The utilization of tidal power in Strangford
Lough is not a new 
concept,
some 1,400 years ago monks at Nendrum
at the northern end of the lough installed a tidal mill to grind grain,
the remains of their mill excavated in 1999 has been carbon dated to
AD 619.
In March 2008 a massive crane barge the Rambas
entered Strangford Lough, it was carrying Seagen which was set to become
Ireland's first tidal power generator. Seagen was designed by Marine
Current Turbines Ltd. based in Bristol (England) it has an output of
1.2 Mw which is enough to supply the electrical needs of 1,000 homes.
Briefly described Seagen consists of a steel tube 3 metres (9 ft 10 inches) in diameter, set on a quadruped base which is attached to the seabed. On the top of the tube well above the water is the control pod from where engineers can monitor Seagen's performance.
Seagen has two generators driven by variable pitch propellers (The angle on the blades is reversed to suit the incoming and outgoing tide) these two propellers ar set on each end of an arm which is attached to a tube surrounding the main tube, this outer tube can slide up and down the main tube, somewhat in the fashion of the squeegee action of a sponge mop.
The reason for this is to enable engineers to bring the generator/propeller unit above water for routine maintenance, this is achieved using hydraulic rams located in the control pod, these rams engage with the jacklegs (The two steel poles visible in many of the pictures) this technology is much used in the offshore oil industry.
The above description is graphically illustrated in an image and some excellant animations on MCT's website
