STÉPHANE HERZOG Heating engineer Fabrice Malla guides us 17 metres below the surface of Lake Geneva, in the area known as Vengeron. Here we are in a concrete cathedral, 70 metres long. In 2024, this sump will receive the equivalent of three Olympic swimming pools of cold water, collected two kilometres offshore, at a depth of 45 metres. From 2024, electric pumps will push this liquid towards two networks. The first, built in a closed loop, will serve the buildings spread around the airport. The second network will feed cold water directly into the buildings of the city centre. Heat pumps installed by Services industriels de Genève (SIG) in a planned total of 300 buildings will enable the extraction and amplification of heat from the water. Welcome to the world of hydrothermal energy, a universe in which cold water can generate heat. Fabrice Malla cites other similar large-scale projects, notably in Toronto and Honolulu. The facility in Vengeron, budgeted at 100 million Swiss francs, will be the starting point of one of the biggest hydrothermal networks in the world. “We are going to irrigate half the canton with hot and cold water,” says the SIG engineer. The operation will drastically reduce the amount of greenhouse gases generated. The electric energy used for running the network will be of hydraulic origin, according to spokesperson Véronique Tanerg Henneberg. But this is not necessarily the rule. “Heat pumps require electricity, but we don’t have enough. The progressive move away from nuclear energy will involve the development of solar and wind energy,” in the view of Martin Schmid, a researcher at the Swiss Federal Institute of Aquatic Science and Technology (Eawag). Due to global warming, summer demand for cooling is ineviAuch Seen werden künftig unsere Gebäude kühlen und heizen Angesichts des Klimawandels wird vermehrt die in Seen gespeicherte Energie genutzt. So wird in Genf künftig eine der grössten hydrothermischen Anlagen der Welt Kälte und Wärme für hunderte von Gebäuden liefern. Das Potenzial der Schweizer Seen ist beachtlich, ihr Zustand jedoch zugleich besorgniserregend. Lakes s t to cool and heat a increasing proportion of our buildings The cl mate emergency is speed ng up the energy exploitation of our lakes. In Geneva, one of he largest hydrothermal faciliti s in the world is set to provide he ting and cooling s rvices fo hund eds of buildi gs. Ther is great potential i the Swiss lakes. But their health pres nts a once n. Swiss Review / July 2022 / No.3 14 Science
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