Performance evaluation of different solar collectors in building cooling, heating, and hot water supply

To evaluate the performance of parabolic trough solar collectors (PTCs) and flat plate solar collectors (FPCs) by different thermal utilization methods, including building cooling, heating, and hot water supply, this study adopted the indices of the primary energy ratio (PER) and unit cost of energy (UCE) and the operating ratio to compare the applicability of collector systems. First, the heat transfer models of FPCs and PTCs were constructed by a lumped parameter method and validated by experiments. Then, the performance of collectors and the operating modes of different thermal utilization methods were obtained. Finally, by inputting the meteorological parameters of Tianjin, the following conclusions can be drawn. (1) The evaluation indices of UCE and PER were consistent when evaluating different collector systems. The FPC system was more appropriate for hot water supply and heating, and the PTC system was more suitable for cooling and heating and cooling. (2) The hot water supply had the best energy saving and was economical compared to other solar thermal utilization methods with FPC and PTC systems, as its UCE was 0.19 RMB/kW h and 0.28 RMB/kW h and PER was 1.38 and 1.17, respectively. (3) The operating ratio of both the hot water supply and cooling was higher than 50% in both collector systems. The heating system had the lowest operating ratio, less than 40%, which was related to its load characteristics.