Wind Power Generation - Renewable Energy: Technology, Economics and Environment - page 345

risk of ice throw at a distance of approximately 200 m is comparatively low and
almost equal to that of a lightning stroke /7-16/.
Natural scenery. Wind energy converters are technical buildings that inevitably
alter the natural scenery. As both plant size and pole height have increased over
the last 10 to 15 years, impacts on the natural scenery have also become increas-
ingly important.
With regard to wind turbines two different impacts on the scenery are ob-
served; on the one hand they alter the scenery's dimensions and on the other hand
they have significant distant effects /7-17/.
This applies far and foremost to plains and exposed sites based in low moun-
tain ranges, as wind turbines are still visible from far distances. Also the number
of wind turbines and the tower height play a major role. However, using appropri-
ate colouring, tower designs and rotor blade number and speed can reduce subjec-
tive irritation. For instance, in most cases solid towers fit better into the scenery
than lattice masts, and, due to their smooth running, rotors provided with three
rotor blades are generally more easily accepted by spectators than rotors equipped
with one or two rotor blades.
Optical assessment of wind turbines is not subject to any objectively defined
parameters but mainly depends on the associations and the personal taste of the
respective spectator. The surroundings of a wind turbine are also a deciding fac-
tor. To date looking at wind turbines is not considered disturbing in most cases.
Furthermore, computerised applications permit to assess and minimise the effect
on the scenery still prior to wind turbine erection.
Preservation of bird-life. With regard to wind power utilisation, in terms of envi-
ronmental effects, interference with feeding and resting birds, impacts on fly-
ing/migrating birds and hitting of birds have been reported.
Resting birds tend to avoid any kind of wind turbine and usually keep at a dis-
tance of several hundreds of metres. In this respect, certain bird types (e.g. cur-
lews, ruffs) are much more sensitive than seagulls, for instance /7-18/.
For many bird species usually no conspicuous behavioural changes have been
observed with regard to wind turbines /7-18/. Yet, also contrary survey results
have been reported; for instance, white storks react most sensitive in the vicinity
of breeding grounds /7-19/. On the whole, different bird types react very differ-
ently to wind turbines. While there is no interference with lapwings or oyster
catchers and wind turbines, impacts on redshanks and blacktailed godwits cannot
be ruled out /7-20/.
With regard to wind turbines, birds hitting has only been observed occasion-
ally, probably due to rotor sounds, and is only of little importance when compared
to the effect caused by other buildings or road traffic. Nine wind turbines sites
have been observed over two years with regard to birds killed by hitting. There
were 32 victims of 15 different bird types at 7 sites /7-18/.