Efficiency and Electrical Properties of a Copper-Indium- Diselenide Photovoltaic Module under Real Operating Conditions

Abstract

This work presents the outdoor testing of a Copper-Indium-Diselenide (CIS) module under real operating conditions, and a semi-empirical model for calculating the efficiency under all relevant operating conditions including varying cell temperature, solar irradiance and relative air mass. Six different models were tried for 1168 measured data sets. The best model contains six correlation parameters in a product of two terms. One term describes the behaviour of the module with decreasing irradiance (part-load behaviour), the other one the temperature and air mass impact. In order to assess the quality of the model, transformation methods were applied, allowing two-dimensional representations of measured data and the calculated efficiency. The model is a highly useful tool to determine accurately the annual output of CIS modules at different sites with known climate data which is indispensable for the calculation of electricity production costs. The model also provides the Standard Test Condition (STC) efficiency of 11.6% and its temperature coefficient of minus 0.050%/°C, before degradation. Both values are important for peak power estimation in system design. The efficiency of 11.6% is remarkably high. Empirical models were also developed for the open circuit voltage and short circuit current.