Thermal and Electric Performance of PV/T Solar Chimney System

Abstract

The residential and service sectors are responsible for the 39% of the total energy consumption. 80% of this energy is used for heating purposes. Achieving nearly zero energy buildings is a major goal for the near future. The design of an integrated electrical and thermal system can substantially help to reach such objective. The façade is the biggest area of a building and could be utilised to convert incident solar energy to electrical and thermal energy. In previous work (2019), the combination of building integrated PV modules with solar chimney on a façade was investigated to study its energetic performance. One of the main findings was that using the thermal energy from the photovoltaic modules on the air inside the cavity of the chimney is not possible due to its low quality of heat. It was concluded that the utilization of heat could be better by using auxiliary systems, like photovoltaic thermal systems for water heating. The aim of this work is to create a computational model to calculate the thermal and electrical performance of PV thermal (PV/T) modules combined with a solar chimney. Two new designs for better heat utilization where considered and compared. The first design is for the PV modules to be installed at the front of the solar chimney with fins (Fins design) and the second design is to couple the PV modules installed on the wall inside the solar chimney with water pipe system (Water pipe design). These designs are also compared with the same configurations but without the thermal systems (No fins & No water pipes designs). In addition, two new strategies are introduced to improve the performance of the model. The first strategy is the optimization of the solar chimney openings with respect of time for the highest power generation. The second strategy is the variation of the water mass flow with respect to time for highest water-thermal energy and optimum cooling of the PV cells. The model was developed in MATLAB and it is based on 2D finite difference transient implicit method. To reduce the computational time, the density of the nodes varies in respect of temperature gradient. In addition, secondary models were created to increase the accuracy and sensibility of the model such as water tank and water pump models. The models were studied for a building in Delft, Netherlands, and the scale of the chosen system is 10m2. It is concluded that Water pipes design provides the overall best energetic performance mainly because of the high water-thermal energy with yearly energy efficiency of 64.3%. However, the best electrical performance is observed from the Fins design and the best air-thermal performance from the No water pipes design.