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Title: Reducing Interanalyst Variability in Photovoltaic Degradation Rate Assessments

Journal Article · · IEEE Journal of Photovoltaics
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [5];  [6]; ORCiD logo [7];  [8]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [9]; ORCiD logo [10];  [11];  [11]; ORCiD logo [11]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. National Univ. of Singapore (Singapore)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Univ. of Utah, Salt Lake City, UT (United States)
  5. Stanford Univ., CA (United States)
  6. Case Western Reserve Univ., Cleveland, OH (United States)
  7. Canadian Solar, Suzhou (China)
  8. Technological Education Inst. of Crete, Heraklion (Greece)
  9. SunPower Corporation, San Jose, CA (United States)
  10. kWh Analytics, San Francisco, CA (United States)
  11. Dubai Electricity & Water Authority, Dubai (United Arab Emirates)

The economic return on investment of a commercial photovoltaic system depends greatly on its performance over the long term and, hence, its degradation rate. Many methods have been proposed for assessing system degradation rates from outdoor performance data. However, comparing reported values from one analyst and research group to another requires a common baseline of performance; consistency between methods and analysts can be a challenge. An interlaboratory study was conducted involving different volunteer analysts reporting on the same photovoltaic performance data using different methodologies. Initial variability of the reported degradation rates was so high that analysts could not come to a consensus whether a system degraded or not. More consistent values are received when written guidance is provided to each analyst. Further improvements in analyst variance was accomplished by using the free open-source software RdTools, allowing a reduction in variance between analysts by more than two orders of magnitude over the first round, where multiple analysis methods are allowed. This article highlights many pitfalls in conducting 'routine' degradation analysis, and it addresses some of the factors that must be considered when comparing degradation results reported by different analysts or methods.

Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Renewable Energy. Solar Energy Technologies Office
Grant/Contract Number:
AC36-08GO28308
OSTI ID:
1592395
Report Number(s):
NREL/JA-5K00-72879; MainId:13079; UUID:1d77b539-63f3-e811-9c19-ac162d87dfe5; MainAdminID:1559
Journal Information:
IEEE Journal of Photovoltaics, Vol. 10, Issue 1; ISSN 2156-3381
Publisher:
IEEECopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 20 works
Citation information provided by
Web of Science

Figures / Tables (6)