Our heat exchanger plants are always aligned to what is called the minimum dry weather flow, i.e. the moment when the least wastewater is flowing through the sewer. This means that the reliable performance of the systems is guaranteed on a highly conservative basis. In addition, for the sake of safety, both the volume and temperature of the wastewater in the sewer in question is measured again beforehand over a long period of time. This ensures that the plant performs efficiently. The data from the sewer network operators, which are always accurate, are thus verified. Essentially: The level of wastewater can be calculated and forecast precisely over decades, which means that the use of wastewater for energy offers a high degree of reliability. What is particularly attractive is the fact that the temperature of wastewater recovers again very quickly even after large quantities of energy have been extracted. This is due firstly to the inflow of new wastewater into the sewers and secondly to the constant uptake of ambient warmth from the ground. It is therefore possible to install a large number of plants to extract energy from wastewater in a sewer network. The only thing that is important is that the plants must be a certain distance apart. The rule of thumb is: After a wastewater heat recovery plant, a “recovery line” around two to three times the length of the plant itself should be incorporated. If a wastewater energy recovery plant is 100 m long, then another plant can be installed around 200 to 300 m afterwards.
