Wind energy in New Zealand – Otago?s first wind farm

Firth Industries has been contracted to Downer NZ Ltd to supply concrete foundations for secure the wind turbines for Trustpower’s new 36 Megawatt (MW) wind farm at a site on the hills overlooking Lake Mahinerangi, 55kms west of Dunedin.

Stage One of the Mahinerangi (Puke Kapo Hau) Wind Farm includes the installation of twelve 3 MW Vestas V90 wind turbines. The wind farm’s official Maori name means “the hill that catches the wind”.

The long term expected annual output from the wind farm is forecast to be 105 GWh (Gigawatt hours) per annum, which is enough power to supply approximately 13,000 Dunedin homes.

“Firth is delighted to be supplying concrete for the new wind power project,” says Dominic Sutton, Regional Sales Manager, Firth Southern. “We will provide a total of approximately 5,000 m3 for the bases of the wind turbines – the first pours began in early November and we expect to be finished by Christmas, 2010,” he says.

Due to the remoteness of the site and the speed with which supply was required Firth installed two mobile concrete plants to supply the wind farm.

The mobile Coneco concrete plant that was installed at the Auckland International Airport was relocated to the remote site as well as Firth’s mobile Zengo plant from Marsden Point near Whangarei.

“We had delays in getting the two mobile concrete plants up the road to the site due to heavy snow in late September,” says Sutton. “But, since then things have been progressing well on the job and with typically two bases being placed per week.”

Each wind turbine will be set in a hexangular shaped foundation. These bases are excavations approximately two metres deep each containing 410 cubic metres of concrete. Each foundation also contains 47 tonnes of steel reinforcing and once the concrete is in will have a total counter weight of approximately 900 tons to anchor each turbine to the hillside.

Firth’s Area Operations/Sales Manager South Canterbury/Coastal Otago Aaron Charteris says the biggest challenge has been coordinating the project teams from Firth plants all around the region to work on the individual pours. “We have had to bring in people from as far afield as Timaru, Geraldine, Fairlie as well as Dunedin,” he says.

Once the concrete is cured the wind towers that the wind turbines will be mounted on will be erected – it’s expected that this will commence in early January.

The wind power from the wind turbines will be fed through Trustpower’s nearby Waipori Power Station and into the local Dunedin electricity network. Completion of the wind farm is expected in April 2011 with full commissioning by May 2011.