gas and fluids. At the same time, during the drilling phase the presence of gas is continuously monitored. This kind of procedure is common practice used in more than 1000 drilling operations in Bavaria. 


Does the thermal water bring dangerous substances to the surface of the earth? 

No. No dangerous substances are released or deposited. The water which is transported emits its energy in the power plant and is then pumped back into the underground reservoir. In this closed cycle the thermal water contacts neither the air nor the groundwater. Besides this, the thermal water has the quality of drinking water and is not a threat in any way. 


Is the groundwater polluted through the drillings?

In professional drillings, it is virtually impossible for the groundwater to be endangered. The groundwater used by communities and towns comes almost exclusively from layers of earth near the surface. In order to protect this groundwater, immediately after the layer bearing the groundwater has been drilled through, the borehole is encased with a steel tube and cemented. Hence the different water-carrying layers are kept separate and the water does not mix. 


What happens when the drilling hits natural gas? 

From the large number of deep boreholes completed in the past few decades in Bavaria, which were mainly for petroleum oil and natural gas, it is known that it was possible to come across layers which contained certain amounts of natural gas. For this reason, the drilling installation has a preventer, a kind of fitting which closes the hole immediately when pressure comes from below. Without such a device, it would not possible to drill so deep here. 


Are the works insured at all?

Every responsible project manager will of course, despite all precautions, insure his drilling works for damage which may be caused by them. Such insurance generally includes the whole range of environmental damage, right up to so-called mining damage.