Immediately upon entering the new store, shoppers can see that it is fitted with environmentally-friendly technology, with a solar electricity display showing how much electricity the photovoltaic modules on the supermarket's roof are currently producing. During peak operation the amount is 80 kilowatts – enough to power 80 washing machines. Each year the system, which is run by Stromwerk, supplies 85,000 kWh

of electricity - enough for 25 households. The purchaser of the Migros roof electricity is the Solar Power Exchange of EWZ, the Zurich-based power company.

”The collaboration between Migros and Stromwerk fits nicely into our model, which places a strong emphasis on sustainability”, says Paul Horber, Head of Store Technology. ”We provide the roof upon which to install solar cells and thereby help a young, innovative start-up company, and simultaneously promote renewable energy and strengthen our image as a sustainable retailer.”

Building services of the future

Migros Parkside’s environmental heart is actually hidden behind the scenes. This is its building services system. The system, which is housed in the top floor and used to control the air conditioning in the store, appears no different to a standard heating system. But it is not a heating system, and it is in no way standard. ”Heat is generated without using oil or gas”, explains Claudius Meier, Engineering Project Manager.

Every supermarket has large energy flows. Lights, people and appliances bring heat into the store. Cooling appliances – also called cooling units – emit cold and waste heat. A few years ago, the latter was allowed to simply evaporate unused, with possibly a small component being used for the domestic hot water. ”Now systematic use is made of this waste heat”, says Meier. And this is how it works: For products to remain cold in the cooling units, a refrigerant is needed. This is circulated in the cooling system and vaporised in the cooling units. There it absorbs the heat, conveys it to the top floor, and feeds into a water system via a heat exchanger, a gigantic storage facility that stretches over three floors and holds 15,000 litres. The heated water then flows into the floor heating system or into so-called radiant ceiling panels, i.e. special radiators mounted onto the ceiling, creating a heating circuit.

Its main component, the heat exchanger, is no bigger than two drinks crates, but replaces an entire heating system. The Denner store inside Parkside also benefits from the new system.

A supermarket doesn’t just need pleasant air conditioning, however. It also needs hot water, especially in the meat and fish department, where crockery needs to be regularly washed. In Rüschlikon hot water is also heated using a cooling system, namely that of the freezer units. The heat generated is fed into the domestic hot water system, and into a boiler that holds up to 800 litres -

enough for an entire store.

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Hot, warm, cool, cold

Migros Parkside not only has an innovative solution for heating and hot water, it also has no need for an air cooling system. The supermarket covers an area of 1750 square metres, and is consequently the right size to benefit from a balanced relationship between cooling units and lighting. Or to put it another way, the amount of cold air emitted by the cooling units is such that it balances out the heat from the lighting, thereby ensuring a pleasant temperature on hot days.

”Last but not least”, says Paul Horber, “we also have a rainwater utilisation system”. Rainfall is gathered on the roof in a tank, filtered, and then used for the customer toilets, flower department and external selling points.

Refrigerant

Since the beginning of 2010, the Migros Cooperative Zurich has been using a CO₂ refrigerant to chill its products in frozen food islands and cooling units. For a long time carbon dioxide (CO₂) was considered a normal refrigerant; only after the introduction of synthetic refrigerants was there a decline in its use. Today, however, in view of global warming, it is once again attracting interest because it has less environmental impact than synthetic refrigerants, which due to unavoidable losses are released as long-lasting greenhouse gases.

The CO₂ refrigerant is obtained from natural sources, and is therefore also already present in the atmosphere. CO₂ refrigerants do not damage the ozone layer, and are neither poisonous nor flammable.