8b OPTIMIZE
8b.1 Introduction .......................................................................................................................................... 2
8b.1.1 Noise Curtailment vs. Layout Curtailment ............................................................................. 2
8b.1.2 The GUI tree-structure ........................................................................................................... 2
8b.1.3 Presentation of results ........................................................................................................... 9
8b.1.4 Storing results ...................................................................................................................... 11
8b.2 Optimization decisions ...................................................................................................................... 12
8b.2.1 The noise model .................................................................................................................. 12
8b.2.2 Noise receptors .................................................................................................................... 13
8b.2.3 Wind resource model ........................................................................................................... 13
8b.2.4 Strategy decisions ............................................................................................................... 14
8b.3 Optimization algorithm ...................................................................................................................... 15
8b.3.1 Noise curtailment optimization algorithm ............................................................................. 15
8b.3.2 Turbine shutdowns .............................................................................................................. 15
8b.3.3 Operation mode curtailment ................................................................................................ 15
8b.4 References .......................................................................................................................................... 15
Introduction 2
© EMD International • www.emd.dk • windPRO 4.1 • September 2024
8b.1 Introduction
Wind farms must comply with noise regulations, and two approaches are being used to ensure compliant noise
immission levels at noise receptors emitted by wind turbines: control the turbine position (Cao et al. 2020) or
control the turbine operation modes (Nyborg et al. 2023). When wind turbines are already installed or the planned
positions are decided upon, the remaining option is, therefore, curtailing the operation modes of the turbines.
The curtailment of wind turbine modes comes with reduced noise emission but also reduced energy production
(Steurer et al. 2017). The purpose of noise curtailment optimization in the context of wind farm planning is to
satisfy acoustic constraints while maximizing the usual benefits, e.g., energy production or profit.
The Noise Curtailment Optimizer (NCO) adds such functionality to the Optimizer module in windPRO to the
Layout Optimizer. The objective of the NCO is to suggest a curtailment strategy for wind farms to comply with
noise receptor thresholds around the wind farm with the lowest production loss possible. If a noise curtailment
is insufficient to comply with defined noise regulations, the tool can also propose to shut turbines down for
specific conditions as a last resort.
The NCO facility in windPRO was developed as part of the Decowind project, supported by the Danish Innovation
Fund.
8b.1.1 Noise Curtailment vs. Layout Optimizer
The Noise Curtailment Optimizer is designed to resemble the Layout optimizer, and a lot of the structure of the
optimizer will look and feel similar. In both cases the objective is to maximize production output of a wind farm,
but the degrees of freedom are different. The Layout Optimizer reaches its objective by moving the turbines
within a set of constraints, while the NCO does the same through changing the operation mode on the turbines.
The constraints of the NCO are controlled by the noise code it must comply with and the possibilities the turbine
type offers. For these reasons, the GUI must diverge from that of the Layout Optimizer as described in the
following. The result of the NCO is not a new layout but a Noise Curtailment Matrix for each turbine.
8b.1.2 The GUI tree-structure
The GUI of the Noise Curtailment Optimizer uses a tree structure like that of the Layout Optimizer with three
levels: Site, Layout and Strategy (Figure 1).
Figure 1: The three hierarchy levels of the GUI tree: Site, Layout, and Strategy.
When the NCO is opened for the first time, a first Site will be available and set with default settings for the country
of the project. The optimizer allows creating several sites, where each site can contain several layouts, and a
layout can have several strategies. Each hierarchy level can be expanded or collapsed and if highlighted, the
options for the level become visible to the right.
New levels can be added, deleted or copied. Sites can be cloned by right-clicking on the Site level:
Introduction 3
© EMD International • www.emd.dk • windPRO 4.1 • September 2024
Figure 2: Option to expand, collapse and clone sites.
There are some restrictions to the upper levels in the structure once lower levels have been added. These
restrictions can be lifted if the lower levels are removed. It is for example not possible to change the noise model
once a Strategy has been added but removing all strategies reenables noise model changes.
8b.1.2.1 Site
The Site level sets up fundamental decisions regarding the noise model and wind resource model. In principle,
the Site will include all the basic conditions of the location and would, ideally not need to be changed when
testing different options. There may be a need or an interest in changing fundamental conditions, such as the
selection of noise receptors, parameters in the noise model or details in the wind model. For such variations,
separate sites can be made. Selecting a Site in the left column enables the Setup & Run field on the right.
Figure 3: On the Site level, three components of the optimization are selected: the noise receptors, the noise
model, and the wind resource.
Noise receptors: On the Noise tab, the relevant receptors are selected by pointing out the layer in which the
receptors are located. As default all receptors in a layer are selected, but by removing the check in Use all
objects from selected layers, specific objects can be pointed out.
Introduction 4
© EMD International • www.emd.dk • windPRO 4.1 • September 2024
Figure 4: Noise model configuration.
It is important that the noise receptors selected match the noise model used, see section 8b.2.2.
Noise model: The NCO gives access to both Decibel and NORD2000 from the Noise tab. To access either
requires a license for the module. The Noise model selection box provides quick access to one of the preset
models in either Decibel or NORD2000. The Edit model parameters button gives access to view or modify the
parameters in the noise model. DECIBEL and NORD2000 are described in detail in section 6 of the windPRO
Environmental manual. The model parameter details are also described in section 6 with additional information
in section 8b.2.1 where the optimizer provides additional or reduced options.
If a model needs to be customized, it is recommended to select the ISO 9613-2 General model from DECIBEL
or General from NORD2000.
It is not possible to use different noise models at the same site. The questions of how to combine multiple models,
e.g. one noise model for existing turbines ad one noise model for new turbines, has not been answered yet.
Introduction 5
© EMD International • www.emd.dk • windPRO 4.1 • September 2024
Figure 5: Noise regulation specification selection.
Wind resource model: On the Energy tab, the wind resource model is selected. The wind resource model is
used to calculate the production loss inflicted by curtailments. The wind resource model can be based on time
series data or a wind resource map. A wind resource map is a precalculated map for the area that provides
Weibull parameters and direction frequencies in each grid cell. Wind resource maps are described in detail in
section 3 of the manual. For the NCO a wind resource map in either .rsf, .wrg or .siteres format can be used. It
is required that it covers the location of all wind turbines in the calculation as well as any reference points (for
the Wind speed inside Wind farm model). A very easy and simple access to a wind resource map is the GASP
data which are freely available world-wide from windPRO. A wind resource map can be used if the only two
dimensions used in the optimization are wind speed and wind direction.
Figure 6: Resource and wake model specification.
The Time series option sets up a time domain model as described in the Chapter 3 Energy. This includes a
Scaler and a time series and is entirely identical to the model in the PARK module. A full description of the Scaler
and selection of time series data can be found in Chapter 3 Energy.
The time series model has the advantage, compared to a wind resource map, that it is not limited to wind speed
and direction. The time domain nature of the model means that the time dimension can be used in the
optimization, i.e. calculation of day and night curtailments. If the time series includes temperature and humidity
data, it is possible to include these dimensions as well. If these dimensions are needed, but not available in the
time series used by the Scaler, time series with those data can be pointed out separately at the bottom of the
field. As the objective is to calculate and minimize curtailment losses, precision on the absolute wind speed is
not required and downscaled mesoscale data is an easy and suitable option for a time series wind model.