Add calcparams_desoto+singlediode example to gallery (#872)

* Create plot_singlediode.py

* Apply suggestions from code review

Co-Authored-By: Cliff Hansen <[email protected]>

* RST cleanup, reorder legend entries

* Formatting fixes

* whatsnew

* whatsnewer

* sorry, one formatting fix

* stickler

Co-authored-by: Cliff Hansen <[email protected]>

Author: kandersolar

docs/examples/plot_singlediode.py

@@ -0,0 +1,143 @@
+"""
+Calculating a module's IV curves
+=====================
+
+Examples of modeling IV curves using a single-diode circuit equivalent model.
+"""
+
+# %%
+# Calculating a module IV curve for certain operating conditions is a two-step
+# process.  Multiple methods exist for both parts of the process.  Here we use
+# the De Soto model [1]_ to calculate the electrical parameters for an IV
+# curve at a certain irradiance and temperature using the module's
+# base characteristics at reference conditions.  Those parameters are then used
+# to calculate the module's IV curve by solving the single-diode equation using
+# the Lambert W method.
+#
+# The single-diode equation is a circuit-equivalent model of a PV
+# cell and has five electrical parameters that depend on the operating
+# conditions.  For more details on the single-diode equation and the five
+# parameters, see the `PVPMC single diode page
+# <https://pvpmc.sandia.gov/modeling-steps/2-dc-module-iv/diode-equivalent-circuit-models/>`_.
+#
+# References
+# ----------
+#  .. [1] W. De Soto et al., "Improvement and validation of a model for
+#     photovoltaic array performance", Solar Energy, vol 80, pp. 78-88, 2006.
+#
+# Calculating IV Curves
+# -----------------------
+# This example uses :py:meth:`pvlib.pvsystem.calcparams_desoto` to calculate
+# the 5 electrical parameters needed to solve the single-diode equation.
+# :py:meth:`pvlib.pvsystem.singlediode` is then used to generate the IV curves.
+
+from pvlib import pvsystem
+import pandas as pd
+import matplotlib.pyplot as plt
+
+# Example module parameters for the Canadian Solar CS5P-220M:
+parameters = {
+    'Name': 'Canadian Solar CS5P-220M',
+    'BIPV': 'N',
+    'Date': '10/5/2009',
+    'T_NOCT': 42.4,
+    'A_c': 1.7,
+    'N_s': 96,
+    'I_sc_ref': 5.1,
+    'V_oc_ref': 59.4,
+    'I_mp_ref': 4.69,
+    'V_mp_ref': 46.9,
+    'alpha_sc': 0.004539,
+    'beta_oc': -0.22216,
+    'a_ref': 2.6373,
+    'I_L_ref': 5.114,
+    'I_o_ref': 8.196e-10,
+    'R_s': 1.065,
+    'R_sh_ref': 381.68,
+    'Adjust': 8.7,
+    'gamma_r': -0.476,
+    'Version': 'MM106',
+    'PTC': 200.1,
+    'Technology': 'Mono-c-Si',
+}
+
+cases = [
+    (1000, 55),
+    (800, 55),
+    (600, 55),
+    (400, 25),
+    (400, 40),
+    (400, 55)
+]
+
+conditions = pd.DataFrame(cases, columns=['Geff', 'Tcell'])
+
+# adjust the reference parameters according to the operating
+# conditions using the De Soto model:
+IL, I0, Rs, Rsh, nNsVth = pvsystem.calcparams_desoto(
+    conditions['Geff'],
+    conditions['Tcell'],
+    alpha_sc=parameters['alpha_sc'],
+    a_ref=parameters['a_ref'],
+    I_L_ref=parameters['I_L_ref'],
+    I_o_ref=parameters['I_o_ref'],
+    R_sh_ref=parameters['R_sh_ref'],
+    R_s=parameters['R_s'],
+    EgRef=1.121,
+    dEgdT=-0.0002677
+)
+
+# plug the parameters into the SDE and solve for IV curves:
+curve_info = pvsystem.singlediode(
+    photocurrent=IL,
+    saturation_current=I0,
+    resistance_series=Rs,
+    resistance_shunt=Rsh,
+    nNsVth=nNsVth,
+    ivcurve_pnts=100,
+    method='lambertw'
+)
+
+# plot the calculated curves:
+plt.figure()
+for i, case in conditions.iterrows():
+    label = (
+        "$G_{eff}$ " + f"{case['Geff']} $W/m^2$\n"
+        "$T_{cell}$ " + f"{case['Tcell']} $C$"
+    )
+    plt.plot(curve_info['v'][i], curve_info['i'][i], label=label)
+    v_mp = curve_info['v_mp'][i]
+    i_mp = curve_info['i_mp'][i]
+    # mark the MPP
+    plt.plot([v_mp], [i_mp], ls='', marker='o', c='k')
+
+plt.legend(loc=(1.0, 0))
+plt.xlabel('Module voltage [V]')
+plt.ylabel('Module current [A]')
+plt.title(parameters['Name'])
+plt.show()
+plt.gcf().set_tight_layout(True)
+
+
+# draw trend arrows
+def draw_arrow(ax, label, x0, y0, rotation, size, direction):
+    style = direction + 'arrow'
+    bbox_props = dict(boxstyle=style, fc=(0.8, 0.9, 0.9), ec="b", lw=1)
+    t = ax.text(x0, y0, label, ha="left", va="bottom", rotation=rotation,
+                size=size, bbox=bbox_props, zorder=-1)
+
+    bb = t.get_bbox_patch()
+    bb.set_boxstyle(style, pad=0.6)
+
+
+ax = plt.gca()
+draw_arrow(ax, 'Irradiance', 20, 2.5, 90, 15, 'r')
+draw_arrow(ax, 'Temperature', 35, 1, 0, 15, 'l')
+
+print(pd.DataFrame({
+    'i_sc': curve_info['i_sc'],
+    'v_oc': curve_info['v_oc'],
+    'i_mp': curve_info['i_mp'],
+    'v_mp': curve_info['v_mp'],
+    'p_mp': curve_info['p_mp'],
+}))

docs/sphinx/source/whatsnew/v0.7.2.rst

@@ -26,6 +26,7 @@ Bug fixes
 Documentation
 ~~~~~~~~~~~~~
 * Add NumFOCUS affiliation to Sphinx documentation :pull:`862`
+* Add example of IV curve generation :pull:`872` 
 
 Requirements
 ~~~~~~~~~~~~
@@ -38,4 +39,4 @@ Contributors
 * Cameron T. Stark (:ghuser:`camerontstark`)
 * Will Holmgren (:ghuser:`wholmgren`)
 * Kevin Anderson (:ghuser:`kanderso-nrel`)
-* Karthikeyan Singaravelan (:ghuser:`tirkarthi`)
+* Karthikeyan Singaravelan (:ghuser:`tirkarthi`)