“So hope for a great sea-change on the far side of revenge, believe that a further shore is reachable from here. Believe in miracles” Seamus Heaney
In May 2013, a wave energy machine called Pelamis P2, sited north of Scotland at Billia Croo, completed an important first year test programme. Named after a type of sea snake that swims on the ocean surface, able to survive in all weather conditions, the Pelamis P2 is inspired and informed by nature. It’s made up of coupled 4m-wide steel tubes that move with the ocean surface to generate energy, whilst inside the tubes, a slick array of hydraulic cylinders, compressors and converters turn wave motion into green electricity. I met Deborah Smith of Pelamis last summer at the Green Business Awards.
How it Works
Central to the Pelamis P2 design is the articulated tube – there are five sections in total and these are linked by universal joints, which give the machine its snake-like flexibility. The machine floats at the surface of the ocean and naturally faces into the waves. As each wave passes, the sections bend and the movement is converted via hydraulic power take-off systems inside the tube. The system basically works by pumping fluid into high-pressure accumulators, to generate smooth and continuous electricity. It’s a rather simple analysis, but there is a detailed description on the Pelamis website, if you seek more info. This power is then transmitted to shore using standard subsea cables and equipment.
Surviving Harsh Conditions
Billia Croo test site is a wild spot off Orkney, subjected to the powerful forces of the North Atlantic Ocean, and enjoying one of the highest wave energy potentials in Europe. The average wave height is 2 – 3 metres, but extremes of up to 17m have been measured and this makes it a perfect place to test the Pelamis P2 with monitored exposure to increasingly large wave conditions.
The designer behind this project is an engineer called Richard Yemm, who has spent many years researching wave power. The ocean is a tough environment, and Pelamis P2 has been designed with survivability in mind, strengthened by steel, able to move with the tides or dive through bigger waves, streamlined to work with the forces of nature.
The success of Pelamis is part of a long held wisdom that we should be working with nature, and not in arrogant or economic isolation. Which is something engineers, farmers and growers, and those living/working closer to earth often grasp early on … and here they are, turning out amazing solutions in response to what is now an urgent scientific consensus on climate change and atmospheric physics.
Wave Energy and Tidal Energy
Waves are formed by winds blowing over the surface of the sea. The size of the waves will depend upon the wind speed, its duration, the distance of water over which it blows, the shape of the sea floor and local currents. Of course each wave carries kinetic energy, but the best wave resources will be in areas where strong winds have travelled long distances with minimal friction from the seabed and these waves in deeper, exposed waters generate much more energy.
Closer to home, in Swansea Bay, the attention has turned to tidal energy. Tidal streams are created by the constantly changing gravitational pull of the moon and sun. Tides never stop, with water moving first one way, then the other. Tidal technologies capture the kinetic energy of the currents flowing in and out, and because the relative positions of the sun and moon can be accurately predicted, so can the tides. This predictability will make tidal energy a particularly valuable resource.
Investing in our future
Pelamis have produced six full-scale Pelamis wave energy machines to date, including two of the latest ‘P2’ design, which were supported by E.ON and Scottish Power Renewables. The stage of improvement and development is not over, but the latest test results are looking good. This early investment in wave power is not wasted money, but an important use of money for the future … a future where sustainable technology meets nature. In the longer term, team Pelamis believe that wave power could become one of the lowest cost forms of clean renewable energy generation. And that is something worth investing in.