Fundamentals of wind energy - Wind Power Generation and Wind Turbine Design - page 28

6 Challenges in wind power generation
While wind power generation offers numerous benefi ts and advantages over con-
ventional power generation, there are also some challenges and problems need to
be seriously addressed. The wide range of challenges and problems, from long-
term environmental infl uences to thermal management of wind turbines, must be
carefully considered in response to the rapid growth of wind power generation.
6.1 Environmental impacts
Modern wind farms today may contain a large number of large-size wind turbines.
Therefore, their impacts on the environment cannot be ignored. One of the impacts
is that poorly sited wind energy facilities may block bird migration routes and hurt
or kill birds.
Though blade rotation speeds are rather low for large wind turbines at their
normal operation, the tangential speeds at the blade tips could be higher than
70 m/s. At such high speeds, birds fl ying through the blade sweeping areas may
be easily hurt or killed by colliding with blades. It has been reported by the US
National Academy of Science that wind turbines may kill up to 40,000 birds per
year in US [57]. Though this number is much smaller than the 80 million birds
killed by cars each year, it is important to evaluate the long-term infl uence on
local geography, seasonal bird abundance and the species at risk. To reduce the
bird death, using bird scares to drive birds away from wind farms has been con-
sidered. A more recent study has revealed that fossil-fuelled power stations
appear to pose a much greater threat to avian wildlife than wind and nuclear
power technologies [58].
Today, this problem becomes less important. Before building a wind farm, a
series of environmental assessments have to be completed to avoid bird migration
routes and to minimize other environmental impacts. Once the wind farm is built,
further monitoring takes place to better understand the ongoing relationship
between birds and the wind farm [59].
Building wind farms will change the character of local landscape. Modern large
wind turbines are more than 100 m tall and thus can be seen at a far distance. In
practice, the visual effect for local residents is a signifi cant consideration and is
always scrutinized for wind projects. To minimize the visual effect, wind turbines
usually use neutral colors such as light grey or off-white [60]. Strategies to mini-
mize visual effects involve the spacing, design, and uniformity of turbines, mark-
ings or lighting, roads and service buildings [61]. There are a number of analytical
tools available to assist understanding and testing of the effect of wind farms on
visual amenity.
6.2 Wind turbine noise
With the extensive build up of wind power plants and the population growth all
over the world, the infl uence of wind turbine noise to the nearby residents becomes