modelBuildingShade

Component for modeling shade cast by distant objects such as buildings and treelines

Extends from IDEAS.Buildings.Components.Shading.Interfaces.PartialShadingDevice.

Information

This model computes the shading cast by a building (or other object) at distance L and relative height dh on a window (or wall) with height hWin. For a window this height corresponds to the window glazing height, excluding the window frame. Diffuse sky solar radiation is reduced by computing a simplified view factor of the building, which blocks the sky view. Diffuse ground solar radiation is unaffected by this model.

illustration

Assumption and limitations

This model assumes that the obstructing object is very wide (infinite) compared to the window/wall and that it is parallel to the window. This model is inaccurate when this is not the case.

We assume that the opposite building is shaded or that its reflectivity is zero, such that it does not reflect solar irradiation towards the window. Partial shading, e.g. when modelling treelines, can be modelled by changing the value of parameter fraSha accordingly.

Parameters

TypeNameDefaultDescription
RealfraSha1Fraction of the light that is shaded, e.g. smaller than 1 for shading cast by tree lines.
RealfraSunDifSky1 - vieAngObj/(Modelica.Constants.pi/2)Fraction of window area exposed to diffuse sun light
Dimensions (see illustration in documentation)
Modelica.Units.SI.LengthLDistance to object perpendicular to window
Modelica.Units.SI.LengthdhHeight difference between top of object and top of window glazing
Modelica.Units.SI.LengthhWin1Window height: distance between top and bottom of window glazing

Components

TypeNameDefaultDescription
RealfraSunDirFraction of window area exposed to direct sun light

Revisions

  • July 18, 2022 by Filip Jorissen:
    Refactored for #1270 for including thermal effect of screens.
  • September 22, 2019 by Filip Jorissen:
    Added assert that checks validity of parameter fraSunDifSky. See #843.
  • April 10, 2019 by Filip Jorissen:
    Revised computation of fraSunDifSky to avoid negative shading fractions. See #1007.
  • February 21, 2019 by Filip Jorissen:
    Added parameter shaFra for lowering shading fraction of the model. See #912.
  • September 25, 2018 by Filip Jorissen:
    Clarified meaning of hWin and grouped parameters with reference to documentation. See #909.
  • May 26, 2017 by Filip Jorissen:
    Added computation of diffuse solar shading. See #735.
  • May 25, 2017, by Filip Jorissen:
    Fixed implementation for non-south oriented windows.
  • December 9, 2016, by Filip Jorissen:
    Fixed implementation for non-circular type building.
  • July 14, 2015, by Filip Jorissen:
    Added documentation.
  • June 12, 2015, by Filip Jorissen:
    First implementation.