Wave power moves ahead

Australian wave power developer Energetech, in a joint venture with BC Hydro of Canada, expects to build a 2MW oscillating water column (OCW) plant on Vancouver Island, British Columbia by 2004. The partners' Memorandum of Understanding (MoU) signed on 26 February 2002 - which is conditional on successful completion of a pioneering 500kW project at Port Kembla, New South Wales, Australia - makes the project the first in wave energy to be commissioned by a major utility.

The project is part of BC Hydro's 20MW exploration of the commercial viability of wind (10MW), mini hydro (6-8MW) and wave (3-4MW) energy in its service area. It signed a second 2MW wave energy MoU on 13 March 2002 with ocean-power-delivery (OPD), that is similarly contingent on successful technical development The two developers were among ten who responded to BC Hydro's July 2001 request for proposals. Among four subsequently shortlisted companies, they were selected ahead of UK-based Wavegen and AquaEnergy Group from the US.

The two selected technologies are very different. Energetech's shore-based (typically port breakwater) OCW system employs a parabolic seawall aligned to be perpendicular to incoming wave fronts to focus wave energy at the parabola's centre. Wave amplitude at the centre, and consequently available wave energy, is roughly three times the average of unfocused heights.

As each focused wave enters the tapered capture chamber, whose broad base is below the deepest wave trough, it forces commensurately more air past a patented Denniss-Auld turbine located in the narrowest portion of the open taper neck. As the wave withdraws, thereby creating a partial vacuum in the chamber, airflow is reversed.

As with the Wells turbine, the Denniss-Auld turbine rotates in the same direction irrespective of the direction of airflow. Energetech claims, however, that its combination of focused waves, large energy capture chamber, and comparatively low-speed high-torque turbine-generator that is microprocessor-primed to react optimally to each individual wave, has over 50% better energy conversion efficiency than a standard Wells-based system.

The company expects first generation plant deployed in moderately good wave 'climates' to generate power at around 10 US cents/kWh. These costs should fall to 5 cents/kWh at an ideal site and 4 cents/kWh at moderate sites with second and third generation plant. It aims to reduce capital costs to US$2000 per net kW (US$430 per gross kW) by 2005.

An ideal site consists of a flat, smooth sea bottom of sufficient depth near shore so that waves that are consistently aligned perform well during focus. Each plant including the parabola dimensions and focal length as well as the microprocessor controls can be tailored to match specific sea conditions.

Ocean Power Delivery's Pelamis floating technology, in contrast, uses offshore wave motion to energise high pressure hydraulic fluid contained in a 'snake' of articulated cylinders. Fluid flows between cylinders drive turbines located at the joints whose power is first transferred to the seabed and then evacuated to shore. OPD estimates a square kilometre of ocean would allow a 30MW installation.

Both companies hope the 2MW plants will be expanded, with Energetech eyeing 100MW at Vancouver Island by 2008. The actual location, Ucluelet on the island's Western coast, is already being wave energy mapped - wave height, period and direction - with a solar-powered buoy for a full year.
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