On the exergetic capacity factor of a wind – solar power generation system

In the recent years, exergy analysis has become a very important tool in the evaluation of systems' efficiency. It aims on minimizing the energy related-system losses and therefore maximizing energy savings and helps society substantially to move towards sustainable development and cleaner production. In this paper, a detailed exergetic analysis aiming to identify the overall Exergetic Capacity Factor (ExCF) for a wind – solar power generation system was done. ExCF, as a new parameter, can be used for better classification and evaluation of renewable energy sources (RES). All the energy and exergy characteristics of wind and solar energy were examined in order to identify the variables that affect the power output of the hybrid system. A validated open source PV optimization tool was also included in the analysis, It was shown that parameters as e.g. air density or tracking losses, low irradiation losses play a crucial role in identifying the real and net wind and solar power output while planning new renewable energy projects and in fact do play a significant role on the wind – solar plant's overall exergetic efficiency. In specific, it was found that air density varies from site to site influencing productivity. A difference of 6.2% on the productivity because of the air density was calculated. The wind and solar potential around a mountainous area were studied and presented based on field measurements and simulations. Since the number and the size of RES projects, over the last few years, are continually increasing, and new areas are required, the basic idea behind this research, was not only to introduce ExCF, as a new evaluation index for RES, but also to investigate the combined use of wind and solar energy under the same area and the benefits coming out of this combination.