Falcon swims in turbulant water for tidal energy study

Alternative Sources of Energy, Energy — By on October 12, 2015 at 10:51 AM

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At Torr Head on Northern Ireland’s rugged and dramatic coast, where the Atlantic Ocean and the Irish Sea meet and turbulent waters, strong tides and currents run fast, a Saab Seaeye Falcon spent three days gathering vital benthic data for an impact assessment of a proposed tidal array installation.

Undertaking the assessment project was Marine Ecological Surveys Limited for
their client, Tidal Ventures Ltd, who intend developing a 100 megawatt tidal array.
Daniel Brutto, general manager at Marine Ecological Surveys (MESL) explained
that a detailed benthic characterisation survey of the habitats and species was
necessary to predict the likely impact of the proposed development of the array on
the marine environment.

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He explains that the survey, apart from being required by government agencies to
evaluate the affect of the proposals on the marine environment, also helps
engineers refine their plans for site location and determine cable runs by
identifying the routes least likely to impact the environment.
He also says that considerable savings in field work costs come from providing
such ground-truthing data.

As such tidal sites are chosen for their high-energy nature, they bring challenges in
the shape of high winds, high tides and strong wave energies, declares Daniel
Brutto.

Consequently, the MESL team had to work within a single neap tide window whilst
surveying 40 sites over a three-day period.
With time so critical the cost implications of missing the tidal window and
remobilising a stood-down vessel or keeping it on standby, were considerable.

In such circumstances they needed an ROV operator able to master difficult sea
states and work to deadlines. Their choice was Roving Eye Enterprises who are
based in the Orkney Isles in the far north of Scotland, and have long experience of
working in harsh and demanding sea conditions whilst undertaking precision
filming tasks.

For the project, Roving Eye added a high definition camera to their Falcon ROV
and spent the three-day window filming at the 40 locations whilst sending the data
topside to a team of MESL marine scientists on board the vessel, who were also
directing the survey.

As the images had to be of extreme clarity for observation and record purposes, it
was essential that the Falcon provided a stable platform for filming whilst
overcoming the effects of strong currents and turbulent waters.
Keith Bichan at Roving Eye describes the challenges:

“The place is deep and very tidal, ” he says, “with tides running at five metres a
second, so we quickly had to learn the slacks and eddies across the 40 locations,
and still work in currents running at over two knots.”

He said it was the exceptional thruster power and agility of the Falcon that enabled
it to stay steady whilst filming.

The reduced drag of the ROV’s thin umbilical was also beneficial when working in
high current areas.

Importantly, he says, worries about working in a tight window of opportunity were
assuaged by the reliability of the Falcon that operated tirelessly without any
downtime over the whole three days. This is typical of the reliability that Keith
Bichan has found in the many years he has operated the Falcon.

Daniel Brutto added that the Falcon ROV was a more effective choice for
countering the tidal energies of the site compared to using a dropdown camera.
Such a camera would have resulted in shorter operational opportunities, a more
prolonged and expensive survey, and lessor quality data.

He concludes that the data gathered by the Falcon has helped their client both in
the engineering of the site and in characterising habitats off Torr Head by building
an understanding of their complexity and distribution, and by developing an
important habitat map of the area.

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