A World First for Pelorus Surveys
In the Spring of 2002, Pelorus Surveys conducted
a Hydrographic, Geophysical and Oceanographic
survey in Yell Sound, Shetland. The survey contract
awarded by The Engineering Business (EB) was part
of a programme of works to extract energy from
tidal streams. The information provided by Pelorus
Surveys was crucial for the positioning of the
worlds first Stingray, a prototype 150kW underwater
tidal power generator.
An area of possible deployment was identified
by EB and it was the job of Pelorus Surveys to
confirm the suitability of the site for Stingray.
Two important factors governing the siting of
the Stingray are a level sea bed and appropriate
current conditions.
After identifying an area of approximately 60m
x 60m in a relatively uniform water depth of 30m
various hydrographic and geophysical survey techniques
were utilised including echo-sounding, sub-bottom
profiling and side scan sonar.
In order to ascertain the direction and magnitude
of the prevailing currents through the water column
an Acoustic Doppler Current Profiler (ADCP) was
mounted aboard the survey vessel and a survey
over a full tidal cycle conducted.
A Benthic survey by means of underwater video
survey was also conducted within the area to identify
the presence of any species of conservation interest.
Once the results of the surveys had been assessed
and the exact location for Stingray decided the
ADCP was mounted in a seabed frame and deployed
to the seabed for a period of one month at the
exact location identified for the installation
of the Stringray Generator. Currents identified
at the site showed a spring tide current velocity
in excess of 5 knots, proving the location ideal
for Stingray which was successfully deployed during
the summer of 2002.
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