skip to main content


Title: Robust PV Degradation Methodology and Application

The degradation rate plays an important role in predicting and assessing the long-term energy generation of photovoltaics (PV) systems. Many methods have been proposed for extracting the degradation rate from operational data of PV systems, but most of the published approaches are susceptible to bias due to inverter clipping, module soiling, temporary outages, seasonality, and sensor degradation. In this paper, we propose a methodology for determining PV degradation leveraging available modeled clear-sky irradiance data rather than site sensor data, and a robust year-over-year rate calculation. We show the method to provide reliable degradation rate estimates even in the case of sensor drift, data shifts, and soiling. Compared with alternate methods, we demonstrate that the proposed method delivers the lowest uncertainty in degradation rate estimates for a fleet of 486 PV systems.
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [2]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. SunPower Corp., San Jose, CA (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 2156-3381
Grant/Contract Number:
AC36-08GO28308; AC36-08-GO28308
Published Article
Journal Name:
IEEE Journal of Photovoltaics
Additional Journal Information:
Journal Volume: 8; Journal Issue: 2; Journal ID: ISSN 2156-3381
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
Country of Publication:
United States
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; degradation; temperature measurement; standards; atmospheric modeling; photovoltaic systems; inverters
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1417794; OSTI ID: 1422266