"Marine power has long been a tantalizing prospect for energy researchers. Tides are much more predictable than wind or sun....
Still, companies here have found that harnessing wave and tidal energy isn't easy. Any device must be tough enough to withstand the sea's constant movement, including what one developer here calls its "horrendous storms." Maintenance is a constant challenge.
The ups and downs of the Pelamis sea snake's segments turn wave motion into power. Pelamis
Near Hoy, in the island group's southwest, a wave device owned by Pelamis has been brought into the harbor for maintenance. The device, a series of large, rocketlike tubes, resembles a giant red and yellow sea snake swimming over the ocean surface. As the sections of the snake, connected by joints, rise and fall, they push and pull connecting pistons, producing power from the sea's movement.
Undersea cables from the Orkney shore connect to the Pelamis device—and others—transmitting the power to EMEC, which owns a substation connected to Britain's national grid."
http://online.wsj.com/news/articles/SB10001424052702304810904579507884217363454?KEYWORDS=+tidal+technologies&mg=reno64-wsj