How to Assess Solar PV Energy Yield and Degradation with Operational Power Curves

Presentation Description: Wood was requested to assess whether any accelerated degradation occurred during an extended outage when a plant was shutdown and disconnected from the grid. This involved conducting an energy yield assessment for the PV plant before and after the shutdown, which presented several obstacles. For example, a trend analysis to analyze degradation during the outage was not possible, since the plant was offline, and a traditional operational energy yield could not be performed due to limited operational data being available in the post-shutdown period.
This presentation will explain the novel approach developed to navigate these obstacles, including discussion of the constraints, available input data, methodology, uncertainties, possible future improvements and lessons learned.
At a high-level, the methodology involved analysis of the site and inverter-level SCADA data before and after the shutdown period, filtered according to the ASTM E2848-13 standard, to develop pre- and post-shutdown period power curves. Using these power curves in conjunction with TMY data and an as-built PVSyst model enabled us to develop energy yield estimates pre and post shutdown. The clipping-adjusted degradation and accelerated degradation was calculated by comparing the energy yield estimates. An uncertainty analysis was also performed to assign a range to the performance drop.