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).
The user has two options to generate DAYSIM weather files.
- 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.
- 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