Add Huld PV model

docs/sphinx/source/reference/pv_modeling/system_models.rst

@@ -47,3 +47,11 @@ ADR model
 
    pvarray.pvefficiency_adr
    pvarray.fit_pvefficiency_adr
+
+PVGIS model
+^^^^^^^^^^^
+
+.. autosummary::
+   :toctree: ../generated/
+
+    pvsystem.huld

docs/sphinx/source/whatsnew/v0.10.4.rst

@@ -7,6 +7,7 @@ v0.10.4 (Anticipated March, 2024)
 
 Enhancements
 ~~~~~~~~~~~~
+* Added the Huld PV model (:pull:`1940`)
 
 
 Bug fixes
@@ -27,4 +28,4 @@ Requirements
 
 Contributors
 ~~~~~~~~~~~~
-
+* Cliff Hansen (:ghuser:`cwhanse`)

pvlib/pvsystem.py

@@ -2845,6 +2845,81 @@ def pvwatts_dc(g_poa_effective, temp_cell, pdc0, gamma_pdc, temp_ref=25.):
     return pdc
 
 
+def _infer_k_huld(cell_type):
+    # from PVGIS documentation, Section 5.2.3, accessed 12/22/2023
+    huld_params = {'cSi': (-0.017237, -0.040465, -0.004702, 0.000149,
+                           0.000170, 0.000005),
+                   'CIS': (-0.005554, -0.038724, -0.003723, -0.000905,
+                           -0.001256, 0.000001),
+                   'CdTe': (-0.046689, -0.072844, -0.002262, 0.000276,
+                            0.000159, -0.000006)}
+    return huld_params[cell_type]
+
+
+def huld(effective_irradiance, temp_mod, pdc0, k=None, cell_type=None):
+    r"""
+    Power (DC) using the Huld model.
+
+    The Huld model [1]_ is used by PVGIS and is given by
+
+
+    .. math::
+
+        P_{dc} = G' ( P_{dc0} + k_1 \log(G') + k_2 \log^2 (G') + k_3 T' +
+                 k_4 T' \log(G') + k_5 T' \log^2 (G') + k_6 T'^2)
+
+        G' = \frac{G_{poa eff}}{1000}
+
+        T' = T_{mod} - 25 °C
+
+
+    Parameters
+    ----------
+    effective_irradiance : numeric
+        The irradiance that is converted to photocurrent. [W/m^2]
+    temp_mod: numeric
+        Module back-surface temperature. [C]
+    pdc0: numeric
+        Power of the modules at 1000 W/m^2 and cell reference temperature. [W]
+    k : tuple, optional
+        Empirical coefficients used in the power model. Length 6. If `k` is
+        not provided, `cell_type` must be specified.
+    cell_type : str, optional
+        If provided, must be one of `'cSi'`, `'CIS'`, or `'CdTe'`. Used to look
+        up default values for `k` if `k` is not specified.
+
+    Returns
+    -------
+    pdc: numeric
+        DC power. [W]
+
+    Raises
+    ------
+    ValueError
+        If neither `k` nor `cell_type` are specified.
+
+    References
+    ----------
+    .. [1] T. Huld, G. Friesen, A. Skoczek, R. Kenny, T. Sample, M. Field,
+           E. Dunlop. A power-rating model for crystalline silicon PV modules.
+           Solar Energy Materials and Solar Cells 95, (2011), pp. 3359-3369.
+           :doi:`10.1016/j.solmat.2011.07.026`.
+    """
+    if k is None:
+        if cell_type is not None:
+            k = _infer_k_huld(cell_type)
+        else:
+            raise ValueError('Either k or cell_type must be specified')
+
+    gprime = effective_irradiance / 1000
+    tprime = temp_mod - 25
+    # Eq. 1 in [1]
+    pdc = gprime * (pdc0 + k[0] * np.log(gprime) + k[1] * np.log(gprime)**2 +
+                    k[2] * tprime + k[3] * tprime * np.log(gprime) +
+                    k[4] * tprime * np.log(gprime)**2 + k[5] * tprime**2)
+    return pdc
+
+
 def pvwatts_losses(soiling=2, shading=3, snow=0, mismatch=2, wiring=2,
                    connections=0.5, lid=1.5, nameplate_rating=1, age=0,
                    availability=3):

pvlib/tests/test_pvsystem.py

@@ -2549,3 +2549,25 @@ def test_Array_temperature_missing_parameters(model, keys):
         array.temperature_model_parameters = params
         with pytest.raises(KeyError, match=match):
             array.get_cell_temperature(irrads, temps, winds, model)
+
+
+def test_huld():
+    pdc0 = 100
+    res = pvsystem.huld(1000, 25, pdc0, cell_type='cSi')
+    assert np.isclose(res, pdc0)
+    exp_sum = np.exp(1) * (np.sum(pvsystem._infer_k_huld('cSi')) + pdc0)
+    res = pvsystem.huld(1000*np.exp(1), 26, pdc0, cell_type='cSi')
+    assert np.isclose(res, exp_sum)
+    res = pvsystem.huld(100, 30, pdc0, k=(1, 1, 1, 1, 1, 1))
+    exp_100 = 0.1 * (pdc0 + np.log(0.1) + np.log(0.1)**2 + + 5 + 5*np.log(0.1)
+                     + 5*np.log(0.1)**2 + 25)
+    assert np.isclose(res, exp_100)
+    # Series input
+    eff_irr = pd.Series([1000, 100])
+    tm = pd.Series([25, 30])
+    expected = pd.Series([pdc0, exp_100])
+    res = pvsystem.huld(eff_irr, tm, pdc0, k=(1, 1, 1, 1, 1, 1))
+    assert_allclose(res, expected)
+    with pytest.raises(ValueError,
+                       match='Either k or cell_type must be specified'):
+        res = pvsystem.huld(1000, 25, 100)