MILTON Keynes-based contractor Project First has helped Tesco make its new ECO store at Wick, Scotland even greener.
The 50,000ft2 store is designed to have a 50% smaller carbon footprint than a conventional supermarket of comparable size. Of timber-frame construction, the store makes best use of natural light, incorporates wind turbines and solar collectors to reduce its reliance on fossil fuels, and uses rainwater harvesting systems.
Project First was set the challenge of reducing the HFC refrigerant charge for the store by a minimum of 50%. It was asked to use natural refrigerants wherever possible, and deliver a heat recovery system that did not compromise the efficiency of the refrigeration system.
The cold rooms at the store were designed to operate with CO2 using dedicated transcritical condensing units.
Project First achieved the stipulated reduction in HFC by providing an integralised direct expansion water-cooled system that consists of a number of slim-line refrigeration pods placed on top of each display case and coldroom. Each pod has a hermetically sealed horizontal scroll compressor, water-cooled by a plate heat exchanger.
The display cases and cold rooms are, unusually, connected to two independent water-cooling systems, which consist of a dual pump and roof-mounted dry air coolers. With this system, the plate heat exchangers provide up to 280kW of recovered heat. The heat exchangers supply low-grade heat (between 20 to 31°C) to pre-heat coils sited in the main air-handling units. The dry air coolers use low-energy EC fan motors that are by-passed at a pre-set temperature, with the cooling medium then being diverted to the heat reclaim system.
The installation of this integralised HFC R404A system has led to the ECO store’s refrigerant charge being 55% lower than if a conventional DX system had been used.
Overall Tesco Wick’s carbon footprint is heading towards 50% of an equivalent store using technology that will be repeatable in future stores.
Project First
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