Capturing Inter-Annual Variability of PV Energy Production in South Asia

Research output: NRELTechnical Report


Long-term variability of solar resource is an important factor in planning a utility-scale photovoltaic (PV) generation plant, and annual generation for a given location can vary significantly from year to year. Based on multiple years of solar irradiance data, an exceedance probability is the amount of energy that could potentially be produced by a power plant in any given year. An exceedance probability accounts for long-term variability and climate cycles (e.g., monsoons or changes in aerosols), which ultimately impact PV energy generation. Study results indicate that a significant bias could be associated with relying solely on typical meteorological year (TMY) resource data to capture long-term variability. While the TMY tends to under-predict annual generation overall compared to the P50, there appear to be pockets of over-prediction as well.
Original languageAmerican English
Number of pages3
StatePublished - 2017

NREL Publication Number

  • NREL/TP-6A20-68955


  • climate cycles
  • exceedance probability
  • solar irradiance data
  • typical meteorological year
  • variability


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