Performance of a concentrating photovoltaic monomodule under real operating conditions: Part II – Power rating

In Part I of this work, a comprehensive outdoor characterisation of a concentrating photovoltaic monomodule was presented where the importance of atmospheric parameters on the performance of such systems was highlighted. In this work, Part II, the power ratings of a concentrating photovoltaic monomodule are determined using different methods and filtering criteria that account for the spectrum. Spectral variations are considered to be a major parameter that contributes to the uncertainty of concentrating photovoltaic power ratings due to the dynamic behaviour of outdoor conditions. In order to address the sensitivity of such variations, Concentrator Standard Operating Conditions (CSOC) and Concentrator Standard Test Conditions (CSTC) power rating estimations are performed using different scenarios and compared with measurements obtained using a Helios 3198 solar simulator. The application of different methods and filtering criteria, in terms of the spectral matching ratio (SMR) of the middle to bottom subcell, exhibits differences of up to 3.64% and 1.37% for the CSOC and CSTC estimations respectively. The comparison with the CSTC power rating obtained indoors shows a difference of up to 8.45%; this is attributed to the tracking errors and also the temperature dependence of the refractive optics. The application of the spectral factor (SF) as filtering criterion reduces the CSTC power rating difference to 6.74% compared to the corresponding value obtained indoors. In addition, the CSOC power rating estimation using the SF filtering exhibits similar results to the standardised procedure using the SMR indices (within 1.21%).