Since the 1980s, there has been concern about the potential interference that wind turbine farms can cause to wireless communication equipment. The focus has been on TV, civilian and military radar and point-to-point microwave systems. This led to studies to evaluate the degradation effects that wind turbine farms have on these systems. They concluded that physical propagation effects such as dispersion and diffraction of electromagnetic signals propagating through wind turbine farms produce low-level, long-delay, multipath distortion on telecommunications equipment  .
In recent years, these conclusions have been used to recommend an overzealous approach to the design of digital microwave paths that go through or over wind turbine farms. Overzealous recommendations with little supporting evidence have made it standard operating procedure to establish “exclusion zones” around wind turbine farms .
In the case of microwave links, the technology has made great improvements since the 1980s. In the 1980s, microwave links were analog and more vulnerable to interference and multipath distortion created by wind turbine blades. New digital microwave radios with Forward Error Correction (FEC), Adaptive Coding and Modulation (ACM) and high dispersive fade margin are better equipped to deal with interference and multipath distortion produced by wind turbine blades. These technological advances were not available in the 1980s and 1990s when the most rigorous studies about wind farm interference were completed.
Besides the improvements in digital microwave technology, wind turbines have also changed. In the 1980s they were smaller (compared to contemporary units) and mostly made of metal; today wind turbines are bigger, and the blades are mainly made of reinforced fiberglass, which is transparent to microwaves. Although obstruction due to the wind turbine pole and generator case will create path loss and possible diffraction of the signal, poles and casings are very thin (compared to the Fresnel zone radius) and would have to be in the direct line of sight of the link to produce significant penetration loss.
Although a conservative approach to microwave path planning is always recommended, and detailed planning and path surveying for each path are necessary, an overzealous design based on outdated studies can lead to unnecessary CapEx and OpEx. More rigorous studies based on detailed field measurements with high performance digital microwave wireless communication equipment must be undertaken to establish wind turbine clearance criteria based on current technology and field measurements.
A good starting point can be to check current links that are intentionally or accidentally traversing the orbits of a wind turbine blade. Aviat Networks would be like to hear from users that have this situation (leave a comment for this blog). Further analysis of a link in this condition can prove or disprove the hypothesis that modern microwave radios are relatively unaffected by modern fiberglass wind turbine blades and thin wind turbine pole structures. If this hypothesis is confirmed, current guidelines can be relaxed to avoid passive repeaters and bigger towers that represent additional costs.
Marketing Engineering Specialist
The Aviat Networks headquarters building in Santa Clara, Calif., has received LEED Gold certification from the U.S. Green Building Council (USGBC). LEED, or Leadership in Energy and Environmental Design, is an internationally recognized green building certification system developed by USGBC.
The Santa Clara building was designed with environmental responsibility in mind; following the five LEED credit categories for construction, décor and location:
1. Site selection
Located close to Light Rail & Capitol Corridor Amtrak train service, the site is prime for reducing car-based commuting. Also, indoor secure bicycle storage, showers and changing rooms have been provided to promote cycling, which will can further reduce car-based commuting.
2. Water efficiency
Aviat Networks installed water efficient fixtures that reduce water use by 40 percent compared to standard fixtures.
3. Energy and atmosphere
We reduced heat island effect by installing cool roofing that has the ability to reflect visible, infrared and ultraviolet light, decreasing heat transfer to the building (i.e., high solar reflectance rating). Our advanced heating and cooling system has variable speed fans monitored by computer. We selected Energy Star rated equipment for the majority of office equipment and appliances. And all the building’s electricity comes from “green” energy sources (i.e., wind power).
4. Materials and resources
During construction, waste was managed so that more than 95 percent of it was diverted from landfills through recycling and salvage efforts. Flooring is based on fast-growing renewable bamboo instead of non-renewable sources and the carpet is made from recycled content such as plastic bottles. Paints and coatings with low emission rates of volatile organic compounds and other air pollutants were used. And carpentry with composite wood products in doors and millwork was installed—saving some trees in the process.
5. Indoor environment
Low E glass windows and interior office-core windows can be left uncovered to allow for maximum natural lighting in the office area. Cube panels are lower and have windows to take advantage of the natural light. We also have a fitness center to promote employee health and wellness. Though this last category did not actually contribute official USGBC green credits to Aviat Networks’ LEED Gold certification, it demonstrates the company’s commitment to this process and contributes to overall employee well-being.
What’s the difference?
Do LEED buildings cost more? The answer is no. It is a design strategy that creates a building that will save energy and money over the long-term. It will also have limited effect on the environment and enhance working conditions.