Cologne has a lot to thank the Rhine for. The river enables trade by ship and thus prosperity, industry is supplied with raw materials and the river is certainly helpful for the tourism location, including a boat trip with a view of the cathedral. The city could soon benefit from another advantage: in up to 50,000 households it could become cozy and the shower water pleasantly hot – thanks to the Rhine.
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This will be made possible by a so-called river water heat pump, which will be Europe’s largest system of its kind with an output of 150 megawatts. The energy company Rheinenergie draws water from a Cologne harbor basin and returns it to the river. Then the water is “completely unchanged,” as the operator emphasizes, but two to four degrees colder.
The heat is extracted from the water in order to feed it into the district heating network and thus reach Cologne city center. The large facility, which is scheduled to go into operation in 2028, costs 280 million euros and is funded with around 100 million euros from the federal government and the EU. The foundation stone will be laid on Thursday, at which Federal Economics Minister Katherina Reiche (CDU) is expected as a guest.
The project is intended to significantly improve the CO₂ balance of Cologne’s heat supply. However, the heat pump will not be in operation all the time, but only when the electricity required is available cheaply – for example in spring or summer, when photovoltaic systems generate a lot of energy. In winter, however, when little solar and wind energy is generated during the “dark doldrums” and electricity prices are high, the heat pump is unlikely to be used much.
Right next to it, Rheinenergie operates two power plants for fossil fuels: The gas and steam turbine systems are intended to help out if the large heat pump is not worth operating. The energy company explains that alternating operation reduces the production costs for district heating and thus also the final prices for customers.
Heat from rivers has great potential
River water heat pumps only play a minor role in Germany, but they are considered to have great potential. Above all, we are talking about aquathermy – not just for rivers, but also for other bodies of water.
In other countries, things have already progressed: in Esbjerg, Denmark, a seawater heat pump is running that has a heat output of 40 megawatts. A similar seawater plant is also to be built in Flensburg, a good 100 kilometers from Esbjerg, which will have an output of 60 megawatts.
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The Federal Association of the Energy and Water Industry (BDEW) points out that aquathermal energy also includes the use of heat from wastewater and other surface water. “Aquathermal energy has great potential that should be tapped.” It is important to combine energy sources and technology. The association refers to a study that shows that almost a fifth of Bavarian communities could cover their heat needs all year round with heat pumps in running water. Such a magnitude could also be realistic for the whole of Germany.
According to BDEW, river water heat pumps are already in use in Mannheim, Berlin, Bremen, Rosenheim and Gießen and Lemgo, and a larger system is planned for Lake Constance. “River thermal energy can make significant contributions locally and regionally – especially in cities with large rivers and developed heating networks.”
There are also risks
If river thermal energy has such great potential, why does it still have a niche character in Germany? According to the think tank Agora Energiewende, two factors are slowing down the ramp-up: on the one hand, electricity is more heavily burdened with taxes and levies than natural gas and, on the other hand, the necessary investments are high.
“The price disadvantages of electricity compared to natural gas must be reduced, heating networks must be built and sufficient funding is needed,” says Agora expert Anna Kraus. She points out that large heat pumps have so far been “custom-made, one-off products”. More standardization is needed to reduce technology costs.
Environmental concerns
The Greens see the new technology positively, but point out risks. “River heat pumps have considerable potential, especially on large rivers like the Rhine – provided that water and species protection is not neglected,” says Green Party member of the Bundestag Alaa Alhamwi. Thorough environmental impact assessments are essential.
Environmentalists see it similarly. According to the Nature Conservation Association of Germany (Nabu), the systems could make an important contribution to climate-friendly heat supply. But: “The use of rivers to generate heat must not come at the expense of already weakened aquatic ecosystems.” Heat is removed from the river and cooler water is returned. “Even comparatively small changes in water temperature can have an impact on animals, plants and ecological processes,” warns Nabu spokesman Julian
Bethke.
The environmental protection organization BUND also sees considerable energy potential in rivers. “A variety of municipalities
could cover the heat requirement by 30 to 50 percent,” says BUND-NRW climate officer Dario Deilmann. However, the technology is not a sure-fire success. Not every river and every body of water is the same. “A large heat pump on the Rhine, which is already heated up by numerous industrial uses and carries a lot of water, is to be assessed completely differently than a system on a smaller or medium-sized river.” Fish and amphibians must be protected.
(olb)
