The Case for Custom TMY's: Examples Using the NSRDB

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1 Scopus Citations


A typical meteorological year (TMY) data set essentially represents an hourly compilation of median months constructed using multi-year datasets. Although TMY data sets are generated from irradiance data in the horizontal plane, they are used in photovoltaic (PV) modeling for systems inclined to various angles. This paper demonstrates that a POA TMY (plane of array TMY) generated by selecting median months from a multi-year POA irradiance timeseries dataset produces significantly different results than a POA TMY generated by transposing a TMY dataset constructed from horizontal data. In some months the differences can be more than 3%. These results point to the need for generating TMY's using POA irradiance timeseries representing the orientation at which PV panels will be deployed.

Original languageAmerican English
Number of pages6
StatePublished - Jun 2019
Event46th IEEE Photovoltaic Specialists Conference, PVSC 2019 - Chicago, United States
Duration: 16 Jun 201921 Jun 2019


Conference46th IEEE Photovoltaic Specialists Conference, PVSC 2019
Country/TerritoryUnited States

Bibliographical note

See NREL/CP-5D00-74063 for preprint

NREL Publication Number

  • NREL/CP-5D00-76337


  • latitude tilt
  • plane of array
  • POA
  • single-axis tracking
  • TGPY
  • TPY
  • typical GHI-based POA year
  • typical meteorological year
  • typical POA year


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