Why doesn't the EnergyPlus Environment:Site Wind Speed correspond to the wind speed in the epw weather file?

asked 2020-01-25 13:57:57 -0600

TPilet gravatar image

updated 2020-01-25 14:19:25 -0600


A similar question was asked here, but the answers don't really solve my problem. I believe their issue was usage of sub-hourly calculations, which is not applicable to me.

In my case, I am creating my own inverse facade heat transfer model. My current goal is to compute the wind speeds felt by facade surfaces, and know that the computed wind speeds and DOE-2 convection coefficients line up with those output by EnergyPlus. I have simulated a building on EnergyPlus using the Atlanta TMY3 EPW file, and the wind speeds output by "Site Wind Speed" do not line up with those from the EPW file. Because these speeds are not the same, my calculation of the wind speeds on my roof surface are off and my convection coefficients are off from the EP model.

When I take the EnergyPlus Output: Site Wind Speed and run it through my calculation, the calculated surface wind speeds exactly match those output by EnergyPlus. This indicates to me that there is something happening within EnergyPlus that converts the EPW wind speeds to Site Wind Speeds. I haven't found anything related to this in the EP Engineering Reference, so does anyone have an idea what's happening here?

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Add Site Wind Speed as a Output:Variable and check if that lines up with EPW. It should be just fine. This variable is registered here, and it's read directly from EPW in WeatherManager::InterpretWeatherDataLine. In the absence of EMS code overriding that, they should line up. Let us know.

Julien Marrec gravatar image Julien Marrec  ( 2020-01-25 16:02:43 -0600 )edit