On 10 July 2024, the Zurich City Council approved expenditure of CHF 303.7 million from the “Thermal grids” framework credit for the realisation of the CoolCity energy network. This will heat and cool Zurich’s city centre with renewable energy from Lake Zurich and thus represents a significant step towards reducing the city’s CO2 emissions to net zero by 2040.
Expansion of thermal grids
The expansion of thermal grids is one of the greatest levers that the city of Zurich has to reduce CO2 emissions. Fossil-fuelled heating systems can be replaced by connecting to district heating and the local gas distribution network can be replaced in stages. The CoolCity energy network, which runs on 100 per cent renewable energy, should make a major contribution to this.
Network area and utilisation of lake water
The network area extends from the main railway station to Bürkliplatz, bordered by the Limmat, Sihl and Schanzengraben rivers. It includes the City, Fraumünster Energy Network and Old Town perimeters. In future, the properties there are to be heated and cooled with Zurich lake water, which will enable the greenhouse gas emissions of the connected properties to be reduced to net zero.
Lake water and energy centres at the heart of the network
The construction of a lake water and energy centre is necessary to realise the network. Lake water will be collected at a depth of 28 metres at the Zürichhorn and transported to the lake water centre in the Kurt Guggenheim complex via a two-kilometre-long pipeline. There, energy is extracted from the lake water using heat exchangers, which is then channelled to the ewz Selnau substation. The cooled lake water is then returned to the Limmat.
The heart of the energy network will be the energy centre in the former ewz Selnau substation. Here, the heat and cold obtained from the lake water will be brought to the required temperature using heat pumps and chillers. Following extensive investigations, the ewz Selnau substation has proven to be the ideal location to fulfil the technical and economic requirements.
Staged construction between 2025 and 2039
The energy network will be realised in stages between 2025 and 2039 and will be implemented in coordination with the civil engineering department’s road and utility projects. The first energy supply is planned for 2031, whereby the continuous expansion will have largely covered the supply area (excluding the perimeter of the old town) by 2035. The connection of the old town is planned for 2035 to 2039.
The city council already approved CHF 8.5 million for preliminary investments from the framework credit in 2023. Ewz has started the initial construction work and is building a connecting structure between the CoolCity and Fraumünster energy networks, which will be completed in spring 2025.
An important step towards climate neutrality
The CoolCity energy network is a key building block on the path to climate neutrality in the city of Zurich. By using 100 per cent renewable energy from Lake Zurich, the city centre is supplied with sustainable and environmentally friendly heating and cooling, making a significant contribution to reducing greenhouse gas emissions.
