Evaluation of PV Generator Performance and Energy Supplied Fraction of the 120 kWp PV Microgrid System in Thailand

Normally, the main generators of microgrid system use controllable energy resources such as fossil fuel, biomass, biogas, hydro, etc for uncomplicated control. However, it is very challenging to control the microgrid system that uses uncontrollable energy resources such as solar and wind for main generators of microgrid system because they have many advantages. From this point, the PV microgrid system is constructed and operated at School of Renewable Energy Technology (SERT), Naresuan University for research and development of the microgrid system that is supplying 50% of total electricity demand by PV main generator. By measuring the important parameters such as solar irradiance, PV array voltage, PV array current, and AC electrical power, these data were collected for a year from November 2008 to October 2009 to use in evaluation processes. The PV generator evaluation result is revealed that the average reference yield (Yr), array yield (YA), and final yield (Yf) are 5.21, 4.32, and 3.84 kWh/kWp day respectively. The average total loss of the PV generator is 26.27% that comes from summing up the average capture losses (LC) 17.21% and average system losses (LS) 9.06%. The average overall PV plant efficiency (ηtot) is 10.41%, and the average performance ratio (PR) is 73.45%. While considering the system efficiency of the PV generator at various solar irradiance, we found that it has the lowest efficiency when the solar irradiance is in the range 0 - 0.10 kW/m2, its efficiency increases with the increasing in the solar irradiance from 0.10 to 0.35 kW/m2, the efficiency becomes highest when the solar irradiance in the range of 0.35 to 0.65 kW/m2, and its efficiency decreases slowly when the solar irradiance is in the range of 0.65 to 1.30 kW/m2. For energy supplied fraction of the microgrid, it can achieve the PV generator producing target by PV generator and external grid supplying 73% and 27% of the total load of the microgrid.