| 1 |
|
.\" RCSid "$Id$" |
| 2 |
|
.TH GENDAYLIT 1 4/12/94 "RADIANCE ISE/ADEME EXTENSIONS" |
| 3 |
|
.SH NAME |
| 4 |
< |
gendaylit - generates a RADIANCE description of the daylit sources using Perez models for diffuse and direct components |
| 4 |
> |
gendaylit - generates a RADIANCE description of the daylight sources using Perez models for direct and diffuse components |
| 5 |
|
.SH SYNOPSIS |
| 6 |
< |
.B "gendaylit month day hour [-P|-W|-L|-G] direct_value diffuse_value " |
| 6 |
> |
.B "gendaylit month day hour [-P|-W|-L|-G|-E] input_value(s) " |
| 7 |
|
[ |
| 8 |
|
.B options |
| 9 |
|
] |
| 10 |
|
.br |
| 11 |
< |
.B "gendaylit -ang altitude azimuth [-P|-W|-L|-G] direct_value diffuse_value " |
| 11 |
> |
.B "gendaylit -ang altitude azimuth [-P|-W|-L|-G|-E] input_value(s) " |
| 12 |
|
[ |
| 13 |
|
.B options |
| 14 |
|
] |
| 31 |
|
sky diffuse to the measured sky diffuse irradiances/illuminances. |
| 32 |
|
|
| 33 |
|
As described below, the radiation can be defined with the pairs direct-normal and diffuse-horizontal irradiance |
| 34 |
< |
(-W option), direct-horizontal and diffuse-horizontal irradiance (-G option) or direct-normal and diffuse-horizontal |
| 35 |
< |
illuminance (-L option). The direct-normal radiation is understood here as the radiant flux coming from the sun |
| 36 |
< |
and an area of approximately 3 degrees around the sun (World Meteorological Organisation specifications |
| 37 |
< |
for measuring the direct radiation. The aperture angle of a pyrheliometer is approximately 6 degrees). |
| 34 |
> |
(-W option), direct-horizontal and diffuse-horizontal irradiance (-G option), direct-normal and diffuse-horizontal |
| 35 |
> |
illuminance (-L option) or global-horizontal irradiation alone (-E option). The direct-normal radiation |
| 36 |
> |
is understood here as the radiant flux coming from the sun and an area of approximately 3 degrees around the sun |
| 37 |
> |
(World Meteorological Organisation specifications for measuring the direct radiation. |
| 38 |
> |
The aperture angle of a pyrheliometer is approximately 6 degrees). |
| 39 |
|
To simplify the calculations for the direct radiation, the sun is represented as a disk and no |
| 40 |
|
circumsolar radiation is modelled in the 3 degrees around the sun. This means that |
| 41 |
|
all the measured/evaluated direct radiation is added to the 0.5 degree sun source. |
| 76 |
|
to model colour (where radiance_integrated_over_visible_range == (RED + GREEN + BLUE)/3). |
| 77 |
|
|
| 78 |
|
From |
| 79 |
< |
.I gensky |
| 79 |
< |
, if the hour is preceded by a plus sign ('+'), then it is interpreted as local solar time instead of standard time. |
| 79 |
> |
.I gensky, if the hour is preceded by a plus sign ('+'), then it is interpreted as local solar time instead of standard time. |
| 80 |
|
The second form gives the solar angles explicitly. The altitude is measured in degrees above the horizon, and the |
| 81 |
|
azimuth is measured in degrees west of South. The x axis points east, the y axis points north, and the z axis |
| 82 |
|
corresponds to the zenith. The actual material and surface(s) used for the sky is left up to the user. |
| 113 |
|
(lm/m^2), |
| 114 |
|
.I diffuse-horizontal-illuminance |
| 115 |
|
(lm/m^2) |
| 116 |
+ |
.TP |
| 117 |
+ |
.BR \-E |
| 118 |
+ |
.I global-horizontal-irradiance |
| 119 |
+ |
(W/m^2) |
| 120 |
|
.PP |
| 121 |
+ |
The -E option calculates the diffuse irradiance fraction with the model of Erbs, Klein and Duffie (Solar Energy 28/4, 1982), |
| 122 |
+ |
being followed by the calculation of the -G option. Due to the high uncertainty of the model, the results have to be handled |
| 123 |
+ |
with care. A second irradiance value, if available, is definitely recommended. |
| 124 |
+ |
.PP |
| 125 |
|
The output can be set to either the radiance of the visible radiation, the solar radiance (full spectrum) or the luminance. |
| 126 |
|
.TP 10n |
| 127 |
|
.BR \-O [0|1|2] |
| 171 |
|
Be sure to give the correct longitude also! |
| 172 |
|
If solar time is given directly, then this option has no effect. |
| 173 |
|
.TP |
| 174 |
< |
.BI -l \ min_angle |
| 174 |
> |
.BI -i \ time_interval [min] |
| 175 |
|
If gendaylit is used with weather files, the specified instantaneous points of time may be incorrect. This error occurs |
| 176 |
|
due to the fact that measurement results are frequently defined for time intervals, not for specific points of time. |
| 177 |
|
Although gendaylit is working correctly, this may lead to wrong outputs especially at low sun altitudes. |
| 178 |
< |
The -l option avoids these errors by returning zero values if the sun altitude is below |
| 179 |
< |
.I min_angle |
| 172 |
< |
degrees over the horizon. The default value is zero; the recommended number for |
| 173 |
< |
.I min_angle |
| 174 |
< |
in the case of using weather files is 1 degree. |
| 178 |
> |
The -i option allows to specify the time interval of the measurements in minutes, causing the solar position to be corrected for low sun |
| 179 |
> |
altitudes. A warning message is returned if a correction has been performed. |
| 180 |
|
|
| 181 |
|
.SH EXAMPLES |
| 182 |
|
A clear non-turbid sky for a solar altitude of 60 degrees and an azimut of 0 degree might be defined by: |
