Merge branch 'celltemp' of https://github.com/cwhanse/pvlib-python into celltemp

Author: cwhanse

pvlib/celltemp.py

@@ -0,0 +1,189 @@
+# -*- coding: utf-8 -*-
+"""
+Created on Fri Mar 29 09:40:42 2019
+
+@author: cwhanse
+"""
+
+import numpy as np
+import pandas as pd
+
+
+TEMP_MODEL_PARAMS = {
+    'sapm': {'open_rack_cell_glassback': (-3.47, -.0594, 3),
+             'roof_mount_cell_glassback': (-2.98, -.0471, 1),
+             'open_rack_cell_polymerback': (-3.56, -.0750, 3),
+             'insulated_back_polymerback': (-2.81, -.0455, 0),
+             'open_rack_polymer_thinfilm_steel': (-3.58, -.113, 3),
+             '22x_concentrator_tracker': (-3.23, -.130, 13)},
+    'pvsyst': {'freestanding': (29.0, 0), 'insulated': (15.0, 0)}
+}
+
+
+def sapm(poa_global, wind_speed, temp_air, model='open_rack_cell_glassback'):
+    '''
+    Estimate cell and module temperatures per the Sandia PV Array
+    Performance Model (SAPM, SAND2004-3535), from the incident
+    irradiance, wind speed, ambient temperature, and SAPM module
+    parameters.
+
+    Parameters
+    ----------
+    poa_global : float or Series
+        Total incident irradiance in W/m^2.
+
+    wind_speed : float or Series
+        Wind speed in m/s at a height of 10 meters.
+
+    temp_air : float or Series
+        Ambient dry bulb temperature in degrees C.
+
+    model : string, list, or dict, default 'open_rack_cell_glassback'
+        Model to be used.
+
+        If string, can be:
+
+            * 'open_rack_cell_glassback' (default)
+            * 'roof_mount_cell_glassback'
+            * 'open_rack_cell_polymerback'
+            * 'insulated_back_polymerback'
+            * 'open_rack_polymer_thinfilm_steel'
+            * '22x_concentrator_tracker'
+
+        If dict, supply the following parameters
+        (if list, in the following order):
+
+            * a : float
+                SAPM module parameter for establishing the upper
+                limit for module temperature at low wind speeds and
+                high solar irradiance.
+
+            * b : float
+                SAPM module parameter for establishing the rate at
+                which the module temperature drops as wind speed increases
+                (see SAPM eqn. 11).
+
+            * deltaT : float
+                SAPM module parameter giving the temperature difference
+                between the cell and module back surface at the
+                reference irradiance, E0.
+
+    Returns
+    --------
+    DataFrame with columns 'temp_cell' and 'temp_module'.
+    Values in degrees C.
+
+    References
+    ----------
+    [1] King, D. et al, 2004, "Sandia Photovoltaic Array Performance
+    Model", SAND Report 3535, Sandia National Laboratories, Albuquerque,
+    NM.
+
+    See Also
+    --------
+    sapm
+    '''
+
+    temp_models = TEMP_MODEL_PARAMS['sapm']
+
+    if isinstance(model, str):
+        model = temp_models[model.lower()]
+
+    elif isinstance(model, (dict, pd.Series)):
+        model = [model['a'], model['b'], model['deltaT']]
+
+    a = model[0]
+    b = model[1]
+    deltaT = model[2]
+
+    E0 = 1000.  # Reference irradiance
+
+    temp_module = pd.Series(poa_global * np.exp(a + b * wind_speed) + temp_air)
+
+    temp_cell = temp_module + (poa_global / E0) * (deltaT)
+
+    return pd.DataFrame({'temp_cell': temp_cell, 'temp_module': temp_module})
+
+
+def pvsyst(poa_global, temp_air, wind_speed=1.0, eta_m=0.1,
+           alpha_absorption=0.9, model_params='freestanding'):
+    """
+    Calculate cell temperature using an emperical heat loss factor model
+    as implemented in PVsyst.
+
+    The heat loss factors provided through the 'model_params' argument
+    represent the combined effect of convection, radiation and conduction,
+    and their values are experimentally determined.
+
+    Parameters
+    ----------
+    poa_global : numeric
+        Total incident irradiance in W/m^2.
+
+    temp_air : numeric
+        Ambient dry bulb temperature in degrees C.
+
+    wind_speed : numeric, default 1.0
+        Wind speed in m/s measured at the same height for which the wind loss
+        factor was determined.  The default value is 1.0, which is the wind
+        speed at module height used to determine NOCT.
+
+    eta_m : numeric, default 0.1
+        Module external efficiency as a fraction, i.e., DC power / poa_global.
+
+    alpha_absorption : numeric, default 0.9
+        Absorption coefficient
+
+    model_params : string, tuple, or list (no dict), default 'freestanding'
+        Heat loss factors to be used.
+
+        If string, can be:
+
+            * 'freestanding' (default)
+                Modules with rear surfaces exposed to open air (e.g. rack
+                mounted).
+            * 'insulated'
+                Modules with rear surfaces in close proximity to another
+                surface (e.g. roof mounted).
+
+        If tuple/list, supply parameters in the following order:
+
+            * constant_loss_factor : float
+                Combined heat loss factor coefficient. Freestanding
+                default is 29, fully insulated arrays is 15.
+
+            * wind_loss_factor : float
+                Combined heat loss factor influenced by wind. Default is 0.
+
+    Returns
+    -------
+    temp_cell : numeric or Series
+        Cell temperature in degrees Celsius
+
+    References
+    ----------
+    [1]"PVsyst 6 Help", Files.pvsyst.com, 2018. [Online]. Available:
+    http://files.pvsyst.com/help/index.html. [Accessed: 10- Dec- 2018].
+
+    [2] Faiman, D. (2008). "Assessing the outdoor operating temperature of
+    photovoltaic modules." Progress in Photovoltaics 16(4): 307-315.
+    """
+
+    pvsyst_presets = TEMP_MODEL_PARAMS['pvsyst']
+
+    if isinstance(model_params, str):
+        model_params = model_params.lower()
+        constant_loss_factor, wind_loss_factor = pvsyst_presets[model_params]
+    elif isinstance(model_params, (tuple, list)):
+        constant_loss_factor, wind_loss_factor = model_params
+    else:
+        raise TypeError(
+            "Please provide model_params as a str, or tuple/list."
+        )
+
+    total_loss_factor = wind_loss_factor * wind_speed + constant_loss_factor
+    heat_input = poa_global * alpha_absorption * (1 - eta_m)
+    temp_difference = heat_input / total_loss_factor
+    temp_cell = temp_air + temp_difference
+
+    return temp_cell