Influence of display cabinet cooling on performance of supermarket buildings

Energy demand attributable to the operation of supermarkets is thought to be responsible for 1% of UK greenhouse gas emissions. Current building regulations in the UK require the “building related” energy use of new commercial buildings to comply with particular requirements. Supermarket buildings are therefore modelled in considerable detail, according to these protocols to establish their predicted energy demand. Lighting, occupancy, and small electrical energy impacts are included in this modelling. However, a large gap is found between the design outputs of this modelling and the energy performance of the store in operation. One reason for this is that thermal interactions at the refrigeration cabinets are not included in this modelling, as refrigeration is classified as “process energy” rather than “building related.” This paper explores the comparative energy demands of supermarket retail floors simulated both with and without the cooling effect of refrigeration cabinets included in the simulation. The retail floor of a recently built supermarket is modelled using EnergyPlus.

Practical applications: It has been shown that the energy demand of the retail floor of a new store could be reduced by 25% by improvement of the envelope, by halving ventilation rates and doubling insulation levels. This has been shown by simulation of the building energy flows with refrigeration cabinets included in the modelling (whereas these are currently excluded as process energy). Changes in modelling protocols, and regulations, to encompass refrigeration energy transfers, could reduce the national load, due to supermarkets, by at least 140 MW in 5 years. Energy costs to the retailer would be reduced by 20%. Additionally, the simulation has shown the contribution of rooflights to the reduction of energy demand to be lower than previously predicted, saving only around 1/3 of design expectations.