A case for generating weather files for Irish locations

By Simeon Oxizidis

Despite the current proliferation of available raw weather data, Ireland still lacks a comprehensive set of weather data files that can be used in a wide array of energy calculations. The weather data and files used today in Ireland have all been derived by ASHRAE. There are two broad categories of such data:

  • The climatic data for design and standards which include annual design conditions and monthly statistics for mainly temperature, humidity and wind speed (16 locations available) [1], [2].
  • The typical weather years that include:
    • The IWEC Weather files (7 locations) with a data coverage between the years 1982 – 1999 [3]. Those are typical weather years of an hourly timestep for a series of weather parameters and are being used in building modelling and simulation. The 7 IWEC weather files can be downloaded for free in epw format from the EnergyPlus website [4].
    • The IWEC2 Weather Files (update of the IWEC ones) including 12 locations with a data coverage spanning from 1983 to 2008 [5]. Those files can be purchased from the White Box Technologies website [6].

Another set of data has been made recently available through White Box Technologies that includes actual weather years for a period between 2001 and 2015 for 21 locations. Those files can be also purchased from the White Box Technologies website [7].

However, all those weather files are facing a serious issue with respect to their solar radiation data which are modelled rather than measured. In addition, they are all derived from a single database (the Integrated Surface Hourly Database (ISD) maintained by the National Center for Environmental Information (NCEI), [8]). But recently, several other sources of weather data have become available including all the unregistered weather stations that have been installed and operated for research or other purposes by non-meteorological institutions and weather data derived from satellite observations. Those additional sources offer vast amount of data that can be appropriately processed to deliver weather files.

A research project that will collate and consolidate the available databases of raw weather data for Ireland and use them to create all types of weather information and respective files, using the state of the art methodologies, will significantly boost the validity of energy research and engineering calculations and will greatly expand the spectrum of energy research and engineering services that can be offered locally.

There are at least four research and engineering fields for which such a comprehensive set of weather data files will be of extreme importance:

  • Provide data for research on smart grids and smart cities (which is a priority research area in Ireland [9]). Such research requires multiple sets of synchronised information of fine resolution (timestep of hour or less).
  • More accurate and informed calculation of buildings performance and better calibration and validation of building models.
  • More accurate and informed calculation of PVs yield. Currently Ireland is moving over supporting the deployment of a few GWs of PVs installations (such support has been explicitly mentioned in the White Paper for Energy [10]). Accurate solar radiation data can significantly help the implementation of feasibility studies and technoeconomic analyses to assess the viability and reduce uncertainty over the performance of PVs projects across Ireland.
  • Calculation of climate change impact on buildings energy performance and indoor conditions and assessment of mitigation strategies.

The availability of such a complete and comprehensive set of weather files in the disposal of the Irish research and engineering community will put Ireland in the forefront of building energy and renewable energy research and of their interaction through the smart grid. In addition, it will substantially improve energy engineering calculations with a subsequent effect on the accuracy and validation of engineering models and predictions that will emphatically reduce uncertainty on energy investments.



  1. ASHRAE (2013) ASHRAE Handbook—Fundamentals. Chapter 14. Climatic Design Information, American Society of Heating Refrigeration and Air conditioning Engineers, Atlanta
  2. ASHRAE (2013) ASHRAE Research Project 1613-RP. Update Climatic Design Data in Chapter 14 of the 2013 Handbook of Fundamentals, American Society of Heating Refrigeration and Air conditioning Engineers, Atlanta
  3. ASHRAE (2001) ASHRAE Research Project 1015-RP. Typical Weather Years for International Locations, American Society of Heating Refrigeration and Air conditioning Engineers, Atlanta
  4. https://energyplus.net/weather-region/europe_wmo_region_6/IRL/
  5. ASHRAE (2010) ASHRAE Research Project 1477-RP. Development of over 2,500 weather files for international locations, American Society of Heating Refrigeration and Air conditioning Engineers, Atlanta
  6. http://weather.whiteboxtechnologies.com/IWEC2
  7. http://weather.whiteboxtechnologies.com/hist
  8. https://www.ncdc.noaa.gov/isd
  9. DJEI (2012) REPORT OF THE RESEARCH PRIORITISATION STEERING GROUP, Department of Jobs, Enterprise and Innovation, Forfas, Dublin
  10. DCENR (2015) White Paper – Ireland’s Transition to a Low Carbon Energy Future, Department of Communications, Energy and Natural Resources, Dublin

Feature Image courtesy of Met.ie

1 Comment

  1. I’d like to clarify that the ISD is not a monolithic weather data source, but the compilation and archival of weather station reports from collaborative countries around the world (practically all of them) under a WMO (World Meteorological Organization) agreement reached in the 1960’s. In other words, the data in the ISD are simply what’s reported to NCEI by the official meteorological stations of the various countries. I agree that the solar radiation on all weather files developed to date are the most problematic for the simple fact that they are never measured by weather stations and must be calculated, although there’ve been decades of work by now so the solar data are not as bad as sometimes feared. A significant development within the last decade is the derivation of solar radiation from weather satellite observations. In the US, such data are now available on a 5-km grid for all of North America below 60 N latitude and a half-hour time resolution from 1998 through 2014. Ireland has the geographical benefit (:-)) of being covered by the SMHI’s (Swedish Meteorological and Hydrological Institute) STRÅNG system providing satellite-derived solar radiation on a 11-km grid (22-km before 2006) starting from 1999 down to today. My recommendation would be to merge the met data from the ISD with the solar data from STRÅNG and search out the other data sources only if there are significant gaps.
    Full disclosure: I was the author of the IWEC2 weather files, as well as the historical weather files now available at the White Box Technologies web site.

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