blockSkyClearness

Sky clearness
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Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Information

This component computes the sky clearness.

Implementation

In the Buildings library, HDirNor is always larger than 1E-4, minus some small undershoot due to regularization. Hence, the implementation is not simplified for HDirNor < Modelica.Constants.small.

The function call Buildings.Utilities.Math.Functions.smoothMax is such that the regularization is usually not triggered.

Connectors

TypeNameDefaultDescription
Modelica.Blocks.Interfaces.RealInputzenZenith angle of the sun beam
Modelica.Blocks.Interfaces.RealInputHDifHorHorizontal diffuse solar radiation
Modelica.Blocks.Interfaces.RealInputHDirNorHorizontal global solar radiation
Modelica.Blocks.Interfaces.RealOutputskyCleSky clearness. skyCle=1: overast sky; skyCle=8: clear sky

Revisions

  • March 4, 2024, by Michael Wetter:
    Corrected displayUnit.
    This is for IBPSA, #1848.
  • September 6, 2021, by Ettore Zanetti:
    Changed lat from being a parameter to an input from weather bus.
    Changed input connector HGloHor to HDirNor.
    This is for IBPSA, #1477.
  • May 2, 2021, by Ettore Zanetti:
    Corrected expression for sky clearness.
    This is for issue 1477.
  • September 23, 2016, by Michael Wetter:
    Changed deltaX from 0.1 to 0.01, and also optimized the code.
    This is for issue 521.
  • May 5, 2015, by Michael Wetter:
    Introduced constant k to reduce number of operations.
  • May 5, 2015, by Filip Jorissen:
    Converted algorithm section into equation section for easier differentiability.
  • July 07, 2010, by Wangda Zuo:
    First implementation.