CNC (Causas de no Cumplimiento)

Technological trends are changing the telecommunications environment. As the demand for greater and greater

telecommunications capacity grows, there is a move away from older systems operating at lower frequencies towards higher frequencies. This benefits wind energy development since higher frequency systems do not require such large obstacle-free zones around their paths. Many communications networks are moving away from fixed terrestrial radio links completely, to other technologies such as satellite and fibre-optic cable. There is also a trend from analogue to digital systems – again a positive trend for wind energy because digital radio is generally more robust in terms of its susceptibility to interference. The developing 3G mobile phone network may generate additional constraints on wind energy projects, but this is not because of the potential impact on signals to/from mobile phones themselves. It is because 3G technology requires more base stations than existing mobile phone systems. This will mean more fixed radio links to/from base stations.

Fixed radio links

Most of these links are at microwave frequencies (3-30 GHz). The Ofcom-

recommended wind turbine clearance zones around microwave links are relatively narrow. However most microwave link operators have not taken up the Ofcom recommendations for the same reasons as outlined above.

The consultation process for wind farm developers investigating potential impacts on fixed microwave links is even more fragmented than for the television industry. The first point of contact is Ofcom's fixed links department. However Ofcom's database is not

comprehensive. Several significant operators, including BT, the CAA and the MOD, are not covered, and the pace of development by mobile phone companies in particular can mean that many new links take some time to enter the Ofcom database. A response of 'no known links' from Ofcom therefore cannot be taken as definitive and it is necessary to contact all individual operators direct. This is compounded by the complexity of contractual arrangements in the industry. A microwave link may be built by one company, operated by another, to carry services for a third. The locus of responsibility for system integrity and performance is sometimes hard to decipher in these cases.

The existence of a scientifically-determined basis, developed by a government agency, for calculating recommended clearance zones between radio links and wind turbines is a valuable asset for both industries. Industry confidence in its accuracy and dependability will grow as experience of co-existence of radio links and wind farms develops. In the meantime, experience has shown that the willingness of wind power developers to address some of the telecommunications industry uncertainties can ease the process of project approval. Re-surveys to more accurate standards of the transmitter and receiver locations on a microwave link have the potential to reduce the required clearance zone around a link by an order of magnitude.

Scanning telemetry systems

The precise required clearances around the link path for scanning telemetry systems (used primarily by the water and power industries) are unclear and are at the discretion of the

telemetry system operator. Some operators have taken Ofcom's consultation trigger distance (1km from a scanning telemetry station) as a required avoidance zone.

The consultation process for scanning telemetry systems is also complex. Ofcom has no remit for and no data on these systems and responsibility for their integrity and performance is held by agency bodies under contract to the system owners. However, these agencies may not hold complete information on the locations of

telemetry links and stations. This is compounded by industry reluctance to release such

information, apparently on security grounds. Wind industry experience has shown that willingness to respect confidentiality, combined with the sharing of examples of successful co- existence of wind farms and a variety of telecommunications systems, can ease the process of consultation with telemetry system operators.

1 Spaven Consulting (2001). Wind Turbines and Radar: Operational Experience and Mitigation Measures. Available at:

http://www.bwea.com/aviation/Wind-Turbines-and-Radar-Operational-Experience-and-Mitigation-Measures.pdf

2 Bacon, D.F. (2002), A proposed method for establishing an exclusion zone around a terrestrial fixed radio link outside of which a wind turbine will cause negligible degradation of the radio link performance, Version 1.1, Radiocommunications Agency. Available at:

http://www.ofcom.org.uk/radiocomms/ifi/licensing/classes/fixed/Windfarms/windfarmdavidbacon.pdf

3 RA/BBC/ITC (1992). Environmental Impact: Effect of wind farms on UHF television reception. Engineering Information Bulletin, June 1992.

FURTHER INFORMATION

In addition to the references cited in the text above, further information is also available from the sources below:

1. A. Knill (2002). Potential Effects of Wind Turbines on Navigational Systems. Available at:

http://www.bwea.com/aviation/Potential-Effects-of-Wind-Turbines-on-Navigational- Systems.pdf

2. Summers, E. (2001). The Operational Effects of Wind Farm Developments on ATC Procedures for Glasgow Prestwick International Airport’. Glasgow Prestwick International Airport. Available at:

http://www.bwea.com/aviation/Operational-Effects-of-Wind-Farm-Developments-on-ATC- Procedures-for-Glasgow-Prestwick-International-Airport.pdf

3. Summers, E. (2002). Wind Turbines and Aviation Interests - European Experience and Practice. ETSU W/14/00624/REP, DTI PUB URN No. 03/515. Available at:

http://www.bwea.com/aviation/European-Experience-and-Practice.pdf

4. DTI/MOD/CAA/BWEA (2002). Wind Energy and Aviation Interests: Interim Guidelines. Available

at: http://www.dti.gov.uk/energy/renewables/publications/pdfs/windwnergyaviation.pdf

5. QinetiQ (2003). Wind Farms Impact On Radar Aviation Interests - Final Report. FES W/14/00614/00/REP, DTI PUB URN 03/1294. Available at:

http://www.dti.gov.uk/energy/renewables/publications/W1400614.shtml

6. Alenia Marconi Systems Ltd (2003). Feasibility Of Mitigating The Effects Of Windfarms On Primary Radar. ETSU W/14/00623/REP, DTI PUB URN No. 03/976. Available at:

How noise is measured

Sound is always associated with small scale change in pressure, which produces sensations (i.e. is ‘heard’) at the human ear. Because of the wide range of sound pressures to which the ear responds, sound pressure is an inconvenient quantity to use in graphs and tables and so noise is measured on a logarithmic scale in decibels (dB). The decibel is a measure of the sound pressure level, i.e. the magnitude of the pressure variations in the air.

A change in sound level of 1 dB cannot be perceived, except under laboratory conditions. Doubling the actual energy of a sound source or doubling the number of identical sound sources corresponds to a 3 dB increase. A 3 dB change in sound level is considered a barely discernible difference, outside the laboratory.

The noise that a machine such as a wind turbine creates is normally expressed in terms of its sound power level. Although this is described in dB(A), it is not a measurement of the noise level but of the power emitted by the machine, which then creates the sound pressure level which can be heard and measured using a sound meter.