Title: Coupled Performance and Reliability Modeling of PV Systems and Components: Evaluating Design and O&M Strategies

Sandia National Laboratories has developed a detailed, component-level, stochastic model which evaluates costs, benefits, and risks associated with different strategies for plant operation and maintenance (O&M). The PV Reliability and Performance Model (PV-RPM) simulates the energy production and O&M costs of a PV plant throughout its operational life, including uncertainties. A plant is represented in the model as a set of user-defined components (e.g., modules, inverters, combiners, etc.), which are connected in a hierarchal fashion, such that when certain components fail (or degrade) they only affect the availability of the system "downstream" of the failed component. Performance is evaluated hourly from weather conditions and plant availability calculated in the reliability submodel. A monthly cash flow calculation is performed: energy produced (excluding any lost to failures) is converted to revenues. All costs incurred during the month are evaluated (debt servicing, repair costs, etc.), including warrantee claims. The model can be configured to match any system design and can be used to help answer numerous questions. Sandia has (1) estimated the value of improving inverter reliability which can be compared to costs associated with making these improvements, (2) explored the relationship between inverter size and performance/costs, and (3) studied how different monitoring and O&M strategies affect system performance. For instance, string-level monitoring increases installation costs but allows prompt identification and repair of string-level failures rather than leaving them to be fixed during routine maintenance. This model aims to help developers compare and choose from different strategies for plant management and design.