Floating PV gallery example

docs/examples/floating-pv/README.rst

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+Floating PV Systems Modelling
+-----------------------------

docs/examples/floating-pv/plot_floating_pv_cell_temperature.py

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+r"""
+Calculating the cell temperature for floating PV
+================================================
+
+This example uses the PVSyst temperature model to calculate the
+cell temperature for floating photovoltaic (FPV) systems.
+
+One of the primary benefits attributed to FPV systems
+is lower operating temperatures, which are expected to increase the
+operating efficiency. In general, the temperature at which a photovoltaic
+module operates is influenced by various factors including solar radiation,
+ambient temperature, wind speed and direction, and the characteristics of the
+cell and module materials, as well as the mounting structure. Both radiative
+and convective heat transfers play roles in determining the module's
+temperature.
+
+A popular model for calculating the PV cell temperature is the
+empirical heat loss factor model suggested by Faiman
+(:py:func:`~pvlib.temperature.faiman`). A modified version of this model is
+implemented in PVSyst (:py:func:`~pvlib.temperature.pvsyst_cell`).
+The PVSyst model for cell temperature :math:`T_{C}` is given by:
+
+.. math::
+ :label: pvsyst
+
+ T_{C} = T_{a} + \frac{\alpha \cdot E \cdot (1 - \eta_{m})}{U_{c} + U_{v} \cdot WS},
+
+where :math:`E` is the plane-of-array irradiance, :math:`T_{a}` is the
+ambient air temperature, :math:`WS` is the wind speed, :math:`\alpha` is the
+absorbed fraction of the incident irradiance, :math:`\eta_{m}` is the
+electrical efficiency of the module, :math:`U_{c}` is the wind-independent heat
+loss coefficient, and :math:`U_{v}` is the wind-dependent heat loss coefficient.
+It should be noted that in many cases, similar to land-based PV systems,
+the wind-dependent heat loss coefficient (:math:`U_{v}`) can be set to zero,
+and the denominator is thus reduced to a single U-value equal to the
+wind-independent heat loss coefficient (:math:`U_{c}`).
+
+However, the default heat loss coefficient values of this model were
+specified for land-based PV systems and are not necessarily representative
+of FPV systems.
+
+In FPV systems, variations in heat loss coefficients are considerable, not
+only due to differences in design but also because of geographic factors.
+Systems with extensive water surfaces, closely packed modules, and restricted
+airflow behind the modules generally exhibit lower heat loss coefficients
+compared to those with smaller water surfaces and better airflow behind the
+modules.
+
+For FPV systems, the module's operating temperature, much like in land-based
+systems, is mainly influenced by the mounting structure (which significantly
+affects both U-value coefficients), wind, and air temperature. Thus, factors
+that help reduce operating temperatures in such systems include lower air
+temperatures and changes in air flow beneath the modules (wind/convection).
+In some designs, where the modules are in direct thermal contact with water,
+cooling effectiveness is largely dictated by the water temperature.
+
+The table below gives heat loss coefficients derived for different systems
+and locations as found in the literature. It should be noted that, for some
+systems, there are two sets of coefficients, where the second set uses only
+one heat loss coefficient (i.e., only :math:`U_{c}`). In this example, the FPV
+cell temperature will be calculated using the coefficients below.
+
+.. table:: Heat transfer coefficients for different PV systems
+ :widths: 40 15 15 15 15
+
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+ | System | Location |:math:`U_{c}` | :math:`U_{v}` | Reference |
+ | | |:math:`[\frac{W}{m^2 \cdot K}]` | :math:`[\frac{W}{m^3 \cdot K \cdot s}]`| |
+ +==========================+=============+================================+========================================+===========+
+ | - Monofacial module | Netherlands | 24.4 | 6.5 | [1]_ |
+ | - Open structure | | | | |
+ | - Two-axis tracking | | 57 | 0 | |
+ | - Small water footprint | | | | |
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+ | - Monofacial module | Netherlands | 25.2 | 3.7 | [1]_ |
+ | - Closed structure | | | | |
+ | - Large water footprint | | 37 | 0 | |
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+ | - Monofacial module | Singapore | 34.8 | 0.8 | [1]_ |
+ | - Closed structure | | | | |
+ | - Large water footprint | | 36 | 0 | |
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+ | - Monofacial module | Singapore | 18.9 | 8.9 | [1]_ |
+ | - Closed structure | | | | |
+ | - Medium water footprint | | 41 | 0 | |
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+ | - Monofacial module | Singapore | 35.3 | 8.9 | [1]_ |
+ | - Open structure | | | | |
+ | - Free-standing | | 55 | 0 | |
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+ | - Monofacial module | Norway | 71 | 0 | [2]_ |
+ | - In contact with water | | | | |
+ | - Calculated using water | | | | |
+ | temperature as | | | | |
+ | :math:`T_{amb}` | | | | |
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+ | - Monofacial module | South Italy | 31.9 | 1.5 | [3]_ |
+ | - Open structure | | | | |
+ | - Free-standing | | | | |
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+ | - Bifacial module | South Italy | 35.2 | 1.5 | [3]_ |
+ | - Open structure | | | | |
+ | - Free-standing | | | | |
+ +--------------------------+-------------+--------------------------------+----------------------------------------+-----------+
+
+References
+----------
+.. [1] Dörenkämper M., Wahed A., Kumar A., de Jong M., Kroon J., Reindl T.
+ (2021), 'The cooling effect of floating PV in two different climate zones:
+ A comparison of field test data from the Netherlands and Singapore'
+ Solar Energy, vol. 214, pp. 239-247, :doi:`10.1016/j.solener.2020.11.029`.
+
+.. [2] Kjeldstad T., Lindholm D., Marstein E., Selj J. (2021), 'Cooling of
+ floating photovoltaics and the importance of water temperature', Solar
+ Energy, vol. 218, pp. 544-551, :doi:`10.1016/j.solener.2021.03.022`.
+
+.. [3] Tina G.M., Scavo F.B., Merlo L., Bizzarri F. (2021), 'Comparative
+ analysis of monofacial and bifacial photovoltaic modules for floating
+ power plants', Applied Energy, vol 281, pp. 116084,
+ :doi:`10.1016/j.apenergy.2020.116084`.
+""" # noqa: E501
+
+# %%
+# Read example weather data
+# ^^^^^^^^^^^^^^^^^^^^^^^^^
+# Read weather data from a TMY3 file and calculate the solar position and
+# the plane-of-array irradiance.
+
+import pvlib
+import matplotlib.pyplot as plt
+from pathlib import Path
+
+# Assume a FPV system on a lake with the following specifications
+tilt = 30 # degrees
+azimuth = 180 # south-facing
+
+# Datafile found in the pvlib distribution
+data_file = Path(pvlib.__path__[0]).joinpath('data', '723170TYA.CSV')
+
+tmy, metadata = pvlib.iotools.read_tmy3(
+ data_file, coerce_year=2002, map_variables=True
+)
+tmy = tmy.filter(
+ ['ghi', 'dni', 'dni_extra', 'dhi', 'temp_air', 'wind_speed', 'pressure']
+) # remaining columns are not needed
+tmy = tmy['2002-06-06 00:00':'2002-06-06 23:59'] # select period
+
+solar_position = pvlib.solarposition.get_solarposition(
+ # TMY timestamp is at end of hour, so shift to center of interval
+ tmy.index.shift(freq='-30T'),
+ latitude=metadata['latitude'],
+ longitude=metadata['longitude'],
+ altitude=metadata['altitude'],
+ pressure=tmy['pressure'] * 100, # convert from millibar to Pa
+ temperature=tmy['temp_air'],
+)
+solar_position.index = tmy.index # reset index to end of the hour
+
+# Albedo calculation for inland water bodies
+albedo = pvlib.albedo.inland_water_dvoracek(
+ solar_elevation=solar_position['elevation'],
+ surface_condition='clear_water_no_waves'
+)
+
+# Use transposition model to find plane-of-array irradiance
+irradiance = pvlib.irradiance.get_total_irradiance(
+ surface_tilt=tilt,
+ surface_azimuth=azimuth,
+ solar_zenith=solar_position['apparent_zenith'],
+ solar_azimuth=solar_position['azimuth'],
+ dni=tmy['dni'],
+ dni_extra=tmy['dni_extra'],
+ ghi=tmy['ghi'],
+ dhi=tmy['dhi'],
+ albedo=albedo,
+ model='haydavies'
+)
+
+# %%
+# Calculate and plot cell temperature
+# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+# The temperature of the PV cell is calculated for lake-based floating PV
+# systems.
+
+# Make a dictionary containing all the sets of coefficients presented in the
+# above table.
+heat_loss_coeffs = {
+ 'open_structure_small_footprint_tracking_NL': [24.4, 6.5, 'C0', 'solid'],
+ 'open_structure_small_footprint_tracking_NL_2': [57, 0, 'C0', 'dashed'],
+ 'closed_structure_large_footprint_NL': [25.2, 3.7, 'C1', 'solid'],
+ 'closed_structure_large_footprint_NL_2': [37, 0, 'C1', 'dashed'],
+ 'closed_structure_large_footprint_SG': [34.8, 0.8, 'C2', 'solid'],
+ 'closed_structure_large_footprint_SG_2': [36, 0, 'C2', 'dashed'],
+ 'closed_structure_medium_footprint_SG': [18.9, 8.9, 'C3', 'solid'],
+ 'closed_structure_medium_footprint_SG_2': [41, 0, 'C3', 'dashed'],
+ 'open_structure_free_standing_SG': [35.3, 8.9, 'C4', 'solid'],
+ 'open_structure_free_standing_SG_2': [55, 0, 'C4', 'dashed'],
+ 'in_contact_with_water_NO': [71, 0, 'C5', 'solid'],
+ 'open_structure_free_standing_IT': [31.9, 1.5, 'C6', 'solid'],
+ 'open_structure_free_standing_bifacial_IT': [35.2, 1.5, 'C7', 'solid'],
+ 'default_PVSyst_coeffs_for_land_systems': [29.0, 0, 'C8', 'solid']
+}
+
+# Plot the cell temperature for each set of the above heat loss coefficients
+for coeffs in heat_loss_coeffs:
+ T_cell = pvlib.temperature.pvsyst_cell(
+ poa_global=irradiance['poa_global'],
+ temp_air=tmy['temp_air'],
+ wind_speed=tmy['wind_speed'],
+ u_c=heat_loss_coeffs[coeffs][0],
+ u_v=heat_loss_coeffs[coeffs][1]
+ )
+ # Convert Dataframe Indexes to Hour format to make plotting easier
+ T_cell.index = T_cell.index.strftime("%H")
+ plt.plot(T_cell, label=coeffs, c=heat_loss_coeffs[coeffs][2],
+ ls=heat_loss_coeffs[coeffs][3], alpha=0.8)
+
+plt.xlabel('Hour')
+plt.ylabel('PV cell temperature\n$[°C]$')
+plt.ylim(20, 45)
+plt.xlim('06', '20')
+plt.grid()
+plt.legend(loc='upper left', frameon=False, ncols=2, fontsize='x-small',
+ bbox_to_anchor=(0, -0.2))
+plt.tight_layout()
+plt.show()
+
+# %%
+# The figure above illustrates the necessity of choosing appropriate heat loss
+# coefficients when using the PVSyst model for calculating the cell temperature
+# for floating PV systems. A difference of up to 10.3°C was obtained when
+# using the default PVSyst coefficients and the coefficients when the panels
+# are in contact with water.
+#
+# It should be noted that, for the systems having both a single U-value and
+# a combination of :math:`U_c` and :math:`U_v`, approximately the same results
+# were obtained in the literature. However, in this example, there is a
+# difference in the calculated cell temperatures. The reason is that the wind
+# speed in the presented example is probably quite different than the one
+# measured in the corresponding test sites.

docs/sphinx/source/whatsnew/v0.11.1.rst

@@ -25,12 +25,15 @@ Testing
 
 Documentation
 ~~~~~~~~~~~~~
-
+* Gallery example on cell temperature for floating PV. (:pull:`2110`)
 
 Requirements
 ~~~~~~~~~~~~
 
 
 Contributors
 ~~~~~~~~~~~~
+* Ioannis Sifnaios (:ghuser:`IoannisSifnaios`)
+* Leonardo Micheli (:ghuser:`lmicheli`)
 * Echedey Luis (:ghuser:`echedey-ls`)
+