There are two turbines on the north facing side of each platform and the final turbine is going up on Bessemer. The units will run in tandem with diesel generators, feeding power into a battery bank. It is expected they will supply 40% of demand, says Vergnet's William Hopkins, but given the wind speeds they could do even better, he adds. "The unmanned platforms are a testing ground for AMOCO as much as they are for us. They are designed to economically exploit small pockets of gas which have life times of between five and eight years. The platforms will then be moved to another site once the gas has been retrieved," explains Hopkins. "If the platforms prove economic many more will be constructed, with the wind turbines being a standard component."
The Vergnet 5 kW, which has a rotor diameter of 5.5 metres, has been specially adapted for North Sea use. Blade material has been changed from wood to carbon composite, the generator is waterproof, a support structure has been designed for platform mounting, a yaw damper will reduce fatigue on blade roots on the turbulent sites, and special marine paint was used to AMOCO standards.
The 13 kVA diesel generator on each platform is backed up by another 40 kVA generator to cater for long periods without wind. For AMOCO the wind turbines mean cash savings. Re-fuelling trips to the platforms will be reduced from every three to every six months.
Hopkins says there have been wisecracks from wind proponents about the wisdom of assisting AMOCO to produce cheaper gas and thereby reducing wind energy's relative competitiveness. "I guess an answer to that would be that a reduction in the cost of anything is good in itself and that it is up to pricing strategies to promote favoured sources of energy; but then again, a few wind turbines are probably not going to change international gas prices," Hopkins wryly comments.