British Columbia wind farm to be built using European techniques

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A Vancouver company is proposing to build an offshore wind farm in northwestern B.C., using unique marine construction techniques and equipment developed in Europe

NaiKun Wind Energy Group is developing plans for the construction of the NaiKun Offshore Wind Energy Project. The project would be located in the shallow waters off the northeast coast of Hecate Strait, between Haida Gwaii (the Queen Charlotte Islands) and Prince Rupert on the B.C. mainland.

“On this wind energy project the work is independent and there is a lot of repetition” said Mike O’Connor, president of Naikun. “The turbines are all identical pieces of construction that are interconnected and link to an offshore platform, which is the most sophisticated component on the project.”

The project involves the construction of 110 wind turbine generators with a plant capacity of 396 megawatts (MW).

“The foundation for the turbine, which is very common in Europe, is a giant open ended steel tube about 4.5 to 5 metres in diameter,” said O’Connor. “They are 55-85 mm in thickness, with the thickest section at the seabed, where there are the greatest forces on the piles. The high strength steel piles are 40 to 50 metres in length.”

Construction of each foundation requires an enormous jack-up vessel, designed to handle high winds and nasty waves. The unique European vessel can accommodate 40 to 50 staff and has amenities such as a café and work out rooms.

The foundations are transported to the site by barge and received by the vessel, which uses a 440 ton crane and a pile guiding frame to lift them into place.

A 200 to 250 ton pile driver places the piles into the seabed, where the water is a depth of 12 to 20 metres at low tide.

“A transition piece, which is 20 metres long, is then slipped on top of the steel pile,” said O’Connor.

“This piece is the transition from the steel pile foundation to the bottom of the turbine tower. It is in the tidal portion, so it is specially treated with anti-corrosive paint. Ladders and bumpers are installed through the tidal zone, so staff can do maintenance.”

There is a five metre overlap between the two sections, which is sealed with a special quick setting high strength grout.

Once the grout sets, the foundation becomes one piece. There is a giant flange on the transition piece that meets up with a flange for the installation of the wind turbine tower.

The jack-up barge has storage for tower sections, which are lifted into place and secured.

The nacelle or hub of the wind turbine generator is lifted about 80 metres above the water to the top of the tower.

The blades are lifted and attached to the rotor.

Once this is completed, the jack-up moves to the next location and continues the same operation.

This construction process is estimated to take about 1.8 days per foundation including an allowance for weather delays.

Actual working time at each site is expected to last less than one day; with the pile driving itself taking 2 to 4 hours.

Foundation installation takes place 24-hours per day, seven days per week.

The platform, that forms the deck of the offshore converter station, will be constructed and installed in the same way.

The platform will accommodate the transformers, equipment, maintenance supplies, fuel, waste storage, boat access facilities, and a helicopter pad. It will be built on four or six steel foundations and supported by a self-elevating platform.

The offshore converter station receives the collected power from all wind turbine generators and converts the AC power to +/-200 kV DC for transmission via an exportsubmarine cable to the mainland landfall on Ridley Island.

The cables will be routed from the seabed up through J-tubes, which protect the cable as it enters the foundation and rises up to the platform.

The Ridley Island station takes the high voltage direct current and converts it to high voltage alternating current for delivery to the existing Port Edward substation.

Marine construction will occur between April and September when weather and sea conditions are most favourable.

More than 200 people will be needed to build the wind project including construction workers, marine operators, cooks, helicopter pilots and administrative support staff to name a few.

Construction is scheduled to begin in 2010 and conclude in 2014. On-site construction works will take place over three seasons from 2012 to 2014.

The project will produce 1.3 gigawatt-hours of energy a year, which is enough electricity for 30,000 homes.

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