Add guidance about temperature modeling to User Guide #2591
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| .. _temperature: | ||
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| Temperature models | ||
| ================== | ||
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| pvlib provides a variety of models for predicting the operating temperature | ||
| of a PV module from irradiance and weather inputs. These models range from | ||
| simple empirical equations requiring just a few multiplications to more complex | ||
| thermal balance models with numerical integration. | ||
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| Types of models | ||
| --------------- | ||
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| Temperature models predict one of two quantities: | ||
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| - *module temperature*: the temperature as measured at the back surface | ||
| of a PV module. Easy to measure, but usually marginally less | ||
| than the cell temperature which determines efficiency. | ||
| - *cell temperature*: the temperature of the PV cell itself. The relevant | ||
| temperature for PV modeling, but almost never measured directly. | ||
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| Temperature models estimate these quantities using inputs like incident | ||
| irradiance, ambient temperature, and wind speed. Each model also takes | ||
| a set of parameter values that represent how a PV module responds to | ||
| those inputs. Parameter values generally depend on both the PV | ||
| module technologies, the mounting configuration of the module, | ||
| and on any weather parameters that are not included in the model. | ||
| Note that, despite models conventionally being associated with either | ||
| cell or module temperature, it is actually the parameter values that determine | ||
| which of the two temperatures are predicted, as they will produce the same | ||
| type of temperature from which they were originally derived. | ||
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| Another aspect of temperature models is whether they account for | ||
| the thermal inertia of a PV module. Temperature models are either: | ||
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| - *steady-state*: the module is assumed to have been at the specified operating | ||
| conditions for a sufficiently long time for its temperature to reach | ||
| equilibrium. | ||
| - *transient*: the module's thermal inertia is included in the model, | ||
| causing a lag in modeled temperature change following changes in the inputs. | ||
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| Other effects that temperature models may consider include the | ||
| photoconversion efficiency and radiative cooling. | ||
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| The temperature models currently available in pvlib are summarized in the | ||
| following table: | ||
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| +----------------------------------------------+--------+------------+---------------------------------------------------------------------------+ | ||
| | Model | Type | Transient? | Inputs | | ||
| | | | +----------------+---------------------+------------+-----------------------+ | ||
| | | | | POA irradiance | Ambient temperature | Wind speed | Downwelling IR [#f1]_ | | ||
| +==============================================+========+============+================+=====================+============+=======================+ | ||
| | :py:func:`~pvlib.temperature.faiman` | either | | ✓ | ✓ | ✓ | | | ||
| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
| | :py:func:`~pvlib.temperature.faiman_rad` | either | | ✓ | ✓ | ✓ | ✓ | | ||
| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
| | :py:func:`~pvlib.temperature.fuentes` | either | ✓ | ✓ | ✓ | ✓ | | | ||
| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
| | :py:func:`~pvlib.temperature.generic_linear` | cell | | ✓ | ✓ | ✓ | | | ||
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| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
| | :py:func:`~pvlib.temperature.noct_sam` | cell | | ✓ | ✓ | ✓ | | | ||
| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
| | :py:func:`~pvlib.temperature.pvsyst_cell` | cell | | ✓ | ✓ | ✓ | | | ||
| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
| | :py:func:`~pvlib.temperature.ross` | cell | | ✓ | ✓ | | | | ||
| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
| | :py:func:`~pvlib.temperature.sapm_cell` | cell | | ✓ | ✓ | ✓ | | | ||
| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
| | :py:func:`~pvlib.temperature.sapm_module` | module | | ✓ | ✓ | ✓ | | | ||
| +----------------------------------------------+--------+------------+----------------+---------------------+------------+-----------------------+ | ||
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| .. [#f1] Downwelling infrared radiation. | ||
| In addition to the core models above, pvlib provides several other functions | ||
| for temperature modeling: | ||
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| - :py:func:`~pvlib.temperature.prilliman`: an "add-on" model that reprocesses | ||
| the output of a steady-state model to apply transient effects. | ||
| - :py:func:`~pvlib.temperature.sapm_cell_from_module`: a model for | ||
| estimating cell temperature from module temperature. | ||
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| Model parameters | ||
| ---------------- | ||
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| Some temperature model functions provide default values for their parameters, | ||
| and several additional sets of temperature model parameter values are | ||
| available in :py:data:`pvlib.temperature.TEMPERATURE_MODEL_PARAMETERS`. | ||
| However, these generic values may not be suitable for all modules and mounting | ||
| configurations. It should be noted that using the default parameter values for each | ||
| model generally leads to different modules temperature predictions. This alone | ||
| does not mean one model is better than another; it's just evidence that the measurements | ||
| used to derive the default parameter values were taken on different PV systems in different | ||
| locations under different conditions. | ||
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| Parameter values for one model (e.g. ``u0``, ``u1`` for :py:func:`~pvlib.temperature.faiman`) | ||
| can be converted to another model (e.g. ``u_c``, ``u_v`` for :py:func:`~pvlib.temperature.pvsyst_cell`) | ||
| using :py:class:`~pvlib.temperature.GenericLinearModel`. | ||
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| Module-specific values can be obtained via testing, for example following | ||
| the IEC 61853-2 standard for the Faiman model; however, such values still do not capture | ||
| the dependency of temperature on system design and other variables. | ||
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| Currently, pvlib provides no functionality for fitting parameter values | ||
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There was a problem hiding this comment. I'm not sure pointing to external functionality makes sense for these pages. Let's save that for a potential follow-up.
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There was a problem hiding this comment. What kind of "sense" are we looking for? Pointing to solutions takes the edge off the foregoing limitation a bit. I think the new spectrum section has similar pointers. But I leave the decision to you. |
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| using measured temperature. | ||
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I see the doc string says cell temperature, but the model is really agnostic as in principle all the others are too. I recommend putting "either" here possibly flag the docstring to be changed. In the class description module temperature is used.