From the archive, originally posted by: [ spectre ]

Underwater turbines set to generate record power
BY Kurt Kleiner  /  21 August 2007

By the end of the year, twin underwater turbines should be generating
1.2 megawatts of electricity off the coast of Northern Ireland in a
landmark demonstration of tidal power technology.

Marine Current Turbines, a company based in Bristol, UK, had hoped to
begin installing the turbines at Strangford Lough (Google map) on
Monday, but the construction barge scheduled to deliver the turbines
was delayed. A company spokesman says the installation will now take
place later in 2007. It will be the world’s largest tidal power

The underwater turbines look and work very much like wind power
turbines. Each blade is 15 to 20 metres across and is mounted on an
axis that attaches to a 3-metre-wide pile driven into the seabed.

Tide-driven currents will move the rotors at speeds of between 10 and
20 revolutions per minute, which the company claims is too slow to
affect marine life. The turbines will drive a gearbox that will, in
turn, drive an electric generator and the resulting electricity will
be transmitted to the shore via an underwater cable.

The Strangford Lough tidal generator is intended purely as a
demonstration project. Eventually, MCT intends to build farms of
turbines consisting of 10 to 20 pairs each.

Each turbine requires a piece of equipment called a jack-up barge for
installation. The barge anchors itself to the sea floor and drills a
hole that sets the turbines in place.

“Of the 60-odd [tidal power] projects I’ve seen, this seems like the
best,” says Dave Elliott, a professor in technology policy at the Open
University in Milton Keynes, UK.

“It’s an interesting period,” Elliott adds. “You have lots of
approaches and lots of innovative projects. The straightforward
underwater propeller seems like the winner.”

Elliott says that tidal and wave power could eventually provide
between 15% and 20% of the UK’s electricity needs. But he believes
that operators need to develop experience with the technology before
the price of energy generated in this way falls to levels comparable
to wind power.

Welcome to the SeaGen Project Website

SeaGen is the name given to the 1.2MW tidal energy convertor that will
be installed in Strangford Lough during 2007. Sea Generation Ltd is
the project company which is a wholly owned subsidiary of Marine
Current Turbines Ltd. SeaGen has been has been licensed for a maximum
installed duration of 5 years.

Marine Current Turbines Ltd have been operating the 300kW Seaflow
tidal energy system at Lynmouth, Devon since May 2003 and are
recognised as being one of the worlds leading tidal energy system

Phone +44 (0) 117 979 1888
Fax +44 (0) 117 906 6140
E-mail info [at] marineturbines [dot] com

Marine current turbines work, in principle, much like submerged
windmills, but driven by flowing water rather than air. They can be
installed in the sea at places with high tidal current velocities, or
in a few places with fast enough continuous ocean currents, to take
out energy from these huge volumes of flowing water. These flows have
the major advantage of being an energy resource which is mostly as
predictable as the tides that cause them, unlike wind or wave energy
which respond to the more random quirks of the weather system.

The technology under development by MCT consists of twin axial flow
rotors of 15m to 20m in diameter, each driving a generator via a
gearbox much like a hydro-electric turbine or a wind turbine. The twin
power units of each system are mounted on wing-like extensions either
side of a tubular steel monopile some 3m in diameter which is set into
a hole drilled into the seabed.

The technology for placing monopiles at sea is well developed by
Seacore Ltd., a specialist offshore engineering company (and MCT’s
largest shareholder) which is co-operating with MCT in this work. The
patented design of our turbine is able to be installed and maintained
entirely without the use of costly underwater operations. A unique,
patented feature of MCT’s technology is that the turbines and
accompanying power units can be raised bodily up the support pile
clear above sea-level to permit access for maintenance from small
service vessels. This is an important feature because underwater
intervention using divers or ROVs (Remotely Operated Vehicles) is
virtually impossible in locations with such strong currents as are
needed for effective power generation. The artist’s impression
indicates a row of turbines and shows one raised for maintenance from
a small workboat.

The submerged turbines, which will generally be rated at from 750 to
1500kW per unit (depending on the local flow pattern and peak
velocity), will be grouped in arrays or “farms” under the sea, at
places with high currents, in much the same way that wind turbines in
a wind farm are set out in rows to catch the wind. The main difference
is that marine current turbines of a given power rating are smaller,
(because water is 800 times denser than air) and they can be packed
closer together (because tidal streams are normally bi-directional
whereas wind tends to be multi-directional).

Environmental Impact Analyses completed by independent consultants
have confirmed our belief that the technology does not offer any
serious threat to fish or marine mammals. The rotors turn slowly (10
to 20 rpm) (a ship’s propeller, by comparison, typically runs 10 times
as fast and moreover our rotors stay in one place whereas some ships
move much faster than sea creatures can swim). The risk of impact from
our rotor blades is extremely small bearing in mind that virtually all
marine creatures that choose to swim in areas with strong currents
have excellent perceptive powers and agility, giving them the ability
to successfully avoid collisions with static or slow-moving underwater

Another key advantage of MCT’s technology as a future large scale
generating technique is that it is modular, so small batches of
machines can be installed with only a short period between investment
in the technology and the time when revenue starts to flow. This is in
contrast to large hydro electric schemes, tidal barrages, nuclear
power stations or other projects involving major civil engineering,
where the lead time between investment and gaining a return can be
many years.

It is expected that MCT’s turbines will generally be installed in
batches of about 10 to 20 machines. Many of the potential sites so far
investigated are large enough to accommodate many hundreds of
turbines. It is worth noting that as a site is developed, the marginal
cost of adding more turbines and of maintaining them will decrease, so
considerable economies of scale can be gained as the project grows.

The design life for MCT’s tidal turbines will exceed 20 years and we
believe the main monopile support structure can be designed to survive
for many decades (the track record of steel offshore structures,
providing they are properly protected, is excellent – many offshore
oil and gas structures have lasted upwards of 40 years). The steel
pile and other main structural elements in an MCT tidal turbine have
cathodic protection and the rotor is constructed from glass and carbon
fibre reinforced composite materials which are not significantly
effected by contact with seawater.

Supplementary R&D projects:-
Various research tasks are being carried through with various

Design and Modelling programme for the Phase II Twin Rotor machine is
being done in conjunction with QinetiQ as an important prelude to the
detailed design of the Phase II machine.  This programme is being
managed by MCT, and is also specifically tasked to develop industrial
partnerships to hasten the technology to market.


Research is planned into specialised generators and power trains.


Research into the tidal stream resource at various locations.  A
detailed GIS database with specialist modelling tools is being


MCT has successfully completed and will continue to carry through
specialist consultancy studies in relevant areas. Past and present
projects include:-

Feasibility study into use of tidal currents in the Philippines
(involved some initial site measurements) – completed under Climate
Change Challenge Fund grant from the UK Foreign and Commonwealth
Office in cooperation with the Department of Energy and with NAMRIA in
the Philippines (2001-2)

Feasibility study into the possibility for using a new bridge
structure planned for Montrose Harbour to generate power from currents
passing underneath – completed for Angus County Council under sub-
contract to Halcrow Crouch Ltd (2001)

Assessment of the tidal stream potential for Scotland for the
Scottish Executive under sub-contract to Garrad-Hassan Ltd (2001)

Supplementary assessment of the tidal stream potential for the
Scottish Western Isles for the Council of the Western Isles under sub-
contract to Garrad-Hassan Ltd (2002)

Contribution to study by Robert Gordon University for Scottish
Enterprise on the energy potential of the Pentland Firth (2001)

Assessment involving site measurements of the tidal stream
energy potential for Northern Ireland in partnership with Queens
University Belfast and with Seacore Ltd; for the government of
Northern Ireland (2002)

Tel: +44 (0)117 979 1888
Fax: +44 (0)117 906 6140
E-mail: sylvie [dot] head [at] marineturbines [dot] com

Dave Elliott

Dr David Elliott is Professor of Technology Policy. He has been
involved with the production of a range of OU courses in Design and
Innovation, with an emphasis on how the design and innovation process
can be steered towards the development of socially and environmentally
appropriate technologies. His main research interests relate to the
development of sustainable energy technologies, and in particular
renewable energy based systems. He is co-Director of the Energy and
Environment Research Unit, which is based in the Department of Design
and Innovation, and he is editor of its journal ‘Renew’.

Email: d [dot] a [dot] elliott [at] open [dot] ac [dot] uk
Phone: +44 (0) 1908 653197
Fax: +44 (0) 1908 654052