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Good morning, this is Michelle and as Geneva prepares to go to the ballot box this Sunday, we take a look at one of the lesser known proposals – the expansion of its hydrothermal network.

The Lake Leman's water has been used to cool the UN and other buildings in the Nations area for the past ten years. The authorities are counting on expanding the eco-friendly project onto other parts of the canton to slash its carbon emissions, including those spewed by International Geneva.

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Michelle Langrand


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Construction site near Vengeron Beach for Geneva's biggest thermal network. (Credit: SIG/Magali Girardin)

🔋Green transition. Geneva will vote on Sunday on whether to expand its thermal power network and grant exclusivity to the canton’s power company Services Industriels de Genève (SIG). The results could prove decisive for Geneva’s plans to slash its CO2 emissions, including the organisations and institutions that make up International Geneva.

Between the Park Perle du Lac and the World Trade Organization (WTO) building, a pump draws water 45 metres deep from Lake Leman. A network of pipes buried deep underground then routes the water towards the Nations district, cooling the various UN buildings in the area. Unlike it may seem, lake water never actually enters building pipes. A device called a heat exchanger transfers the lake water’s thermal energy to the water running in the buildings without ever mixing the two. Lake water then flows back into the lake. This renewable energy system is now being extended to other districts through the Genilac expansion project by the SIG.

Estimated at CHF800 million, Genilac will cut the city’s CO2 emissions by 70,000 tonnes by 2035, the SIG says, by replacing oil and gas-powered air conditioning and heating systems in the buildings sector, which currently accounts for half of the thermal power used in Geneva – of which over 90 per cent comes from fossil fuels, according to the canton.

Read more in Geneva Solutions (EN)

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