Germany’s first “climate supermarket“ uses CO₂ refrigeration

On 2 December, German retail group Tengelmann opened its first supermarket to save 50% of energy and reduce greenhouse gas emissions to zero. A CO₂ refrigeration system cooled by rainwater is part of an impressive package of technical innovations.

In a record time of only 8 weeks, German retailer Tengelmann built its first zero-emissions “climate store” ready to cut energy consumption by half. Already before its official opening on 2 December, the store, using only renewable energies and climate-friendly technologies, was lauded by public authorities and industry experts as a major step towards a more sustainable food retail industry. The fact that Tengelmann renovated an existing building instead of investing in an entirely new construction would, even more importantly, prove that renovated stores could deliver the same outstanding energy performance as new buildings.

“This new Tengelmann climate store is a supermarket for the next generation, it is a role model for others to follow across Germany. From an energy perspective, they have pulled out all the stops and have shown that climate protection and economic benefits can go hand in hand,” the Energy Agency of Northern Rhine-Westphalia praised the facility located in Mülheim an der Ruhr.

The CO₂-rainwater system

The eco store, seen by Tengelmann already as a “lighthouse for the German food retail industry”, uses a CO₂ multicompressor refrigeration system. The installation significantly brings about significant energy savings while using a refrigerant with a Global Warming Potential 3,900 times lower than previously used fluids. The system planning and installation was done by manufacturer Epta Germany.

To save energy and water also during summer, at high ambient temperatures the R744 installation is cooled by rainwater which is constantly supplied by a reservoir located outside the store in the delivery area. The reservoir is able to collect 100,000 litres of rainwater below surface.

For more technical details, please see the images, illustrations, and control schemes in the photo gallery below.

Other Technical Innovations

Besides the innovative cooling system, the “climate store” features the following technologies:

Using the earth’s energy: Six tubes, reaching 130 metres down below the surface, collect geothermal energy through a water-glycol blend. Connected to a heat pump, the geothermal system provides 25% of all required heating to the store, as well as cooling during summer. The remaining 75% is covered by waste heat recovered from the R744 refrigeration system. As a result, the store is entirely independent from fossil energy sources.

Keeping the cold inside: To save 35% of energy for refrigeration shelves and even up to 50% for low temperature freezing chests, all CO₂ refrigeration equipment is covered by glass doors.

Using the sun’s energy: The store uses two photo-voltaic modules vertically installed at the building’s south and west façade, and a roof-top solar panel to generate electric energy. Together, they cover an area of 1,140 m2, generating 45,000 kWh of “green” electricity each year - 100% of the electricity needed.

Using natural light: To adapt the lighting level to different periods of the day, the store has an integrated glass ceiling to capture all incoming natural day light. Once the incoming amount of light is no longer enough to provide the level required in a supermarket, a control system ensures that artificial lighting is only partly enabled to balance out the difference to the requested total. All lighting for the refrigeration systems is done by energy-saving LED technology. The integrated concept saves around 40% of all energy normally required for lighting.

Tengelmann’s climate strategy

The climate store is the group’s latest move to fill Tengelmann’s sustainability concept with life. For more than 40 years, the retail group has been active in the field of climate protection, with recent activities especially aimed at reducing GHG emissions. Energy efficiency and the use of renewable energies are key pillars to achieve a 20% CO₂ emissions reduction by 2020.