def get_solarposition(self,
times,
pressure=None,
temperature=12,
**kwargs):
"""
Uses the :py:func:`solarposition.get_solarposition` function
to calculate the solar zenith, azimuth, etc. at this location.
Parameters
----------
times : DatetimeIndex
pressure : None, float, or array-like
If None, pressure will be calculated using
:py:func:`atmosphere.alt2pres` and ``self.altitude``.
temperature : None, float, or array-like
kwargs passed to :py:func:`solarposition.get_solarposition`
Returns
-------
solar_position : DataFrame
Columns depend on the ``method`` kwarg, but always include
``zenith`` and ``azimuth``.
"""
if pressure is None:
pressure = atmosphere.alt2pres(self.altitude)
return solarposition.get_solarposition(times,
latitude=self.latitude,
longitude=self.longitude,
altitude=self.altitude,
pressure=pressure,
temperature=temperature,
**kwargs)
def get_solarposition(self, times, pressure=None, temperature=12,
**kwargs):
"""
Uses the :py:func:`solarposition.get_solarposition` function
to calculate the solar zenith, azimuth, etc. at this location.
Parameters
----------
times : DatetimeIndex
pressure : None, float, or array-like, default None
If None, pressure will be calculated using
:py:func:`atmosphere.alt2pres` and ``self.altitude``.
temperature : None, float, or array-like, default 12
kwargs passed to :py:func:`solarposition.get_solarposition`
Returns
-------
solar_position : DataFrame
Columns depend on the ``method`` kwarg, but always include
``zenith`` and ``azimuth``.
"""
if pressure is None:
pressure = atmosphere.alt2pres(self.altitude)
return solarposition.get_solarposition(times, latitude=self.latitude,
longitude=self.longitude,
altitude=self.altitude,
pressure=pressure,
temperature=temperature,
**kwargs)
def get_solarposition(time,
latitude,
longitude,
altitude=None,
pressure=None,
temperature=10,
**kwargs):
#calculate the altitude and pressure based on default vales
if altitude is None and pressure is None:
altitude = 0
pressure = 101325
elif altitude is None:
altitude = atmosphere.pres2alt(pressure)
elif pressure is None:
pressure = atmosphere.alt2pres(altitude)
#converting the time into DatetimeIndex
time = pd.DatetimeIndex([
time,
])
#Normalizing the time
t = time.tz_localize(tz='UTC')
spa_python(t, latitude, longitude, altitude, pressure, temperature,
**kwargs)
def get_clearsky(self, times, model='ineichen', **kwargs):
"""
Calculate the clear sky estimates of GHI, DNI, and/or DHI
at this location.
Parameters
----------
times : DatetimeIndex
model : str
The clear sky model to use. Must be one of
'ineichen', 'haurwitz', 'simplified_solis'.
kwargs passed to the relevant functions. Climatological values
are assumed in many cases. See code for details.
Returns
-------
clearsky : DataFrame
Column names are: ``ghi, dni, dhi``.
"""
if model == 'ineichen':
cs = clearsky.ineichen(times, latitude=self.latitude,
longitude=self.longitude,
altitude=self.altitude,
**kwargs)
elif model == 'haurwitz':
solpos = self.get_solarposition(times, **kwargs)
cs = clearsky.haurwitz(solpos['apparent_zenith'])
elif model == 'simplified_solis':
# these try/excepts define default values that are only
# evaluated if necessary. ineichen does some of this internally
try:
dni_extra = kwargs.pop('dni_extra')
except KeyError:
dni_extra = irradiance.extraradiation(times.dayofyear)
try:
pressure = kwargs.pop('pressure')
except KeyError:
pressure = atmosphere.alt2pres(self.altitude)
try:
apparent_elevation = kwargs.pop('apparent_elevation')
except KeyError:
solpos = self.get_solarposition(
times, pressure=pressure, **kwargs)
apparent_elevation = solpos['apparent_elevation']
cs = clearsky.simplified_solis(
apparent_elevation, pressure=pressure, dni_extra=dni_extra,
**kwargs)
else:
raise ValueError('{} is not a valid clear sky model'
.format(model))
return cs
def rho(L, theta):
# From altitude, calculate pressure
# Assume T = 288.15K and 0% humidity
P = atmosphere.alt2pres(L * np.sin(theta))
T = 288.15
R = 287.058 # Specific gas constant of air
return P / (R * T)
def get_airmass(self,
times=None,
solar_position=None,
model='kastenyoung1989'):
"""
Calculate the relative and absolute airmass.
Automatically chooses zenith or apparant zenith
depending on the selected model.
Parameters
----------
times : None or DatetimeIndex, default None
Only used if solar_position is not provided.
solar_position : None or DataFrame, default None
DataFrame with with columns 'apparent_zenith', 'zenith'.
model : str, default 'kastenyoung1989'
Relative airmass model. See
:py:func:`pvlib.atmosphere.get_relative_airmass`
for a list of available models.
Returns
-------
airmass : DataFrame
Columns are 'airmass_relative', 'airmass_absolute'
See also
--------
pvlib.atmosphere.get_relative_airmass
"""
if solar_position is None:
solar_position = self.get_solarposition(times)
if model in atmosphere.APPARENT_ZENITH_MODELS:
zenith = solar_position['apparent_zenith']
elif model in atmosphere.TRUE_ZENITH_MODELS:
zenith = solar_position['zenith']
else:
raise ValueError(f'{model} is not a valid airmass model')
airmass_relative = atmosphere.get_relative_airmass(zenith, model)
pressure = atmosphere.alt2pres(self.altitude)
airmass_absolute = atmosphere.get_absolute_airmass(
airmass_relative, pressure)
airmass = pd.DataFrame(index=solar_position.index)
airmass['airmass_relative'] = airmass_relative
airmass['airmass_absolute'] = airmass_absolute
return airmass
def get_perfect_voltage_for_a_day(start, freq):
"""This method is used to build a pandas serie with voltage values.
This serie has DateTime index and contains a value for every "freq"
seconds during 24 hours starting from "start" date.
There are several assumptions:
1. Location is Munich
2. A battery is pointing to the south, amount of blocks is 20
3. Sandia Module database is used
4. pvlib library is heavily used
:param start: datetime. First timestamp in result series
:param freq: str. How often voltage should be sampled
:return: voltage : Series
"""
surface_tilt = _munich_location.latitude
surface_azimuth = 180 # pointing south
date_range = pd.date_range(start=start,
end=start + dt.timedelta(
hours=23, minutes=59, seconds=59),
freq=freq, tz=_munich_location.tz)
clearsky_estimations = _munich_location.get_clearsky(date_range)
dni_extra = irradiance.extraradiation(date_range)
solar_position = solarposition.get_solarposition(
date_range, _munich_location.latitude, _munich_location.longitude)
airmass = atmosphere.relativeairmass(solar_position['apparent_zenith'])
pressure = atmosphere.alt2pres(_munich_location.altitude)
am_abs = atmosphere.absoluteairmass(airmass, pressure)
total_irrad = irradiance.total_irrad(surface_tilt,
surface_azimuth,
solar_position['apparent_zenith'],
solar_position['azimuth'],
clearsky_estimations['dni'],
clearsky_estimations['ghi'],
clearsky_estimations['dhi'],
dni_extra=dni_extra,
model='haydavies')
temps = pvsystem.sapm_celltemp(total_irrad['poa_global'], 0, 15)
aoi = irradiance.aoi(surface_tilt, surface_azimuth,
solar_position['apparent_zenith'],
solar_position['azimuth'])
# add 0.0001 to avoid np.log(0) and warnings about that
effective_irradiance = pvsystem.sapm_effective_irradiance(
total_irrad['poa_direct'], total_irrad['poa_diffuse'], am_abs,
aoi, _sandia_module) + 0.0001
sapm = pvsystem.sapm(effective_irradiance, temps['temp_cell'],
_sandia_module)
return sapm['p_mp'] * _module_count
def get_airmass(self,
times=None,
solar_position=None,
model='kastenyoung1989'):
"""
Calculate the relative and absolute airmass.
Automatically chooses zenith or apparant zenith
depending on the selected model.
Parameters
----------
times : None or DatetimeIndex
Only used if solar_position is not provided.
solar_position : None or DataFrame
DataFrame with with columns 'apparent_zenith', 'zenith'.
model : str
Relative airmass model
Returns
-------
airmass : DataFrame
Columns are 'airmass_relative', 'airmass_absolute'
"""
if solar_position is None:
solar_position = self.get_solarposition(times)
if model in atmosphere.APPARENT_ZENITH_MODELS:
zenith = solar_position['apparent_zenith']
elif model in atmosphere.TRUE_ZENITH_MODELS:
zenith = solar_position['zenith']
else:
raise ValueError('{} is not a valid airmass model'.format(model))
airmass_relative = atmosphere.relativeairmass(zenith, model)
pressure = atmosphere.alt2pres(self.altitude)
airmass_absolute = atmosphere.absoluteairmass(airmass_relative,
pressure)
airmass = pd.DataFrame()
airmass['airmass_relative'] = airmass_relative
airmass['airmass_absolute'] = airmass_absolute
return airmass
def get_airmass(self, times=None, solar_position=None,
model='kastenyoung1989'):
"""
Calculate the relative and absolute airmass.
Automatically chooses zenith or apparant zenith
depending on the selected model.
Parameters
----------
times : None or DatetimeIndex
Only used if solar_position is not provided.
solar_position : None or DataFrame
DataFrame with with columns 'apparent_zenith', 'zenith'.
model : str
Relative airmass model
Returns
-------
airmass : DataFrame
Columns are 'airmass_relative', 'airmass_absolute'
"""
if solar_position is None:
solar_position = self.get_solarposition(times)
if model in atmosphere.APPARENT_ZENITH_MODELS:
zenith = solar_position['apparent_zenith']
elif model in atmosphere.TRUE_ZENITH_MODELS:
zenith = solar_position['zenith']
else:
raise ValueError('{} is not a valid airmass model'.format(model))
airmass_relative = atmosphere.relativeairmass(zenith, model)
pressure = atmosphere.alt2pres(self.altitude)
airmass_absolute = atmosphere.absoluteairmass(airmass_relative,
pressure)
airmass = pd.DataFrame()
airmass['airmass_relative'] = airmass_relative
airmass['airmass_absolute'] = airmass_absolute
return airmass
def test_ineichen_series():
tus = Location(32.2, -111, 'US/Arizona', 700)
times = pd.date_range(start='2014-06-24', end='2014-06-25', freq='3h')
times_localized = times.tz_localize(tus.tz)
ephem_data = solarposition.get_solarposition(times_localized, tus.latitude,
tus.longitude)
am = atmosphere.relativeairmass(ephem_data['apparent_zenith'])
am = atmosphere.absoluteairmass(am, atmosphere.alt2pres(tus.altitude))
expected = pd.DataFrame(
np.array([[0., 0., 0.], [0., 0., 0.],
[91.12492792, 321.16092181, 51.17628184],
[716.46580533, 888.90147035, 99.5050056],
[1053.42066043, 953.24925854, 116.32868969],
[863.54692781, 922.06124712, 106.95536561],
[271.06382274, 655.44925241, 73.05968071], [0., 0., 0.],
[0., 0., 0.]]),
columns=['ghi', 'dni', 'dhi'],
index=times_localized)
out = clearsky.ineichen(ephem_data['apparent_zenith'], am, 3)
assert_frame_equal(expected, out)
def test_ineichen_series():
tus = Location(32.2, -111, 'US/Arizona', 700)
times = pd.date_range(start='2014-06-24', end='2014-06-25', freq='3h')
times_localized = times.tz_localize(tus.tz)
ephem_data = solarposition.get_solarposition(times_localized, tus.latitude,
tus.longitude)
am = atmosphere.relativeairmass(ephem_data['apparent_zenith'])
am = atmosphere.absoluteairmass(am, atmosphere.alt2pres(tus.altitude))
expected = pd.DataFrame(np.
array([[ 0. , 0. , 0. ],
[ 0. , 0. , 0. ],
[ 91.12492792, 321.16092181, 51.17628184],
[ 716.46580533, 888.90147035, 99.5050056 ],
[ 1053.42066043, 953.24925854, 116.32868969],
[ 863.54692781, 922.06124712, 106.95536561],
[ 271.06382274, 655.44925241, 73.05968071],
[ 0. , 0. , 0. ],
[ 0. , 0. , 0. ]]),
columns=['ghi', 'dni', 'dhi'],
index=times_localized)
out = clearsky.ineichen(ephem_data['apparent_zenith'], am, 3)
assert_frame_equal(expected, out)
def get_solarposition(self,
times,
pressure=None,
temperature=12,
**kwargs):
"""
Uses the :py:func:`pvlib.solarposition.get_solarposition` function
to calculate the solar zenith, azimuth, etc. at this location.
Parameters
----------
times : pandas.DatetimeIndex
Must be localized or UTC will be assumed.
pressure : None, float, or array-like, default None
If None, pressure will be calculated using
:py:func:`pvlib.atmosphere.alt2pres` and ``self.altitude``.
temperature : None, float, or array-like, default 12
kwargs
passed to :py:func:`pvlib.solarposition.get_solarposition`
Returns
-------
solar_position : DataFrame
Columns depend on the ``method`` kwarg, but always include
``zenith`` and ``azimuth``. The angles are in degrees.
"""
if pressure is None:
pressure = atmosphere.alt2pres(self.altitude)
return solarposition.get_solarposition(times,
latitude=self.latitude,
longitude=self.longitude,
altitude=self.altitude,
pressure=pressure,
temperature=temperature,
**kwargs)
def get_clearsky(self,
times,
model='ineichen',
solar_position=None,
dni_extra=None,
**kwargs):
"""
Calculate the clear sky estimates of GHI, DNI, and/or DHI
at this location.
Parameters
----------
times: DatetimeIndex
model: str
The clear sky model to use. Must be one of
'ineichen', 'haurwitz', 'simplified_solis'.
solar_position : None or DataFrame
DataFrame with with columns 'apparent_zenith', 'zenith',
'apparent_elevation'.
dni_extra: None or numeric
If None, will be calculated from times.
kwargs passed to the relevant functions. Climatological values
are assumed in many cases. See source code for details!
Returns
-------
clearsky : DataFrame
Column names are: ``ghi, dni, dhi``.
"""
if dni_extra is None:
dni_extra = irradiance.extraradiation(times)
try:
pressure = kwargs.pop('pressure')
except KeyError:
pressure = atmosphere.alt2pres(self.altitude)
if solar_position is None:
solar_position = self.get_solarposition(times,
pressure=pressure,
**kwargs)
apparent_zenith = solar_position['apparent_zenith']
apparent_elevation = solar_position['apparent_elevation']
if model == 'ineichen':
try:
linke_turbidity = kwargs.pop('linke_turbidity')
except KeyError:
interp_turbidity = kwargs.pop('interp_turbidity', True)
linke_turbidity = clearsky.lookup_linke_turbidity(
times,
self.latitude,
self.longitude,
interp_turbidity=interp_turbidity)
try:
airmass_absolute = kwargs.pop('airmass_absolute')
except KeyError:
airmass_absolute = self.get_airmass(
times, solar_position=solar_position)['airmass_absolute']
cs = clearsky.ineichen(apparent_zenith,
airmass_absolute,
linke_turbidity,
altitude=self.altitude,
dni_extra=dni_extra)
elif model == 'haurwitz':
cs = clearsky.haurwitz(apparent_zenith)
elif model == 'simplified_solis':
cs = clearsky.simplified_solis(apparent_elevation,
pressure=pressure,
dni_extra=dni_extra,
**kwargs)
else:
raise ValueError(
('{} is not a valid clear sky model. Must be ' +
'one of ineichen, simplified_solis, haurwitz').format(model))
return cs
def basic_chain(times,
latitude,
longitude,
module_parameters,
inverter_parameters,
irradiance=None,
weather=None,
surface_tilt=None,
surface_azimuth=None,
orientation_strategy=None,
transposition_model='haydavies',
solar_position_method='nrel_numpy',
airmass_model='kastenyoung1989',
altitude=None,
pressure=None,
**kwargs):
"""
An experimental function that computes all of the modeling steps
necessary for calculating power or energy for a PV system at a given
location.
Parameters
----------
times : DatetimeIndex
Times at which to evaluate the model.
latitude : float.
Positive is north of the equator.
Use decimal degrees notation.
longitude : float.
Positive is east of the prime meridian.
Use decimal degrees notation.
module_parameters : None, dict or Series
Module parameters as defined by the SAPM.
inverter_parameters : None, dict or Series
Inverter parameters as defined by the CEC.
irradiance : None or DataFrame, default None
If None, calculates clear sky data.
Columns must be 'dni', 'ghi', 'dhi'.
weather : None or DataFrame, default None
If None, assumes air temperature is 20 C and
wind speed is 0 m/s.
Columns must be 'wind_speed', 'temp_air'.
surface_tilt : None, float or Series, default None
Surface tilt angles in decimal degrees.
The tilt angle is defined as degrees from horizontal
(e.g. surface facing up = 0, surface facing horizon = 90)
surface_azimuth : None, float or Series, default None
Surface azimuth angles in decimal degrees.
The azimuth convention is defined
as degrees east of north
(North=0, South=180, East=90, West=270).
orientation_strategy : None or str, default None
The strategy for aligning the modules.
If not None, sets the ``surface_azimuth`` and ``surface_tilt``
properties of the ``system``. Allowed strategies include 'flat',
'south_at_latitude_tilt'. Ignored for SingleAxisTracker systems.
transposition_model : str, default 'haydavies'
Passed to system.get_irradiance.
solar_position_method : str, default 'nrel_numpy'
Passed to solarposition.get_solarposition.
airmass_model : str, default 'kastenyoung1989'
Passed to atmosphere.relativeairmass.
altitude : None or float, default None
If None, computed from pressure. Assumed to be 0 m
if pressure is also None.
pressure : None or float, default None
If None, computed from altitude. Assumed to be 101325 Pa
if altitude is also None.
**kwargs
Arbitrary keyword arguments.
See code for details.
Returns
-------
output : (dc, ac)
Tuple of DC power (with SAPM parameters) (DataFrame) and AC
power (Series).
"""
# use surface_tilt and surface_azimuth if provided,
# otherwise set them using the orientation_strategy
if surface_tilt is not None and surface_azimuth is not None:
pass
elif orientation_strategy is not None:
surface_tilt, surface_azimuth = \
get_orientation(orientation_strategy, latitude=latitude)
else:
raise ValueError('orientation_strategy or surface_tilt and '
'surface_azimuth must be provided')
times = times
if altitude is None and pressure is None:
altitude = 0.
pressure = 101325.
elif altitude is None:
altitude = atmosphere.pres2alt(pressure)
elif pressure is None:
pressure = atmosphere.alt2pres(altitude)
solar_position = solarposition.get_solarposition(
times,
latitude,
longitude,
altitude=altitude,
pressure=pressure,
method=solar_position_method,
**kwargs)
# possible error with using apparent zenith with some models
airmass = atmosphere.get_relative_airmass(
solar_position['apparent_zenith'], model=airmass_model)
airmass = atmosphere.get_absolute_airmass(airmass, pressure)
dni_extra = pvlib.irradiance.get_extra_radiation(solar_position.index)
aoi = pvlib.irradiance.aoi(surface_tilt, surface_azimuth,
solar_position['apparent_zenith'],
solar_position['azimuth'])
if irradiance is None:
linke_turbidity = clearsky.lookup_linke_turbidity(
solar_position.index, latitude, longitude)
irradiance = clearsky.ineichen(solar_position['apparent_zenith'],
airmass,
linke_turbidity,
altitude=altitude,
dni_extra=dni_extra)
total_irrad = pvlib.irradiance.get_total_irradiance(
surface_tilt,
surface_azimuth,
solar_position['apparent_zenith'],
solar_position['azimuth'],
irradiance['dni'],
irradiance['ghi'],
irradiance['dhi'],
model=transposition_model,
dni_extra=dni_extra)
if weather is None:
weather = {'wind_speed': 0, 'temp_air': 20}
temps = pvsystem.sapm_celltemp(total_irrad['poa_global'],
weather['wind_speed'], weather['temp_air'])
effective_irradiance = pvsystem.sapm_effective_irradiance(
total_irrad['poa_direct'], total_irrad['poa_diffuse'], airmass, aoi,
module_parameters)
dc = pvsystem.sapm(effective_irradiance, temps['temp_cell'],
module_parameters)
ac = pvsystem.snlinverter(dc['v_mp'], dc['p_mp'], inverter_parameters)
return dc, ac
def test_alt2pres():
out = atmosphere.alt2pres(np.array([-100, 0, 1000, 8000]))
expected = np.array([102532.073, 101324.999, 89874.750, 35600.496])
assert_allclose(out, expected, atol=0.001)
def ineichen(time,
location,
linke_turbidity=None,
solarposition_method='pyephem',
zenith_data=None,
airmass_model='young1994',
airmass_data=None,
interp_turbidity=True):
'''
Determine clear sky GHI, DNI, and DHI from Ineichen/Perez model
Implements the Ineichen and Perez clear sky model for global horizontal
irradiance (GHI), direct normal irradiance (DNI), and calculates
the clear-sky diffuse horizontal (DHI) component as the difference
between GHI and DNI*cos(zenith) as presented in [1, 2]. A report on clear
sky models found the Ineichen/Perez model to have excellent performance
with a minimal input data set [3].
Default values for montly Linke turbidity provided by SoDa [4, 5].
Parameters
-----------
time : pandas.DatetimeIndex
location : pvlib.Location
linke_turbidity : None or float
If None, uses ``LinkeTurbidities.mat`` lookup table.
solarposition_method : string
Sets the solar position algorithm.
See solarposition.get_solarposition()
zenith_data : None or Series
If None, ephemeris data will be calculated using ``solarposition_method``.
airmass_model : string
See pvlib.airmass.relativeairmass().
airmass_data : None or Series
If None, absolute air mass data will be calculated using
``airmass_model`` and location.alitude.
interp_turbidity : bool
If ``True``, interpolates the monthly Linke turbidity values
found in ``LinkeTurbidities.mat`` to daily values.
Returns
--------
DataFrame with the following columns: ``ghi, dni, dhi``.
Notes
-----
If you are using this function
in a loop, it may be faster to load LinkeTurbidities.mat outside of
the loop and feed it in as a keyword argument, rather than
having the function open and process the file each time it is called.
References
----------
[1] P. Ineichen and R. Perez, "A New airmass independent formulation for
the Linke turbidity coefficient", Solar Energy, vol 73, pp. 151-157, 2002.
[2] R. Perez et. al., "A New Operational Model for Satellite-Derived
Irradiances: Description and Validation", Solar Energy, vol 73, pp.
307-317, 2002.
[3] M. Reno, C. Hansen, and J. Stein, "Global Horizontal Irradiance Clear
Sky Models: Implementation and Analysis", Sandia National
Laboratories, SAND2012-2389, 2012.
[4] http://www.soda-is.com/eng/services/climat_free_eng.php#c5 (obtained
July 17, 2012).
[5] J. Remund, et. al., "Worldwide Linke Turbidity Information", Proc.
ISES Solar World Congress, June 2003. Goteborg, Sweden.
'''
# Initial implementation of this algorithm by Matthew Reno.
# Ported to python by Rob Andrews
# Added functionality by Will Holmgren (@wholmgren)
I0 = irradiance.extraradiation(time.dayofyear)
if zenith_data is None:
ephem_data = solarposition.get_solarposition(
time, location, method=solarposition_method)
time = ephem_data.index # fixes issue with time possibly not being tz-aware
try:
ApparentZenith = ephem_data['apparent_zenith']
except KeyError:
ApparentZenith = ephem_data['zenith']
logger.warning('could not find apparent_zenith. using zenith')
else:
ApparentZenith = zenith_data
#ApparentZenith[ApparentZenith >= 90] = 90 # can cause problems in edge cases
if linke_turbidity is None:
TL = lookup_linke_turbidity(time,
location.latitude,
location.longitude,
interp_turbidity=interp_turbidity)
else:
TL = linke_turbidity
# Get the absolute airmass assuming standard local pressure (per
# alt2pres) using Kasten and Young's 1989 formula for airmass.
if airmass_data is None:
AMabsolute = atmosphere.absoluteairmass(
airmass_relative=atmosphere.relativeairmass(
ApparentZenith, airmass_model),
pressure=atmosphere.alt2pres(location.altitude))
else:
AMabsolute = airmass_data
fh1 = np.exp(-location.altitude / 8000.)
fh2 = np.exp(-location.altitude / 1250.)
cg1 = 5.09e-05 * location.altitude + 0.868
cg2 = 3.92e-05 * location.altitude + 0.0387
logger.debug('fh1=%s, fh2=%s, cg1=%s, cg2=%s', fh1, fh2, cg1, cg2)
# Dan's note on the TL correction: By my reading of the publication on
# pages 151-157, Ineichen and Perez introduce (among other things) three
# things. 1) Beam model in eqn. 8, 2) new turbidity factor in eqn 9 and
# appendix A, and 3) Global horizontal model in eqn. 11. They do NOT appear
# to use the new turbidity factor (item 2 above) in either the beam or GHI
# models. The phrasing of appendix A seems as if there are two separate
# corrections, the first correction is used to correct the beam/GHI models,
# and the second correction is used to correct the revised turibidity
# factor. In my estimation, there is no need to correct the turbidity
# factor used in the beam/GHI models.
# Create the corrected TL for TL < 2
# TLcorr = TL;
# TLcorr(TL < 2) = TLcorr(TL < 2) - 0.25 .* (2-TLcorr(TL < 2)) .^ (0.5);
# This equation is found in Solar Energy 73, pg 311.
# Full ref: Perez et. al., Vol. 73, pp. 307-317 (2002).
# It is slightly different than the equation given in Solar Energy 73, pg 156.
# We used the equation from pg 311 because of the existence of known typos
# in the pg 156 publication (notably the fh2-(TL-1) should be fh2 * (TL-1)).
cos_zenith = tools.cosd(ApparentZenith)
clearsky_GHI = (cg1 * I0 * cos_zenith * np.exp(-cg2 * AMabsolute *
(fh1 + fh2 * (TL - 1))) *
np.exp(0.01 * AMabsolute**1.8))
clearsky_GHI[clearsky_GHI < 0] = 0
# BncI == "normal beam clear sky radiation"
b = 0.664 + 0.163 / fh1
BncI = b * I0 * np.exp(-0.09 * AMabsolute * (TL - 1))
logger.debug('b=%s', b)
# "empirical correction" SE 73, 157 & SE 73, 312.
BncI_2 = (clearsky_GHI * (1 - (0.1 - 0.2 * np.exp(-TL)) /
(0.1 + 0.882 / fh1)) / cos_zenith)
clearsky_DNI = np.minimum(BncI, BncI_2)
clearsky_DHI = clearsky_GHI - clearsky_DNI * cos_zenith
df_out = pd.DataFrame({
'ghi': clearsky_GHI,
'dni': clearsky_DNI,
'dhi': clearsky_DHI
})
df_out.fillna(0, inplace=True)
return df_out
def basic_chain(times, latitude, longitude,
module_parameters, inverter_parameters,
irradiance=None, weather=None,
surface_tilt=None, surface_azimuth=None,
orientation_strategy=None,
transposition_model='haydavies',
solar_position_method='nrel_numpy',
airmass_model='kastenyoung1989',
altitude=None, pressure=None,
**kwargs):
"""
An experimental function that computes all of the modeling steps
necessary for calculating power or energy for a PV system at a given
location.
Parameters
----------
times : DatetimeIndex
Times at which to evaluate the model.
latitude : float.
Positive is north of the equator.
Use decimal degrees notation.
longitude : float.
Positive is east of the prime meridian.
Use decimal degrees notation.
module_parameters : None, dict or Series
Module parameters as defined by the SAPM.
inverter_parameters : None, dict or Series
Inverter parameters as defined by the CEC.
irradiance : None or DataFrame
If None, calculates clear sky data.
Columns must be 'dni', 'ghi', 'dhi'.
weather : None or DataFrame
If None, assumes air temperature is 20 C and
wind speed is 0 m/s.
Columns must be 'wind_speed', 'temp_air'.
surface_tilt : float or Series
Surface tilt angles in decimal degrees.
The tilt angle is defined as degrees from horizontal
(e.g. surface facing up = 0, surface facing horizon = 90)
surface_azimuth : float or Series
Surface azimuth angles in decimal degrees.
The azimuth convention is defined
as degrees east of north
(North=0, South=180, East=90, West=270).
orientation_strategy : None or str
The strategy for aligning the modules.
If not None, sets the ``surface_azimuth`` and ``surface_tilt``
properties of the ``system``.
transposition_model : str
Passed to system.get_irradiance.
solar_position_method : str
Passed to location.get_solarposition.
airmass_model : str
Passed to location.get_airmass.
altitude : None or float
If None, computed from pressure. Assumed to be 0 m
if pressure is also None.
pressure : None or float
If None, computed from altitude. Assumed to be 101325 Pa
if altitude is also None.
**kwargs
Arbitrary keyword arguments.
See code for details.
Returns
-------
output : (dc, ac)
Tuple of DC power (with SAPM parameters) (DataFrame) and AC
power (Series).
"""
# use surface_tilt and surface_azimuth if provided,
# otherwise set them using the orientation_strategy
if surface_tilt is not None and surface_azimuth is not None:
pass
elif orientation_strategy is not None:
surface_tilt, surface_azimuth = \
get_orientation(orientation_strategy, latitude=latitude)
else:
raise ValueError('orientation_strategy or surface_tilt and ' +
'surface_azimuth must be provided')
times = times
if altitude is None and pressure is None:
altitude = 0.
pressure = 101325.
elif altitude is None:
altitude = atmosphere.pres2alt(pressure)
elif pressure is None:
pressure = atmosphere.alt2pres(altitude)
solar_position = solarposition.get_solarposition(times, latitude,
longitude,
altitude=altitude,
pressure=pressure,
**kwargs)
# possible error with using apparent zenith with some models
airmass = atmosphere.relativeairmass(solar_position['apparent_zenith'],
model=airmass_model)
airmass = atmosphere.absoluteairmass(airmass, pressure)
dni_extra = pvlib.irradiance.extraradiation(solar_position.index)
dni_extra = pd.Series(dni_extra, index=solar_position.index)
aoi = pvlib.irradiance.aoi(surface_tilt, surface_azimuth,
solar_position['apparent_zenith'],
solar_position['azimuth'])
if irradiance is None:
irradiance = clearsky.ineichen(
solar_position.index,
latitude,
longitude,
zenith_data=solar_position['apparent_zenith'],
airmass_data=airmass,
altitude=altitude)
total_irrad = pvlib.irradiance.total_irrad(
surface_tilt,
surface_azimuth,
solar_position['apparent_zenith'],
solar_position['azimuth'],
irradiance['dni'],
irradiance['ghi'],
irradiance['dhi'],
model=transposition_model,
dni_extra=dni_extra)
if weather is None:
weather = {'wind_speed': 0, 'temp_air': 20}
temps = pvsystem.sapm_celltemp(total_irrad['poa_global'],
weather['wind_speed'],
weather['temp_air'])
dc = pvsystem.sapm(module_parameters, total_irrad['poa_direct'],
total_irrad['poa_diffuse'],
temps['temp_cell'],
airmass,
aoi)
ac = pvsystem.snlinverter(inverter_parameters, dc['v_mp'], dc['p_mp'])
return dc, ac
def test_alt2pres():
out = atmosphere.alt2pres(np.array([-100, 0, 1000, 8000]))
expected = np.array([102532.073, 101324.999, 89874.750, 35600.496])
assert_allclose(out, expected, atol=0.001)
def ineichen(time,
location,
linke_turbidity=None,
solarposition_method='pyephem',
zenith_data=None,
airmass_model='young1994',
airmass_data=None,
interp_turbidity=True):
'''
Determine clear sky GHI, DNI, and DHI from Ineichen/Perez model
Implements the Ineichen and Perez clear sky model for global horizontal
irradiance (GHI), direct normal irradiance (DNI), and calculates
the clear-sky diffuse horizontal (DHI) component as the difference
between GHI and DNI*cos(zenith) as presented in [1, 2]. A report on clear
sky models found the Ineichen/Perez model to have excellent performance
with a minimal input data set [3].
Default values for montly Linke turbidity provided by SoDa [4, 5].
Parameters
-----------
time : pandas.DatetimeIndex
location : pvlib.Location
linke_turbidity : None or float
If None, uses ``LinkeTurbidities.mat`` lookup table.
solarposition_method : string
Sets the solar position algorithm.
See solarposition.get_solarposition()
zenith_data : None or pandas.Series
If None, ephemeris data will be calculated using ``solarposition_method``.
airmass_model : string
See pvlib.airmass.relativeairmass().
airmass_data : None or pandas.Series
If None, absolute air mass data will be calculated using
``airmass_model`` and location.alitude.
interp_turbidity : bool
If ``True``, interpolates the monthly Linke turbidity values
found in ``LinkeTurbidities.mat`` to daily values.
Returns
--------
DataFrame with the following columns: ``GHI, DNI, DHI``.
Notes
-----
If you are using this function
in a loop, it may be faster to load LinkeTurbidities.mat outside of
the loop and feed it in as a variable, rather than
having the function open the file each time it is called.
References
----------
[1] P. Ineichen and R. Perez, "A New airmass independent formulation for
the Linke turbidity coefficient", Solar Energy, vol 73, pp. 151-157, 2002.
[2] R. Perez et. al., "A New Operational Model for Satellite-Derived
Irradiances: Description and Validation", Solar Energy, vol 73, pp.
307-317, 2002.
[3] M. Reno, C. Hansen, and J. Stein, "Global Horizontal Irradiance Clear
Sky Models: Implementation and Analysis", Sandia National
Laboratories, SAND2012-2389, 2012.
[4] http://www.soda-is.com/eng/services/climat_free_eng.php#c5 (obtained
July 17, 2012).
[5] J. Remund, et. al., "Worldwide Linke Turbidity Information", Proc.
ISES Solar World Congress, June 2003. Goteborg, Sweden.
'''
# Initial implementation of this algorithm by Matthew Reno.
# Ported to python by Rob Andrews
# Added functionality by Will Holmgren
I0 = irradiance.extraradiation(time.dayofyear)
if zenith_data is None:
ephem_data = solarposition.get_solarposition(
time, location, method=solarposition_method)
time = ephem_data.index # fixes issue with time possibly not being tz-aware
try:
ApparentZenith = ephem_data['apparent_zenith']
except KeyError:
ApparentZenith = ephem_data['zenith']
logger.warning('could not find apparent_zenith. using zenith')
else:
ApparentZenith = zenith_data
#ApparentZenith[ApparentZenith >= 90] = 90 # can cause problems in edge cases
if linke_turbidity is None:
# The .mat file 'LinkeTurbidities.mat' contains a single 2160 x 4320 x 12
# matrix of type uint8 called 'LinkeTurbidity'. The rows represent global
# latitudes from 90 to -90 degrees; the columns represent global longitudes
# from -180 to 180; and the depth (third dimension) represents months of
# the year from January (1) to December (12). To determine the Linke
# turbidity for a position on the Earth's surface for a given month do the
# following: LT = LinkeTurbidity(LatitudeIndex, LongitudeIndex, month).
# Note that the numbers within the matrix are 20 * Linke Turbidity,
# so divide the number from the file by 20 to get the
# turbidity.
try:
import scipy.io
except ImportError:
raise ImportError(
'The Linke turbidity lookup table requires scipy. ' +
'You can still use clearsky.ineichen if you ' +
'supply your own turbidities.')
# consider putting this code at module level
this_path = os.path.dirname(os.path.abspath(__file__))
logger.debug('this_path={}'.format(this_path))
mat = scipy.io.loadmat(
os.path.join(this_path, 'data', 'LinkeTurbidities.mat'))
linke_turbidity = mat['LinkeTurbidity']
LatitudeIndex = np.round_(
_linearly_scale(location.latitude, 90, -90, 1, 2160))
LongitudeIndex = np.round_(
_linearly_scale(location.longitude, -180, 180, 1, 4320))
g = linke_turbidity[LatitudeIndex][LongitudeIndex]
if interp_turbidity:
logger.info('interpolating turbidity to the day')
g2 = np.concatenate([[g[-1]], g, [g[0]]]) # wrap ends around
days = np.linspace(
-15, 380, num=14) # map day of year onto month (approximate)
LT = pd.Series(np.interp(time.dayofyear, days, g2), index=time)
else:
logger.info('using monthly turbidity')
ApplyMonth = lambda x: g[x[0] - 1]
LT = pd.DataFrame(time.month, index=time)
LT = LT.apply(ApplyMonth, axis=1)
TL = LT / 20.
logger.info('using TL=\n{}'.format(TL))
else:
TL = linke_turbidity
# Get the absolute airmass assuming standard local pressure (per
# alt2pres) using Kasten and Young's 1989 formula for airmass.
if airmass_data is None:
AMabsolute = atmosphere.absoluteairmass(
AMrelative=atmosphere.relativeairmass(ApparentZenith,
airmass_model),
pressure=atmosphere.alt2pres(location.altitude))
else:
AMabsolute = airmass_data
fh1 = np.exp(-location.altitude / 8000.)
fh2 = np.exp(-location.altitude / 1250.)
cg1 = 5.09e-05 * location.altitude + 0.868
cg2 = 3.92e-05 * location.altitude + 0.0387
logger.debug('fh1={}, fh2={}, cg1={}, cg2={}'.format(fh1, fh2, cg1, cg2))
# Dan's note on the TL correction: By my reading of the publication on
# pages 151-157, Ineichen and Perez introduce (among other things) three
# things. 1) Beam model in eqn. 8, 2) new turbidity factor in eqn 9 and
# appendix A, and 3) Global horizontal model in eqn. 11. They do NOT appear
# to use the new turbidity factor (item 2 above) in either the beam or GHI
# models. The phrasing of appendix A seems as if there are two separate
# corrections, the first correction is used to correct the beam/GHI models,
# and the second correction is used to correct the revised turibidity
# factor. In my estimation, there is no need to correct the turbidity
# factor used in the beam/GHI models.
# Create the corrected TL for TL < 2
# TLcorr = TL;
# TLcorr(TL < 2) = TLcorr(TL < 2) - 0.25 .* (2-TLcorr(TL < 2)) .^ (0.5);
# This equation is found in Solar Energy 73, pg 311.
# Full ref: Perez et. al., Vol. 73, pp. 307-317 (2002).
# It is slightly different than the equation given in Solar Energy 73, pg 156.
# We used the equation from pg 311 because of the existence of known typos
# in the pg 156 publication (notably the fh2-(TL-1) should be fh2 * (TL-1)).
cos_zenith = tools.cosd(ApparentZenith)
clearsky_GHI = cg1 * I0 * cos_zenith * np.exp(
-cg2 * AMabsolute * (fh1 + fh2 *
(TL - 1))) * np.exp(0.01 * AMabsolute**1.8)
clearsky_GHI[clearsky_GHI < 0] = 0
# BncI == "normal beam clear sky radiation"
b = 0.664 + 0.163 / fh1
BncI = b * I0 * np.exp(-0.09 * AMabsolute * (TL - 1))
logger.debug('b={}'.format(b))
# "empirical correction" SE 73, 157 & SE 73, 312.
BncI_2 = clearsky_GHI * (1 - (0.1 - 0.2 * np.exp(-TL)) /
(0.1 + 0.882 / fh1)) / cos_zenith
#return BncI, BncI_2
clearsky_DNI = np.minimum(BncI,
BncI_2) # Will H: use np.minimum explicitly
clearsky_DHI = clearsky_GHI - clearsky_DNI * cos_zenith
df_out = pd.DataFrame({
'GHI': clearsky_GHI,
'DNI': clearsky_DNI,
'DHI': clearsky_DHI
})
df_out.fillna(0, inplace=True)
#df_out['BncI'] = BncI
#df_out['BncI_2'] = BncI
return df_out
def get_solarposition(time,
latitude,
longitude,
altitude=None,
pressure=None,
method='nrel_numpy',
temperature=12,
**kwargs):
"""
A convenience wrapper for the solar position calculators.
Parameters
----------
time : pandas.DatetimeIndex
latitude : float
longitude : float
altitude : None or float, default None
If None, computed from pressure. Assumed to be 0 m
if pressure is also None.
pressure : None or float, default None
If None, computed from altitude. Assumed to be 101325 Pa
if altitude is also None.
method : string, default 'nrel_numpy'
'nrel_numpy' uses an implementation of the NREL SPA algorithm
described in [1] (default, recommended): :py:func:`spa_python`
'nrel_numba' uses an implementation of the NREL SPA algorithm
described in [1], but also compiles the code first:
:py:func:`spa_python`
'pyephem' uses the PyEphem package: :py:func:`pyephem`
'ephemeris' uses the pvlib ephemeris code: :py:func:`ephemeris`
'nrel_c' uses the NREL SPA C code [3]: :py:func:`spa_c`
temperature : float, default 12
Degrees C.
Other keywords are passed to the underlying solar position function.
References
----------
[1] I. Reda and A. Andreas, Solar position algorithm for solar radiation
applications. Solar Energy, vol. 76, no. 5, pp. 577-589, 2004.
[2] I. Reda and A. Andreas, Corrigendum to Solar position algorithm for
solar radiation applications. Solar Energy, vol. 81, no. 6, p. 838, 2007.
[3] NREL SPA code: http://rredc.nrel.gov/solar/codesandalgorithms/spa/
"""
if altitude is None and pressure is None:
altitude = 0.
pressure = 101325.
elif altitude is None:
altitude = atmosphere.pres2alt(pressure)
elif pressure is None:
pressure = atmosphere.alt2pres(altitude)
method = method.lower()
if isinstance(time, dt.datetime):
time = pd.DatetimeIndex([
time,
])
if method == 'nrel_c':
ephem_df = spa_c(time, latitude, longitude, pressure, temperature,
**kwargs)
elif method == 'nrel_numba':
ephem_df = spa_python(time,
latitude,
longitude,
altitude,
pressure,
temperature,
how='numba',
**kwargs)
elif method == 'nrel_numpy':
ephem_df = spa_python(time,
latitude,
longitude,
altitude,
pressure,
temperature,
how='numpy',
**kwargs)
elif method == 'pyephem':
ephem_df = pyephem(time,
latitude,
longitude,
altitude=altitude,
pressure=pressure,
temperature=temperature,
**kwargs)
elif method == 'ephemeris':
ephem_df = ephemeris(time, latitude, longitude, pressure, temperature,
**kwargs)
else:
raise ValueError('Invalid solar position method')
return ephem_df
def get_clearsky(self, times, model='ineichen', **kwargs):
"""
Calculate the clear sky estimates of GHI, DNI, and/or DHI
at this location.
Parameters
----------
times : DatetimeIndex
model : str
The clear sky model to use. Must be one of
'ineichen', 'haurwitz', 'simplified_solis'.
kwargs passed to the relevant functions. Climatological values
are assumed in many cases. See code for details.
Returns
-------
clearsky : DataFrame
Column names are: ``ghi, dni, dhi``.
"""
if model == 'ineichen':
cs = clearsky.ineichen(times,
latitude=self.latitude,
longitude=self.longitude,
altitude=self.altitude,
**kwargs)
elif model == 'haurwitz':
solpos = self.get_solarposition(times, **kwargs)
cs = clearsky.haurwitz(solpos['apparent_zenith'])
elif model == 'simplified_solis':
# these try/excepts define default values that are only
# evaluated if necessary. ineichen does some of this internally
try:
dni_extra = kwargs.pop('dni_extra')
except KeyError:
dni_extra = irradiance.extraradiation(times.dayofyear)
try:
pressure = kwargs.pop('pressure')
except KeyError:
pressure = atmosphere.alt2pres(self.altitude)
try:
apparent_elevation = kwargs.pop('apparent_elevation')
except KeyError:
solpos = self.get_solarposition(times,
pressure=pressure,
**kwargs)
apparent_elevation = solpos['apparent_elevation']
cs = clearsky.simplified_solis(apparent_elevation,
pressure=pressure,
dni_extra=dni_extra,
**kwargs)
else:
raise ValueError('{} is not a valid clear sky model'.format(model))
return cs
def get_clearsky(self, times, model='ineichen', solar_position=None,
dni_extra=None, **kwargs):
"""
Calculate the clear sky estimates of GHI, DNI, and/or DHI
at this location.
Parameters
----------
times: DatetimeIndex
model: str, default 'ineichen'
The clear sky model to use. Must be one of
'ineichen', 'haurwitz', 'simplified_solis'.
solar_position : None or DataFrame, default None
DataFrame with columns 'apparent_zenith', 'zenith',
'apparent_elevation'.
dni_extra: None or numeric, default None
If None, will be calculated from times.
kwargs passed to the relevant functions. Climatological values
are assumed in many cases. See source code for details!
Returns
-------
clearsky : DataFrame
Column names are: ``ghi, dni, dhi``.
"""
if dni_extra is None:
dni_extra = irradiance.get_extra_radiation(times)
try:
pressure = kwargs.pop('pressure')
except KeyError:
pressure = atmosphere.alt2pres(self.altitude)
if solar_position is None:
solar_position = self.get_solarposition(times, pressure=pressure,
**kwargs)
apparent_zenith = solar_position['apparent_zenith']
apparent_elevation = solar_position['apparent_elevation']
if model == 'ineichen':
try:
linke_turbidity = kwargs.pop('linke_turbidity')
except KeyError:
interp_turbidity = kwargs.pop('interp_turbidity', True)
linke_turbidity = clearsky.lookup_linke_turbidity(
times, self.latitude, self.longitude,
interp_turbidity=interp_turbidity)
try:
airmass_absolute = kwargs.pop('airmass_absolute')
except KeyError:
airmass_absolute = self.get_airmass(
times, solar_position=solar_position)['airmass_absolute']
cs = clearsky.ineichen(apparent_zenith, airmass_absolute,
linke_turbidity, altitude=self.altitude,
dni_extra=dni_extra, **kwargs)
elif model == 'haurwitz':
cs = clearsky.haurwitz(apparent_zenith)
elif model == 'simplified_solis':
cs = clearsky.simplified_solis(
apparent_elevation, pressure=pressure, dni_extra=dni_extra,
**kwargs)
else:
raise ValueError('{} is not a valid clear sky model. Must be '
'one of ineichen, simplified_solis, haurwitz'
.format(model))
return cs
def ineichen(time, latitude, longitude, altitude=0, linke_turbidity=None,
solarposition_method='nrel_numpy', zenith_data=None,
airmass_model='young1994', airmass_data=None,
interp_turbidity=True):
'''
Determine clear sky GHI, DNI, and DHI from Ineichen/Perez model
Implements the Ineichen and Perez clear sky model for global horizontal
irradiance (GHI), direct normal irradiance (DNI), and calculates
the clear-sky diffuse horizontal (DHI) component as the difference
between GHI and DNI*cos(zenith) as presented in [1, 2]. A report on clear
sky models found the Ineichen/Perez model to have excellent performance
with a minimal input data set [3].
Default values for montly Linke turbidity provided by SoDa [4, 5].
Parameters
-----------
time : pandas.DatetimeIndex
latitude : float
longitude : float
altitude : float
linke_turbidity : None or float
If None, uses ``LinkeTurbidities.mat`` lookup table.
solarposition_method : string
Sets the solar position algorithm.
See solarposition.get_solarposition()
zenith_data : None or Series
If None, ephemeris data will be calculated using ``solarposition_method``.
airmass_model : string
See pvlib.airmass.relativeairmass().
airmass_data : None or Series
If None, absolute air mass data will be calculated using
``airmass_model`` and location.alitude.
interp_turbidity : bool
If ``True``, interpolates the monthly Linke turbidity values
found in ``LinkeTurbidities.mat`` to daily values.
Returns
--------
DataFrame with the following columns: ``ghi, dni, dhi``.
Notes
-----
If you are using this function
in a loop, it may be faster to load LinkeTurbidities.mat outside of
the loop and feed it in as a keyword argument, rather than
having the function open and process the file each time it is called.
References
----------
[1] P. Ineichen and R. Perez, "A New airmass independent formulation for
the Linke turbidity coefficient", Solar Energy, vol 73, pp. 151-157, 2002.
[2] R. Perez et. al., "A New Operational Model for Satellite-Derived
Irradiances: Description and Validation", Solar Energy, vol 73, pp.
307-317, 2002.
[3] M. Reno, C. Hansen, and J. Stein, "Global Horizontal Irradiance Clear
Sky Models: Implementation and Analysis", Sandia National
Laboratories, SAND2012-2389, 2012.
[4] http://www.soda-is.com/eng/services/climat_free_eng.php#c5 (obtained
July 17, 2012).
[5] J. Remund, et. al., "Worldwide Linke Turbidity Information", Proc.
ISES Solar World Congress, June 2003. Goteborg, Sweden.
'''
# Initial implementation of this algorithm by Matthew Reno.
# Ported to python by Rob Andrews
# Added functionality by Will Holmgren (@wholmgren)
I0 = irradiance.extraradiation(time.dayofyear)
if zenith_data is None:
ephem_data = solarposition.get_solarposition(time,
latitude=latitude,
longitude=longitude,
altitude=altitude,
method=solarposition_method)
time = ephem_data.index # fixes issue with time possibly not being tz-aware
try:
ApparentZenith = ephem_data['apparent_zenith']
except KeyError:
ApparentZenith = ephem_data['zenith']
logger.warning('could not find apparent_zenith. using zenith')
else:
ApparentZenith = zenith_data
#ApparentZenith[ApparentZenith >= 90] = 90 # can cause problems in edge cases
if linke_turbidity is None:
TL = lookup_linke_turbidity(time, latitude, longitude,
interp_turbidity=interp_turbidity)
else:
TL = linke_turbidity
# Get the absolute airmass assuming standard local pressure (per
# alt2pres) using Kasten and Young's 1989 formula for airmass.
if airmass_data is None:
AMabsolute = atmosphere.absoluteairmass(airmass_relative=atmosphere.relativeairmass(ApparentZenith, airmass_model),
pressure=atmosphere.alt2pres(altitude))
else:
AMabsolute = airmass_data
fh1 = np.exp(-altitude/8000.)
fh2 = np.exp(-altitude/1250.)
cg1 = 5.09e-05 * altitude + 0.868
cg2 = 3.92e-05 * altitude + 0.0387
logger.debug('fh1=%s, fh2=%s, cg1=%s, cg2=%s', fh1, fh2, cg1, cg2)
# Dan's note on the TL correction: By my reading of the publication on
# pages 151-157, Ineichen and Perez introduce (among other things) three
# things. 1) Beam model in eqn. 8, 2) new turbidity factor in eqn 9 and
# appendix A, and 3) Global horizontal model in eqn. 11. They do NOT appear
# to use the new turbidity factor (item 2 above) in either the beam or GHI
# models. The phrasing of appendix A seems as if there are two separate
# corrections, the first correction is used to correct the beam/GHI models,
# and the second correction is used to correct the revised turibidity
# factor. In my estimation, there is no need to correct the turbidity
# factor used in the beam/GHI models.
# Create the corrected TL for TL < 2
# TLcorr = TL;
# TLcorr(TL < 2) = TLcorr(TL < 2) - 0.25 .* (2-TLcorr(TL < 2)) .^ (0.5);
# This equation is found in Solar Energy 73, pg 311.
# Full ref: Perez et. al., Vol. 73, pp. 307-317 (2002).
# It is slightly different than the equation given in Solar Energy 73, pg 156.
# We used the equation from pg 311 because of the existence of known typos
# in the pg 156 publication (notably the fh2-(TL-1) should be fh2 * (TL-1)).
cos_zenith = tools.cosd(ApparentZenith)
clearsky_GHI = ( cg1 * I0 * cos_zenith *
np.exp(-cg2*AMabsolute*(fh1 + fh2*(TL - 1))) *
np.exp(0.01*AMabsolute**1.8) )
clearsky_GHI[clearsky_GHI < 0] = 0
# BncI == "normal beam clear sky radiation"
b = 0.664 + 0.163/fh1
BncI = b * I0 * np.exp( -0.09 * AMabsolute * (TL - 1) )
logger.debug('b=%s', b)
# "empirical correction" SE 73, 157 & SE 73, 312.
BncI_2 = ( clearsky_GHI *
( 1 - (0.1 - 0.2*np.exp(-TL))/(0.1 + 0.882/fh1) ) /
cos_zenith )
clearsky_DNI = np.minimum(BncI, BncI_2)
clearsky_DHI = clearsky_GHI - clearsky_DNI*cos_zenith
df_out = pd.DataFrame({'ghi':clearsky_GHI, 'dni':clearsky_DNI,
'dhi':clearsky_DHI})
df_out.fillna(0, inplace=True)
return df_out
def get_solarposition(time, latitude, longitude,
altitude=None, pressure=None,
method='nrel_numpy',
temperature=12, **kwargs):
"""
A convenience wrapper for the solar position calculators.
Parameters
----------
time : pandas.DatetimeIndex
latitude : float
longitude : float
altitude : None or float
If None, computed from pressure. Assumed to be 0 m
if pressure is also None.
pressure : None or float
If None, computed from altitude. Assumed to be 101325 Pa
if altitude is also None.
method : string
'pyephem' uses the PyEphem package: :func:`pyephem`
'nrel_c' uses the NREL SPA C code [3]: :func:`spa_c`
'nrel_numpy' uses an implementation of the NREL SPA algorithm
described in [1] (default): :func:`spa_python`
'nrel_numba' uses an implementation of the NREL SPA algorithm
described in [1], but also compiles the code first: :func:`spa_python`
'ephemeris' uses the pvlib ephemeris code: :func:`ephemeris`
temperature : float
Degrees C.
Other keywords are passed to the underlying solar position function.
References
----------
[1] I. Reda and A. Andreas, Solar position algorithm for solar radiation
applications. Solar Energy, vol. 76, no. 5, pp. 577-589, 2004.
[2] I. Reda and A. Andreas, Corrigendum to Solar position algorithm for
solar radiation applications. Solar Energy, vol. 81, no. 6, p. 838, 2007.
[3] NREL SPA code: http://rredc.nrel.gov/solar/codesandalgorithms/spa/
"""
if altitude is None and pressure is None:
altitude = 0.
pressure = 101325.
elif altitude is None:
altitude = atmosphere.pres2alt(pressure)
elif pressure is None:
pressure = atmosphere.alt2pres(altitude)
method = method.lower()
if isinstance(time, dt.datetime):
time = pd.DatetimeIndex([time, ])
if method == 'nrel_c':
ephem_df = spa_c(time, latitude, longitude, pressure, temperature,
**kwargs)
elif method == 'nrel_numba':
ephem_df = spa_python(time, latitude, longitude, altitude,
pressure, temperature,
how='numba', **kwargs)
elif method == 'nrel_numpy':
ephem_df = spa_python(time, latitude, longitude, altitude,
pressure, temperature,
how='numpy', **kwargs)
elif method == 'pyephem':
ephem_df = pyephem(time, latitude, longitude, pressure, temperature,
**kwargs)
elif method == 'ephemeris':
ephem_df = ephemeris(time, latitude, longitude, pressure, temperature,
**kwargs)
else:
raise ValueError('Invalid solar position method')
return ephem_df
def ineichen(
time,
location,
linke_turbidity=None,
solarposition_method="pyephem",
zenith_data=None,
airmass_model="young1994",
airmass_data=None,
interp_turbidity=True,
):
"""
Determine clear sky GHI, DNI, and DHI from Ineichen/Perez model
Implements the Ineichen and Perez clear sky model for global horizontal
irradiance (GHI), direct normal irradiance (DNI), and calculates
the clear-sky diffuse horizontal (DHI) component as the difference
between GHI and DNI*cos(zenith) as presented in [1, 2]. A report on clear
sky models found the Ineichen/Perez model to have excellent performance
with a minimal input data set [3].
Default values for montly Linke turbidity provided by SoDa [4, 5].
Parameters
-----------
time : pandas.DatetimeIndex
location : pvlib.Location
linke_turbidity : None or float
If None, uses ``LinkeTurbidities.mat`` lookup table.
solarposition_method : string
Sets the solar position algorithm.
See solarposition.get_solarposition()
zenith_data : None or pandas.Series
If None, ephemeris data will be calculated using ``solarposition_method``.
airmass_model : string
See pvlib.airmass.relativeairmass().
airmass_data : None or pandas.Series
If None, absolute air mass data will be calculated using
``airmass_model`` and location.alitude.
interp_turbidity : bool
If ``True``, interpolates the monthly Linke turbidity values
found in ``LinkeTurbidities.mat`` to daily values.
Returns
--------
DataFrame with the following columns: ``GHI, DNI, DHI``.
Notes
-----
If you are using this function
in a loop, it may be faster to load LinkeTurbidities.mat outside of
the loop and feed it in as a variable, rather than
having the function open the file each time it is called.
References
----------
[1] P. Ineichen and R. Perez, "A New airmass independent formulation for
the Linke turbidity coefficient", Solar Energy, vol 73, pp. 151-157, 2002.
[2] R. Perez et. al., "A New Operational Model for Satellite-Derived
Irradiances: Description and Validation", Solar Energy, vol 73, pp.
307-317, 2002.
[3] M. Reno, C. Hansen, and J. Stein, "Global Horizontal Irradiance Clear
Sky Models: Implementation and Analysis", Sandia National
Laboratories, SAND2012-2389, 2012.
[4] http://www.soda-is.com/eng/services/climat_free_eng.php#c5 (obtained
July 17, 2012).
[5] J. Remund, et. al., "Worldwide Linke Turbidity Information", Proc.
ISES Solar World Congress, June 2003. Goteborg, Sweden.
"""
# Initial implementation of this algorithm by Matthew Reno.
# Ported to python by Rob Andrews
# Added functionality by Will Holmgren
I0 = irradiance.extraradiation(time.dayofyear)
if zenith_data is None:
ephem_data = solarposition.get_solarposition(time, location, method=solarposition_method)
time = ephem_data.index # fixes issue with time possibly not being tz-aware
try:
ApparentZenith = ephem_data["apparent_zenith"]
except KeyError:
ApparentZenith = ephem_data["zenith"]
logger.warning("could not find apparent_zenith. using zenith")
else:
ApparentZenith = zenith_data
# ApparentZenith[ApparentZenith >= 90] = 90 # can cause problems in edge cases
if linke_turbidity is None:
# The .mat file 'LinkeTurbidities.mat' contains a single 2160 x 4320 x 12
# matrix of type uint8 called 'LinkeTurbidity'. The rows represent global
# latitudes from 90 to -90 degrees; the columns represent global longitudes
# from -180 to 180; and the depth (third dimension) represents months of
# the year from January (1) to December (12). To determine the Linke
# turbidity for a position on the Earth's surface for a given month do the
# following: LT = LinkeTurbidity(LatitudeIndex, LongitudeIndex, month).
# Note that the numbers within the matrix are 20 * Linke Turbidity,
# so divide the number from the file by 20 to get the
# turbidity.
try:
import scipy.io
except ImportError:
raise ImportError(
"The Linke turbidity lookup table requires scipy. "
+ "You can still use clearsky.ineichen if you "
+ "supply your own turbidities."
)
# consider putting this code at module level
this_path = os.path.dirname(os.path.abspath(__file__))
logger.debug("this_path={}".format(this_path))
mat = scipy.io.loadmat(os.path.join(this_path, "data", "LinkeTurbidities.mat"))
linke_turbidity = mat["LinkeTurbidity"]
LatitudeIndex = np.round_(_linearly_scale(location.latitude, 90, -90, 1, 2160))
LongitudeIndex = np.round_(_linearly_scale(location.longitude, -180, 180, 1, 4320))
g = linke_turbidity[LatitudeIndex][LongitudeIndex]
if interp_turbidity:
logger.info("interpolating turbidity to the day")
g2 = np.concatenate([[g[-1]], g, [g[0]]]) # wrap ends around
days = np.linspace(-15, 380, num=14) # map day of year onto month (approximate)
LT = pd.Series(np.interp(time.dayofyear, days, g2), index=time)
else:
logger.info("using monthly turbidity")
ApplyMonth = lambda x: g[x[0] - 1]
LT = pd.DataFrame(time.month, index=time)
LT = LT.apply(ApplyMonth, axis=1)
TL = LT / 20.0
logger.info("using TL=\n{}".format(TL))
else:
TL = linke_turbidity
# Get the absolute airmass assuming standard local pressure (per
# alt2pres) using Kasten and Young's 1989 formula for airmass.
if airmass_data is None:
AMabsolute = atmosphere.absoluteairmass(
AMrelative=atmosphere.relativeairmass(ApparentZenith, airmass_model),
pressure=atmosphere.alt2pres(location.altitude),
)
else:
AMabsolute = airmass_data
fh1 = np.exp(-location.altitude / 8000.0)
fh2 = np.exp(-location.altitude / 1250.0)
cg1 = 5.09e-05 * location.altitude + 0.868
cg2 = 3.92e-05 * location.altitude + 0.0387
logger.debug("fh1={}, fh2={}, cg1={}, cg2={}".format(fh1, fh2, cg1, cg2))
# Dan's note on the TL correction: By my reading of the publication on
# pages 151-157, Ineichen and Perez introduce (among other things) three
# things. 1) Beam model in eqn. 8, 2) new turbidity factor in eqn 9 and
# appendix A, and 3) Global horizontal model in eqn. 11. They do NOT appear
# to use the new turbidity factor (item 2 above) in either the beam or GHI
# models. The phrasing of appendix A seems as if there are two separate
# corrections, the first correction is used to correct the beam/GHI models,
# and the second correction is used to correct the revised turibidity
# factor. In my estimation, there is no need to correct the turbidity
# factor used in the beam/GHI models.
# Create the corrected TL for TL < 2
# TLcorr = TL;
# TLcorr(TL < 2) = TLcorr(TL < 2) - 0.25 .* (2-TLcorr(TL < 2)) .^ (0.5);
# This equation is found in Solar Energy 73, pg 311.
# Full ref: Perez et. al., Vol. 73, pp. 307-317 (2002).
# It is slightly different than the equation given in Solar Energy 73, pg 156.
# We used the equation from pg 311 because of the existence of known typos
# in the pg 156 publication (notably the fh2-(TL-1) should be fh2 * (TL-1)).
cos_zenith = tools.cosd(ApparentZenith)
clearsky_GHI = (
cg1 * I0 * cos_zenith * np.exp(-cg2 * AMabsolute * (fh1 + fh2 * (TL - 1))) * np.exp(0.01 * AMabsolute ** 1.8)
)
clearsky_GHI[clearsky_GHI < 0] = 0
# BncI == "normal beam clear sky radiation"
b = 0.664 + 0.163 / fh1
BncI = b * I0 * np.exp(-0.09 * AMabsolute * (TL - 1))
logger.debug("b={}".format(b))
# "empirical correction" SE 73, 157 & SE 73, 312.
BncI_2 = clearsky_GHI * (1 - (0.1 - 0.2 * np.exp(-TL)) / (0.1 + 0.882 / fh1)) / cos_zenith
# return BncI, BncI_2
clearsky_DNI = np.minimum(BncI, BncI_2) # Will H: use np.minimum explicitly
clearsky_DHI = clearsky_GHI - clearsky_DNI * cos_zenith
df_out = pd.DataFrame({"GHI": clearsky_GHI, "DNI": clearsky_DNI, "DHI": clearsky_DHI})
df_out.fillna(0, inplace=True)
# df_out['BncI'] = BncI
# df_out['BncI_2'] = BncI
return df_out
