According to a study by the University of Aalborg, district heating networks will need to supply around 48 percent of the EU’s heat demand by 2050 in order to meet the targets of the Paris Agreement. Heat suppliers in such networks often include fired power plants and combined heat and power units. However, recovering energy from lake or seawater has not been considered so often so far. These resources have an enormous potential for clean, local, and inexhaustible energy.
Innovative Project in Les Sables d’Olonne
In Les Sables d’Olonne, construction crews have been digging trenches several hundred meters long. Similar works were carried out 25 years ago: at that time, a system of drainage pipes was buried to facilitate beach reconstruction and limit erosion. Before this drained water is discharged into the sea, it is now used to feed a heat pump system in a process called thalassothermy. The French company Ecoplage conceived and has overseen the project from the outset under its Enerplage® brand as prime contractor. In this process, seawater is pumped and sent to filters to remove any impurities which could damge the heat exchangers. It then progresses to the titanium heat exchangers which transfer this energy to the refrigeration cycle of the heat pump. The latter supplies the infrastructures it is allocated to with heat and/or cold, depending on the needs. In Les Sables d’Olonne warmed freshwater is transported through a network entirely separate from the seawater intake and redistributed within the town center.
Special Transport
“In early February, six reels—each containing 205 meters of Calpex Pur King district heating pipes—were delivered to France. A special transport was required for the 3.8 meter high reels, each weighing 910 kg,” says Martin Rigaud, Head of District Heating at Brugg Pipes. The pipe type delivered was recognized by the Danish Technological Institute (DTI) as the pipe with the world’s lowest heat loss. Its polyurethane insulation material has a thermal conductivity of just 0.0199 watts per metre and Kelvin at a measuring temperature of 50 °C. “The continuous length delivery of these piping systems, as well as the custom made branch fittings, were decisive factors in Brugg Pipes winning the contract,” Rigaud adds. The pipes were installed by the French company Atlantique Travaux Publics (ATP).
The piping systems were transported from Kleindöttingen in Switzerland to Les Sables d’Olonne via special haulage. Source: BRUGG Pipes
Untapped Potential in Germany
Although Germany has great potential for using lake, river, or seawater, it largely remains untapped. A systematic analysis by the German Heat Pump Association (BWP) shows that, in addition to possible economic concerns and low public awareness, German water law also hinders the use of seawater driven heat pumps.
“Our potential analysis determined that within a 1,000 m radius of all lakes larger than 50 ha, the annual heat demand amounts to 58.73 TWh. This is equivalent to 4.6 percent of Germany’s total heat demand. If this heat were supplied by lake water driven heat pumps (WPSee), 8.58 million t of CO₂ equivalents could be avoided. This is some 1.13 percent of the energy sector’s total greenhouse gas emissions in Germany,” the study states.
How large a role lake, river, and seawater will play in the expansion of Europe’s district heating networks thus remains to be seen. What is certain, however, is that by 2026, 17 buildings in Les Sables d’Olonne, including the swimming pool, convention center, town hall, Collège Pierre Mauger, the horticultural school, and the Musée de l’Abbaye Sainte Croix, will be heated with seawater.
Further information is given at Ecoplage and Brugg.
