At the same time, the heat from the waste water is used to recharge the geothermal storage tanks on the Lagarde campus. In this way alone, the public utilities want to produce around 2,300,000 million kWh of heat annually and thus save the equivalent of 230,000 liters of heating oil.
Heat exchanger is 250 meters long
Where many people live, a lot of wastewater is produced. When it arrives in the sewer, the wastewater is still between 5 and 25°C warm, depending on the season – and therefore warmer than the ambient temperature, especially in the cold months: “All of these are ideal conditions for further use of the heat – also because this Energy is constantly available all year round in the immediate vicinity of the site,” says Stefan Loskarn from Stadtwerke Bamberg. Loskarn is the project manager for the construction of the heating system on the Bamberg Lagarde campus and he is fine with any renewable source that can be used to produce ecological heat on site.
In the case of waste water, this works via large heat exchanger mats made of stainless steel, which were installed in 2021 on the floor of the sewer below Zollnerstraße. The heat exchanger extends over a length of 250 meters, making it the longest in Bavaria. On an area of 720 square meters, a water cycle in the steel mesh absorbs the residual energy from the waste water flowing over it. The wastewater heat obtained is first transported to the energy center of the Lagarde campus and from there to the heat pumps in the new buildings via a connection that is around one kilometer long and will be built starting in spring.
Geothermal energy and waste water are to make the heat 70 percent CO2-neutral
The public utilities will generate around 70 percent of the heat required on the Lagarde campus in a CO2-free way: together with geothermal heat, the wastewater heat is the most important energy source for operating the heat pumps. The electricity for the heat pumps is also generated from renewable sources: in photovoltaic systems that the public utility company installs on the roofs of the new buildings.
“The technology is mature, but it also has to be economical so that the residents don’t raise their heating costs,” explains project manager Loskarn many highly efficient new buildings are also being built here, in which this energy can be optimally recycled. (gun)