Creating a new EPW weather file from weather station data - issues with radiations and wet bulb temperature

grasshopper honeybee
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#1

Hi all,

I have the weather data from one of the weather stations in New Delhi, operated by the Central Pollution Control Board in India. I would like to create an EPW weather file from the given data. But here is the problem.

  1. I believe these are the parameters one needs to create an EPW file: Dry bulb temperature, Wet bulb temperature, Atmospheric pressure, Relative Humidity, Dew Point Temperature, Global Solar radiations, Normal solar radiations, Diffuse solar radiations and wind speed. Please correct me if I am wrong (Image attached:
    EPW weather file as seen in elements
    EPW weather file as seen in elements1523×833 203 KB

But the weather data I have does not contain Wet bulb temperature, Dew point temperature, Normal and Direct solar radiations. Is there any component in ladybug/honeybee that can be used to calculate (Image attached:

2- weather data from weather station
2- weather data from weather station1563×543 23 KB

a) Wet bulb and dew point point temperatures from Dry bulb temperature and Relative humidity

b) Direct and diffuse radiations from global radiations (assuming the ‘solar radiation’ data mean global radiations)

  1. is the wind speed in the EPW file directional (it seems so)?. But when I look at the data using the Elements software, it shows no direction, and only a single column for speed. Weather data that I have has wind speed, wind direction and vertical wind speed. How can I convert this data to one number (given this is the right approach)

Thank you

/ Anurag

#2

There is a component under Analyze Weather Data tab for Wet bulb temperature calculation.

There are established formulas to calculate these. I don’t think we have a component for that. @chris knows more about this than I do.

There are two separate columns for wind speed and wind direction in the epw file. See the import epw component.

1 Like
#3

Take a look at the post here on the historical weather data API that I’m currently beta-testing. The API provides all the parameters needed to create EPW file, including diffuse and direction radiation. I don’t think wetbulb temperature is needed for EPW but it’s also available if you need it. In the post, there is a script that @chris wrote that creates EPW file using this API and ladybug components.

#4

Using @josephyang 's workflow is a good option if you’re ok using the re-analysis data of the API that Joseph’s working on (there’s a good description of this data in the post he linked to).

If you are somehow wedded to your current data set (I don’t know if you measured it yourself or if you need to use it as is), there are some Grasshopper components to help you out. In particular, this sample file shows you the Grasshopper components you can use to create your own EPW from streams of data with some metadata (aka. Data Collections). Note that you need to have the latest Honeybee[+] installed from Food4Rhino in order to be able to run that sample file. The latest Ladybug[+] has some components to help you build DataCollections from lists of numbers that you can feed into the EPW component. You’ll also see that the “Zhang-Huang” Wea component in that sample file can estimate solar radiation using some of the other variables you typically get with climate data sets. There’s also a luminous efficacy component that can estimate illuminance from solar radiation.

I’ll say, though, that the most flexible option is just avoid Grasshopper and write your own Python script using the ladybug-core Python library. You can see the SDK documentation for the library here. I realize you need to know some Python for this last one, though, so it may not be feasible for everyone. But the ladybug-core Python library is effectively what is being used in the workflow Joseph linked to.