Thin film photovoltaic module characterisation based in indoor and outdoor methods

Photovoltaic modules are normally tested under standard test conditions defined by the International Electrotechnical Commission, but these conditions are different from typical field condition. The standard test conditions for PV modules is specified as 1000 W/m² irradiance and 25°C cell temperature and reference spectral American Society for Testing and Materials (ASTM) G173. The light source may be natural or simulated, but it must match the reference standard as described in IEC 60904-3. The effect of spectral variations on the 1-V measurements can may have a big impact on the accuracy of the performance measurements. This effect was quantified during in this the study at the Indoor and Outdoor PV testing facility in Council for Scientific and Industrial research, Energy Initiative Pretoria campus. Results show different spectral mismatch values were obtained when two different spectral reference cells were used on the indoor measurements of modules under test. The obtained spectral mismatch values were affected by the absence of true spectral data of modules under test. The irradiance corrected Isc outdoor measurement values were higher than measured uncorrected Isc measurements due to the first order impact from the measured irradiance in the plane of array. The spectral mismatch between the reference device and the PV module results in an additional error for thin film modules.