DAYSIM Subprogram: ds_shortterm

ds_shorterm is an optional DAYSIM Subprogram that can be used to reduce the time step a DAYSIM weatherfile below an hour. The program was written and validated by Oliver Walkenhorst (et. al) at the Fraunhofer Institute for Solar Energy Systems and is based on a modified auto-correlation model from Olseth and Skarveith (Paper in Solar Energy).

Workflow Description

The user has two options to generate DAYSIM weather files.

  1. Most users will probably download an EPW weather file form the US Department of Energy and convert the file into a DAYSIM weather using the epw2wea program in which case the resulting file has a 60 minute time step. The file is specified via the header file keyword wea_data_short_file.
  2. In case a user desires to work with a simulation time step smaller than 60 minutes the weather data file generated by epw_2wea has to be further processed by ds_shortterm. A possible reason to work with shorter time steps is for an annual glare analysis when the sun might temporarily be in the field of view of a building occupant. In order to use ds_shortterm, an additional DAYSIm header keyword, ea_data_file is required. The keyword has the exact same format as wea_data_short_file but serves as the input file for ds_shortterm.

file_60min.epw  <epw2wea> file_60min.wea <ds_shortterm> file_5min.wea

See also the Daysim Subprogram Flowchart.

Program Author: Oliver Walkenhorst

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