The Idex group has been granted all required permissions to develop and operate the upcoming renewable heating and cooling network designed to provide temperature management solutions for the Les Trésums district currently being built on the shores of Lake Annecy.

Made possible thanks to the city’s support, this 30-year construction and development project is the only one of its kind in France. It draws on water from Lake Annecy as an energy source to heat and cool neighbouring buildings via heat pumps and exchangers.

A heating and cooling network powered by 65% renewable energy thanks to water from Lake Annecy

The future heating and cooling network will provide thermal comfort for the occupants of the 18 housing units, senior residence, hotel, and the upcoming municipal water sports centre. The Idex group designed an eco-friendly installation based on a water loop system powered by the lake to cover 95% of all heating and domestic hot water needs (11,000 MWh per year), with the remaining 5% provided by gas-fired boilers, which will also serve as emergency back-up if needed. 100% of air-conditioning needs, meanwhile, will be covered by the water loop (400 MWh per year).

The water will be pumped out of the lake at 20 metres deep, where the temperature remains a constant 7°C throughout the year. This water will be fed into heat pumps linked up to an urban heating network that provides all the neighbourhood’s buildings with heating.

All of the water pumped out will then be returned to the lake, thereby recovering 65% renewable energy.

A climate-friendly cooling network

  • To cool down the buildings, water from the lake will be used directly, with exchangers and geo-cooling systems used to power a cooling distribution network for the hotel, senior residence, and water sports centre.

    With a view to avoiding using individual air-conditioning units that widely contribute to heat island effects, Annecy’s cooling system will draw on a green, renewable energy source – the lake – thereby using 15 times less electricity than traditional air-conditioning systems.

    In terms of heating, the lake’s waters will ensure the area saves 2,250 tonnes of CO2 per year.

    An environmental study was conducted to assess the project’s impact on Lake Annecy. The measures that are being taken will ensure the surrounding natural setting is monitored and the quality of local habitat is preserved.

    Building works will kick off in early 2020 with a view to being operational in the autumn of 2021. The project will cost a total of €5.7m, with a €1.7m ADEME grant awarded.

95% of heating and domestic hot water needs covered

65% renewable energy recovered

2 250 tonnes of CO2 saved every year

20 metres deep