Author: Alicia Webb
Wind farms are, by nature, located on elevated sites (such as hill tops) where wind flow is the fastest. And they're often close to or share sites with telecommunication transmission towers, which also need high elevations and open land to provide good broadcast coverage.
Telecommunication systems use a variety of electromagnetic waves, commonly described as radio waves. If wind turbines are sited directly in the way of a communications signal beam, they can interfere with these signals. You can usually avoid this by researching existing telecommunication systems thoroughly at the design stage of your wind farm project.
What is electromagnetic interference?
Electromagnetic interference (EMI) is the effect wind turbines can have on some radio or television signals. This includes affecting analogue television, broadcast radio, mobile phones and point-to-point microwave links. As well as 'public' communications, emergency services and transport operations can also be affected. And in rural areas, GPS systems are sometimes used to guide agricultural machinery, so you also need to evaluate these services.
There are three main types of EMI:
- Reflection: a large structure, such as a wind turbine generator, can interfere with licensed telecommunication systems by reflecting or obstructing electromagnetic signals.
- Emission: all electrical apparatus (including electrical components in wind turbines), emit electromagnetic radiation. Depending on signal strengths, this radiation can interfere with other equipment, or with telecommunication signals.
- Electrical noise: induced by wind turbines on the power lines that feed the telecommunications equipment.
The Australian Communications and Media Authority (ACMA) is responsible for licensing radio communications. It has a database of licenses you can search to identify possible radio communication stakeholders.
EMI exclusion zones
Generally, a consultant will start by searching ACMA's databases for all communications towers and services (beams) within a 20 or 30 km radius of your wind farm. They will then draw the services onto a map, and for any services which are close to or intersecting your wind farm site, they will calculate the recommended exclusion zone. The width of the exclusion zone for each communication service will depend on the frequency of the signal.
Consultant reports generally calculate safe operating zones for wind turbines, and if all turbines are sited inside these zones, it may be possible to proceed to planning approval with no need for further studies. However, if a turbine needs to be sited outside the safe operating zone, then there will probably be a much closer analysis of the particular case by a qualified radio engineer.
If a communications service intersects your wind farm site, it's best to contact the owner of that service to discuss their requirements before you do any further studies.
Scoping the job for a consultant
When you employ a consultant to write an EMI report, it's best to follow the tips and tricks in the Engaging specialists for environmental and technical studies article. Essentially, the article suggests writing a tight scope and getting multiple quotes for the job.
The scope should generally include:
- a detailed description of your wind farm, including turbine types or dimensions and their locations. If this is still unknown, it's best to include a 'wind farm envelope' — the largest area in which turbines could be sited
- the reason you're having the report written (for example, to satisfy planning conditions)
- who needs to read the report
- what you expect to see in the report (See 'what to expect' below).
Information a consultant will need
A detailed EMI report will include:
- GPS coordinates of all wind turbines
- GPS coordinates of the site boundary
- a digital topographical map with height contours at intervals of not less than 10 m, extending a minimum of 30 kms from the wind turbines
- details of the type of wind turbines you can use, or at least the dimensions (hub height and blade length).
What to expect in the consultant report
A good consultant report will have thorough explanations, so even someone who's not an expert in the field can interpret it. It will also have appendices listing locations of other turbines and communications towers in the area.
A few things to look for are:
- a description of electromagnetic signals
- a description of all inputs and assumptions including the database used to source the communications services and tower locations, and the radius used to search for them
- a description of the applicable guidelines and limits
- a description of the methodology used to calculate exclusion zones
- maps or images showing the wind farm site relative to all communications towers and services included in the study
- maps or images showing exclusion zones and where they impact upon the wind farm boundary area
- recommendations for mitigating any interference
- contact details for the owner of any services intersecting the wind farm site. You'll need to contact these owners before you do any further studies or start building your wind farm.