Meeting Europe's renewable energy targets in harmony with - RSPB

40 MEETING EUROPE’S RENEWABLE ENERGY TARGETS IN HARMONY WITH NATURE
2.5 TIDAL STREAM
AND WAVE ENERGY
Wave power devices are designed to absorb the
energy from waves and convert it to electricity.
There are three main types of wave technology:
buoyancy devices, fixed or semi-fixed pressure
differential devices and channelling devices.
Wave energy is an emerging technology, with
the potential to supply a very significant amount of
renewable electricity. For example, theoretically
the wave power resource around the UK’s coast
is more than twice UK electricity consumption.
The greatest potential is in the Atlantic seas, for
example off western Scotland and Portugal.
Test centres for wave power technologies
have been established in both countries.
Tidal power also has the potential to generate
significant quantities of energy. BirdLife has serious
concerns regarding ecological impacts where this is
exploited by impounding water at high tides and
then releasing it through “high head” barrages (large
dams). Tidal barrages of this kind were discussed in
Section 2.1. Here the focus is on more innovative and
potentially less risky technologies that make use of
energy in tidal streams.
Currently, there is limited experience of operational
wave and tidal devices at sea and hence little
information about their impacts on marine birds
(McCluskie et al., unpubl.). Therefore, this section
makes inferences about potential effects derived
from existing knowledge of marine processes and
engineering, as well as bird ecology and behaviour.
Fish and marine mammals may also experience
risks and/or benefits where tidal stream or wave
energy devices are installed, but this section does
not attempt to address these for the same reasons.
2.5.1 MAIN CONSERVATION RISKS
Marine birds can be potentially affected by tidal
stream or wave energy devices in a number of
ways. These may be direct (eg, from the device
itself) or indirect (eg, reducing visibility through
increased turbidity), they may be adverse (eg,
collision mortality) or beneficial (eg, creation of
new foraging habitat). Additionally, the impacts
may be temporary or long-term, and last the
lifetime of the device or beyond. In most cases,
little or nothing is known about the likelihood
of occurrence or scale of potential impacts. An
understanding of potential cumulative effects
will also be vital (McCluskie et al., unpubl.).
Collision risk
Wave and tidal devices are likely to present much
smaller collision risks to birds than wind turbines
(Grecian et al., 2010), with the risk related to
species, size and location. It has been argued that
nocturnal and crepuscular species may be more
vulnerable to collision (Daunt, 2006), but such
species often have enhanced visual capabilities,
and this may make them more able to respond to
the presence of devices.
Collision may occur above or below the water
surface, and risk to diving birds could be a concern.
Little information exists regarding collision risk of
animals with underwater structures (Wilson et al.,
2006; Inger et al., 2009; Grecian et al., 2010), and
collisions are more poorly understood for birds
than other species groups (Wilson et al., 2006). This
lack of knowledge has meant that few mitigation
measures have been developed. Wave and tidal
stream devices with rotating turbines are likely to
pose a greater threat to birds than those without
such blades (McCluskie et al., unpubl.).
While in many ways analogous to both wind
turbines and the propellers on ships and boats,
turbines of wave and tidal devices spin at
considerably slower speeds (at or below 12 ms-1)
which may pose a lower risk of injury, although this
may not apply to less manoeuvrable species. The
burst speed of birds, while considerably slower
than the speed of the turbine blade tip (Fraenkel,