Supermarket refrigeration and air conditioning systems integration via a water storage

One of the most challenging targets for the Commercial Refrigeration sector nowadays is spreading the use of pure CO2 systems in mild climate countries. In recent years several solutions have been proposed in order to improve the performance of CO2 transcritical cycles. Among these improvements, the reduction of the discharge pressure by means of subcooling the refrigerant at the exit of the gas cooler is very interesting when a cold storage is available, or when the rejected heat may be recovered for other thermal systems in the supermarket. In this paper the exploitation of a large fire prevention tank as a condenser/subcooler for a supermarket CO2 booster refrigeration system and as a heat source for a heat pump for the HVAC system is investigated. The whole system is modelled in the Trnsys environment and the effects of the thermal capacity on the energy efficiency are compared with the case of the two systems running separately. The energy savings range from about 3% to more than 5% at two different locations in Northern Italy.