Weather file altitude VS building altitude (EnergyPlus)

asked 2018-09-24 16:30:48 -0600

Gio
1148 ●1 ●13

updated 2018-09-25 07:39:31 -0600

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

If the weather file altitude and the building altitude (Site:Location -> Elevation) differs, does E+ automatically apply a correction?

In my case, the objects Site:WeatherStation and Site:HeightVariation are blank.

From what I can read in the documentation, the correction (if set) is applied to altitude variations within the model, for example between ground floor and the attic of a high building. Is it correct?

answered 2018-10-11 16:06:29 -0600

MJWitte

9740 ●6 ●10 http://www.gard.com/

Site:Location "Elevation" is used to establish the elevation of the ground above sea level. It is used primarily to set the standard barometric pressure at the site which is used for the standard air density to convert air volume flow rate to mass flow rate. Elevation is also used in the Sandia photovoltaic (PV) model to compute the absolute air mass.
If a weather file is present, the location data (including elevation) on the weather file will always be used in place of the Site:Location inputs. This is true for both sizing period and weather file run period simulations. Most EnergyPlus interfaces always require that a weather file be selected for the simulation. EP-Launch offers the option to run with "No Weather File" in which case the Site:Location object is used.
Height is the distance above the ground. Zero height (z=0) is at the local elevation and goes up from there. By default, wind speed and temperatures vary with height. Site:WeatherStation and Site:HeightVariation may be used to alter the shape of these profiles or disable them altogether.

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Update to this answer. In the upcoming EnergyPlus release (v24.2, planned to be released at the end of Sept 2024), there will be a new field "Keep Site Location Information" in the Site:Location object that allows you to force EnergyPlus to use the elevation you provide in the Site:Location object, rather than the elevation of the EPW weather station.