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cal_sun.py
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cal_sun.py
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import numpy as N
class SunPosition:
def __init__(self):
pass
def days(self, dd, mm):
'''
Arguement:
dd - int, the day in the month
mm - str, the month
reference: J Duffie pp14, Table 1.6.1
'''
if mm=='Jan':
days=dd
elif mm=='Feb':
days=31+dd
elif mm=='Mar':
days=59+dd
if mm=='Apr':
days=90+dd
elif mm=='May':
days=120+dd
elif mm=='Jun':
days=151+dd
if mm=='Jul':
days=181+dd
elif mm=='Aug':
days=212+dd
elif mm=='Sep':
days=243+dd
if mm=='Oct':
days=273+dd
elif mm=='Nov':
days=304+dd
elif mm=='Dec':
days=334+dd
return days
def declination(self, days, form='detail'):
'''
Reference: Solar Engineering of Thermal Processes, 4th edition, John A. Duffie and William A. Beckman, page 13
declination angle: delta=23.45*sin(360*(284+day)/365)
Arguement:
day - int, day of the year (1-365)
form - str, 'detail' or simple' model
Return:
delta - declination angle (deg)
'''
if form=='detail':
B=float(days-1)*360./365.*N.pi/180.
delta=(180./N.pi)*(0.006918 - 0.399912*N.cos(B) +0.070257*N.sin(B)- 0.006758*N.cos(2.*B) + 0.000907*N.sin(2.*B)- 0.002697*N.cos(3.*B) + 0.00148*N.sin(3.*B))
else:
delta=23.45*N.sin(360.*float(284+days)/365.*N.pi/180.) # deg
return delta
def solarhour(self, delta, latitude):
'''
Reference: Solar Engineering of Thermal Processes, 4th edition, John A. Duffie and William A. Beckman, page 17
Arguement:
delta: declination angle- float, deg
latitude: latitude angle: float, deg
return:
hour: length of the daylight hour
sunrise: the solar hour angle of the sunrise, deg
'''
sunset=N.arccos(-N.tan(latitude*N.pi/180.)*N.tan(delta*N.pi/180.))*180./N.pi # deg
sunrise=-sunset
hour=(sunset-sunrise)/15.
return hour, sunrise
def zenith(self, latitude, delta, omega):
'''
ref. eq.1.6.5
Arguement:
latitude: latitude angle, float, deg
delta: declination angle, float, deg
omega: solar hour angle, float, deg
return:
theta: the zenith angle, float, deg
'''
latitude*=N.pi/180.
delta*=N.pi/180.
omega*=N.pi/180.
theta=N.arccos(N.cos(latitude)*N.cos(delta)*N.cos(omega)+N.sin(latitude)*N.sin(delta))*180./N.pi
return theta
def azimuth(self, latitude, theta, delta, omega):
'''
ref: eq. 1.6.6
from South to West
Arguement:
latitude: latitude angle, deg
delta: declination angle ,deg
theta: zenith angle, deg
omega: solar hour angle, deg
return:
phi: azimuth angle, deg, from South to west
'''
latitude*=N.pi/180.
delta*=N.pi/180.
theta*=N.pi/180.
a1=N.cos(theta)*N.sin(latitude)-N.sin(delta)
a2=N.sin(theta)*N.cos(latitude)
b=a1/a2
if abs(b+1.)<1e-10:
phi=N.pi
elif abs(b-1.)<1e-10:
phi=0.
else:
phi=abs(N.arccos((N.cos(theta)*N.sin(latitude)-N.sin(delta))/(N.sin(theta)*N.cos(latitude)))) # unit radian
if omega<0:
phi=-phi
phi*=180./N.pi
return phi
def convert_AZEL_to_declination_hour(self, theta, phi, latitude):
'''
Arguement:
theta: zenith angle, deg
phi: azimuth angle deg
latitude: latitude latitude , deg
return:
delta: declination angle, deg
omega: solar hour angle, deg
'''
phi*=N.pi/180.
theta*=N.pi/180.
latitude*=N.pi/180.
delta=N.arcsin(N.cos(theta)*N.sin(latitude)-N.cos(abs(phi))*N.sin(theta)*N.cos(latitude))
omega=N.arccos((N.cos(theta)-N.sin(latitude)*N.sin(delta))/(N.cos(latitude)*N.cos(delta)))
if phi<0:
omega=-omega
delta*=180./N.pi
omega*=180./N.pi
return delta, omega
if __name__=='__main__':
# example: PS10, summer solstice, solar noon
latitude=34.96
sun=SunPosition()
dd=sun.days(22, 'Jun')
delta=sun.declination(dd)
print 'Declination angle', delta
daytime,sunrise=sun.solarhour(delta, latitude)
print 'Day timeS', daytime
print 'sun rise', sunrise
print ''
omega=3.*15 # solar noon
theta=sun.zenith(latitude, delta, omega)
phi=sun.azimuth(latitude, theta, delta, omega)
print 'elevation', 90.-theta
print 'azimuth', phi