Edit / translate hourly weather data

The Edit/Translate Hourly Weather Data dialog can be accessed from the Tools menu and can be used to process hourly weather data.  You may wish to do this for various reasons:

• Convert EnergyPlus epw data to be compatible with DesignBuilder day of week results for daily, hourly and sub-hourly output (set the year to 2002).
• Translate weather data in other formats to the epw format so that it can be used in DesignBuilder.
• Generating modified weather data sets for investigating climate change scenarios.

Translating

Use this dialog to convert weather data to and from a range of file formats. Supported formats are:

•     EnergyPlus data files (.epw)
•     EnergyPlus 'comma separated values' files (.csv)
•     TMY2 data files (.tmy2 or tm2)
•     TMY data files (.tmy)
•     IWEC data files (.iwec or iwc)
•     Samson data files (.samson or dat)
•     WYEC2 data files (.wyec2 or wy2)
•     DOE-2 formatted data files (.fmt or txt)
•     ESP-r formatted data files (.esp-r or clm)
•     BLAST ASCII formatted data files (.blast or asc)

Required extensions are shown in brackets.  To edit/convert a file or files:

1. Select the folder containing the file(s) using the browse box at the top of the left-hand side of the screen.  All relevant weather data files are then loaded into the table on the left.
2. Check the check box next to each file that is to be converted.
3. Ensure that the correct options have been set on the Options tab.
4. Press the Convert button to start the process.

Converted files are stored in the Weather data folder. You can access these files by clicking on the 'Edit/Review' tab.

Converting from Other Formats

If you have data in a format that is not supported by the DesignBuilder weather data translator there are 2 ways this can be used to generate an equivalent weather file in epw format.

1. Use the EnergyPlus custom weather data translation tool. Detailed descriptions on its use are provided in the Auxiliary Programs Guide (which is an essential guide for all epw weather data conversion/analysis. The EnergyPlus weather converter tool can be obtained by downloading the EnergyPlus software and is not supported by DesignBuilder support desk. However if you run into problems with it, you should be able to get help from the EnergyPlus support desk or forum.
   
   
2. The second option is to use an existing epw file as a template and copy columns of data across from your weather data source file using the csv spreadsheet format.

The rest of this article provides details on the second of these methods.

To translate weather data from any format follow these instructions. Note that as a starting point you will need to have the main data required by EnergyPlus stored in a csv format file or spreadsheet. The data required is:

• Air temperature
• Dew point temperature
• Relative Humidity
• Atmospheric pressure
• Global horizontal solar radiation
• Diffuse Horizontal solar radiation

• Direct normal radiation

• Wind Speed
• Wind Direction
• Cloud cover

If any of the above parameters are missing and you are unsure about how to derive them, you may wish to consider using the EnergyPlus custom weather translator instead which has built-functions to derive some missing parameters based on other equivalent data. e.g. Direct normal radiation can be derived based on known solar position and global and diffuse horizontal radiation.

If you do have all the required data in columns of a csv file then you are ready. The process is as follows:

1. To start the process, generate a template for a similar location in csv format. To do this use the weather data translation tool, selecting the 'EnergyPlus 'comma separated values' files' output option on the Options tab.
2. Load the csv file created in step 1 into a spreadsheet to use as the template.
3. In a separate spreadsheet load the new data.
4. Copy and paste the data column by column from the new data spreadsheet into the equivalent columns in template spreadsheet. A 'missing value indicator' value can be entered in any of the places EnergyPlus doesn't use the data. The 'missing value indicator' value is different for each field and details can be found in the Auxiliary Programs Guide.
5. Check that the header data at the top of the template spreadsheet is correct.
6. Ensure the year is set to 2002 in all rows.
7. Save the template as a csv file.
8. Use the weather file translator to translate the template csv file to epw format.
9. Rename the epw file as required.
10. Check that the data has been copied correctly by loading the file into DesignBuilder and clicking on the Simulation tab when at site level. You'll need to set up a new Hourly weather data component referencing the new epw file and select this first.
11. Check carefully that data output from simulations that use the new weather file makes sense. Pay particular attention to solar radiation. To do this you could check hourly incident solar radiation on a few surfaces in a model.

Note 1: If your regional settings aren't like UK/US, you could run into a couple of problems, such as the spreadsheet program changing the DataPeriods line from 1/1, 12/31 to 01-Jan -- you'd need to hand edit that before step 7

Note 2: Be aware that specific year data is not usually deemed appropriate for Energy Analysis. See this document for more information on selecting weather data:

Drury B. Crawley. 1998. "Which Weather Data Should You Use for Energy Simulations of Commercial Buildings?" in ASHRAE Transactions, pp. 498-515, Vol. 104, Pt. 2. Atlanta: ASHRAE. (PDF 197 KB) PDF: http://energyplus.gov/pdfs/bibliography/whichweatherdatashouldyouuseforenergysimulations.pdf