Different concept for offshore efficiency -- Innovations from ABB

The giant ABB concern, with 165,000 employees in 100 countries, has released details of what it claims is a new type of wind energy conversion system, the Windformer. Use of the Windformer can increase wind energy production by 20%, according to ABB. This article takes a detailed look at the technology.

At the same time as the giant ABB concern, with 165,000 employees in 100 countries, announced last month that it would invest $300 million in renewable energy over the next five years, it also released details of what it claims is a new type of wind energy conversion system, the Windformer. Use of the Windformer can increase wind energy production by 20%, according to ABB.

Despite broad wind industry scepticism that this claim can be substantiated, ABB's announcement was followed by falling share prices for both Vestas and NEG Micon on the Danish stock exchange. The drop was sparked by fears that ABB was preparing to directly compete on the market with a new wind turbine model, a supposition firmly denied by the company.

The Windformer is a two-part technical innovation based on a direct drive, multipole generator which is to be tested by Swedish utility Vattenfall in a planned 3 MW variable speed wind turbine being supplied by the Norwegian-Swedish ScanWind Group. In appearance the wind turbine will resemble a giant version of the German Enercon or Dutch Lagerwey gearless machines with their distinctive nacelle "collars" which house the ring generator. The ScanWind turbine's 43 metre blades will be from Dutch Aerpac.

Neither a gear box nor transformer are needed thanks to the Windformer's innovations, says ABB. First, the direct drive generator delivers power at an unusually high voltage of 25 kV DC -- and all the connections within a wind farm can be made at this voltage. Second, use of the Windformer's HVDC Light technology means the high voltage power can be transformed from DC to AC, to be acceptable to the grid. Normally wind plant generate AC power at voltages less than 1 kV. As a result, step-up transformers at each wind turbine are used to raise the voltage and so reduce interconnection losses, both within the wind farm and on the way to the distribution network.

Not only will the Windformer DC generator work at high voltage, it will also be the first time that permanent magnets are used instead of coils of electro magnets, adding simplicity and further efficiency gains in a machine of this size, says ABB.

The ABB engineers behind the Windformer, Niels Immerkjær and Frederik Owman, claim that the huge direct drive generator -- seven to eight metres in diameter and turning only at rotor speed -- is as efficient as a conventional fast running induction generator. The 20% increase in production, according to Mats Leijon from ABB's Zurich office, comes from more energy production at low wind speeds and other benefits from using variable speed (8%); reduced losses with sending DC power to the grid over long distances, instead of AC power (8-9%); and reduced outages which may add another 3% to energy production. ABB accepts, however, that there will be small losses from transforming the generator's DC power to AC at the point of connection to the network.

Immerkjær and Owman stress that the technology has been developed for the truly offshore market and it is here that the Windformer's efficiencies can be realised -- both greater production and lower costs. ABB estimates a generation cost of $0.04/kWh, claiming that installed costs offshore will be reduced with the Windformer as there will be less electrical equipment.

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