Evaporative Cooling of a Large Open Retail Shed, Stockport
Decathlon UK Ltd has 5 stores throughout the UK, each specialising in selling a full range of sports equipment. The store at Stockport is based in Georges Road and comprises 2 bays of lightly constructed low bay design and has an overall retail area of 4,000m2.
In the summer of 2009 the store became very hot, reaching levels of 40°C, causing customers to leave the store. Their existing mechanical air conditioning provided 100kW cooling capacity which was clearly well below the capacity required.
The solution was to calculate the correct cooling capacity and evaluate how this could be provided. This was based on the following criteria:]
• the thermal conductivity of the existing construction
• the exposed nature of the site
• the minimum requirement of 12ltrs/sec of fresh air per person
• an ambient peak temperature of 30°C
The total cooling load requirement was calculated at 400kW. It was clear that an extra 300kW cooling capacity was necessary to bring it to the point where conditions within the store could be maintained at satisfactory levels during summer periods.
Austin Broady Air Conditioning & Ventilation provided comparisons between traditional air conditioning and evaporative cooling. These were:
• Installation costs – £70,000 for evaporative cooling rather than £250,000 for traditional air conditioning
• Running costs – £800/year (water and electricity) rather than £12,000/year
• Shorter installation time – It took just 3 weeks to install 12 coolers whereas the conventional air conditioning would take a minimum of 3 months.
• Low Carbon Emissions – The carbon emissions produced by conventional mechanical air conditioning are 20 times greater than the carbon emissions produced by evaporative cooling.
This system was installed in June 2009 and has proved to be a great success. The temperature of the store is now comfortable with large volumes of fresh air helping to maintain a comfortable environment. After the system was installed a Temperature Data Logger recorded conditions at 6 different locations within the store every 10 mins. When external temperatures were in excess of 32°C, the internal store temperatures (centre, front and rear) never exceeded 24°C.