CELSIUS Site Cologne

In large cities such as Cologne, heat generation accounts for more than two-thirds of stationary energy consumption. This is why it is necessary to consider ways to make more efficient use of non-fossil energy sources and create more sustainable heating systems in metropolitan areas. One idea is to recover heat from wastewater systems that is currently simply flushed away. Within the CELSIUS project, the city of Cologne focused on using wastewater along with geothermal energy, solar energy and wood pellets as a sustainable source of heat for large buildings – a sensible addition to an economically viable mix of energy sources that includes natural gas, district heating systems and local heating sources.

Wastewater systems promise major heat recovery potential. Studies have shown that around 20 % of all buildings in Germany could be heated using this technology. However, so far most projects have failed in the face of technical and/or financial obstacles. The CELSIUS project seeked to identify the most effective methods so as to increase the success rate of future projects. The potential of this technology is demonstrated in two locations in Cologne: the districts of Wahn and Mulheim.

Furthermore, as part of CELSIUS Cologne tested an additional way to use a district heating network – for the operation of certain household appliances (white goods) – and in so doing reduce electricity demand and related carbon emissions. This is achieved by replacing the vast majority of the electricity used to operate household appliances with energy in the form of hot water. Dishwashers, washing machines and dryers used electricity both for running the moving parts in the machines and for heating the water and air used in them. The proposed machines use the heat provided by the district heating systems to meet the heating demands in the machines and then only use electricity for the engines and for rare peak heat-demand situations.