Forthbank Wind Energy Development - Partnerships for Renewables

Forthbank Wind Energy Development
being used to dress back working areas to facilitate re-vegetation or agricultural use. Existing
vegetation will be scraped off and stored separately with the topsoil prior to re-use as the top
layer of any restored areas. This approach will maximise the potential for natural re-vegetation
from the seed bank. Vegetation and soils will be stored in accordance with best practice. In
the majority of cases (alongside tracks), restoration will occur within a few days of the removal
of vegetation, so desiccation will be unlikely. Restoration within the main landfill area will be
subject to specific agreement with SEPA and Clackmannanshire Council.
4.11 Operation of the Proposed Wind Energy Development
4.11.1 The power output from a wind energy development largely depends on the strength of the wind
blowing across the site. Wind turbines start to generate electricity at a wind speed of about
3m/s. Output increases with wind speed up to the maximum rated power at a wind speed of
about 15m/s. As the wind speed increases further, the output is limited to the maximum until
the wind speed reaches 25m/s when the wind turbine shuts down automatically in order to
protect components from excessive wear.
4.11.2 The proportion of time that the turbines will be generating electricity is therefore dependent on
the time that the wind speed is between 3m/s and 25m/s. Generation output from a wind
energy development is also seasonally dependent, such that approximately two thirds of the
total annual energy yield from the wind energy development is expected to be delivered in the
six months between October and March, with the remaining six months delivering the
remaining third.
Meteorological Effects
4.11.3 Although wind turbines are designed to stop generating electricity at wind speeds over 25m/s,
they are built to withstand very high wind speeds, and are normally certified against structural
failure for wind speeds up to 60m/s (in excess of 120mph).
4.11.4 Lightning generally has no effect on turbines, though as with all structures there is a risk of
damage if hit directly by lightning. Turbines are fitted with a lightning protection system as part
of their design.
4.11.5 Snow does not generally pose problems other than with access to the site. Occasionally very
heavy snow and ice may affect the anemometer or aerodynamics of the turbine blades
resulting in temporary automatic shutdown. The wind turbine will restart automatically after
accumulations have naturally thawed. Modern turbines have sensitive blade balance controls
which detect accretion on the blades (e.g. ice) and do not begin operation until it is safe to do
so. The following points provide a summary of the key protection measures:
• The ice detector is installed on the roof of the nacelle. It measures the temperature
and the relative air humidity of the environment. If certain values are exceeded the
turbine is stopped by the control system of the turbine. The meteorological values
are determined from "Deutschen Wetterdienst" or national weather institutes.
• In any error state, the turbine is secured against autonomous restart so that the
projection of ice can be excluded.
November 2010 Chapter 4 Page 14
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