Marine power promises predictable, reliable, clean energy, and there are also some tempting targets for development. The Pentland Firth, which separates the Orkney Islands from the north coast of Scotland, for example, is estimated to contain 60 gigawatts of energy as the Atlantic Ocean is pushed into the North Sea at high tide. Similarly energetic tides exist in New Zealand, Ireland, and Canada.
Efforts to harness the sea for electricity generation are still in their infancy, though. A wide range of devices and methods have been proposed; many have been tested in controlled conditions, such as marine engineering tanks. A few have even made it as far as sea trials.
Rough seas might contain a lot of energy, but they’re also one of the most demanding environments in which to operate machinery. Tidal power is a challenge because the difference in water height between low and high tides varies widely around the world. And, with both tidal and wave power, you have to design a machine that can cope with the environment and a method of transmitting the electricity from sea to land.
The device shown here is the one that started it all. Back in 1974, Stephen Salter, then a professor of engineering design at the University of Edinburgh, developed this device, which floats and has a component that turns as a wave passes under it. This movement operates a high-pressure oil-hydraulic system, pushing oil through a turbine to generate electricity.
Tested extensively in tanks, the duck design was intended to be moored in deep water on “slack” lines that would allow it to move with the sea; however, it is now thought to be too fragile to survive in rough conditions.