Case study of effect of temperature on module performance
The maximum power point voltage of the module is affected by temperature and most of the manufactures specify voltage temperature co-efficient in V/ deg C. in order to ensure that the output voltage of the array, do not fall outside the range of Inverter input voltage range. If a inverter is having a operating voltage window 450 to 750 V and a module selected has a MPP voltage of 36 V there will be about 16 module connected in series which will provide a MPP voltage 576 V, which is in line with the input voltage of the inverter, if the voltage coefficient for the module is 0.2 V/o C, at an operating temperature of 75oC, the temp de-rating of module will take place and as the operating temp of module is 50o C higher than the slandered condition (25oC). The MPP voltage of the given module will be of the order of 35-(0.2 * (75-25))= 25 V. As the 16 modules are connected in series in array, the overall MPP voltage will be reduced from 576 V to 400 V. As the input voltage window for inverter is of the range of 450 V to 750 V. the inverter will start tripping because of array voltage beyond the inverter input voltage window. Hence, the site temperature conditions become important while selecting inverter and PV module. The temperature can play a significant role in de-rating the overall plant performance.