Wave energy

Pelamis

Waves contain great power within them. The Pelamis can utilise this source of power to drive generators to create electricity

Each Pelamis has three power conversion modules that together generate 750KW. A wave farm of twenty Pelamis machines generates power for 10,000 homes.

Waves move across the sea and cause the Pelamis to rise and fall in a snake-like motion. Sections move against each other on hinges resisted by hydraulic rams that drive generators to produce electricity.

The three 140m-long “snake” structures each weigh 350 tonnes and consist of four long cylindrical tubes, interconnected by three smaller tubes. They are semi-submerged in the water, and positioned so that each of the larger tubes can move up and down as waves pass under and along them.

The three units installed so far generate 2.25MW of electricity. Another 25 machines are planned for the site, to generate a total of 21MW.

The smaller tubes each contain four pistons, connected to two tanks – one high pressure and the other low pressure – and a motor connected to a generator.
Waves cause one pair of pistons to open and close from the up and down motion of the long cylinders and the other pair to do the same from their side-to-side movement.

As the pistons open they draw hydraulic fluid from the low-pressure tank, forcing it into the high-pressure tank as they close. The flow of the fluid generates electricity.
“The bigger the wave, the more the energy,” said Max Carcas, business development director of Pelamis. Crucially, the machines have been developed to survive storm waves, but they cannot harness energy from waves above 7m. “When you have a machine like this, the most important thing is that it can withstand the waves,” said Carcas.

see more at Ocean Power Delivery