Temperature and irradiance dependences of the current and voltage at maximum power of crystalline silicon PV devices

The temperature and irradiance dependences of the current at maximum power (I-mp) and the voltage at maximum power (V-mp) of crystalline silicon photovoltaic (PV) devices are investigated by experiments and numerical simulations based on a single diode model. It is shown that the experimental I-mp is nearly constant for temperature variation at fixed irradiances, which agrees with the simulation results being within +/- 0.02%/K over 273.15-343.15 K (0-70 degrees C) over the range of parameters represents typical commercial crystalline silicon PV devices. The experimental I-mp is nearly proportional to irradiance (G) at fixed temperature, which also agrees with the simulation results that the I-mp/G is nearly constant within +/- 1.3% for the irradiance range between 0.5 and 1.2 kW/m(2). Based on these results, a new formula for the temperature correction of V-mp is proposed. It does not require advance information of diode parameters and temperature coefficient. The I-mp - V-mp curves which are measured outdoors and corrected to 25 degrees C by using the formula showed good reproducibility within +/- 0.13% for many days, which confirms the validity of the formula. The maximum power P-max can be also precisely estimated by the temperature correction of V-mp. These results are useful for characterizing the performance of crystalline silicon PV devices by using the I-mp and V-mp values, which can be measured during their maximum power point tracking (MPPT) operation.