Energy performance of the photovoltaic system in urban area - case study

Abstract

Nowadays, photovoltaic systems installed in urban areas may be essential for distributed generation and lead to increase energy security and improve economy of building exploitation. Unfortunately, in many cases their operation in urban area is not so efficient. It is connected with shadowing by neighbouring buildings, trees or by the HVAC systems installed on roofs (including such elements as fans, compressors, etc). Moreover, HVAC systems often occupy “the best” place on roofs. Level of shadowing varies during a day, and a year, significantly influencing on the power generation from PV installations. It caused serious difficulties in designing such installations (e.g. choosing position, orientation, number of modules etc.). In the paper a PV efficiency analysis was performed for the case of photovoltaic installation located on the roof of didactic building in Krakow centre. The projected power of the installation was 8.48 kWp (total nominal power of panels), and 7.5 kWp at the output of the inverters used for own building demand and car load station. The available area for PV system was strongly limited and achieving of the optimal tilting angle was impossible. Presented simulations have been conducted using two commercially available software: TRNSYS and Polysun. Results of the simulations were used for improving operation parameters of the installation. A three approaches was considered: avoiding the shadow, tilting angle optimization and redirecting of additional light stream.