An improved model for output power of grid-connected photovoltaic system under Malaysian climate / Noorfarhana Mat Yusoff

The electrical power production of photovoltaic (PV) systems in the field depends on many factors and can be broadly clustered into three categories which are: effect from heat, sunlight and external factors. Among the external factors are shading, soiling and type of PV array mounting. The direct contribution to all these factors is PV module temperature (Tcell) that has a direct effect on the electrical output power. Due to the rapid growth of PV installations and applications in Malaysia, several studies have been conducted on modelling of Tcell to quantify the output power based on Malaysia climate. Whilst much efforts have been put into modelling the Tcell based on ambient environmental factors, very few studies were conducted on the effect to the type of PV array mounting. Moreover, very few of these studies have related it to the output power generation of PV modules under operation in equatorial climate conditions. Therefore, this study presents the development of a new de-rating factor of output power prediction for grid-connected photovoltaic (GCPV) system in Malaysian climate due to PV array mounting type. Three objectives have been identified which are: determination of the de-rating factor of PV array due to module temperature; determination of effective cell temperature and temperature difference using logged data; and development of a new de-rating factor for output power for each PV array mounting type. This new de-rating factor is defined as PV array mounting configuration factor (fm_p). The data used in this study were obtained from the testing and commissioning (T&C) data of GCPV systems from Feed-in Tariff (FiT) scheme under Sustainable Energy Development Authority (SEDA), Malaysia. Several filtration processes were performed to ensure the selection of only reliable data. Mathematical and statistical approaches were employed to examine the correlation and relationship between the parameters. The results showed that building integrated (BI) PV mounting type has the highest de-rating temperature factor (ftemp_p) followed by retrofitted (RF) and free-standing (FS) mounting type. The highest effective cell temperature (Tcell_eff) was recorded by BI followed by RF and FS mounting type. BI mounting also recorded the highest temperature difference (ΔT). The ΔT represents the difference in temperature between Tcell and ambient temperature (Tamb). Finally, a new de-rating factor due to PV array mounting type was developed to modify existing output power prediction for GCPV system in Malaysia. The results showed that with the addition of fm_p to the existing output power formula, a better prediction of expected output power was obtained.