Harnessing the heat from beneath – geothermal district heating of Erding, Germany

A recent article in local publication Merkur from Germany reported on how the search for oil ended up with a geothermal heating plant that today supplies the city of Erding with heat.

For now more than 20 years STEAG New Energies GmbH Erding has supplied the city of Erding with geothermal energy from resources at a depth of 2,350 meters.  Today, about one fifth of the total heat demand of Erding can be covered by climate-friendly geothermal energy. The article published yesterday, looks behind the scenes of the geothermal heating plant Erding 2.

The history of Erdinger Erdwärmeversorgung began in 1983, when oil firm Texaco drilled for oil. With heavy equipment the company drilled to ab depth of 2,359 meters into the earth’s surface. No oil was found, but 65 degrees Celsius hot thermal water. The oil company had no interest whatsoever in the water, which resulted in the city and the the larger municipality founding a joint venture to use the “hot gold”, as they call it in 1989.

In 1994, STEAG New Energies was brought on board, which then started to operate the district heating the same year. Plans were initiated for the local thermal bath Therme Erding in 1994, which then opened in 1999. The bath was planned as there was no second well planned at the time, through which the cooled down water could have been returned into the reservoir below.

At the time, it was more economical to treat the thermal water and use it in a spa, almost incidentally a recreational “temple” was created that has made Erding famous around the world. The spa is today by far the largest customer of the joint venture for thermal water and STEAG for geothermal heating.

After a second well was drilled in 2008, a new building the Geothermal Heat Plant, Geoheizwerk 2 was put into operation in 2009. This also doubled the maximum flow rate with approved 48 liters per second.

The Geoheizwerk “Erding 2” stands at the end of a cul-de-sac in the commercial area of the city and nothing indicates that the most essential heat supply for Erding is generated on this site. Beside from the many residential homes, municipal facilities, such as almost all schools, the hospital, the local bank, the city hall, the municapality administration, the new mensa, many shops and hotels in the city are connected to and enjoy the geothermal district heating network.

Today, the district heating network is about 32 kilometers long with a connected supply capacity of 69 MW thermal. The control room is the heart of the system, where five employees monitor the smooth operation of the heating plant.

The hot thermal water is pumped out of well 1 with the help of a pump that sits at a depth of 230 meters and distributed to both heating plants. In both locations, the thermal water heats the return flow from the customers via heat exchangers and a so-called absorption heat pump.

On very cold days in winter, the geothermal heat is though not enough. Then, with heat primarily heated with natural gas boilers. They also ensure that nobody has to sit in the cold in case of a loss of geothermal energy. The thermal water is cooled down to 20 degrees in the heating plants and reintroduced into the soil through well 2 – by the way, at a sufficiently great distance from well 1, so that there is no “thermal short circuit” in the subsoil.

The generation plants with innumerable electric cables and many pipe strings around heat exchangers and boiler plants stand in a large hall. The tubes are labeled, a variety of gauges, thermometers and other measuring instruments. Here also the layman understands why the specialist speaks of the heating plant, even if the plant is remarkably clean.

With the geothermal heating plants, the city saves almost two-thirds of carbon dioxide (CO2) and nitrogen dioxide (NO2)  emissions each year compared to decentralized boiler technology.