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| 1 | +.. _temperature: |
| 2 | + |
| 3 | +Temperature models |
| 4 | +================== |
| 5 | + |
| 6 | +pvlib provides a variety of models for predicting the operating temperature |
| 7 | +of a PV module from irradiance and weather inputs. These models range from |
| 8 | +simple empirical equations requiring just a few multiplications to complex |
| 9 | +thermal balance models with numerical integration. |
| 10 | + |
| 11 | +Types of models |
| 12 | +--------------- |
| 13 | + |
| 14 | +Temperature models predict one of two quantities: |
| 15 | + |
| 16 | +- *module temperature*: the temperature as measured at the back surface |
| 17 | + of a PV module. Easy to measure, but not directly related to PV |
| 18 | + efficiency. |
| 19 | +- *cell temperature*: the temperature of the PV cell itself. The relevant |
| 20 | + temperature for PV modeling, but almost never measured directly. |
| 21 | + |
| 22 | +Cell temperature is typically thought to be slightly higher than module |
| 23 | +temperature. |
| 24 | +Temperature models estimate these quantities using inputs like incident |
| 25 | +irradiance, ambient temperature, and wind speed. Each model also takes |
| 26 | +a set of parameter values that represent how a PV module responds to |
| 27 | +those inputs. Different parameter values may be used for different PV |
| 28 | +module technologies and/or the mounting conditions of the module. |
| 29 | + |
| 30 | +Another way to classify temperature models is whether they account for |
| 31 | +the thermal inertia of a PV module. Temperature models are either: |
| 32 | + |
| 33 | +- *steady-state*: the module is assumed to have been at the specified operating |
| 34 | + conditions for a sufficiently long time for its temperature to reach |
| 35 | + equilibrium. |
| 36 | +- *transient*: the module's thermal inertia is included in the model, |
| 37 | + causing a lag in modeled temperature change following changes in the inputs. |
| 38 | + |
| 39 | +Other effects that temperature models may consider include variation in |
| 40 | +photoconversion efficiency and radiative cooling. |
| 41 | + |
| 42 | +The temperature models currently available in pvlib are summarized in the |
| 43 | +following table: |
| 44 | + |
| 45 | ++-------------------------------------------+--------+------------+--------------------------------------------------------------------+ |
| 46 | +| Model | Type | Transient? | Inputs | |
| 47 | +| | | +----------------+---------------------+------------+----------------+ |
| 48 | +| | | | POA irradiance | Ambient temperature | Wind speed | Downwelling IR | |
| 49 | ++===========================================+========+============+================+=====================+============+================+ |
| 50 | +| :py:func:`~pvlib.temperature.faiman` | either | | ✓ | ✓ | ✓ | | |
| 51 | ++-------------------------------------------+--------+------------+----------------+---------------------+------------+----------------+ |
| 52 | +| :py:func:`~pvlib.temperature.faiman_rad` | either | | ✓ | ✓ | ✓ | ✓ | |
| 53 | ++-------------------------------------------+--------+------------+----------------+---------------------+------------+----------------+ |
| 54 | +| :py:func:`~pvlib.temperature.fuentes` | cell | ✓ | ✓ | ✓ | ✓ | | |
| 55 | ++-------------------------------------------+--------+------------+----------------+---------------------+------------+----------------+ |
| 56 | +| :py:func:`~pvlib.temperature.noct_sam` | cell | | ✓ | ✓ | ✓ | | |
| 57 | ++-------------------------------------------+--------+------------+----------------+---------------------+------------+----------------+ |
| 58 | +| :py:func:`~pvlib.temperature.pvsyst_cell` | cell | | ✓ | ✓ | ✓ | | |
| 59 | ++-------------------------------------------+--------+------------+----------------+---------------------+------------+----------------+ |
| 60 | +| :py:func:`~pvlib.temperature.ross` | cell | | ✓ | ✓ | | | |
| 61 | ++-------------------------------------------+--------+------------+----------------+---------------------+------------+----------------+ |
| 62 | +| :py:func:`~pvlib.temperature.sapm_cell` | cell | | ✓ | ✓ | ✓ | | |
| 63 | ++-------------------------------------------+--------+------------+----------------+---------------------+------------+----------------+ |
| 64 | +| :py:func:`~pvlib.temperature.sapm_module` | module | | ✓ | ✓ | ✓ | | |
| 65 | ++-------------------------------------------+--------+------------+----------------+---------------------+------------+----------------+ |
| 66 | + |
| 67 | + |
| 68 | +Model parameters |
| 69 | +---------------- |
| 70 | + |
| 71 | +Some temperature model functions provide default values for their parameters, |
| 72 | +and several additional sets of temperature model parameter values are |
| 73 | +available in :py:data:`pvlib.temperature.TEMPERATURE_MODEL_PARAMETERS`. |
| 74 | +However, these generic values may not be suitable for all modules. |
| 75 | + |
| 76 | +Module-specific values can be obtained via testing, for example following |
| 77 | +the IEC 61853-2 standard. |
| 78 | + |
| 79 | +Currently, pvlib provides no functionality for fitting parameter values |
| 80 | +using measured temperature. |
| 81 | + |
| 82 | + |
| 83 | +Other functions |
| 84 | +--------------- |
| 85 | + |
| 86 | +pvlib also provides a few other functions for temperature modeling: |
| 87 | + |
| 88 | +- :py:func:`~pvlib.temperature.prilliman`: an "add-on" model that introduces |
| 89 | + transience to steady-state models. |
| 90 | +- :py:func:`~pvlib.temperature.sapm_cell_from_module`: a model for |
| 91 | + estimating cell temperature from module temperature. |
| 92 | +- :py:func:`~pvlib.temperature.generic_linear`: a generic linear model form, |
| 93 | + equivalent to several conventional temperature models. |
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