PV System Reliability: An Operator's Perspective

The long-term performance of a photovoltaic (PV) system is one of the fundamental sources of its value; the other being the unit value of the energy it is generating. The industry operates under the assumption that a PV system can keep converting photons to electrons quite reliably with minimal interruptions in service for the typical 20-25-year duration of the energy purchase contracts. However, manually assembled macroscopic systems, comprising components with a high quotient of manual labor, and which operate outdoors under noncontrolled conditions, do tend to exhibit issues. The inverter software which is critical for their operation is an additional potential source of failure. In the case of an operator with global presence, relying on local assembly crews and sourcing components from a large number of suppliers, the challenge in keeping hundreds of power plants in optimal operation with regional teams of roving technicians cannot be easily overstated. Outages of mission-critical subsystems comprise 69% of identified service issues and are responsible for 75% of the associated energy losses. Most of the issues manifest at the inverter, but ac subsystem failures and externally caused outages comprise a large share of the biggest losses. Module failures represent a small fraction of identified issues.