UWG, CreateEPW, Relative Humidity

Kristi · August 30, 2023, 8:19pm

Dear Ladybug Community,
I am trying to run the UWG engine and I am interested in obtaining Dry Bulb temperature and relative humidity as an output of the urban area that I have as a case study.
I wanted to create a new EPW file, in which I have inserted dry bulb, wind speed, wind direction, dew point (all from the airport which I am using as the rural site) of the year I am interested. I want to use as an input also the relative humidity since I am interested to obtain the urban output of relative humidity too, but I cannot find any way, how to insert and connect it, as I have done with the other inputs. The “CreateEPW” tool does not have it as an option (as can be seen in the image). I know the EPW base provides this info (considering many years), but I want to be accurate with the year I am studying.
I would really appreciate if someone could guide me and help me.

(P.S. solver is locked)

Best,
Kristiana

chris · August 30, 2023, 10:01pm

Hi @Kristi ,

I feel like there might be a few questions here but I can answer this one

… where I’m assuming “it” refers to relative humidity.

The component automatically computes the relative humidity from the dry bulb and dew point as you can see in the component code here:

github.com

ladybug-tools/dragonfly-grasshopper/blob/master/dragonfly_grasshopper/src/DF Create EPW.py#L152-L157


      
          # calculate properties that are derived from other inputs
          if _dry_bulb_temp_ and _dew_point_temp_:
              rel_humid = HourlyContinuousCollection.compute_function_aligned(
                  rel_humid_from_db_dpt, [_dry_bulb_temp_, _dew_point_temp_],
                  RelativeHumidity(), '%')
              epw_obj.relative_humidity.values = rel_humid.values

So there’s no need to plug in a separate relative humidity since this would be redundant.
Hope that helps.

Kristi · August 31, 2023, 7:52am

Thank you very much for your fast and very helpful reply!
Best,
Kristi