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Geothermal Heat Turns the Switches: Reliable Rail Traffic in Winter

The functionality of approximately 120,000 switches used within the German rail transport system is decisive for the smooth operation of the rails. In the winter months, the moving parts of the switches are therefore heated in order to prevent them from freezing. Pintsch Aben geotherm GmbH, a company from Dinslaken, has developed an energy self-sufficient alternative to gas or electric switch heating systems, that uses geothermal heat.

Heating the 64,000 Deutsche Bahn switches alone requires approximately 230 million kilowatt hours (kWh) of electric energy per year. This corresponds to 138,000 tonnes of CO2 and consumption equivalent to 60,000 households. 90 per cent of all switches in Germany are still heated electrically. Pintsch Aben geotherm GmbH, a company from Dinslaken, in collaboration with ZAE Bavaria has developed an alternative using near-surface geothermal energy, in order to enable self-regulating, energy self-sufficient switch heating. Depending on the geographical and geological location, boreholes of up to 100 metres in depth are drilled in order to achieve the required quantity of energy at ground temperatures of between ten and twelve degrees centigrade. A closed heating pipe that uses CO2 as a working medium transmits the heat from there to the switch.

Engine for progress:

• current potential CO2 savings of 26,000 tonnes/a
• a self-regulating system with low maintenance costs
• supports climate-friendly mobility in winter
• uses heat from a renewable source of energy
• amortisation period of five to ten years

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Photo: PINTSCH ABEN geotherm


Self-regulating system without the use of external energy

With this system, depending on its size, one or more probes are installed in the ground next to a switch. The probe consists of several pipes that each represent a heat pipe in itself. The CO2 working medium is pressurised in the heat pipe, so that it exists in both gaseous and liquid form at ground temperatures. As soon as the outside temperature, i.e. the temperature of the switches, falls below the ground temperature, the working medium condenses in the switch components to be heated and evaporates in the probe. This sets the process in motion and the latent energy is absorbed in the ground through the phase transition from liquid to gas. Through condensation in the switch component, this is delivered again in the form of heat. The condensed CO2 then flows back into the ground, where it again absorbs geothermal heat and condenses. This process is driven entirely by the temperature difference between the heated components, the switch and the probe. The higher the temperature difference, the greater the amount of energy transported.

The first pilot systems have already been installed

The first pilot systems were installed as early as in 2011 at various locations throughout Germany and have proven the functionality of the system. The system was finally approved by the Eisenbahnbundesamt – EBA (Federal Office for Railways) in December 2013. It is currently suitable for two types of rail profiles commonly used in the DB AG regional networks. In order to drive distribution of the energy self-sufficient system forward, potential applications are being developed for further rail profiles and switch types.



Partners and sponsors


Partners:
  • Pintsch Aben geotherm GmbH
  • Zentrum für angewandte Energieforschung Bayern (ZAE)
Sponsors:
  • Bundesministerium für Wirtschaft und Energie (BmWi)