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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'How does the wind blow behind wind turbines and in wind farms?' taking place on Tuesday, 11 March 2014 at 16:30-18:00. The meet-the-authors will take place in the poster area.

Itziar Angulo University of the Basque Country (UPV/EHU), Spain
Co-authors:
David de la Vega (1) F P David Guerra (1) Itziar Angulo (1) Josune Cañizo (1) Pablo Angueira (1)
(1) University of the Basque Country (UPV/EHU), Bilbao, Spain

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Abstract

ALGORITHMS FOR ESTIMATING THE POTENTIAL DEGRADATION OF WIND TURBINES ON TELECOMMUNICATION SYSTEMS

Introduction

The impact that a new wind farm may cause on the surrounding telecommunication services can only be determined on a case-by-case basis, due to the multiple factors that must be considered in the analysis. For this purpose, a set of algorithms have been developed and integrated in the SOPCAWIND tool for wind farm design (Software for the Optimal Place CAlculation for WIND farms [1]). They use the requirements of each telecommunication service and the interference criteria proposed by the regulatory organizations in order to avoid the impact of a specific wind farm layout.

Approach

In the recent years some cases of degradation on certain telecommunication systems (mainly radars, fixed radio links and terrestrial television) have arisen due to the presence of wind farms [2]-[10]. In such situations, corrective measurements are usually expensive and technically complex. For this reason, the development of accurate impact studies before the wind farm is installed allows the modification of the wind farm configuration (layout and wind turbine model), or the planning of alternative solutions in order to minimize the impact [11].

The degradation mechanisms that may occur in the presence of wind farms are related to the structure and working regimes of the turbines. The wind turbines act as great reflectors of the electromagnetic waves, generating interfering signals and great echoes in radar receivers. Additionally, the reflected signals are Doppler shifted due to the blade rotation. These effects may generate false targets and areas of lower detection ability in all types of radars, and quality degradation in fixed radio links and broadcasting services.

Some guidelines have been published by the regulatory administrations in the recent years. Most of them are intended to provide overall rules-of-thumb that give a first approach to the problem. An accurate study requires a case-by-case analysis and complex calculations, and the handling of multidisciplinary databases, such as terrain data, technical specifications of telecommunication transmissions and data about the wind farm deployment are needed. Last, results must provide numerically the potential impact on the surrounding services and the set of locations where a turbine would generate a disturbance. These results should be shown in a clear and understandable way to the user, not necessarily expert in this topic.


Main body of abstract

The algorithms presented in this paper fulfilled the requirements outlined in the previous section. Accordingly, they provide accurate results, shown as constraint masks, viewable on Google Earth, representing the areas that should be avoided in the analysis of the wind farm layout in order to prevent the degradation of the surrounding telecommunication services. Hence, the software tool provides a safeguarding area for each analyzed service.

This analysis may be applied within the wind farm design process, before the turbines micro-siting study is carried out. These algorithms are a valuable help in order to obtain the definite wind farm layout, which will be the optimal solution in energy production without causing interference in the telecommunication services.

The algorithms have been integrated in a new version of the Wi2 software tool, and also in the SOPCAWIND GIS tool. Wi2 is a stand-alone software tool specifically developed for the impact analysis of wind farms on radiocommunication services [11]. SOPCAWIND is a project for developing a multidisciplinary data pool and a GIS tool for wind farms deployment [1]. The SOPCAWIND GIS tool will include functionalities for optimizing the energy production of the wind farm, and also for developing impact studies related to different issues, such as impact on environment, telecommunication services, heritage, transport networks and near settlements, and flicker and noise studies of a specific wind farm.

The analysis procedure divides the candidate area selected by the user for the wind farm deployment into a grid composed of small cells. Then, an iterative process is carried out consisting on locating the wind turbine model selected by the user at each cell of the grid, and developing the impact study on a specific service. For each cell, the potential interference is evaluated in order to decide if such location is susceptible of generating a severe degradation on the service, in case a wind turbine is installed. As a result, a mask containing all the cells where a wind turbine might degrade a specific telecommunication service is generated. That is, the results consist of a categorization of the candidate area, differentiating the areas that should be avoided for the deployment of the wind farm.

In the impact study developed at each cell of the candidate area, the turbine dimensions, the technical specifications of the telecommunication service and the terrain altimetry data are considered. The evaluation of the impact level of a wind turbine is based on the technical requirements of the telecommunication service for a proper quality, and also on the limits or safeguarding threshold values proposed by the regulatory bodies.

The results provided by the algorithms consist on constraint masks represented on the terrain of the candidate area, showing the specific locations where a wind turbine may degrade or interfere a specific service. The constraint masks are easy to combine with other constraint masks (such as environment protected areas, nesting areas and buffer distances to settlements or transport networks), or other datasets used in the wind farm design process (such as wind data, terrain slope or topographic features).


Conclusion

The algorithms presented in this paper allow the accurate analysis of the degradation of the different radiocommunication systems, according to the guidelines and interference criteria proposed by the regulatory organizations. The calculations are based on the configuration of a specific wind farm (dimensions and locations of the turbines), the requirements of the telecommunication services (transmitter location, coverage area and service requirements), and a terrain database containing high resolution altimetry data. Specific calculation algorithms and interference criteria are applied for each type of service, and numerical results of the analysis are presented on a map, which allows an on-the-spot evaluation of the potential impact.

The novelty of these algorithms is that they estimate the safeguarding areas that should be avoided in the wind farm deployment, and therefore, they can be applied without a previous definition of the wind turbine locations. Therefore, results consist on the set of locations where a wind turbine might interfere in a specific service. These results are represented as safeguarding areas on the terrain, easy to be used on GIS systems or Google Earth, and they are easy to combine with other constraints or datasets used in the wind farm design process (wind data, terrain slope, environmental protected areas, etc.). They will contribute to reduce the time required in the wind farm design process, mainly in the turbine micro-siting.

The estimation of the potential impact of a wind farm on the existing telecommunication services allows the modification of the wind farm layout or the planning of alternative solutions to guarantee the installation of a new wind farm without disturbing the surrounding services.



Learning objectives
New algorithms for the evaluation of the effect of a wind farm on telecommunication services are presented. They estimate, for each specific telecommunication service, the safeguarding areas that should be avoided in the wind farm deployment, providing clear and useful information to the wind farm designer. These algorithms will contribute to simplify and reduce the time required in the wind farm design process.


References
[1] SOPCAWIND project (European Union Framework Programme 7, grant n° 296164). www.sopcawind.eu.
[2] J.J. Lemmon, J.E. Carroll, F.H. Sanders and D. Turner, “Assessment of the Effects of Wind Turbines on Air Traffic Control radars”, NTIA Technical Report TR-08-454, July 2008.
[3] International Civil Aviation Organization, “European Guidance Material on Managing Building Restricted Areas”, ICAO EUR Doc 015, September 2009.
[4] M. Borely, “Guidelines on How to Assess the Potential Impact of Wind Turbines on Surveillance Sensors”, Eurocontrol, June 2010.
[5] P. Tristant, “Impact of Wind Turbines on Weather Radars Band”, World Meteorological Organization, CBS/SG-RFC 2006/Doc. 3.1, March 2006.
[6] “Impact of Wind Turbines on Weather Radars”, OPERA II WP 1.8, December 2006.
[7] United Kingdom Civil Aviation Authority, “CAP 670 ATS Safety Requirements”, April 1998
[8] D.F. Bacon, “Fixed-link wind-turbine exclusion zone method”, OFCOM, October 2002.
[9] International Telecommunication Union, Rec. ITU R BT.805, “Assessment of impairment caused to television reception by a wind turbine”, 1992.
[10] International Telecommunication Union, Rec. ITU R BT.1893, “Assessment of impairment caused to digital television reception by a wind turbine”, May 2011.
[11] D. de la Vega, C. Fernandez, O. Grande, I. Angulo, D. Guerra, Y. Wu, P. Angueira and J.L. Ordiales, "Software tool for the analysis of potential impact of wind farms on radiocommunication services," 2011 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB), pp.1-5, 8-10, June 2011.