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Merged
merged 15 commits into from
May 31, 2018
Merged

Expose first_solar_spectral_correction #466

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ffd685c
Add first_solar_spectral_correction method, improve infer_spectral_model
cwhanse May 23, 2018
0881f01
edits: input testing, first_solar_spectral_coefficients name
cwhanse May 25, 2018
6d47188
rename first_solar_spectral_correction method to first_solar_spectral…
cwhanse May 25, 2018
7a04b02
add test for pvsystem.first_solar_spectral_loss
cwhanse May 25, 2018
88fe65e
Fix declarations of weather and airmass in test_spectral_models
cwhanse May 26, 2018
2da94e3
Correct errors and expected value in test_spectral_models
cwhanse May 28, 2018
210e813
Fix space error
cwhanse May 28, 2018
dec5d95
Fix handling of weather in test_spectral_models
cwhanse May 28, 2018
0732b4c
Change test_PVSystem_first_solar_spectral_loss and test_spectral_models
cwhanse May 29, 2018
ce78670
Fix error in first_solar_spectral_loss
cwhanse May 29, 2018
e8de2e0
Formatting and flake8
cwhanse May 30, 2018
bd7e119
Add constant_spectral_loss back to test_spectral_models arguments
cwhanse May 30, 2018
19de627
Fix line continuation in pvsystem.py
cwhanse May 30, 2018
67a4561
whatsnew, docstring for pvsystem.first_solar_spectral_loss, remove no…
cwhanse May 30, 2018
e4724ae
Fix typo in pvsystem.py
cwhanse May 30, 2018
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13 changes: 10 additions & 3 deletions pvlib/modelchain.py
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Original file line number Diff line number Diff line change
Expand Up @@ -532,7 +532,7 @@ def spectral_model(self, model):
elif isinstance(model, str):
model = model.lower()
if model == 'first_solar':
raise NotImplementedError
self._spectral_model = self.first_solar_spectral_loss
elif model == 'sapm':
self._spectral_model = self.sapm_spectral_loss
elif model == 'no_loss':
Expand All @@ -546,13 +546,20 @@ def infer_spectral_model(self):
params = set(self.system.module_parameters.keys())
if set(['A4', 'A3', 'A2', 'A1', 'A0']) <= params:
return self.sapm_spectral_loss
elif ('Technology' in params or
'Material' in params or
'fs_spectral_coefficients' in params):
return self.first_solar_spectral_loss
else:
raise ValueError('could not infer spectral model from '
'system.module_parameters')

def first_solar_spectral_loss(self):
raise NotImplementedError

self.spectral_modifier = self.system.first_solar_spectral_loss(
self.weather['precipitable_water'],
self.airmass['airmass_absolute'])
return self

def sapm_spectral_loss(self):
self.spectral_modifier = self.system.sapm_spectral_loss(
self.airmass['airmass_absolute'])
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85 changes: 85 additions & 0 deletions pvlib/pvsystem.py
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Original file line number Diff line number Diff line change
Expand Up @@ -421,6 +421,91 @@ def sapm_effective_irradiance(self, poa_direct, poa_diffuse,
poa_direct, poa_diffuse, airmass_absolute, aoi,
self.module_parameters, reference_irradiance=reference_irradiance)

def first_solar_spectral_correction(self, pw, airmass_absolute):

"""
Use the :py:func:`first_solar_spectral_correction` function to
calculate the spectral loss modifier.
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Doc string should have some kind of reference to self.module_parameters. Most of the other PVSystem method doc strings have some examples. This method is a little more complicated though, so might be worth being more explicit about what is looked for. For example...

Use the :py:func:first_solar_spectral_correction function to calculate the spectral loss modifier. The spectral loss modifier is determined by searching for one of the following keys in self.module_parameters (in order): 'first_solar_spectral_coefficients', 'Technology', 'Material'.

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    Use the :py:func:`first_solar_spectral_correction` function to
    calculate the spectral loss modifier. The model coefficients are
    specific to the module's cell type, and are determined by searching
    for one of the following keys in self.module_parameters (in order):
        'first_solar_spectral_coefficients (user-supplied coefficients)
        'Technology' - a string describing the cell type, can be read from
        the CEC module parameter database
        'Material' - a string describing the cell type, can be read from
        the Sandia module database.


Parameters
----------
pw : array-like
atmospheric precipitable water (cm).

airmass_absolute : array-like
absolute (pressure corrected) airmass.

Returns
-------
modifier: array-like
spectral mismatch factor (unitless) which is can be multiplied
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typo (is can) that is carried over from the original function's doc string.

with broadband irradiance reaching a module's cells to estimate
effective irradiance, i.e., the irradiance that is converted to
electrical current.
"""

if self.module_parameters['fs_spectral_coefficients']:
coefficients = self.module_parameters['fs_spectral_coefficients']
module_type = None
else:
module_type = self._infer_cell_type()
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module vs. cell is unfortunate here. No objection to what you've done, but we might need a separate discussion to try to clean up the terminology within the library.

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Here I'm inclined to break the API and change the keyword argument from module_type to cell_type. module_type is only used by the first_solar function.

coefficients = None

if (module_type is not None and coefficients is None) or \
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Recommend removing this if/else statement. If this method doesn't have the information necessary to successfully compute the spectral correction, then this method should say so rather than defaulting to 1.

Consistent with Python's style, the atmosphere.first_solar_spectral_correction function throws a TypeError with some hint as to what the user needs to supply. We could (ideally/optionally) catch that error here and reraise it with a more specific message for how to modify module_parameters to make this work.

I am guessing that raising an exception here will cause issues in a ModelChain calculation for the few module/cell types for which _infer_cell_type mapping returns None. One approach to avoid that may be to make the ModelChain.infer_spectral_model preemptively call pvsystem._infer_cell_type.

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Good idea. I'll move the test to ModelChain.infer_spectral_model and put a warning in place of that check in the actual functions.

(module_type is None and coefficients is not None):
return atmosphere.first_solar_spectral_correction(pw,
airmass_absolute,
module_type,
coefficients)
else:
# default to no_spectral_loss function
return 1

def _infer_cell_type(self):

"""
Examines module_parameters and maps the Technology key for the CEC
database and the Material key for the Sandia database to a common
list of strings for cell type.

Returns
-------
cell_type: str

"""

_cell_type_dict = {'Multi-c-Si': 'multisi',
'Mono-c-Si': 'monosi',
'Thin Film': 'cigs',
'a-Si/nc': 'asi',
'CIS': 'cigs',
'CIGS': 'cigs',
'1-a-Si': 'asi',
'CdTe': 'cdte',
'a-Si': 'asi',
'2-a-Si': None,
'3-a-Si': None,
'HIT-Si': 'monosi',
'mc-Si': 'multisi',
'c-Si': 'multisi',
'Si-Film': 'asi',
'CdTe': 'cdte',
'EFG mc-Si': 'multisi',
'GaAs': None,
'a-Si / mono-Si': 'monosi'}

if 'Technology' in self.module_parameters.keys():
# CEC module parameter set
cell_type = _cell_type_dict[self.module_parameters['Technology']]
elif 'Material' in self.module_parameters.keys():
# Sandia module parameter set
cell_type = _cell_type_dict[self.module_parameters['Material']]
else:
cell_type = None

return cell_type


def singlediode(self, photocurrent, saturation_current,
resistance_series, resistance_shunt, nNsVth,
ivcurve_pnts=None):
Expand Down