Modelling the performance of a large area plastic solar collector

A mathematical model for simulating the performance of a large area plastic solar collector was developed. The collector was installed and used to supply hot water to a hotel in Almeria, Spain. It consists of three main components, namely a plastic water bag, a UV-stabilized plastic sheet cover and an insulated floor. The plastic materials were used in this collector in order to reduce the investment cost. To develop the model, the various modes of heat transfer in the collector were analysed. A system of equations representing the model was simultaneously solved using the implicit finite difference method. The data obtained from the experiments were used to validate the model. It was found that the outlet water temperature calculated using the model agreed well with the experimental data. The model was then used to investigate the effect of various parameters on the performance of the collector. The results were used as a guideline to improve the performance of the existing collector. According to the investigation, the original design of the total collector length of 48.2 m was too long for the operational flow rate of 0.083 kg/s. From the simulation, the new values of the water depth and the flow rate were also recommended in order to increase the efficiency of the collector. The time lags between the radiation peak and the outlet water temperature peak were relatively large for all cases. It was also found that wind speed slightly affects the outlet water temperature.