PV/T heat pump system, TRNSYS, Polygeneration, Radiative cooling
Using photovoltaic modules (PVs) and solar collectors separately for the generation of electricity and heating is a convention in the field. In contrast, PV/T collector is a single device that combines PV and solar collector together that can convert solar radiation to electricity and heat simultaneously. Because the heat transfer medium (e.g., air or water) used to collect thermal energy reduces the operating solar cell temperature, PV/T normally leads to a higher efficiency compared to PV or solar collector alone. Traditionally, PV/T applications have focused on the use of thermal energy for heating. However, PV/T collectors can be used for cooling through long wave radiation exchange with the sky over clear nights. The potential of using PV/T collectors for space cooling has rarely been studied. This paper presents a hybrid PV/T heat pump system used in a single family house located in Baltimore, MD. Consisting of PV/T collectors, a water-to-water heat pump, an outdoor swimming pool, a domestic hot water tank and pumps, the system is used to provide electricity generation, space heating and cooling, and domestic hot water. Different operational modes are considered according to space conditioning needs and the temperature of PV/T collectors and swimming pool. The house has a hydronic radiant floor system for space conditioning. Depending on the operation modes, the energy source/sink side of the heat pump can be connected to either PV/T collectors or the outdoor swimming pool. Outdoor swimming pool acts as the thermal storage, which is charged by the PV/T collectors when space conditioning is not needed. TRNSYS energy simulation software package is used to model the system performance. In the TRANSYS model, the PV/T heat pump system is connected to a multi-zone building model (TYPE 56) to evaluate the impact of PV/T collectors and operational modes on the house heating and cooling energy consumption. The energy performance of the proposed PV/T heat pump system is compared to a reference split air conditioning system consisting of direct expansion coils for cooling and gas furnace for heating.