def test_earthsun_distance():
times = pd.date_range(datetime.datetime(2003, 10, 17, 13, 30, 30),
periods=1,
freq='D')
assert_almost_equals(
1,
solarposition.pyephem_earthsun_distance(times).values[0], 0)
def test_earthsun_distance():
times = pd.date_range(datetime.datetime(2003, 10, 17, 13, 30, 30),
periods=1,
freq='D')
distance = solarposition.pyephem_earthsun_distance(times).values[0]
assert_allclose(1, distance, atol=0.1)
def extraradiation(datetime_or_doy, solar_constant=1366.1, method='spencer'):
"""
Determine extraterrestrial radiation from day of year.
Parameters
----------
datetime_or_doy : int, float, array, pd.DatetimeIndex
Day of year, array of days of year e.g. pd.DatetimeIndex.dayofyear,
or pd.DatetimeIndex.
solar_constant : float
The solar constant.
method : string
The method by which the ET radiation should be calculated.
Options include ``'pyephem', 'spencer', 'asce'``.
Returns
-------
float or Series
The extraterrestrial radiation present in watts per square meter
on a surface which is normal to the sun. Ea is of the same size as the
input doy.
'pyephem' always returns a series.
Notes
-----
The Spencer method contains a minus sign discrepancy between
equation 12 of [1]. It's unclear what the correct formula is.
References
----------
[1] M. Reno, C. Hansen, and J. Stein, "Global Horizontal Irradiance Clear
Sky Models: Implementation and Analysis", Sandia National
Laboratories, SAND2012-2389, 2012.
[2] <http://solardat.uoregon.edu/SolarRadiationBasics.html>,
Eqs. SR1 and SR2
[3] Partridge, G. W. and Platt, C. M. R. 1976.
Radiative Processes in Meteorology and Climatology.
[4] Duffie, J. A. and Beckman, W. A. 1991.
Solar Engineering of Thermal Processes,
2nd edn. J. Wiley and Sons, New York.
See Also
--------
pvlib.clearsky.disc
"""
pvl_logger.debug('irradiance.extraradiation()')
method = method.lower()
if isinstance(datetime_or_doy, pd.DatetimeIndex):
doy = datetime_or_doy.dayofyear
input_to_datetimeindex = lambda x: datetime_or_doy
elif isinstance(datetime_or_doy, (int, float)):
doy = datetime_or_doy
input_to_datetimeindex = _scalar_to_datetimeindex
else: # assume that we have an array-like object of doy. danger?
doy = datetime_or_doy
input_to_datetimeindex = _array_to_datetimeindex
B = (2 * np.pi / 365) * doy
if method == 'asce':
pvl_logger.debug('Calculating ET rad using ASCE method')
RoverR0sqrd = 1 + 0.033 * np.cos(B)
elif method == 'spencer':
pvl_logger.debug('Calculating ET rad using Spencer method')
RoverR0sqrd = (1.00011 + 0.034221 * np.cos(B) + 0.00128 * np.sin(B) +
0.000719 * np.cos(2 * B) + 7.7e-05 * np.sin(2 * B))
elif method == 'pyephem':
pvl_logger.debug('Calculating ET rad using pyephem method')
times = input_to_datetimeindex(datetime_or_doy)
RoverR0sqrd = solarposition.pyephem_earthsun_distance(times) ** (-2)
Ea = solar_constant * RoverR0sqrd
return Ea
def extraradiation(datetime_or_doy, solar_constant=1366.1, method='spencer'):
"""
Determine extraterrestrial radiation from day of year.
Parameters
----------
datetime_or_doy : int, float, array, pd.DatetimeIndex
Day of year, array of days of year e.g. pd.DatetimeIndex.dayofyear,
or pd.DatetimeIndex.
solar_constant : float
The solar constant.
method : string
The method by which the ET radiation should be calculated.
Options include ``'pyephem', 'spencer', 'asce'``.
Returns
-------
float or Series
The extraterrestrial radiation present in watts per square meter
on a surface which is normal to the sun. Ea is of the same size as the
input doy.
'pyephem' always returns a series.
Notes
-----
The Spencer method contains a minus sign discrepancy between
equation 12 of [1]. It's unclear what the correct formula is.
References
----------
[1] M. Reno, C. Hansen, and J. Stein, "Global Horizontal Irradiance Clear
Sky Models: Implementation and Analysis", Sandia National
Laboratories, SAND2012-2389, 2012.
[2] <http://solardat.uoregon.edu/SolarRadiationBasics.html>,
Eqs. SR1 and SR2
[3] Partridge, G. W. and Platt, C. M. R. 1976.
Radiative Processes in Meteorology and Climatology.
[4] Duffie, J. A. and Beckman, W. A. 1991.
Solar Engineering of Thermal Processes,
2nd edn. J. Wiley and Sons, New York.
See Also
--------
pvlib.clearsky.disc
"""
pvl_logger.debug('irradiance.extraradiation()')
method = method.lower()
if isinstance(datetime_or_doy, pd.DatetimeIndex):
doy = datetime_or_doy.dayofyear
input_to_datetimeindex = lambda x: datetime_or_doy
elif isinstance(datetime_or_doy, (int, float)):
doy = datetime_or_doy
input_to_datetimeindex = _scalar_to_datetimeindex
else: # assume that we have an array-like object of doy. danger?
doy = datetime_or_doy
input_to_datetimeindex = _array_to_datetimeindex
B = (2 * np.pi / 365) * doy
if method == 'asce':
pvl_logger.debug('Calculating ET rad using ASCE method')
RoverR0sqrd = 1 + 0.033 * np.cos(B)
elif method == 'spencer':
pvl_logger.debug('Calculating ET rad using Spencer method')
RoverR0sqrd = (1.00011 + 0.034221 * np.cos(B) + 0.00128 * np.sin(B) +
0.000719 * np.cos(2 * B) + 7.7e-05 * np.sin(2 * B))
elif method == 'pyephem':
pvl_logger.debug('Calculating ET rad using pyephem method')
times = input_to_datetimeindex(datetime_or_doy)
RoverR0sqrd = solarposition.pyephem_earthsun_distance(times)**(-2)
Ea = solar_constant * RoverR0sqrd
return Ea
def test_earthsun_distance():
times = pd.date_range(datetime.datetime(2003,10,17,13,30,30), periods=1, freq='D')
assert_almost_equals(1, solarposition.pyephem_earthsun_distance(times).values[0], 0)
def test_earthsun_distance():
times = pd.date_range(datetime.datetime(2003,10,17,13,30,30),
periods=1, freq='D')
distance = solarposition.pyephem_earthsun_distance(times).values[0]
assert_allclose(1, distance, atol=0.1)
