Risk mitigation of performance ratio guarantees in commercial photovoltaic systems

This study demonstrates the importance of managing the risk of performance ratio guarantees, which typically are applicable to most commercial PV projects. A qualitative assessment of the performance metrics has shown multiple performance parameters, which could influence the Performance Ratio. Alternative performance metrics, including the Temperature Corrected Performance Ratio and the Weather Corrected Performance Ratio were evaluated by means of a quantitative analysis. The Temperature– and Weather Corrected Performance Ratios have both demonstrated the capability of reducing the inter-annual and seasonal variance experienced with the conventional Performance Ratio. The respective performance metrics were further calculated from multiple years of meteorological data in order to construct a statistical distribution for each performance metric. The resulting probability distribution function was then used to determine the probable risk percentiles for each of the respective performance metrics and compared with the separately calculated performance metrics referring to a long-term mean data set. It was demonstrated that the long-term mean derived performance parameters did present a risk for overstating the facilities’ performance. The risk was mitigated by referring to the multi-year’s P90 percentile instead.