.TransiEnt.Producer.Heat.SolarThermal.Base.Skymodel_Klucher

Information

1. Purpose of model

Anisotropic approach to calculate solar radiation on a tilted surface.

2. Level of detail, physical effects considered, and physical insight

Theoretical model based on the assumption that the diffuse irradiance has a peak next to the angle of the sun so that this circumsolar irradiance can be added to direct irradiance.

3. Limits of validity

Usage for small values of angleOfSunIncidence.horizontal is not recommended because of refraction by atmosphere.

4. Interfaces

(no remarks)

5. Nomenclature

direct_tilted, diffuse_tilted and ground_tilted are the calculated irradiances of tilted surface.

6. Governing Equations

eff= 1-(diffuse_horizontal / max(1,(direct_horizontal + diffuse_horizontal)))^2

direct_tilted= (direct_horizontal+diffuse_horizontal*anisotropy_index)*ratio_beam

diffuse_tilted= diffuse_horizontal*(1-anisotropy_index)*((1+cos(slope))/2)*(1+eff*(sin(slope/2))^3)

ground_tilted= (direct_horizontal+diffuse_horizontal)*reflectance_ground*(1-cos(slope))/2

7. Remarks for Usage

None.

8. Validation

Purely theoretical model

9. References

Duffie & Beckman (2006): Solar Engineering of Thermal Processes, p. 91 f.

10. Version History

Model created by Tobias Toerber (tobias.toerber@tuhh.de), Jul 2015

Edited by Sascha Guddusch (sascha.guddusch@tuhh.de), May 2016

Modified by Anne Senkel (anne.senkel@tuhh.de), Mar 2017

Modified by Lisa Andresen (andresen@tuhh.de), Apr. 2017

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