Zonnestraling in Nederland - Knmi

to various time scales. Successively the following categories are presented:
- the direct irradiance model for an hour or less;
- direct irradiance models for a day or longer, according to the algorithms developed by
Revfeim and Page;
- diffuse irradiance models for an hour or less, with the isotropic model and the algorithms
according to Hay, Gueymard and Perez as examples;
- sky diffuse irradiance algorithms applicable to time integrals of a day or longer.
According to the results of the IEA study and a separate test by Van den Brink (1987), the
algorithm according to Perez is recommended to be used in the Netherlands to calculate
diffuse radiation on inclined surfaces.
Section 5.3 gives the results of two years measurements of global radiation for 11 differently
inclined surfaces at Cabauw. The data are given in Table 5.2 for 24 days distributed
across the year, and are displayed in Figure 5.5 for every month.
Since no measurements of the spectral distribution of global radiation have been made in
the Netherlands, an algorithm developed by Slob (1985) has been used to adapt spectral data
collected in Ukkel (Belgium) to Netherlands' circumstances. The results are given in Table
5.5 for eight spectral bands bet ween 300 and 1000 nm.
Chapter 5 concludes with section 5.5 on photometry, the luminous efficiency of the human
eye and the conversion of radiation quantities in photometric quantities.
Various appendices have been combined in chapter 6. The first appendix, section 6.1, treats
the different coordinate systems for the position of the Sun in the sky, and gives conversion
formulas as well as equations for the calculation of the Sun's declination, elevation and
azimuth.
Local mean, national and Standard times are introduced in appendix 6.2, with an emphasis
on the history in the Netherlands. Also expressions for the equation of time and the length of
the day are given.
The third appendix, section 6.3, is devoted to radiometric and photometric units and their
definitions, and to the various radiometric scales that are or have been in use.
With a list of symbols as the fourth appendix (section 6.4) chapter 6 is completed.
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