Comparison of local solar radiation parameters with data from a typical meteorological year

Abstract

Precise determination of local climate characteristics has a huge impact on predicting the efficiency of solar energy systems, as well as simulations of energy demand of buildings. Among many weather data, solar conditions are a very relevant parameter, and the solar irradiance is an important part of a Typical Meteorological Year. TMY sets are created by averaging and modeling data, which unfortunately significantly differs from real conditions. The article presents a comparison of locally measured values of solar irradiance, with particular emphasis on the summer period, in relation to TMY data developed in Poland and TMY data from European Photovoltaic Geographical Information System databases. Significant differences between the data were found. The percentage share of solar irradiance in the range of 600 ÷ 1300 W/m2 in summer, for each of the three TMY PVGIS was 19.86%, 23.75%, 22.50% respectively, while for TMY PL only 8.89%. In the measurements for this range in the summer of 2018 this share was 25.14%, and 20.39% in 2006. Despite the fact that TMY databases include average values of individual parameters, TMY PVGIS data do not differ much from those obtained in summer measurements, which contain also extreme values. In addition, the structure similarity indicator used to compare the data sets confirmed these relationships. This suggests the need to update the TMY PL database, for specific locations, especially in relation to the summer season. The analysis also concerned local sunshine duration in various time intervals as well as factors limiting the availability of solar radiation.