7.5 Improve layouts
Once a layout satisfying the distance constraints are establishe, we recommend to run optimized layouts using with wake effects, (see (8) on figure 7.1 ), where the number in the dropdown menu defines the number of times the simulated annealing process is run for wake effect adjustments. For each run , there will be a new folder with layout files.
Performing wake effect adjustment will modify the layouts and write the files to Results_Directory\OPT_OUT\wake_effect_adjusted. The following method is employed for each layout :
Let PC and Ct be the turbine specific power-curve and thrust-coefficient, as defined in the Turbine File ( set in the Energy Map module) and let A(s), k(s), f(s) be the Weibull parameters for sector s of points in the Wind Resource file.
The energy production at each point , incorporating wake effects, is calculated as follows
- A dV – change in wind speed due to wake – matrix is constructed for each sector accounting for each turbine position p. Let at a turbine position p ( we are using the A parameter as an approximation to the average wind speed ).
Then dV for sector s , dV(s), due to turbine at position p is
where and D = Rotor Diameter, and where the calculation is done for values of x within a cone downwind of the turbine position p inside +/- 15 deg (if the data-set has 12 sectors; correspondingly less for 16 and 24 sectors) of the sector s direction and radius . If a point is affected by more than 1 wake, the values are added.
- The energy at each point , incorporating wake effects, is the sum over the sectors s of , over where wbl is the Weibull probability distribution function
This wake effect adjusted energy map is then used to move turbines so that the total energy production will be higher. The optimization method is based on Simulated Annealing.
The figure below illustrates the wake adjustment. Press the Figure button (see (11) in above figure) in the gui to produce the figures ( note that the circles are markers, and do not indicate distance ). The layout size can be chosend from the nearby dropdown menu (see 10 on the above figure)
All optimization results are stored in the folder OPT_OUT, containing
in the form of text files with turbine coordinates, as well as an energy_curve.txt file containing the corresponding energy yield for each layout size.
Existing layouts can be downloaded into the project.