Ventilative cooling and energy use in supermarkets

Supermarkets are a category of non-domestic buildings with high energy use because of their operation. Recent work indicates that by improvements to the energy delivery systems through which internal environmental conditions are maintained such as thermal properties of external envelope including airtightness, HVAC systems and lighting, substantial energy savings can be achieved. Work to date has focused on typical supermarkets while the present paper examines frozen food supermarkets which include more refrigeration cabinets and therefore result in higher energy use per sales floor area. The work is based on measured energy and environmental data from a newly built supermarket in South London that was used to create and optimise an energy and thermal model of the supermarket using EnergyPlus. With the calibrated model, a parametric analysis was carried out to determine strategies for improved energy performance. Results indicate that changes in the operational times of the existing HVAC system, as well as different temperature set points in the sales area can lead to energy savings of 6.5%. Night Ventilation has the potential for energy demand reduction across the majority of the operating systems and could save 81 kWh/m2sales area annually and up to 51% cooling energy. Improved envelope airtightness is also being investigated and in combination with thermal insulation retrofits, a further reduction is predicted to the energy demand. Light intensity monitoring data have indicated that additional energy savings can be achieved by introducing a daylighting control strategy. Compared to the baseline supermarket model as it operates currently, the above changes can reduce the energy use and CO2 emissions by 13.1% annually. Finally, the potential of the implementation of different HVAC systems (CAV and VAV) to the store indicated that the VRF system can maintain more efficiently the indoor air temperature of the store with the minimum total energy use. Night Ventilation strategies through r the different HVAC systems showed that the CAV system presents higher dependence on the air flow rates of night ventilation.