Use scipy.constants (#1617)

* use scipy.constants rather than hard-coded values

* update requirements to scipy>=1.4.0

* setup.py

* whatsnew"

* update scipy in asv

Author: cwhanse

benchmarks/asv.conf.json

@@ -117,7 +117,7 @@
             "build": "",
             "numpy": "1.16.0",
             "pandas": "0.25.0",
-            "scipy": "1.2.0",
+            "scipy": "1.4.0",
             // Note: these don't have a minimum in setup.py
             "h5py": "2.10.0",
             "ephem": "3.7.6.0",

ci/requirements-py3.10.yml

@@ -23,7 +23,7 @@ dependencies:
     - python=3.10
     - pytz
     - requests
-    - scipy >= 1.2.0
+    - scipy >= 1.4.0
     - shapely  # pvfactors dependency
     # - siphon  # conda-forge
     - statsmodels

ci/requirements-py3.7-min.yml

@@ -17,7 +17,7 @@ dependencies:
         - h5py==3.1.0
         - numpy==1.16.0
         - pandas==0.25.0
-        - scipy==1.2.0
+        - scipy==1.4.0
         - pytest-rerunfailures # conda version is >3.6
         - pytest-remotedata # conda package is 0.3.0, needs > 0.3.1
         - requests-mock

ci/requirements-py3.7.yml

@@ -23,7 +23,7 @@ dependencies:
     - python=3.7
     - pytz
     - requests
-    - scipy >= 1.2.0
+    - scipy >= 1.4.0
     - shapely  # pvfactors dependency
     - siphon  # conda-forge
     - statsmodels

ci/requirements-py3.8.yml

@@ -23,7 +23,7 @@ dependencies:
     - python=3.8
     - pytz
     - requests
-    - scipy >= 1.2.0
+    - scipy >= 1.4.0
     - shapely  # pvfactors dependency
     - siphon  # conda-forge
     - statsmodels

ci/requirements-py3.9.yml

@@ -23,7 +23,7 @@ dependencies:
     - python=3.9
     - pytz
     - requests
-    - scipy >= 1.2.0
+    - scipy >= 1.4.0
     - shapely  # pvfactors dependency
     # - siphon  # conda-forge
     - statsmodels

docs/sphinx/source/whatsnew/v0.9.4.rst

@@ -73,7 +73,7 @@ Benchmarking
 
 Requirements
 ~~~~~~~~~~~~
-
+* Minimum version of scipy advanced from 1.2.0 to 1.4.0 (:issue:`483`, :pull:`1617`)
 
 Contributors
 ~~~~~~~~~~~~

pvlib/ivtools/sdm.py

@@ -8,7 +8,7 @@
 
 import numpy as np
 
-import scipy.constants
+from scipy import constants
 from scipy import optimize
 from scipy.special import lambertw
 from scipy.misc import derivative
@@ -20,6 +20,9 @@
 from pvlib.ivtools.sde import _fit_sandia_cocontent
 
 
+CONSTANTS = {'E0': 1000.0, 'T0': 25.0, 'k': constants.k, 'q': constants.e}
+
+
 def fit_cec_sam(celltype, v_mp, i_mp, v_oc, i_sc, alpha_sc, beta_voc,
                 gamma_pmp, cells_in_series, temp_ref=25):
     """
@@ -204,7 +207,7 @@ def fit_desoto(v_mp, i_mp, v_oc, i_sc, alpha_sc, beta_voc, cells_in_series,
     """
 
     # Constants
-    k = scipy.constants.value('Boltzmann constant in eV/K')
+    k = constants.value('Boltzmann constant in eV/K')  # in eV/K
     Tref = temp_ref + 273.15  # [K]
 
     # initial guesses of variables for computing convergence:
@@ -340,9 +343,9 @@ def fit_pvsyst_sandia(ivcurves, specs, const=None, maxiter=5, eps1=1.e-3):
         T0 : float
             cell temperature at STC, default 25 [C]
         k : float
-            1.38066E-23 J/K (Boltzmann's constant)
+            Boltzmann's constant [J/K]
         q : float
-            1.60218E-19 Coulomb (elementary charge)
+            elementary charge [Coulomb]
 
     maxiter : int, default 5
         input that sets the maximum number of iterations for the parameter
@@ -417,7 +420,7 @@ def fit_pvsyst_sandia(ivcurves, specs, const=None, maxiter=5, eps1=1.e-3):
     """
 
     if const is None:
-        const = {'E0': 1000.0, 'T0': 25.0, 'k': 1.38066e-23, 'q': 1.60218e-19}
+        const = CONSTANTS
 
     ee = ivcurves['ee']
     tc = ivcurves['tc']
@@ -520,9 +523,9 @@ def fit_desoto_sandia(ivcurves, specs, const=None, maxiter=5, eps1=1.e-3):
         T0 : float
             cell temperature at STC, default 25 [C]
         k : float
-            1.38066E-23 J/K (Boltzmann's constant)
+            Boltzmann's constant [J/K]
         q : float
-            1.60218E-19 Coulomb (elementary charge)
+            elementary charge [Coulomb]
 
     maxiter : int, default 5
         input that sets the maximum number of iterations for the parameter
@@ -579,7 +582,7 @@ def fit_desoto_sandia(ivcurves, specs, const=None, maxiter=5, eps1=1.e-3):
     """
 
     if const is None:
-        const = {'E0': 1000.0, 'T0': 25.0, 'k': 1.38066e-23, 'q': 1.60218e-19}
+        const = CONSTANTS
 
     ee = ivcurves['ee']
     tc = ivcurves['tc']

pvlib/pvsystem.py

@@ -10,6 +10,7 @@
 import os
 from urllib.request import urlopen
 import numpy as np
+from scipy import constants
 import pandas as pd
 from dataclasses import dataclass
 from abc import ABC, abstractmethod
@@ -2043,8 +2044,8 @@ def calcparams_desoto(effective_irradiance, temp_cell,
          Source: [4]
     '''
 
-    # Boltzmann constant in eV/K
-    k = 8.617332478e-05
+    # Boltzmann constant in eV/K, 8.617332478e-05
+    k = constants.value('Boltzmann constant in eV/K')
 
     # reference temperature
     Tref_K = temp_ref + 273.15
@@ -2301,10 +2302,10 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     '''
 
     # Boltzmann constant in J/K
-    k = 1.38064852e-23
+    k = constants.k
 
     # elementary charge in coulomb
-    q = 1.6021766e-19
+    q = constants.e
 
     # reference temperature
     Tref_K = temp_ref + 273.15
@@ -2576,8 +2577,8 @@ def sapm(effective_irradiance, temp_cell, module):
     temp_ref = 25
     irrad_ref = 1000
 
-    q = 1.60218e-19  # Elementary charge in units of coulombs
-    kb = 1.38066e-23  # Boltzmann's constant in units of J/K
+    q = constants.e  # Elementary charge in units of coulombs
+    kb = constants.k  # Boltzmann's constant in units of J/K
 
     # avoid problem with integer input
     Ee = np.array(effective_irradiance, dtype='float64') / irrad_ref

setup.py

@@ -38,7 +38,7 @@
                     'pandas >= 0.25.0',
                     'pytz',
                     'requests',
-                    'scipy >= 1.2.0',
+                    'scipy >= 1.4.0',
                     'h5py',
                     'importlib-metadata; python_version < "3.8"']