Concept: Heating grid 4.0 around the Dortmund Zoo

DEW 21 und Öko-Zentrum NRW

The Dortmund Zoo has set itself the goal of becoming climate neutral by 2030. To do this, Dortmunder Energie- und Wasserversorgung GmbH (DEW21) has developed a concept for a cold local heating grid: with the help of geothermal energy and photovoltaics, the zoo and other adjacent buildings are to be supplied with heating and hot water from renewable sources.

Front view of DEW21

Project overview

Participating companies

Dortmunder Energie- und Wasserversorgung GmbH (DEW21) and Ökowerk NRW GmbH

Project location



Energy services

Technologies used

Cold local heating grid with decentralised heat pumps, geothermal energy (flow and return probes at a depth of 150 m), solar thermal energy (vacuum tube collectors).

Projected energy efficiency

Since the potential heating grid connectees’ secondary grid side remains initially unchanged in the first step, no significant energy savings occur. Nevertheless, the heat is generated almost entirely from renewable energy sources (over 10 GWh/yr).

Projected CO2 savings

1,152 t CO2e/yr

Planned investment

€13.5 million

Payback period

The payback period will be approximately 20 years with the planned funding.

Planned funding programmes

 ‘Heating grid systems 4.0’

In 2020, the zoo reached out to DEW21 via the Ökozentrum NRW (Eco-centre North Rhein-Westphalia) with the question of how the various buildings could be sustainably supplied with heat in order to meet its goal of becoming climate-neutral by 2030. DEW21 then developed the innovative concept of a cold local heating grid.

In addition to Dortmund Zoo, the local heating network will also supply an adjacent vocational training centre, plant conservatories in a nearby park and a rehabilitation centre that is currently in the planning stage. DEW21’s in-depth tests showed that sufficient thermal energy can be provided with the help of geothermal energy and solar collectors. The geothermal wells will be about 150 m deep. The cold local heating grid is planned to operate with a temperature difference of five to seven degrees Kelvin between the feed and return lines – depending on the distance of the grid connectees. The determined maximum output of the geothermal boreholes is about 4,270 kW and can provide about 10,255 MWh/yr of heat. Efficient vacuum tube collectors will be used to collect the solar thermal energy. The nearly 835 m² of installed solar thermal surfaces can provide about 542 MWh of heat per year. The heat obtained via the geothermal and solar thermal systems is distributed to the decentralised heat pumps in the individual buildings via a cold local heating grid, providing a total of nearly 10.8 GWh per year and next to no losses. The building load to be covered is about 3.7 MW. Low-temperature and high-temperature heat pumps (depending on the temperature requirements) in the respective buildings provide the necessary heat for heating and hot water.


Project managers Annika Kiko and Gabriele Kilian at the Dortmund Zoo


Cold local heating grids can be built almost anywhere. The concept shows that a sustainable heat supply can also be established for existing buildings with an extremely wide range of heat requirements.

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