plot_oedi_9068.py

"""
4.7 MW CdTe single-axis tracking (OEDI System 9068)
===================================================

A basic model of a 4.7 MW single-axis tracking CdTe system located in
Colorado, United States.
"""
# %%
# This example model uses satellite-based solar resource data from the
# NSRDB PSM3. This approach is useful for pre-construction energy modeling
# and in retrospective analyses where the system’s own irradiance
# measurements are not present or unreliable.
#
# The system has public monitoring data available at the Open Energy Data
# Initiative (OEDI) under `System ID
# 9068 <https://data.openei.org/s3_viewer?bucket=oedi-data-lake&prefix=pvdaq%2F2023-solar-data-prize%2F9068_OEDI%2F>`__.
# For more information about the system, see its `OEDI
# page <https://openei.org/wiki/PVDAQ/Sites/SR_CO>`__.

# sphinx_gallery_thumbnail_path = "_images/OEDI_9068_daily_timeseries.png"
import pvlib
import pandas as pd
import matplotlib.pyplot as plt

# %%
# System parameters
# -----------------
#
# The system description on the OEDI provides some high-level system
# information, but unfortunately we have to make some guesses about other
# aspects of the system’s configuration.
#
# The cells below define the system parameter values required in the
# simulation.

# information provided by system description on OEDI

latitude = 40.3864
longitude = -104.5512

# the inverters have identical PV array topologies:
modules_per_string = 15
strings_per_inverter = 1344

# %%

# "unofficial" information

# We know the system uses 117.5 W CdTe modules. Based on the system vintage
# (data begins in 2017), it seems likely that the array uses First Solar
# Series 4 modules (FS-4117).
cec_module_db = pvlib.pvsystem.retrieve_sam('cecmod')
module_parameters = cec_module_db['First_Solar__Inc__FS_4117_3']
# ensure that correct spectral correction is applied
module_parameters['Technology'] = 'CdTe'

# default Faiman model parameters:
temperature_model_parameters = dict(u0=25.0, u1=6.84)
module_unit_mass = 12 / 0.72  # kg/m^2, taken from datasheet values

# The OEDI metadata says the inverters have AC capacities of 1910 kW,
# but the clipping level in the measured inverter output is more like 1840 kW.
# It's not clear what specific model is installed, so let's just assume
# this inverter, which the CEC database lists as having a nominal AC
# capacity of 1833 kW:
cec_inverter_db = pvlib.pvsystem.retrieve_sam('cecinverter')
inverter_parameters = cec_inverter_db['TMEIC__PVL_L1833GRM']

# We'll use the PVWatts v5 losses model. Set shading to zero as it is
# accounted for elsewhere in the model, and disable availability loss since
# we want a "clean" simulation.
# Leaving the other pvwatts loss types (mismatch, wiring, etc) unspecified
# causes them to take their default values.
losses_parameters = dict(shading=0, availability=0)

# Google Street View images show that each row is four modules high, in
# landscape orientation. Assuming the modules are First Solar Series 4,
# each of them is 600 mm wide.
# Assume ~1 centimeter gap between modules (three gaps total).
# And from Google Earth, the array's pitch is estimated to be about 7.0 meters.
# From these we calculate the ground coverage ratio (GCR):
pitch = 7  # meters
gcr = (4 * 0.6 + 3 * 0.01) / pitch

# The tracker rotation measurements reveal that the tracker rotation limits
# are +/- 60 degrees, and backtracking is not enabled:
max_angle = 60  # degrees
backtrack = False

# Google Earth shows that the tracker axes are very close to north-south:
axis_azimuth = 180  # degrees

# Estimated from Google Street View images
axis_height = 1.5  # meters

# %%
# Create system objects
# ---------------------
#
# The system has two inverters which seem to have identical specifications
# and arrays. To save some code and computation repetition, we will just
# model one inverter.

location = pvlib.location.Location(latitude, longitude)
mount = pvlib.pvsystem.SingleAxisTrackerMount(
    gcr=gcr,
    backtrack=backtrack,
    max_angle=max_angle,
    axis_azimuth=axis_azimuth
)
array = pvlib.pvsystem.Array(
    mount,
    module_parameters=module_parameters,
    modules_per_string=modules_per_string,
    temperature_model_parameters=temperature_model_parameters,
    strings=strings_per_inverter
)
system = pvlib.pvsystem.PVSystem(
    array,
    inverter_parameters=inverter_parameters,
    losses_parameters=losses_parameters
)

model = pvlib.modelchain.ModelChain(
    system,
    location,
    spectral_model='first_solar',
    aoi_model='physical',
    losses_model='pvwatts'
)

# %%
# Fetch weather data
# ------------------
#
# The system does have measured plane-of-array irradiance data, but the
# measurements suffer from row-to-row shading and tracker stalls. In this
# example, we will use weather data taken from the NSRDB PSM3 for the year
# 2019.

api_key = 'DEMO_KEY'
email = 'your_email@domain.com'

keys = ['ghi', 'dni', 'dhi', 'temp_air', 'wind_speed',
        'albedo', 'precipitable_water']
psm3, psm3_metadata = pvlib.iotools.get_psm3(latitude, longitude, api_key,
                                             email, interval=5, names=2019,
                                             map_variables=True, leap_day=True,
                                             attributes=keys)

# %%
# Pre-generate some model inputs
# ------------------------------
#
# This system’s trackers are configured to not backtrack, meaning the
# array shades itself when the sun is low in the sky. pvlib’s
# ``ModelChain`` currently has no shade modeling ability, so we will model
# it separately.
#
# Since this system uses thin-film modules, oriented in such a way that
# row-to-row shadows affect each cell in the module equally, we can assume
# that the effect of shading is linear with the reduction in incident beam
# irradiance. That means we can use pvlib’s infinite sheds model, which
# penalizes incident beam irradiance according to the calculated shaded
# module fraction and returns the average irradiance over the total module
# surface.

solar_position = location.get_solarposition(psm3.index, latitude, longitude)
tracker_angles = mount.get_orientation(
    solar_position['apparent_zenith'],
    solar_position['azimuth']
)
dni_extra = pvlib.irradiance.get_extra_radiation(psm3.index)

# note: this system is monofacial, so only calculate irradiance for the
# front side:
averaged_irradiance = pvlib.bifacial.infinite_sheds.get_irradiance_poa(
    tracker_angles['surface_tilt'], tracker_angles['surface_azimuth'],
    solar_position['apparent_zenith'], solar_position['azimuth'],
    gcr, axis_height, pitch,
    psm3['ghi'], psm3['dhi'], psm3['dni'], psm3['albedo'],
    model='haydavies', dni_extra=dni_extra,
)

# %%
# ``ModelChain`` does not consider thermal transience either, so since we
# are using 5-minute weather data, we will precalculate the cell
# temperature as well:

cell_temperature_steady_state = pvlib.temperature.faiman(
    poa_global=averaged_irradiance['poa_global'],
    temp_air=psm3['temp_air'],
    wind_speed=psm3['wind_speed'],
    **temperature_model_parameters,
)

cell_temperature = pvlib.temperature.prilliman(
    cell_temperature_steady_state,
    psm3['wind_speed'],
    unit_mass=module_unit_mass
)

# %%
# Run the model
# -------------
#
# Finally, we are ready to run the rest of the system model. Since we want
# to use pre-calculated plane-of-array irradiance, we will use
# :py:meth:`~pvlib.modelchain.ModelChain.run_model_from_poa`:

weather_inputs = pd.DataFrame({
    'poa_global': averaged_irradiance['poa_global'],
    'poa_direct': averaged_irradiance['poa_direct'],
    'poa_diffuse': averaged_irradiance['poa_diffuse'],
    'cell_temperature': cell_temperature,
    'precipitable_water': psm3['precipitable_water'],  # for the spectral model
})
model.run_model_from_poa(weather_inputs)


# %%
# Compare with measured production
# --------------------------------
#
# Now, let’s compare our modeled AC power with the system’s actual
# inverter-level AC power measurements:

fn = r"path/to/9068_ac_power_data.csv"
df_inverter_measured = pd.read_csv(fn, index_col=0, parse_dates=True)
df_inverter_measured = df_inverter_measured.tz_localize('US/Mountain',
                                                        ambiguous='NaT',
                                                        nonexistent='NaT')
# convert to standard time to match the NSRDB-based simulation
df_inverter_measured = df_inverter_measured.tz_convert('Etc/GMT+7')

# %%

inverter_ac_powers = [
    'inverter_1_ac_power_(kw)_inv_150143',
    'inverter_2_ac_power_(kw)_inv_150144'
]
df = df_inverter_measured.loc['2019', inverter_ac_powers]
df['model'] = model.results.ac / 1000  # convert W to kW

# %%

for column_name in inverter_ac_powers:
    fig, axes = plt.subplots(1, 3, figsize=(12, 4))
    df.plot.scatter('model', column_name, ax=axes[0], s=1, alpha=0.1)
    axes[0].axline((0, 0), slope=1, c='k')
    axes[0].set_ylabel('Measured 5-min power [kW]')
    axes[0].set_xlabel('Modeled 5-min power [kW]')

    hourly_average = df.resample('h').mean()
    hourly_average.plot.scatter('model', column_name, ax=axes[1], s=2)
    axes[1].axline((0, 0), slope=1, c='k')
    axes[1].set_ylabel('Measured hourly energy [kWh]')
    axes[1].set_xlabel('Modeled hourly energy [kWh]')

    daily_total = hourly_average.resample('d').sum()
    daily_total.plot.scatter('model', column_name, ax=axes[2], s=5)
    axes[2].axline((0, 0), slope=1, c='k')
    axes[2].set_ylabel('Measured daily energy [kWh]')
    axes[2].set_xlabel('Modeled daily energy [kWh]')

    fig.suptitle(column_name)
    fig.tight_layout()


# %%
# .. image:: ../../_images/OEDI_9068_inverter1_comparison.png
#
# .. image:: ../../_images/OEDI_9068_inverter2_comparison.png

fig, ax = plt.subplots(figsize=(12, 4))
daily_energy = df.clip(lower=0).resample('h').mean().resample('d').sum()
daily_energy.plot(ax=ax)
plt.ylim(bottom=0)
plt.ylabel('Daily Production [kWh]')
plt.tight_layout()

# %%
# .. image:: ../../_images/OEDI_9068_daily_timeseries.png