An Investigation of the Energy Efficiency of a Grid Connected Photovoltaic System

A photovoltaic system installed on the roof of an industrial site has been studied. The total maximal installed power of the system is 117.24 kWp. Poly- and mono-crystalline photovoltaic modules have been used. The energy efficiency of the system has been studied through the changes of the performance ratio (PR) and of the energy efficiency coefficient (efficiency) for a period of 8 years and 9 months (105 months - from January 2009 to and including September 2017). It has been found out that the changes in the values of PR and efficiency over the years are insignificant. Studies on photovoltaic modules in operational conditions show that polycrystalline ones are more efficient than mono-crystalline ones during the summer periods when the minimal values of efficiency and PR are observed. Their differences for the two types of modules remain almost constant over the years and are respectively 4% and 0.1.