In large cities such as Cologne, heat generation accounts for more than two thirds of stationary energy consumption. That’s why the search is in for ways to make more efficient use of non-fossil energy sources to create more sustainable heating systems in metropolitan areas. One idea is to recover heat from wastewater systems that is currently simply flushed away. The City of Cologne will begin to use 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 including natural gas, district heating systems and local heating sources.

Wastewater systems promise major heat recovery potential. Studies have shown that around 20 per cent 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 seeks to identify the most effective methods so as to increase the success rate of future projects.

Cologne has divided the four-year project into two stages. Beginning in late summer 2013, demonstration facilities will be set up in three locations near six schools and gyms across the city to test a range of different heat recovery methods. From 2014 onwards the technology will be rolled out and tested in other types of buildings.

CELSIUS site in Mülheim

Area to be heated ca. 12,800 m“
Total installed power ca. 1,000 kW (150 kW heat pump + 850 kW gas boiler)
Anticipated heat requirements ˜ ca. 850,000 kWh p.a.
Watch a short film about the Mülheim demonstrator > >

CELSIUS site in Nippes

Area to be heated ca. 28,200 m“
Total installed power ca. 2,500 kW (400 kW heat pump + 2,100 kW gas boiler)
Anticipated heat requirements ˜ 2,130,000 kWh p.a.

CELSIUS site in Wahn

Area to be heated ca. 21,650 m“
Total installed power ca. 1,200 kW (200 kW heat pump + 1,000 kW gas boiler)
Anticipated heat requirements ca. 1,220,000 kWh p.a.​