8000 Temperature model parameter translation code by adriesse · Pull Request #1463 · pvlib/pvlib-python · GitHub
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Temperature model parameter translation code #1463

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Merged
merged 17 commits into from
Sep 13, 2022
Merged

Temperature model parameter translation code #1463

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2698d32
First commit to gather feedback on class design.
adriesse May 25, 2022
4ca0216
Changed set_*/get_* pattern to use_*/to_*
adriesse Jun 22, 2022
7f7acba
Add generic_linear() as a separate module temperature function and ad…
adriesse Jun 22, 2022
d924450
Merge branch 'pvlib:master' into tempmods
adriesse Aug 18, 2022
0b83f26
Add tests.
adriesse Aug 31, 2022
62f7367
Minor test edits.
adriesse Aug 31, 2022
2b2136a
One more test to achieve 100% coverage (hopefully).
adriesse Sep 1, 2022
0c36211
Some formatting, docstring development.
adriesse Sep 1, 2022
fbdec34
Try to update sphynx.
adriesse Sep 1, 2022
a3188f4
Try sphynx again.
adriesse Sep 1, 2022
91af074
Docstrings nearing completion.
adriesse Sep 1, 2022
12009c5
Docstrings complete.
adriesse Sep 1, 2022
5b2bc65
One more small name change.
adriesse Sep 1, 2022
21036ca
Fix problems identified in reviews.
adriesse Sep 3, 2022
602af41
Merge branch 'pvlib:master' into tempmods
adriesse Sep 12, 2022
62d1ca7
Update whatsnew.
adriesse Sep 12, 2022
d19b7e6
Merge branch 'master' into tempmods
kandersolar Sep 13, 2022
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Fix problems identified in reviews.
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@adriesse
adriesse committed Sep 3, 2022
commit 21036ca1214ea28af1ef076839559b71c26b3c2f
140 changes: 81 additions & 59 deletions pvlib/temperature.py
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Original file line number Diff line number Diff line change
Expand Up @@ -983,11 +983,11 @@ def prilliman(temp_cell, wind_speed, unit_mass=11.1, coefficients=None):
def generic_linear(poa_global, temp_air, wind_speed, u_const, du_wind,
module_efficiency, absorptance):
"""
Calculate cell temperature using a generic linear heat loss factor model
as developed in [1]_.
Calculate cell temperature using a generic linear heat loss factor model.

The parameters for this model can be obtained using
:py:class:`GenericLinearModel`
The parameters for this model can be obtained from other model
parameters using :py:class:`GenericLinearModel`. A description of this
model and its relationship to other temperature models is found in [1]_.

Parameters
----------
Expand All @@ -1000,10 +1000,10 @@ def generic_linear(poa_global, temp_air, wind_speed, u_const, du_wind,
wind_speed : numeric
Wind speed at a height of 10 meters [m/s].

u_const : numeric
u_const : float
Combined heat transfer coefficient at zero wind speed [(W/m^2)/C]

du_wind : numeric
du_wind : float
Influence of wind speed on combined heat transfer coefficient
[(W/m^2)/C/(m/s)]

Expand Down Expand Up @@ -1038,29 +1038,23 @@ def generic_linear(poa_global, temp_air, wind_speed, u_const, du_wind,

class GenericLinearModel():
'''
A generic linear temperature model class that can both use and convert
parameters of several well-known equivalent or nearly equivalent models:
faiman, pvsyst, noct-sam and sapm.

Normally this class is used on an ad hoc basis to make a needed conversion
to a target model, and the converted parameters are then used for
subsequent simulations running the target model. The parameters are
always returned as dictionaries that are compatible with the respective
model functions in pvlib.temperature.

An instance of the class represents a specific module type, therefore,
the module properties *efficiency* and *absorptance* must be provided.
A class that can both use and convert parameters of linear module
temperature models: faiman, pvsyst, noct_sam, sapm_module
and generic_linear.

Parameters are converted between models by first converting
to the generic linear heat transfer model [1]_ by the ``use_``
methods. The equivalent parameters for the target temperature
model are then obtained by the ``to_`` method.
Parameters are returned as a dictionary that is compatible with the
target model function to use in simulations.

An instance of the class represents a specific module type and
the parameters ``module_efficiency`` and ``absorptance`` are required.
Although some temperature models do not use these properties, they
nevertheless exist and affect operating temperature.

Since these are empirical models, their parameters are determined
from a limited set of measurements (usually high irradiance).
The values of efficiency and absorptance should be interpreted
as representative of the efficiency and absorptance actually
occuring during those measurements.

When used for time series simulation, efficiency and absorptance may
vary, and each empirical model handles this differently.
nevertheless exist and affect operating temperature. Values
should be representative of the conditions at which the input
model parameters were determined (usually high irradiance).

Parameters
----------
Expand All @@ -1073,8 +1067,9 @@ class GenericLinearModel():
Notes
-----
After creating a GenericLinearModel object using the module properties,
one of the use_* methods must be called to provide thermal model
parameters.
one of the ``use_`` methods must be called to provide thermal model
parameters. If this is not done, the ``to_`` methods will return ``nan``
values.

References
----------
Expand All @@ -1084,15 +1079,19 @@ class GenericLinearModel():

Examples
--------
glm = GenericLinearModel(module_efficiency=0.19, absorptance=0.88)

glm.use_faiman(16, 8)
>>> glm = GenericLinearModel(module_efficiency=0.19, absorptance=0.88)

glm.to_pvsyst()
>>> glm.use_faiman(16, 8)
GenericLinearModel: {'u_const': 11.04, 'du_wind': 5.52,
'eta': 0.19, 'alpha': 0.88}

parmdict = glm.to_pvsyst()
>>> glm.to_pvsyst()
{'u_c': 11.404800000000002, 'u_v': 5.702400000000001,
'module_efficiency': 0.19, 'alpha_absorption': 0.88}

pvsyst_cell(800, 20, 1, **parmdict)
>>> parmdict = glm.to_pvsyst()
>>> pvsyst_cell(800, 20, 1, **parmdict)
53.33333333333333

See also
--------
Expand All @@ -1106,6 +1105,7 @@ def __init__(self, module_efficiency, absorptance):
self.du_wind = np.nan
self.eta = module_efficiency
self.alpha = absorptance

return None

def __repr__(self):
Expand All @@ -1115,7 +1115,7 @@ def __repr__(self):
def __call__(self, poa_global, temp_air, wind_speed,
module_efficiency=None):
'''
Calculate module temperature using the generic linear model and
Calculate module temperature using the generic_linear model and
previously initialized parameters.

Parameters
Expand All @@ -1132,7 +1132,7 @@ def __call__(self, poa_global, temp_air, wind_speed,

module_efficiency : numeric, optional
Module electrical efficiency. The default value is the one
that was specified initially. [pu]
that was specified initially. [-]

Returns
-------
Expand All @@ -1146,19 +1146,17 @@ def __call__(self, poa_global, temp_air, wind_speed,
if module_efficiency is None:
module_efficiency = self.eta

heat_input = poa_global * (self.alpha - module_efficiency)
total_loss_factor = self.u_const + self.du_wind * wind_speed
temp_difference = heat_input / total_loss_factor

return temp_air + temp_difference
return generic_linear(poa_global, temp_air, wind_speed,
self.u_const, self.du_wind,
module_efficiency, self.alpha)

def get_generic_linear(self):
'''
Get the generic linear model parameters to use with the separate
generic linear module temperature calculation function.

Returns:
--------
Returns
-------
model_parameters : dict

See also
Expand All @@ -1170,9 +1168,9 @@ def get_generic_linear(self):
module_efficiency=self.eta,
absorptance=self.alpha)

def use_faiman(self, u0, u1, **kwargs):
def use_faiman(self, u0, u1):
'''
Use the Faiman model parameters to set the generic equivalents.
Use the Faiman model parameters to set the generic_model equivalents.

Parameters
----------
Expand Down Expand Up @@ -1204,7 +1202,7 @@ def to_faiman(self):
def use_pvsyst(self, u_c, u_v, module_efficiency=None,
alpha_absorption=None):
'''
Use the PVsyst model parameters to set the generic equivalents.
Use the PVsyst model parameters to set the generic_model equivalents.

Parameters
----------
Expand Down Expand Up @@ -1259,7 +1257,7 @@ def to_pvsyst(self):
def use_noct_sam(self, noct, module_efficiency=None,
transmittance_absorptance=None):
'''
Use the NOCT SAM model parameters to set the generic equivalents.
Use the NOCT SAM model parameters to set the generic_model equivalents.

Parameters
----------
Expand All @@ -1286,6 +1284,7 @@ def use_noct_sam(self, noct, module_efficiency=None,
u_noct = 800.0 * self.alpha / (noct - 20.0)
self.u_const = u_noct * 0.6
self.du_wind = u_noct * 0.4 * wind_adj

return self

def to_noct_sam(self):
Expand All @@ -1303,13 +1302,14 @@ def to_noct_sam(self):
wind_adj = 0.51
u_noct = self.u_const + self.du_wind / wind_adj
noct = 20.0 + (800.0 * self.alpha) / u_noct

return dict(noct=noct,
module_efficiency=self.eta,
transmittance_absorptance=self.alpha)

def use_sapm(self, a, b, wind_fit_low=1.4, wind_fit_high=5.4):
'''
Use the SAPM module model parameters to set the generic equivalents.
Use the SAPM model parameters to set the generic_model equivalents.

In the SAPM the heat transfer coefficient increases exponentially
with windspeed, whereas in the other models the increase is linear.
Expand All @@ -1320,12 +1320,22 @@ def use_sapm(self, a, b, wind_fit_low=1.4, wind_fit_high=5.4):
Parameters
----------
a, b : float
See :py:func:`pvlib.temperature.noct_sam` for details.
See :py:func:`pvlib.temperature.sapm_module` for details.

wind_fit_low, wind_fit_high : float, optional
Two wind speed values at which the generic linear model
must be equal to the SAPM model. The default
values represent wind speed at 10m height. [m/s]
wind_fit_low : float, optional
First wind speed value at which the generic linear model
must be equal to the SAPM model. [m/s]

wind_fit_high : float, optional
Second wind speed value at which the generic linear model
must be equal to the SAPM model. [m/s]

Notes
-----
The two default wind speed values are based on measurements
at 10 m height. Both the SAPM model and the conversion
functions can work with wind speed data at different heights as
long as the same height is used consistently throughout.
'''
u_low = 1.0 / np.exp(a + b * wind_fit_low)
u_high = 1.0 / np.exp(a + b * wind_fit_high)
Expand All @@ -1336,6 +1346,7 @@ def use_sapm(self, a, b, wind_fit_low=1.4, wind_fit_high=5.4):
net_absorptance = self.alpha - self.eta
self.u_const = u_const * net_absorptance
self.du_wind = du_wind * net_absorptance

return self

def to_sapm(self, wind_fit_low=1.4, wind_fit_high=5.4):
Expand All @@ -1350,16 +1361,26 @@ def to_sapm(self, wind_fit_low=1.4, wind_fit_high=5.4):

Parameters
----------
wind_fit_low, wind_fit_high : float, optional
Two wind speed values at which the generic linear model
must be equal to the SAPM model. The default
values represent wind speed at 10m height. [m/s]
wind_fit_low : float, optional
First wind speed value at which the generic linear model
must be equal to the SAPM model. [m/s]

wind_fit_high : float, optional
Second wind speed value at which the generic linear model
must be equal to the SAPM model. [m/s]

Returns
----------
model_parameters : dict
See :py:func:`pvlib.temperature.sapm_module` for
model parameter details.

Notes
-----
The two default wind speed values are based on measurements
at 10 m height. Both the SAPM model and the conversion
functions can work with wind speed data at different heights as
long as the same height is used consistently throughout.
'''
net_absorptance = self.alpha - self.eta
u_const = self.u_const / net_absorptance
Expand All @@ -1371,4 +1392,5 @@ def to_sapm(self, wind_fit_low=1.4, wind_fit_high=5.4):
b = - ((np.log(u_high) - np.log(u_low)) /
(wind_fit_high - wind_fit_low))
a = - (np.log(u_low) + b * wind_fit_low)

return dict(a=a, b=b)
0