Innovative real estate concepts require the courage to break new ground in order to come up with creative solutions. In the residential neighborhood on Subbelrather Straße, we generate energy right where it’s needed.
Where a former factory site once lay fallow on an area of approximately 10,733 m² in Cologne-Ehrenfeld, a new residential neighborhood now stands—called LÜCK. It comprises 216 apartments in four buildings, connected by a quiet, green inner courtyard with play areas. The neighborhood courtyard was deliberately designed as a car-free residential complex and serves as a gathering place and play area for children. The development includes owner-occupied apartments, privately financed rental apartments, and subsidized rental apartments. A neighborhood-owned package station ensures that residents can pick up their packages and send pre-paid shipments around the clock.
What makes this neighborhood special is its energy concept:
Heating with municipal wastewater
Heat exchangers have been installed along a 120-meter stretch of the municipal sewer line. These extract thermal energy from the wastewater flowing past them. This heat is transported to the neighborhood’s heating plant via pipes that are intentionally left uninsulated—to also extract heat from the surrounding soil. There, a large heat pump with 87 kilowatts of electrical input power and 352 kilowatts of thermal output raises the temperature of the heating water. Thanks to the KfW 55 building standard, a temperature of just 40 degrees Celsius is sufficient in the local heating network, enabling efficient heating. A 20-cubic-meter thermal buffer tank ensures that energy is recovered evenly and made available as needed.
Photovoltaic Power for the Heating System
However, LÜCK does not rely solely on wastewater energy. Photovoltaic systems on the roofs of the residential buildings supply part of the electricity needed by the heating plant. Modules with a total output of 99 kilowatts-peak generate approximately 91,000 kilowatt-hours per year. About one-fifth of this is used directly in the heating plant. In total, at least ten percent of the electricity required by the central large-scale heat pump can be generated directly on-site. Given the mismatch between the generation and demand curves for photovoltaic power and heat, this is an acceptable figure.
For the remaining electricity, naturstrom—as the operator of the heating system—supplies green electricity from local wind, solar, and hydroelectric power plants via the public grid. A 100 percent renewable heat supply is guaranteed in LÜCK.
Power-to-Heat System for Peak Load and Generation
A power-to-heat system with a thermal output of 250 kilowatts, integrated into the heating system, provides exceptional flexibility. This system serves several functions: First, it covers peak household consumption by rapidly supplying heat should the heat pump be unable to meet demand quickly enough.
Second, it can also utilize peak generation from the photovoltaic system to “overcharge” the connected thermal buffer tank: Up to 20 cubic meters of heating water can thus be heated to up to 70 degrees. Since the tank is insulated and buried in the ground, the energy can be stored for extended periods of time.
Third, the power-to-heat system is also intended to take advantage of fluctuating electricity market prices—particularly during periods of low or even negative prices—to generate heat at a particularly low cost. This energy concept is thus already prepared for the upcoming climate-neutral electricity system with its characteristically volatile electricity generation.
Efficient Drinking Water Heating
LÜCK’s heating network is also made possible by a partially decoupled hot water system: Cold drinking water is fed into the individual apartments, where the heating network preheats it to temperatures of about 35 degrees Celsius via heat exchangers. Depending on demand, it is then heated there by decentralized apartment stations to up to 60 degrees. This on-demand reheating saves energy and increases overall efficiency. naturstrom AG is responsible for and operates the measurement and control technology required for the heating system. This technology is continuously improved and learns from residents’ usage patterns to become even more efficient.
