Friday, 31 March 2017

Supermarket Central Refrigeration

Retail food outlets in the UK are responsible for around 3% of total electrical energy consumption and 1% of total GHG emissions. They are characterised by their average sales area and are normally classified as:

  • Hypermarkets - 5000m2 to over 10,000m2 sales area
  • Superstores - 1400m2 to 5000 m2
  • Supermarkets (mid-range stores) - 280m2  - 1400 m2
  • Convenience stores including forecourts less than 280 m2
Source - Applied Thermal Engineering 31 (2011) 147 – 156

In this same article the author states that the average annual electrical consumption is 1480kWh per m2 with integral or display refrigeration adding a further 300kWh per m2 when compared with centrally located refrigeration plant.

"No food supermarket should ever be bigger than 45,000 square feet," says Bruno Monteyne, senior analyst of food retail at investment firm Bernstein.

This is about the half the size of a Premier League football pitch and if we use that as a benchmark, the average supermarket will spend £689,000 per year on energy, with 70% being spent on electricity.

Most this electricity, 52%, is spent on refrigeration with an additional 9% on HVAC services.
In our average supermarket, the refrigeration cost per annum will be £250,000 with an additional £43,000 on HVAC.

When energy efficiency of fin-tube coils is mentioned, engineers immediately think of heat transfer co-efficient, newer fin designs, smaller diameter tubes, non-circular tubes, thinner tubes and other factors for better heat transfer.

Reducing the coil face velocity and increasing the number of fins per cm will provide the additional heat transfer needed to reach the required design temperature. Airside pressure drop is less, but the lower face velocity alleviates concerns about moisture carryover. 

Unfortunately, a reduction in fin spacing increases the likelihood of coil clogging which adversely effects the heat transfer and increases the fan speed to maintain face velocity.

During a recent survey, the out of town location of a major supermarket was surrounded by fields, woodland and a water treatment plant. Depending upon the season this will give rise to high levels of pollen, insects and seeds which will be drawn into the gaps between the fins. This increases the resistance, pressure drop and electrical energy use.

Cooling coil dirt on unprotected chiller requiring air intake screenUnprotected chiller requiring air intake screen

The average temperature for this town is 14oC (58oF). For 7 months of the year the ambient air temperature exceeds 13oC (55oF) peaking at over 22oC (72oF) for 8 weeks. In the absence of sub-metering, we have calculated that the cooling plant, with its associated compressors, will cost the store £110,000 per annum to run + quarterly maintenance rising to monthly in peak debris months.

Upon consultation, manufacturers advised that the optimum efficiency of the fans would be compromised should the coil fins, which provide up to 70% of the cooling capacity, become clogged. They also warned against a screen being attached to the coil face. 

Our installation comprises a base screen at decking level, two side screens and two end screens to maximize airborne particulate capture.

This installation is part of a trial. 

Unit 1 will be fitted with the RABScreen air intake screens.
Unit 2 will be left unprotected. 

During this 6-month trial, various data readings will be taken to demonstrate why the RABScreen has a typical ROI of less than 6 months.

Easy to clean, easy to fit and long lasting, this supermarket will improve its operational efficiency and reduce the maintenance cost of the plant in what is a highly competitive market place. .

For further information or to talk to an adviser just call 0800 999 5750 or email

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