# Study on the Coexistence of Offshore Wind Farms and Cage Culture

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## Abstract

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## 1. Introduction

## 2. Methodology

#### 2.1. Wave Model

#### 2.2. Hydrodynamic Model

- Continuity equation:$$\frac{\partial \eta}{\partial t}+\frac{\partial}{\partial x}\left[U\left(h+\eta \right)\right]+\frac{\partial}{\partial y}\left[V\left(h+\eta \right)\right]=0$$
- Momentum equations:$$\begin{array}{l}\frac{\partial U}{\partial t}+U\frac{\partial U}{\partial x}+V\frac{\partial U}{\partial y}=fV-g\frac{\partial \eta}{\partial x}+\frac{1}{\rho}\left(\frac{\partial {\tau}_{xx}}{\partial x}+\frac{\partial {\tau}_{yx}}{\partial y}\right)+\frac{1}{\rho \left(h+\eta \right)}\left({\tau}_{sx}-{\tau}_{bx}\right)\\ \begin{array}{cc}& -\frac{1}{\rho \left(h+\eta \right)}\left(\frac{\partial {S}_{xx}}{\partial x}+\frac{\partial {S}_{yx}}{\partial y}\right)\end{array}\end{array}$$$$\begin{array}{l}\frac{\partial V}{\partial t}+U\frac{\partial V}{\partial x}+V\frac{\partial V}{\partial y}=-fU-g\frac{\partial \eta}{\partial y}+\frac{1}{\rho}\left(\frac{\partial {\tau}_{xy}}{\partial x}+\frac{\partial {\tau}_{yy}}{\partial y}\right)+\frac{1}{\rho \left(h+\eta \right)}\left({\tau}_{sy}-{\tau}_{by}\right)\\ \begin{array}{cc}& -\frac{1}{\rho \left(h+\eta \right)}\left(\frac{\partial {S}_{xy}}{\partial x}+\frac{\partial {S}_{yy}}{\partial y}\right)\end{array}\end{array}$$$$U=\frac{1}{\left(h+\eta \right)}{\displaystyle {\int}_{-h}^{\eta}udz}\begin{array}{cc},& V=\end{array}\frac{1}{\left(h+\eta \right)}{\displaystyle {\int}_{-h}^{\eta}vdz}$$

- Left boundary:$${\eta}_{L}={A}_{L}^{t}\mathrm{sin}\left[\frac{2\pi}{{T}_{t}}\left(t+{T}_{t}+{T}_{start}\right)\right]\begin{array}{cc},& {T}_{t}\end{array}=\frac{{L}_{y}}{\sqrt{g{h}_{Max}}}$$
- Right boundary:$${\eta}_{R}={A}_{R}^{t}\mathrm{sin}\left[\frac{2\pi}{{T}_{t}}\left(t+{T}_{start}\right)\right]$$
- Offshore boundary:$${\eta}_{0}=\left[{A}_{R}^{t}+\left({A}_{L}^{t}-{A}_{R}^{t}\right)\left(\frac{{N}_{y}-j}{{N}_{y}-1}\right)\right]\mathrm{sin}\left\{\frac{2\pi}{{T}_{t}}\left[t+{T}_{t}\left(\frac{{N}_{y}-j}{{N}_{y}-1}\right)+{T}_{start}\right]\right\}$$

#### 2.3. Hydrodynamic Characteristics at the Coast

## 3. Analysis of the Interaction between the Marine Environment and Wind Turbines

#### 3.1. Modeling Procedure and Setting

#### 3.2. Analysis of the Influence of the Wind Turbine on the Wave and Current Pattern

#### 3.3. Analysis of the Local Wind Turbines Impact on the Marine Environment

#### 3.4. Discussion

^{2}not affected by the offshore wind turbine can be obtained. After referring to the research on the relevant offshore cage culture [34,35,36], this study took the circular cage culture with a diameter of 20 m as an example and configured it with the cage culture system of Figure 16. From the range of the outer anchoring system, a diameter of approximately 100 m can be obtained. If preparations are made in a regular arrangement, approximately 40 cage cultures can be placed in the area not affected by the wind turbines. If this is expanded to the entire offshore wind farm, it should be possible to configure 720 cage cultures. It is worth mentioning that the use of this configuration does not take into account the future operation of the entire offshore wind farm. If the operation and maintenance of offshore wind farms are not affected, and if the consent of the developer is obtained, it should be possible to use this method to provide economically large-scale farming areas and as a mutually beneficial method for offshore wind power generation and fishery.

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 2.**Schematic diagram of Taiwan’s offshore wind power generation area. Source: Ministry of Economic Affairs, Taiwan (2018).

**Figure 3.**The jacket-type offshore wind turbine support structure [30].

**Figure 5.**Comparison between the numerical model and the measured data. Blue line, measurement data; Red line, simulation results.

**Figure 6.**Simulation results of wave and current under summer conditions. (

**a**) Wave height and direction distribution; (

**b**) flood tide current pattern; (

**c**) ebb tide current pattern.

**Figure 7.**Simulation results of wave and current under winter conditions. (

**a**) Wave height and direction distribution; (

**b**) flood tide current pattern; (

**c**) ebb tide current pattern.

**Figure 8.**The target offshore wind farm in this study. Source: Environmental Impact Assessment Inquiry System (https://eiadoc.eap.gov.tw/EIAWEB/Default.aspx, (accessed on 28 March 2021)).

**Figure 10.**Simulation results of wave and current under summer conditions after the establishment of the wind turbine. (

**a**) Wave height and direction distribution; (

**b**) flood tide current pattern; (

**c**) ebb tide current pattern.

**Figure 11.**Simulation results of wave and current under winter conditions after the establishment of the wind turbine. (

**a**) Wave height and direction distribution; (

**b**) flood tide current pattern; (

**c**) ebb tide current pattern.

**Figure 12.**Simulation results of local wave patterns after wind turbines were established. (

**a**) Summer condition; (

**b**) winter condition.

**Figure 13.**Simulation results of local current patterns in summer after wind turbines were established. (

**a**) Flood tide current pattern; (

**b**) ebb tide current pattern.

**Figure 14.**Simulation results of local current patterns in winter after wind turbines were established. (

**a**) Flood tide current pattern; (

**b**) ebb tide current pattern.

Item | Model Setup |
---|---|

Area | 50 km × 35 km |

Grid size | 0.5 m × 0.5 m |

Number of grid points | 100,000 × 70,000 |

Coordinate of the origin (TWD97) | 168,110, 2621,287 |

Angle of deviation (counterclockwise from the north) | 60° |

Time step size | 1.0 s |

Wave condition [31] | SSW direction; H = 1.2 m; T = 6.5 s NNW direction; H = 3.0 m; T = 7.5 s |

Period (s) | Wavelength (m) | Φ3.0 m | |
---|---|---|---|

Summer | 6.5 | 65.91 | 1/22 |

Winter | 7.5 | 87.75 | 1/29 |

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**MDPI and ACS Style**

Wang, H.-Y.; Fang, H.-M.; Chiang, Y.-C.
Study on the Coexistence of Offshore Wind Farms and Cage Culture. *Water* **2021**, *13*, 1960.
https://doi.org/10.3390/w13141960

**AMA Style**

Wang H-Y, Fang H-M, Chiang Y-C.
Study on the Coexistence of Offshore Wind Farms and Cage Culture. *Water*. 2021; 13(14):1960.
https://doi.org/10.3390/w13141960

**Chicago/Turabian Style**

Wang, Hsing-Yu, Hui-Ming Fang, and Yun-Chih Chiang.
2021. "Study on the Coexistence of Offshore Wind Farms and Cage Culture" *Water* 13, no. 14: 1960.
https://doi.org/10.3390/w13141960