A Bi-fluid PV/T Solar Collector and Its Potential Application in Solar Drying

Abstract

A bi-fluid PV/T solar collector incorporates two types of working fluid (air and water) under the same PV/T solar collector. In addition to the electricity generated, this type of collector enables the production of thermal energy in the form of heated air and water. The use of both fluids (bi-fluid) also creates a greater range of thermal applications and offers options in which three modes of fluid operation, namely, the air mode, the water mode, and the simultaneous mode (air and water), can be produced depending on the energy needs and applications. In this paper using a validated mathematical model, we have simulated the performance of a glazed single-pass bi-fluid PVT solar collector in terms of its temperature output and thermal energy performance when operated simultaneously. In the simulation we have used amorphous silicon polycrystalline PV panels operated under typical hot climatic conditions, of Perlis, Malaysia. We found that, when both working fluids are operated at its optimum flow rate (air mass flow rate of 0.027 kg/s and water mass flow rate of 0.0066 kg/), the PV/T solar collector could produce an average of 40–53 °C air output temperature in addition to hot water output between 50 and 70 °C. By taking into account both thermal and electrical energy of the collector, for 2 m2 collector aperture area, on average, the PV/T collector could produce in total of 11 kWh thermal energy and 1.2 kWh electrical energy during the day. It is important to note that the working fluid cools down the PV cells temperature which leads to increase in electrical efficiency. In hot climate, space heating is not required for typical residential and commercial building applications. The potential application of the PV/T bi-fluid solar collector is seen in a solar drying system for fruits, crops, vegetables, and marine products. From the simulation, the air temperature range is clearly within the average temperature requirement for solar drying. In addition to air heating, the heat output from the hot water can be supplied into the chamber via water to air heat exchanger arrangement, thus enhancing the drying rate by reducing the moisture content inside the drying chamber. The warm water leaving the chamber can be stored for later usage or for different useful application. In this paper two designs of bi-fluid PV/T solar collector integrated with a greenhouse drying chamber are presented. Future studies will include detail simulation and experimental work of the proposed drying systems.