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solpos00.h
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solpos00.h
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/*============================================================================
*
* NAME: solpos00.h
*
* Contains:
* S_solpos (computes the solar position and intensity
* from time and place)
* INPUTS: (from posdata)
* year, month, day, hour, minute, second,
* latitude, longitude, timezone, interval
* OPTIONAL: (from posdata; defaults from S_init function)
* press DEFAULT 1013.0 (standard pressure)
* temp DEFAULT 10.0 (standard temperature)
* tilt DEFAULT 0.0 (horizontal panel)
* aspect DEFAULT 180.0 (South-facing panel)
* sbwid DEFAULT 7.6 (shadowband width)
* sbrad DEFAULT 31.7 (shadowband radius)
* sbsky DEFAULT 0.04 (shadowband sky factor)
*
* OUTPUTS: (posdata) daynum, amass, ampress, azim, cosinc,
* elevref, etr, etrn, etrtilt, prime,
* sbcf, sretr, ssetr, unprime, zenref
*
* RETURNS: Long int status code (defined in solpos.h)
*
* Usage:
* In calling program, along with other 'includes', insert:
*
* #include "solpos.h"
*
* Martin Rymes
* National Renewable Energy Laboratory
* 25 March 1998
*----------------------------------------------------------------------------*/
/*============================================================================
*
* Define the function codes
*
*----------------------------------------------------------------------------*/
#define L_DOY 0x0001
#define L_GEOM 0x0002
#define L_ZENETR 0x0004
#define L_SSHA 0x0008
#define L_SBCF 0x0010
#define L_TST 0x0020
#define L_SRSS 0x0040
#define L_SOLAZM 0x0080
#define L_REFRAC 0x0100
#define L_AMASS 0x0200
#define L_PRIME 0x0400
#define L_TILT 0x0800
#define L_ETR 0x1000
#define L_ALL 0xFFFF
/*============================================================================
*
* Define the bit-wise masks for each function
*
*----------------------------------------------------------------------------*/
#define S_DOY ( L_DOY )
#define S_GEOM ( L_GEOM | S_DOY )
#define S_ZENETR ( L_ZENETR | S_GEOM )
#define S_SSHA ( L_SSHA | S_GEOM )
#define S_SBCF ( L_SBCF | S_SSHA )
#define S_TST ( L_TST | S_GEOM )
#define S_SRSS ( L_SRSS | S_SSHA | S_TST )
#define S_SOLAZM ( L_SOLAZM | S_ZENETR )
#define S_REFRAC ( L_REFRAC | S_ZENETR )
#define S_AMASS ( L_AMASS | S_REFRAC )
#define S_PRIME ( L_PRIME | S_AMASS )
#define S_TILT ( L_TILT | S_SOLAZM | S_REFRAC )
#define S_ETR ( L_ETR | S_REFRAC )
#define S_ALL ( L_ALL )
/*============================================================================
*
* Enumerate the error codes
* (Bit positions are from least significant to most significant)
*
*----------------------------------------------------------------------------*/
/* Code Bit Parameter Range
=============== === =================== ============= */
enum {S_YEAR_ERROR, /* 0 year 1950 - 2050 */
S_MONTH_ERROR, /* 1 month 1 - 12 */
S_DAY_ERROR, /* 2 day-of-month 1 - 31 */
S_DOY_ERROR, /* 3 day-of-year 1 - 366 */
S_HOUR_ERROR, /* 4 hour 0 - 24 */
S_MINUTE_ERROR, /* 5 minute 0 - 59 */
S_SECOND_ERROR, /* 6 second 0 - 59 */
S_TZONE_ERROR, /* 7 time zone -12 - 12 */
S_INTRVL_ERROR, /* 8 interval (seconds) 0 - 28800 */
S_LAT_ERROR, /* 9 latitude -90 - 90 */
S_LON_ERROR, /* 10 longitude -180 - 180 */
S_TEMP_ERROR, /* 11 temperature (deg. C) -100 - 100 */
S_PRESS_ERROR, /* 12 pressure (millibars) 0 - 2000 */
S_TILT_ERROR, /* 13 tilt -180 - 180 */
S_ASPECT_ERROR, /* 14 aspect -360 - 360 */
S_SBWID_ERROR, /* 15 shadow band width (cm) 1 - 100 */
S_SBRAD_ERROR, /* 16 shadow band radius (cm) 1 - 100 */
S_SBSKY_ERROR}; /* 17 shadow band sky factor -1 - 1 */
struct posdata
{
/***** ALPHABETICAL LIST OF COMMON VARIABLES *****/
/* Each comment begins with a 1-column letter code:
I: INPUT variable
O: OUTPUT variable
T: TRANSITIONAL variable used in the algorithm,
of interest only to the solar radiation
modelers, and available to you because you
may be one of them.
The FUNCTION column indicates which sub-function
within solpos must be switched on using the
"function" parameter to calculate the desired
output variable. All function codes are
defined in the solpos.h file. The default
S_ALL switch calculates all output variables.
Multiple functions may be or'd to create a
composite function switch. For example,
(S_TST | S_SBCF). Specifying only the functions
for required output variables may allow solpos
to execute more quickly.
The S_DOY mask works as a toggle between the
input date represented as a day number (daynum)
or as month and day. To set the switch (to
use daynum input), the function is or'd; to
clear the switch (to use month and day input),
the function is inverted and and'd.
For example:
pdat->function |= S_DOY (sets daynum input)
pdat->function &= ~S_DOY (sets month and day input)
Whichever date form is used, S_solpos will
calculate and return the variables(s) of the
other form. See the soltest.c program for
other examples. */
/* VARIABLE I/O Function Description */
/* ------------- ---- ---------- ---------------------------------------*/
int day; /* I/O: S_DOY Day of month (May 27 = 27, etc.)
solpos will CALCULATE this by default,
or will optionally require it as input
depending on the setting of the S_DOY
function switch. */
int daynum; /* I/O: S_DOY Day number (day of year; Feb 1 = 32 )
solpos REQUIRES this by default, but
will optionally calculate it from
month and day depending on the setting
of the S_DOY function switch. */
int function; /* I: Switch to choose functions for desired
output. */
int hour; /* I: Hour of day, 0 - 23, DEFAULT = 12 */
int interval; /* I: Interval of a measurement period in
seconds. Forces solpos to use the
time and date from the interval
midpoint. The INPUT time (hour,
minute, and second) is assumed to
be the END of the measurement
interval. */
int minute; /* I: Minute of hour, 0 - 59, DEFAULT = 0 */
int month; /* I/O: S_DOY Month number (Jan = 1, Feb = 2, etc.)
solpos will CALCULATE this by default,
or will optionally require it as input
depending on the setting of the S_DOY
function switch. */
int second; /* I: Second of minute, 0 - 59, DEFAULT = 0 */
int year; /* I: 4-digit year (2-digit year is NOT
allowed */
/***** FLOATS *****/
float amass; /* O: S_AMASS Relative optical airmass */
float ampress; /* O: S_AMASS Pressure-corrected airmass */
float aspect; /* I: Azimuth of panel surface (direction it
faces) N=0, E=90, S=180, W=270,
DEFAULT = 180 */
float azim; /* O: S_SOLAZM Solar azimuth angle: N=0, E=90, S=180,
W=270 */
float cosinc; /* O: S_TILT Cosine of solar incidence angle on
panel */
float coszen; /* O: S_REFRAC Cosine of refraction corrected solar
zenith angle */
float dayang; /* T: S_GEOM Day angle (daynum*360/year-length)
degrees */
float declin; /* T: S_GEOM Declination--zenith angle of solar noon
at equator, degrees NORTH */
float eclong; /* T: S_GEOM Ecliptic longitude, degrees */
float ecobli; /* T: S_GEOM Obliquity of ecliptic */
float ectime; /* T: S_GEOM Time of ecliptic calculations */
float elevetr; /* O: S_ZENETR Solar elevation, no atmospheric
correction (= ETR) */
float elevref; /* O: S_REFRAC Solar elevation angle,
deg. from horizon, refracted */
float eqntim; /* T: S_TST Equation of time (TST - LMT), minutes */
float erv; /* T: S_GEOM Earth radius vector
(multiplied to solar constant) */
float etr; /* O: S_ETR Extraterrestrial (top-of-atmosphere)
W/sq m global horizontal solar
irradiance */
float etrn; /* O: S_ETR Extraterrestrial (top-of-atmosphere)
W/sq m direct normal solar
irradiance */
float etrtilt; /* O: S_TILT Extraterrestrial (top-of-atmosphere)
W/sq m global irradiance on a tilted
surface */
float gmst; /* T: S_GEOM Greenwich mean sidereal time, hours */
float hrang; /* T: S_GEOM Hour angle--hour of sun from solar noon,
degrees WEST */
float julday; /* T: S_GEOM Julian Day of 1 JAN 2000 minus
2,400,000 days (in order to regain
single precision) */
float latitude; /* I: Latitude, degrees north (south negative) */
float longitude; /* I: Longitude, degrees east (west negative) */
float lmst; /* T: S_GEOM Local mean sidereal time, degrees */
float mnanom; /* T: S_GEOM Mean anomaly, degrees */
float mnlong; /* T: S_GEOM Mean longitude, degrees */
float rascen; /* T: S_GEOM Right ascension, degrees */
float press; /* I: Surface pressure, millibars, used for
refraction correction and ampress */
float prime; /* O: S_PRIME Factor that normalizes Kt, Kn, etc. */
float sbcf; /* O: S_SBCF Shadow-band correction factor */
float sbwid; /* I: Shadow-band width (cm) */
float sbrad; /* I: Shadow-band radius (cm) */
float sbsky; /* I: Shadow-band sky factor */
float solcon; /* I: Solar constant (NREL uses 1367 W/sq m) */
float ssha; /* T: S_SRHA Sunset(/rise) hour angle, degrees */
float sretr; /* O: S_SRSS Sunrise time, minutes from midnight,
local, WITHOUT refraction */
float ssetr; /* O: S_SRSS Sunset time, minutes from midnight,
local, WITHOUT refraction */
float temp; /* I: Ambient dry-bulb temperature, degrees C,
used for refraction correction */
float tilt; /* I: Degrees tilt from horizontal of panel */
float timezone; /* I: Time zone, east (west negative).
USA: Mountain = -7, Central = -6, etc. */
float tst; /* T: S_TST True solar time, minutes from midnight */
float tstfix; /* T: S_TST True solar time - local standard time */
float unprime; /* O: S_PRIME Factor that denormalizes Kt', Kn', etc. */
float utime; /* T: S_GEOM Universal (Greenwich) standard time */
float zenetr; /* T: S_ZENETR Solar zenith angle, no atmospheric
correction (= ETR) */
float zenref; /* O: S_REFRAC Solar zenith angle, deg. from zenith,
refracted */
};
/* For users that wish to access individual functions, the following table
lists all output and transition variables, the L_ mask for the function
that calculates them, and all the input variables required by that function.
The function variable is set to the L_ mask, which will force S_solpos to
only call the required function. L_ masks may be ORed as desired.
VARIABLE Mask Required Variables
--------- ---------- ---------------------------------------
amass L_AMASS zenref, press
ampress L_AMASS zenref, press
azim L_SOLAZM elevetr, declin, latitude, hrang
cosinc L_TILT azim, aspect, tilt, zenref, coszen,etrn
coszen L_REFRAC elevetr, press, temp
dayang L_GEOM All date, time, and location inputs
declin L_GEOM All date, time, and location inputs
eclong L_GEOM All date, time, and location inputs
ecobli L_GEOM All date, time, and location inputs
ectime L_GEOM All date, time, and location inputs
elevetr L_ZENETR declin, latitude, hrang
elevref L_REFRAC elevetr, press, temp
eqntim L_TST hrang, hour, minute, second, interval
erv L_GEOM All date, time, and location inputs
etr L_ETR coszen, solcon, erv
etrn L_ETR coszen, solcon, erv
etrtilt L_TILT azim, aspect, tilt, zenref, coszen, etrn
gmst L_GEOM All date, time, and location inputs
hrang L_GEOM All date, time, and location inputs
julday L_GEOM All date, time, and location inputs
lmst L_GEOM All date, time, and location inputs
mnanom L_GEOM All date, time, and location inputs
mnlong L_GEOM All date, time, and location inputs
rascen L_GEOM All date, time, and location inputs
prime L_PRIME amass
sbcf L_SBCF latitude, declin, ssha, sbwid, sbrad, sbsky
ssha L_SRHA latitude, declin
sretr L_SRSS ssha, tstfix
ssetr L_SRSS ssha, tstfix
tst L_TST hrang, hour, minute, second, interval
tstfix L_TST hrang, hour, minute, second, interval
unprime L_PRIME amass
utime L_GEOM All date, time, and location inputs
zenetr L_ZENETR declination, latitude, hrang
zenref L_REFRAC elevetr, press, temp
*/
/*============================================================================
* Long int function S_solpos, adapted from the NREL VAX solar libraries
*
* This function calculates the apparent solar position and intensity
* (theoretical maximum solar energy) based on the date, time, and
* location on Earth. (DEFAULT values are from the optional S_posinit
* function.)
*
* Requires:
* Date and time:
* year
* month (optional without daynum)
* day (optional without daynum)
* daynum
* hour
* minute
* second
* Location:
* latitude
* longitude
* Location/time adjuster:
* timezone
* Atmospheric pressure and temperature:
* press DEFAULT 1013.0 mb
* temp DEFAULT 10.0 degrees C
* Tilt of flat surface that receives solar energy:
* aspect DEFAULT 180 (South)
* tilt DEFAULT 0 (Horizontal)
* Shadow band parameters:
* sbwid DEFAULT 7.6 cm
* sbrad DEFAULT 31.7 cm
* sbsky DEFAULT 0.04
* Functionality
* function DEFAULT S_ALL (all output parameters computed)
*
* Returns:
* everything defined at the top of this listing.
*----------------------------------------------------------------------------*/
long S_solpos (struct posdata *pdat);
/*============================================================================
* Void function S_init
*
* This function initiates all of the input functions to S_Solpos().
* NOTE: This function is optional if you initialize all input parameters
* in your calling code.
*
* Requires: Pointer to a posdata structure, members of which are
* initialized.
*
* Returns: Void
*
*----------------------------------------------------------------------------*/
void S_init(struct posdata *pdat);
/*============================================================================
* Void function S_decode
*
* This function decodes the error codes from S_solpos return value
*
* INPUTS: Long integer S_solpos return value, struct posdata*
*
* OUTPUTS: Descriptive text of errors to stderr
*----------------------------------------------------------------------------*/
void S_decode(long code, struct posdata *pdat);