Turbine turbulence


Here’s a look at the pros and cons of wind energy.

There is some concern in clean energy circles that pressure groups could hamper the development of wind farms. Public fears range from the so-called wind turbine syndrome (WTS), to predictions that a proliferation of wind turbine projects could eventually contribute to climate change rather than stall it – by changing temperatures and rainfall. It is conceivable that turbines could affect the micro-climate in their immediate vicinity to varying degrees, but could their combined effect really be that drastic?

Because the industry is so young in South Africa, no results from long-term studies are yet available, but scientific papers from reputable international institutions agree on several key issues:

  • Whatever damage the installations might do, they are more desirable than coal-fired power stations.
  • As long as environmental impact assessments are adequate and farms are built far enough from residential areas, there is little to worry about. 
  • Wind is the cheapest form of renewable energy.

In addition, wind turbines save water resources and connect to the national grid. Finally, micro-turbines, like solar energy systems, can readily be installed in rural areas for local consumption.The amount of energy that a wind farm produces within the first few months of operation is equal to the energy used to transport materials and build the plant. Once the turbine is running it has a small footprint, allowing farm and wild animals to graze around the towers, seemingly unperturbed by vibrations and noise. Wind farms secure their sites for up to 20 years, preventing potentially more destructive activities such as housing or industry.

Researchers concede that birds and bats in particular are in danger, but argue that these mortalities should be weighed against the devastation that coal mining causes to wildlife, the countryside and the atmosphere.The feeling amongst these scientists is that most of the disadvantages of wind farms, apart from their visual impact, can either be limited or overcome with proper planning and technology. In contrast, the impact of thermal or nuclear energy production is slow to appear, long-term, and difficult, if not impossible, to minimise.

READ: How to avoid the pitfalls of green power

Although there has been heavy criticism of some environmental impact assessments, the location of wind farms generally take many factors into account, including the amount and reliability of wind, and whether the highest wind level is experienced during peak demand periods.

Effects on people, birds and animals
What appears to be growing public opposition might not be so easy to counter. Environmental protests about the effect of turbines on bats and endangered, migrating, and even ground-nesting birds, are well-documented. Other common objections are that noise, shadow flicker, vibrations and electromagnetic fields cause a variety of ailments in nearby residents and animals, notably dogs.

Less well-known, in the case of offshore wind farms, is that sharks, rays, and skates may be attracted by electric fields from underwater cables, which appear similar to the bioelectric fields of their prey. So far, however, few courts have judged in favour of claims in this regard. In fact, there is evidence that people living near wind farms report more health complaints during anti-wind power campaigns than otherwise.

While the number of birds killed by wind turbines are said to be negligible compared with the effect of other human activities, this is one of the main conservation concerns. In the article ‘Environmental impact of wind energy’ by the faculty of engineering at the University of Malaya in Kuala Lumpur, researchers offer suggestions to reduce this problem. Although migrating birds generally fly at altitudes higher than 150m, they come in lower during overcast weather, high winds and rain. This increases the danger of flying through turbines, especially when attracted by light. One solution is to reduce the number of aviation warning lights at the facility.

READ: Wind farm poses a threat to the birds and beauty of the Karoo

Studies also suggest that older turbines, with lower hub heights, faster rotors, and tighter turbine spacing than newer models, are more lethal. Older turbines also have lattice towers that attract nesting birds. Avian radar, developed for NASA to detect birds as far away as 7km, can shut down wind turbines automatically when birds are in danger and restart when they have crossed over safely.

Another major impact on the environment is noise pollution, which can lower property values. Aerodynamic noise is developed by the flow of air over and past the blades of a turbine. Lower blade tip speed results in lower noise levels. Wind turbine blades’ interaction with the air, resulting in the characteristic ‘whooshing’ sound, is particularly concerning. However, modern turbines are much quieter than earlier models due to limited tip speeds and advanced blade design.

Other irritants are shadow flickering, caused by sun reflecting from a moving blade, and moving shadows cast on the ground. According to the University of Malaya study, flicker can be reduced by blade design, optimising blade smoothness, and coating the turbine with a less reflective material. Solving the shadow problem would be more complicated.

Email Roelof Bezuidenhout at [email protected].