modelSkymodel_HDKR
Extends from SkymodelBase (Base model for modeling the influence of orientation of a surface for calculation of irradiance).
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
Hay and Davies (1980) estimate the fraction of the diffuse that is circumsolar and consider it to be all from the same direction as the beam radiation; they do not treat horizon brightening. Reindl et al. (1990b) add a horizon-brightening term to the Hay and Davies model, as proposed by Klucher (1979), giving a model to be
referred to as the HDKR model (see Duffie & Beckman, 2006).
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
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
Model modified by Oliver Schülting (oliver.schuelting@tuhh.de), Jun 2018: no anisotropy if irradiance_extraterrestrial<=25 since this lead to unrealistic high irradiation peaks at morning and/or evening
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | offset (from SolarTime) | {0, 0, 0, 0} | |
| SI.Angle | longitude_local (from SolarTime) | Modelica.Units.Conversions.from_deg(10) | East positive, west negative, 10 for Hamburg |
| SI.Angle | longitude_standard (from SolarTime) | Modelica.Units.Conversions.from_deg(15) | 15 needed for offset calculation of central european time, 30 for central european summer time |
| Real | utc (from SolarTime) | longitude_standard*12/Const.pi | Difference between UTC and zone time; i.e. +1 in Amsterdam/Berlin/Bern/Rome; default works for standard time, beware of summer time ! |
| SI.Irradiance | solarConstant (from ExtraTerrestrialIrradiance) | 1367 | |
| SI.Angle | latitude (from ExtraTerrestrialIrradiance) | Modelica.Units.Conversions.from_deg(53.55) | latitude of the position, north posiive, 53,55 N for Hamburg |
| SI.Angle | slope (from ExtraTerrestrialIrradiance) | Modelica.Units.Conversions.from_deg(30) | slope of the tilted surface, Assumption |
| SI.Angle | surfaceAzimuthAngle (from ExtraTerrestrialIrradiance) | 0 | Angle between the local meridian and the projection of the normal of the surface on a horizontal surface, west positive |
| Boolean | fixedMounting (from ExtraTerrestrialIrradiance) | true | choose if surface is fix mounted - if 'true' the sun position is ideally tracked |
| Real | reflectance_ground (from SkymodelBase) | 0.2 | Reflection coefficient of the ground |
| Boolean | direct_normal (from SkymodelBase) | true | =true, if the direct irradiance measured on a surface is normal to irradiance |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.NonSI.Time_day | dayoftheyear (from SolarTime) | Day as floating point number. 0.0 at 1.1. 00:00:00, 1.0 at 2.1. 00:00:00 a.s.o. | |
| Modelica.Units.NonSI.Time_day | totaldays (from SolarTime) | 365 | total days of the year, standard=365, leap year=366 |
| SI.Time | solarTime (from SolarTime) | Local solar time in seconds | |
| SI.Time | offset_sec (from SolarTime) | ||
| SI.Angle | angle_horizontal (from ExtraTerrestrialIrradiance) | ||
| SI.Angle | angle_tilted (from ExtraTerrestrialIrradiance) | ||
| SI.Irradiance | irradiance_extraterrestrial (from ExtraTerrestrialIrradiance) | ||
| SI.Angle | declination (from ExtraTerrestrialIrradiance) | ||
| SI.Angle | hourAngle (from ExtraTerrestrialIrradiance) | ||
| SI.Irradiance | irradiance_direct_measured (from SkymodelBase) | Measured direct irradiance | |
| SI.Irradiance | irradiance_diffuse_horizontal (from SkymodelBase) | Measured diffuse irradiance | |
| SI.Irradiance | irradiance_direct_horizontal (from SkymodelBase) | Direct horizontal irradiance | |
| SI.Irradiance | irradiance_direct_tilted (from SkymodelBase) | ||
| SI.Irradiance | irradiance_diffuse_tilted (from SkymodelBase) | ||
| SI.Irradiance | irradiance_ground_tilted (from SkymodelBase) | ||
| Real | ratio_beam (from SkymodelBase) | Ratio between direct irradiance on a tilted surface and irradiance on a horizontal surface |