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How to generate a DDY file for Openstudio/Energyplus

asked 2014-12-01 23:34:26 -0600

Xandrika gravatar image

updated 2020-01-20 13:39:13 -0600

I am simulating for locations that are not in the energyplus weather database. I have EPW files generated by meteonorm using long term stations data. For simulating HVAC systems in OS or energyplus, I need a ddy file or define SizingPeriod:DesignDay. I was trying to generate the DDY file with energyplus weather converter but the converted DDY file only contains Site:Location class. How can I get Design Day data from my EPW files?

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answered 2014-12-02 05:51:43 -0600

The Weather converter program normally creates a DDY file containing SizingPeriod:DesignDay objects with data from the ASHRAE Handbook of Fundamentals 2009. Since no data is available for your location, you can use the use the data that is shown in the STAT file that is also generated to create SizingPeriod:DesignDay objects by hand. The AuxiliaryProgram documentation states:

Using the WMO field (or determining it from the WBAN field), the Weather Converter performs table look up in the Design Condition files to see if there are recorded design conditions for the subject location. If this location is found, then design day objects are produced on the resultant design day object (ddy extension) file – ready for inclusion into an EnergyPlus input data file. If no design conditions are located, then the design day object file will still include a location object for inclusion with EnergyPlus. However, statistics using the weather file are displayed to the statistics file – these “can” be used to create your own design day definitions but you should read the warning that is issued and take care if your weather file is only a “single instance” weather data representation.

Another option is to choose design day data from a location that is most similar, perhaps by comparing data from the STAT file. I would also suggest that you contact the vendor that provided you the data and see if they can provide design day data.

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@JasonGlazer Yes, I already saw the STAT file but could not really understand which data to use. Here you will find what is there under Design stats of my locations. If I understand right I could take, e.g. the coldesr winter day adn the hottest summer day for my design conidtions? I found another thread here that points out that there is no methodolody for getting Design Days out of a weather file:-(

Xandrika gravatar image Xandrika  ( 2014-12-02 11:32:29 -0600 )edit

@JasonGlazer My weather files (in Nepal) are generated with METEONORM using station data (normals) that I got from the government authority DHM Nepal. They are not able to provide me design day data:-( I read about the opention to uses Weather file Days as Design days using the class SizingPeriod:WeatherFileDays. But I guess this cannot be done in OS but in Energyplus. Am I right?

Xandrika gravatar image Xandrika  ( 2014-12-02 11:47:09 -0600 )edit

The most accurate would be to go back to the DHM Nepal and request additional climate data as a basis for the design days. Alternatively, look at the most similar station with SizingPeriod:DesignDays and use your judgement to adjust those number considering the statistical results from your climate and the climate with the with SizingPeriod:DesignDays.

JasonGlazer gravatar image JasonGlazer  ( 2014-12-02 12:35:07 -0600 )edit

@Xandrika did you find the the solution for weather files for Nepal?.

dipen609 gravatar image dipen609  ( 2016-07-06 05:14:10 -0600 )edit

@dipen609 Yes, I took the data from the stat files. If you are interested in Weather data for Nepal, please, contact me via email xandrika77 at I can share it with you. What kind of research are you doing in Nepal?

Xandrika gravatar image Xandrika  ( 2016-07-06 06:08:01 -0600 )edit

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Asked: 2014-12-01 23:34:26 -0600

Seen: 3,101 times

Last updated: Dec 02 '14