Evaluation of solar spectral irradiance distribution using an index from a limited range of the solar spectrum

The output energy of photovoltaic (PV) modules under outdoor conditions is greatly influenced by the spectral irradiance distribution of the solar spectrum. To analyze this effect on PV modules, the spectral irradiance distribution, which is one-dimensional data, has to be represented by a zero-dimensional index. The average photon energy (APE) is an index for spectral irradiance distributions, which represents the average energy per photon in a spectrum. We have previously analyzed the uniqueness of the shape of the solar spectrum in the wavelength range of 350–1050 nm, and one corresponding value of APE showed a specific shape of spectral irradiance distribution. In this study, new indexes were calculated for a limited wavelength range of 350–750 nm and multiple bands of 450–500 nm and 800–850 nm of the solar spectrum for easy measurement and calculation. The result shows the uniqueness of new indexes to the shape of measured solar spectrum and the standard deviations were found to be quite small. This indicates that the new indexes are reasonable for representing the spectral irradiance distribution and its effect on PV performance.     

Impact of average photon-energy coefficient of solar spectrum on the short circuit current of photovoltaic modules

The output energy of photovoltaic (PV) modules is influenced by the spectral irradiance distribution of the solar spectrum under outdoor conditions. To rate the precise output energy of PV modules, the correction of short circuit current (I_SC) based on actual environmental conditions is needed, because I_SC significantly depends on the shape of the spectral irradiance distribution. The average photon energy (APE) is a zero-dimensional index for spectral irradiance distribution, and APE value uniquely describes the shape of a solar spectrum. Thus, APE has an impact on I_SC of PV modules. In this contribution, the relationship between APE coefficient and I_SC of the multi-crystalline silicon, single-crystalline silicon, heterojunction intrinsic thin-layer, back contact, copper indium selenide and cadmium telluride PV modules has explored. It is revealed that APE value changes the I_SC of PV modules which appeared to have immense possibilities of I_SC correction using APE coefficient. This new approach can be very effective for precise rating the output energy of PV modules under actual outdoor conditions.