Energy supplier

Lake as air conditioning and heating for 3400 buildings

Lake Constance is a leisure paradise and an important source of drinking water. Now it is also becoming a source of energy.

(Bild: Dietmar Stiplovsek)

The latest study on the use of lake water comes to a pleasing conclusion: not only Bregenz, but also Hard and Lochau could be supplied with climate-neutral lake heat. The project would also be ecologically justifiable.

The idea is simple: water is taken from Lake Constance at a depth of 25 meters. The water then flows into a so-called "lake energy center". There, depending on the season, heat or cold is extracted from the water using heat exchangers. While the liquid gold from the lake is returned to a depth of 30 meters, the heat or cold obtained can be used for heating or cooling.

Together with the municipalities of Bregenz, Hard and Lochau, the state has commissioned a study to determine the potential - and of course the economic viability - of this idea. "The results are very promising," concluded Climate Protection Councillor Daniel Zadra (Greens) at the presentation of the study paper on Monday.

Although the investments in sea heating projects are high, they pay for themselves over time. In addition, we can guarantee customers cheap energy in the long term.

Landesrat Daniel Zadra

Bild: Grüne Vorarlberg

Although the investments are high, they will pay for themselves over time. "And we could guarantee customers favorable tariffs," he said, referring to the price increases for heating oil and natural gas. For Bregenz in particular, where 90 percent of households are still heated with fossil fuels, implementing the idea would make sense.

No impact on drinking water and nature
Particularly pleasing: according to the study, not only the provincial capital, but also Lochau and Hard would be suitable as extraction points or locations. Four "lake energy centers" could be built in Bregenz, two in Lochau and one in Hard. "A total of 3400 buildings with several thousand residential units could then be heated or cooled," calculated Zadra. The system would have no negative impact on nature conservation. Bathing areas and the drinking water supply would also not be affected.

However, the use of lake water will not solve all energy problems. "At peak times, gas would still be needed to cover demand," reported study author Markus Frei from the Swiss firm "PB Ingenieure". In addition, the use of cooling in summer is much smaller than the use of heating in winter.

Energy autonomy by 2050

• By 2050, Vorarlberg's entire energy supply should be converted to renewable energy sources and thus no longer release any CO2 emissions.
• One of the biggest challenges here is the entire heat supply in households, service companies, commerce and industry - tens of thousands of gas and oil heating systems must be replaced by systems based on renewable energy sources.
• Lake Constance has the potential to enable a climate-neutral heat supply for the neighboring communities.

The fact that the use of lake water for heating and cooling is more than just a pipe dream can be seen in Switzerland. A corresponding project was launched on Lake Lucerne back in 2020. Currently, 30 percent of the targeted 6,800 households have been connected, and the expansion should be completed by 2035. "Lines have to be built and customers acquired. The whole thing is happening step by step and should be seen as a generational project," emphasized Zadra.

Bregenz city councillor Heribert Hehle (Greens) takes a similar view. The first "lake energy center" in the state capital is due to be completed in December and will be used to heat and cool the new indoor swimming pool. The festival is also on board. "Talks are currently being held with interested hoteliers, bankers and property managers," Hehle reported on the current status. The pioneering project will cost 15 million euros - eight million euros will be contributed by the federal government, with the remaining seven million euros coming from the state capital.