BRUGG Pipes recently delivered six pipe drums to Les Sables d’Olonne, France, in a special transport. The pipe system with the lowest heat loss in the world is being used on the French coast for an innovative district heating network using energy from the sea. A 25-year-old drainage system laid the foundation for today’s district heating network.
According to a study by Aalborg University, district heating networks should cover around 48 per cent of the EU’s heating requirements by 2050 in order to achieve the goals of the Paris Agreement. What many people don’t realise: Sea or ocean water could also be an important source of energy in the future, as the potential for clean, local and inexhaustible energy is enormous.
Innovative project in Les Sables d’Olonne with pipes from Switzerland
In Les Sables d’Olonne, around 100 kilometres south of Nantes, construction machinery is at work, mainly excavators, digging trenches several hundred metres long under the astonished gaze of the local population. Similar work was carried out 25 years ago: Back then, the aim was to bury a system of drainage pipes to facilitate the reconstruction of the beach and limit its erosion. Before this drained water is discharged into the sea, it is now used to feed a heat pump system, a process known as thalassothermia. The French company ECOPLAGE has designed and supported the project under the Enerplage® brand as the main contractor from the outset. The heated fresh water is transported in a network separate from the seawater and redistributed to the city centre. ‘With water heated to 7°C, we produce water heated to 80°C and therefore imagine being able to release 1,000 tonnes of CO₂ into the atmosphere per year,’ explains the mayor and president of the Les Sables d’Olonne agglomeration, Yannick Moreau, to France Bleu. ‘There were already drainage pipes under the beach at Les Sables d’Olonne that had been pumping seawater for decades to keep the sand on the beach. We are using the water from the drainage and the pumps that already exist on the coast to generate energy with a heat pump to heat these buildings.’
Pipes from Switzerland
‘At the beginning of February, six drums each containing 205 metres of CALPEX PUR-KING district heating pipes were delivered from Kleindöttingen to France. Special transport was required for the 3.8 metre high pipe drums, each weighing 910 kg,’ says Martin Rigaud, Head of District Heating at BRUGG Pipes. In mid-January, the Danish Technological Institute (DTI) recognised the type of pipe supplied as the pipe with the lowest heat loss in the world for the 7th time in a row. ‘The length of the pipe systems supplied in one piece and the customised branch pieces were also decisive factors in awarding the contract to BRUGG Pipes,’ adds Rigaud. The pipes were laid and installed by the French company Atlantique Travaux Publics (ATP).
©ECOPLAGE
Also in Switzerland: lake and river water as a source of energy
And in Switzerland? The use of lake water as an energy source is actually nothing new in Switzerland. As early as 1938, Zurich used water from the River Limmat to heat the town hall. In the following years, there were further projects, such as for the City swimming pool and buildings in the city centre. After the Second World War, development stagnated, partly due to low oil prices. The topic only became relevant again after the oil crisis of the 1970s. Since the 1980s, Stockholm has been using seawater for its district heating network, with the world’s largest heat pump system (180 MW). In Switzerland, too, the use of lake water has regained importance, especially since the turn of the millennium with new lake water connections on large lakes, such as in Zurich from Lake Zurich, in Lucerne from Lake Lucerne, in Basel from the Rhine and in Geneva from Lac Léman. The study by EnergieSchweiz (Swiss Federal Office of Energy SFOE) states that bodies of water such as rivers and lakes have enormous potential for heating and cooling. According to Energie 360°, heating and cooling energy for one to two million people could be generated from Swiss lakes alone. According to Energie 360°, the potential is up to two gigawatts, which is equivalent to the output of two nuclear power plants. BRUGG Pipes also supports Swiss projects with the supply and installation of district heating and cooling pipes. In March 2022, for example, BRUGG Pipes was able to implement a project with lake water together with Energie Wasser Luzern (ewl). The district heating and cooling pipes connect the energy centre of the multi-purpose ‘House of Energy’ building with the existing exhibition buildings via the outdoor area. As temperatures rise in Switzerland in the future, the importance of cooling with lake or river water is likely to increase in the long term.
How a lake water catchment system works
‘Water is pumped from the lake to the shore at a depth of 20 to 40 metres. A heat exchanger transfers the thermal energy of the lake water, which is 4 to 10 degrees centigrade at this depth, to a refrigerant in a separate circuit. Once the energy has been released, the lake water is returned to the lake clean and intact. Important to know: The coolant circulates in a closed circuit. It never comes into contact with either the lake water or the heating and domestic hot water. The coolant at the right temperature in the heat exchanger evaporates and increases its temperature as it flows through a compressor. Similar to the air that heats up when it is compressed in a bicycle pump. In a further heat exchanger, the coolant transfers the heat energy to the heating and domestic hot water. This is heated to the desired temperature and then channelled into the connected households. The same principle – only in reverse – is used for cooling.’
Unutilised potential in Germany
Although there is also great potential for the use of lake, river or sea water in the large neighbouring country of Germany, this remains largely untapped. A study by the German Heat Pump Association shows that, in addition to possible economic efficiency problems and the low level of awareness, German water legislation also makes the use of seawater heat pumps difficult. ‘With the potential analysis, an annual heat demand totalling 58.73 TWh was determined within a radius of 1000 m around all lakes > 50 ha; this corresponds to 4.6% of the total heat demand in Germany. If this heat were now provided by seawater-driven heat pumps (WPSee), 8.58 million tonnes of CO2 equivalents could be avoided in this way. This in turn corresponds to 1.13% of total greenhouse gas emissions from the energy industry in Germany,’ the study states. The extent to which lake, river and sea water will be used for the expansion of district heating networks in Europe therefore remains to be seen. What is certain, however, is that 17 buildings in les Sables d’Olonne – including the swimming pool, the congress centre, the town hall, the Pierre Mauger College, the garden school and the Sainte-Croix Abbey Museum – will be heated with seawater as early as 2026.
