15 Jul First commercial wave power plant opens
The new plant works with the Oscillating Water Column (OWC) technology of Voith Siemens Hydro’s Scottish subsidiary Wavegen, where it has been successfully field tested for seven years. Mutriku Harbour stands in a small natural bay, in an area regularly hit by Biscay storms, which over the years have damaged the piers in the harbour and caused major instability and choppy seas in the channel leading into the harbour and the inner docks. This choppiness, combined with the narrowness of the harbour mouth has often made it hazardous or even impossible for boats to enter the harbour. To address this problem, the Basque Government’s Directorate of Ports and Maritime Affairs examined no fewer than 17 different alternatives for layouts, including extending the existing breakwater, building an outer breakwater or a submerged breakwater, among others.
The project finally approved and put out to tender involved a detached breakwater approximately 440m in length with a pierhead at either end. The breakwater is accessed by way of a path some 370m long, protected by rockfill. The breakwater is sloped, with a concrete haunch and masonry facing running along the entire length. With the initial project defined, and as part of an overall strategy of developing renewable energy sources, the Basque Government’s Department of Transport and Public Works signed a collaboration agreement with the Ente Vasco de la Energía, the Basque energy board to take advantage of construction of this infrastructure to install an ocean energy generation plant.
With the design completed for a breakwater to resolve problems of access to the harbour at Mutriku, the Basque Government’s Department of Transport and Public Works contacted EVE to examine the possibility of taking advantage of the construction work to introduce some form of wave-based power generating arrangement. Given that the project was at an advanced state of definition, there were two initial conditions. The proposed solution should not interfere with the breakwater’s primary function, to improve sea access to the port, and the design of the breakwater should not suffer too many alterations. It emerged that OWC (Oscillating Water Column) technology could be incorporated into the design of the breakwater. The OWC devices are simple and non-disruptive. They use the oscillating movement of the waves and it is not actually the seawater itself that moves the turbines. The turbines never come into contact with the water.
The arrangement consists of a hollow structure, open to the sea below water level with a hole at the top of the chamber. When the wave comes in, the water enters the chamber, compressing the air inside which is pushed out at high pressure through an opening at the top. This pressurised air turns the turbine, which in turn drives the alternator, generating electricity. When the wave falls, it sucks air through the same opening, again driving the turbine which continues to generate electricity. The fact that it is the air and not the water that moves the turbine considerably extends the service life of the equipment. “Mutriku is a milestone in the history of wave energy, said Dr. Hubert Lienhard, president and CEO of Voith Siemens Hydro. “We are proud that the first breakwater wave energy plant will rely on Wavegen’s technology”.
The new project sees the integration of 16 Wells turbines into Mutriku’s new breakwater. Voith Hydro’s wave power technology can be deployed in new and existing breakwaters, and in purpose-built structures. The worldwide potential of the ocean energies is an estimated 1.8 terawatts and still remains largely untapped.