Switching from FLORIS v3 to v4

Switching from FLORIS v3 to v4#

There are several major changes introduced in FLORIS v4. The largest underlying change is that, where FLORIS v3 had a "wind directions" and a "wind speeds" dimension to its internal data structures, FLORIS v4 collapses these into a single dimension, which we refer to as the findex dimension. This dimension contains each "configuration" or "condition" to be run, and is conceptually similar to running FLORIS v3 in time_series mode. At the user interface level, the largest implication of this change is that users must specify wind_directions, wind_speeds, and turbulence_intensities (new) as arrays of equal length; and these are "zipped" to create the conditions for FLORIS to run, rather than creating a grid of all combinations. This is discussed further in Setting and Running.

Setting and running#

In FLORIS v3, users interacted with FLORIS by instantiating a FlorisInterface object, nominally called fi. The notion here is that the users "interface" with the underlying FLORIS code using fi. For FLORIS v4, we acknowledge that to most users, this main "interface" object, for all intents and purposes, is FLORIS. We therefore have renamed the FlorisInterface the FlorisModel, nominally instantiated as fmodel. To instantiate a FlorisModel, the code is very similar to before, i.e.

from floris import FlorisModel

fmodel = FlorisModel("input_file.yaml")

Previously, to set the atmospheric conditions on fi, users called the reinitialize() method; and to run the calculations, as well as provide any control setpoints such as yaw angles, users generally called calculate_wake(). Some of the other methods on FlorisInterface also called calculate_wake() internally, most notably get_farm_AEP().

For FLORIS v4, we have changed from the (reinitialize(), calculate_wake()) paradigm to a new pair of methods (set(), run()). set() is similar to the retired reinitialize() method, and run() is similar to the retired calculate_wake() method. However, there are some important differences:

  • FlorisModel.set() accepts both atmospheric conditions and control setpoints.

  • FlorisModel.run() accept no arguments. Its sole function is to run the FLORIS calculation.

  • Control setpoints are now "remembered". Previously, if control setpoints (yaw_angles) were passed to calculate_wake(), they were discarded at the end of the calculation. In FLORIS v4, the control setpoints passed to set() are stored, and invoking run() multiple times will continue to use those control setpoints.

  • To "forget" previously provided control setpoints, use the new method FlorisModel.reset_operation().

  • When providing arguments to set(), all arguments much have the same length, as they will be "paired" (rather than gridded) for the computation. For instance, if the user provides n_findex wind directions, they must provide n_findex wind speeds and n_findex turbulence intensities; as well as n_findexxn_turbines yaw angles, if yaw angles are being used.

  • Providing varying turbulence_intensities is new for FLORIS v4.

  • To facilitate "easier" use of the set() method (for instance, to run all combinations of wind directions and wind speeds), we now provide WindData objects that can be passed directly to set()'s wind_data keyword argument. See Wind data as well as Wind Data Objects for more information.

  • calculate_no_wake() has been replaced with run_no_wake()

  • get_farm_AEP() no longer calls run(); to compute the farm AEP, users should run() the fmodel themselves before calling get_farm_AEP().

An example workflow for using set and run is:

import numpy as np
from floris import FlorisModel

fmodel = FlorisModel("input_file.yaml") # Input file with 3 turbines

# Set up a base case and run
fmodel.set(
    wind_directions=np.array([270., 270.]),
    wind_speeds=np.array([8.0, 8.0]),
    turbulence_intensities=np.array([0.06, 0.06])
)
fmodel.run()
turbine_powers_base = fmodel.get_turbine_powers()

# Provide yaw angles
fmodel.set(
    yaw_angles=np.array([[10.0, 0.0, 0.0], [20.0, 0.0, 0.0]]) # n_findex x n_turbines
)
fmodel.run()
turbine_powers_yawed = fmodel.get_turbine_powers()

# If we run again, this time with no wake, the provided yaw angles will still be used
fmodel.run_no_wake()
turbine_powers_yawed_nowake = fmodel.get_turbine_powers()

# To "forget" the yaw angles, we use the reset_operation method
fmodel.reset_operation()
fmodel.run_no_wake()
turbine_powers_base_nowake = fmodel.get_turbine_powers()

For more advanced users, it is best to group many conditions into single calls of set and run than to step through various conditions individually, as this will make the best use of FLORIS's vectorization capabilities.

Input files#

As in FLORIS v3, there are two main input files to FLORIS v4:

  1. The "main" FLORIS input yaml, which contains wake model parameters and wind farm data

  2. The "turbine" input yaml, which contains data about the wind turbines

Examples for main FLORIS input yamls are in examples/inputs/. Default turbine yamls, which many users may use if they do not have their own turbine models to use, can be found in floris/turbine_library/. See also Turbine Library Interface and Main Input File Reference.

Conceptually, both the main FLORIS input yaml and the turbine input yaml is much the same in v4 as in v3. However, there are a few changes to the fields on each that mean that existing yamls for v3 will not run in v4 as is.

Main FLORIS input yaml#

On the main FLORIS input file, the turbulence_intensity field (onflow_field), which was specified as a scalar in FLORIS v3, has been changed to turbulence_intensities, and should now contain a list of turbulence intensities that is of the same length as wind_directions and wind_speeds. Additionally, the length of the lists for wind_directions and wind_speeds must now be of equal length.

In addition, a new field enable_active_wake_mixing has been added to the wake field, which users may set to false unless they would like to use active wake mixing strategies such as Helix.

Turbine input yaml#

To reflect the transition to more flexible operation models, there are a number of changes to the fields on the turbine yaml. The changes are mostly regrouping and renaming of the existing fields.

  • The power_thrust_table field now has wind_speed and power fields, as before; however, the thrust field has been renamed thrust_coefficient for clarity, and the power field now specifies the turbine absolute power (in kW) rather than the power coefficient.

  • Additionally, any extra parameters and data required by operation models to evaluate the power and thrust curves have been moved onto the power_thrust_table field. This includes ref_density_cp_ct (renamed ref_air_density and moved onto the power_thrust_table); ref_tilt_cp_ct (renamed ref_tilt and moved onto the power_thrust_table); and pP and pT (renamed cosine_loss_exponent_yaw and cosine_loss_exponent_tilt, respectively, and moved onto the power_thrust_table).

  • The generator_efficiency field has been removed. The power field on power_thrust_table should reflect the electrical power produced by the turbine, including any losses.

  • A new field operation_model has been added, whose value should be a string that selects the operation model the user would like to evaluate. The default is "cosine-loss", which recovers FLORIS v3-type turbine operation. See Operation model and Turbine Operation Models for details.

Converting v3 yamls to v4#

To aid users in converting their existing v3 main FLORIS input yamls and turbine input, we provide two utilities:

  • floris/tools/convert_floris_input_v3_to_v4.py

  • floris/tools/convert_turbine_v3_to_v4.py

These can be executed from the command line and expect to be passed the exiting v3 yaml as an input; the will then write a new v4-compatible yaml of the same name but appended _v4.

python convert_floris_input_v3_to_v4.py your_v3_input_file.yaml
python convert_floris_turbine_v3_to_v4.py your_v3_turbine_file.yaml

Additionally, a function for building a turbine dictionary that can be passed directly to the turbine_type argument of FlorisModel.set() is provided:

from floris.turbine_library.turbine_utilities import build_cosine_loss_turbine_dict

Reference turbine updates#

The power and thrust curves for the NREL 5MW, IEA 10MW, and IEA 15MW turbines have been updated slightly do reflect publicly available data. The x_20MW reference turbine has been removed, as data was not readily available. See Turbine Library Interface.

Wind data#

To aid users in setting the wind conditions they are interested in running, we provide "wind data" classes, which can be passed directly to FlorisModel.set()'s wind_data keyword argument in place of wind_directions, wind_speeds, and turbulence_intensities. The wind data objects enable, for example, gridding inputs (WindRose and WindTIRose) and broadcasting a scalar-valued turbulence intensity (TimeSeries).

import numpy as np
from floris import FlorisModel
from floris import TimeSeries

fmodel = FlorisModel("input_file.yaml") # Input file with 3 turbines

time_series = TimeSeries(
    wind_directions=np.array([270.0, 270.0]),
    wind_speeds=8.0,
    turbulence_intensities=0.06
)
fmodel.set(wind_data=time_series)
fmodel.set(wind_data=time_series)turbine_powers_base = fmodel.get_turbine_powers()
turbine_powers = fmodel.get_turbine_powers()

More information about the various wind data classes can be found at Wind Data Objects.

Operation model#

FLORIS v4 allows for significantly more flexible turbine operation via Turbine Operation Models. These allow users to specify how a turbine loses power when yaw misaligned; how a turbine operates when derated; and how turbines produce power and thrust when operating with active wake mixing strategies. The default operation model is the "cosine-loss" model, which models a turbine's power loss when in yaw misalignment using the same cosine model as was hardcoded in FLORIS v3.

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