Example: Floating vs fixed-bottom farm

This example demonstrates the impact of floating on turbine power and thrustand wake behavior. A floating turbine in FLORIS is defined by including afloating_tilt_table in the turbine input yaml which sets the steady tiltangle of the turbine based on wind speed. This tilt angle is computed for eachturbine based on effective velocity. This tilt angle is then passed onto the respective wake model.The value of the parameter ref_tilt is the value of tilt at which thect/cp curves have been defined.With correct_cp_ct_for_tilt True, the difference between the currenttilt as interpolated from the floating tilt table is used to scale the turbinepower and thrust.In the example below, a 20-turbine, gridded wind farm is simulated usingthe Empirical Gaussian wake model to show the effects of floating turbines onboth turbine power and wake development.fmodel_fixed: Fixed bottom turbine (no tilt variation with wind speed)fmodel_floating: Floating turbine (tilt varies with wind speed)

import matplotlib.pyplot as plt
import numpy as np
import pandas as pd
from scipy.interpolate import NearestNDInterpolator

import floris.flow_visualization as flowviz
from floris import FlorisModel, WindRose


# Declare the Floris Interface for fixed bottom, provide layout
fmodel_fixed = FlorisModel("../inputs_floating/emgauss_fixed.yaml")
fmodel_floating = FlorisModel("../inputs_floating/emgauss_floating.yaml")
x, y = np.meshgrid(np.linspace(0, 4*630., 5), np.linspace(0, 3*630., 4))
x = x.flatten()
y = y.flatten()
for fmodel in [fmodel_fixed, fmodel_floating]:
    fmodel.set(layout_x=x, layout_y=y)

# Compute a single wind speed and direction, power and wakes
for fmodel in [fmodel_fixed, fmodel_floating]:
    fmodel.set(
        layout_x=x,
        layout_y=y,
        wind_speeds=[10],
        wind_directions=[270],
        turbulence_intensities=[0.06],
    )
    fmodel.run()

powers_fixed = fmodel_fixed.get_turbine_powers()
powers_floating = fmodel_floating.get_turbine_powers()
power_difference = powers_floating - powers_fixed

# Show the power differences
fig, ax = plt.subplots()
ax.set_aspect('equal', adjustable='box')
sc = ax.scatter(
    x,
    y,
    c=power_difference.flatten()/1000,
    cmap="PuOr",
    vmin=-30,
    vmax=30,
    s=200,
)
ax.set_xlabel("x coordinate [m]")
ax.set_ylabel("y coordinate [m]")
ax.set_title("Power increase due to floating for each turbine.")
plt.colorbar(sc, label="Increase (kW)")

print("Power increase from floating over farm (10m/s, 270deg winds): {0:.2f} kW".\
    format(power_difference.sum()/1000))

# Visualize flows (see also 02_visualizations.py)
horizontal_planes = []
y_planes = []
for fmodel in [fmodel_fixed, fmodel_floating]:
    horizontal_planes.append(
        fmodel.calculate_horizontal_plane(
            x_resolution=200,
            y_resolution=100,
            height=90.0,
        )
    )
    y_planes.append(
        fmodel.calculate_y_plane(
            x_resolution=200,
            z_resolution=100,
            crossstream_dist=0.0,
        )
    )

# Create the plots
fig, ax_list = plt.subplots(2, 1, figsize=(10, 8))
ax_list = ax_list.flatten()
flowviz.visualize_cut_plane(horizontal_planes[0], ax=ax_list[0], title="Horizontal")
flowviz.visualize_cut_plane(y_planes[0], ax=ax_list[1], title="Streamwise profile")
fig.suptitle("Fixed-bottom farm")

fig, ax_list = plt.subplots(2, 1, figsize=(10, 8))
ax_list = ax_list.flatten()
flowviz.visualize_cut_plane(horizontal_planes[1], ax=ax_list[0], title="Horizontal")
flowviz.visualize_cut_plane(y_planes[1], ax=ax_list[1], title="Streamwise profile")
fig.suptitle("Floating farm")

# Compute AEP
# Load the wind rose from csv as in example 003
wind_rose = WindRose.read_csv_long(
    "../inputs/wind_rose.csv", wd_col="wd", ws_col="ws", freq_col="freq_val", ti_col_or_value=0.06
)


for fmodel in [fmodel_fixed, fmodel_floating]:
    fmodel.set(
        wind_data=wind_rose,
    )
    fmodel.run()

# Compute the AEP
aep_fixed = fmodel_fixed.get_farm_AEP()
aep_floating = fmodel_floating.get_farm_AEP()
print("Farm AEP (fixed bottom): {:.3f} GWh".format(aep_fixed / 1.0e9))
print("Farm AEP (floating): {:.3f} GWh".format(aep_floating / 1.0e9))
print(
    "Floating AEP increase: {0:.3f} GWh ({1:.2f}%)".\
    format((aep_floating - aep_fixed) / 1.0e9, (aep_floating - aep_fixed)/aep_fixed*100)
)

plt.show()
import warnings
warnings.filterwarnings('ignore')

Power increase from floating over farm (10m/s, 270deg winds): 373.89 kW

Farm AEP (fixed bottom): 358.771 GWh
Farm AEP (floating): 358.978 GWh
Floating AEP increase: 0.206 GWh (0.06%)