This program computes the solar azimuth angle, solar altitude angle, and the intensity of the direct solar beam for any hour of a typical 365-day year. It also calculates the time of sunrise and sunset for that particular day. The program is based on the format recommended by the American Society of Heating, Refrigeration and Air Conditioning Engineers.

Program Notes:
This program does not take into account the one hour adjustment for daylight-saving time.

WARNING! The program was incomplete in the book:  The following line was published as shown and then modified by best guess to provide the answer in the provided test case:

F3 = .17167 -.03475 * COS (as published)

F3 = .17167 -.03475 * COS(F1 -.12534) (my modification)

If you have any insight into this program, please share it!

Downloads:

basic program (liberty basic) lbsi.bas

Test Case:

Find the solar position and intensity for July 21 at 2:00 PM (14 hours past midnight) for an observer in
time zone 8 at latitude 240 north and longitude 1200 west.

SOLAR INTENSITY

INPUT MONTH (1-12)=  7
INPUT DAY (1-31) =  21
INPUT HOUR (0-23) =  14

EASTERN STANDARD = 5
CENTRAL STANDARD = 6
MOUNTAIN STANDARD = 7
PACIFIC STANDARD = 8

INPUT TIME ZONE NUMBER = 8

INPUT LATITUDE (DEGREES) =   24
INPUT LONGITUDE (DEGREES) =  120

DAY NUMBER (1-365)       = 202.583333
TIME OF SUNRISE (HOURS)  =5.46942551
TIME OF SUNSET (HOURS)   = 18.5305745
DECLINATION ANGLE (DEG)  =20.4260354
EQUATION OF TIME(MIN)    =-6.34256236
SOLAR ALTITUDE (DEGREES) =63.4981071
SOLAR AZIMUTH (DEGREES)  =267.891428
SOLAR INTENSITY (BTU/FT^2)= 274.285491

RERUN PROGRAM WITH NEW DATA (Y/N)?   n