Temperature and Irradiance Dependence of Current and Voltage at Maximum Power of Crystalline Silicon Photovoltaic Modules |
Manit Seapan^{1}, Yoshihiro Hishikawa^{2}, Masahiro Yoshita^{2}, Keiichi Okajima^{1} ^{1}Department of Risk Engineering, University of Tsukuba, Tsukuba, Ibaraki, Japan /^{2}Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan |
The temperature and irradiance dependences of the current and voltage at maximum power point (I_{mp} and V_{mp}) were analytically and experimentally investigated. The I_{mp} and V_{mp} were simulated in the range of the series resistance (R_{s}) of 3 - 7 milliohm and the diode ideality factor (n) of 1.0 - 1.2, which includes typical commercial crystalline silicon photovoltaic (PV) modules. The I_{mp} formula was reorganized by using the one-diode model and was shown to be nearly constant within 1.4% for temperature variation over 10 - 70 °C. The simulation also showed that the I_{mp} is nearly proportional to irradiance (G), and its non-linearity for irradiance was within 0.2% in the irradiance range between 0.5 and 1.2 kW/m^{2}. The simulation for V_{mp} showed a linear decrease by increasing temperature over 10 - 70 °C. The V_{mp} was constant within 2.4% with irradiance between 0.5 and 1.2 kW/m^{2}. Since the I_{mp} was shown to be nearly constant with respect to temperature, the voltage-dependent temperature coefficient in ref. [5] can be approximately used for the V_{mp}-temperature correction. This work investigated the V_{mp}-temperature correction without current-voltage characteristic (IV curve) information. Experiments of the V_{mp}-temperature correction to 25 °C for a crystalline silicon PV module showed good reproducibility for 28 days. These results are useful for characterizing the performance of commercial crystalline silicon PV modules by using the V_{mp} and I_{mp} values. The relation between P_{max} and G was also analytically investigated and compared with experiments. |