Tasmania may have only a small portion of Australia's total population but it has some of the best conditions for green energy, harnessing both wind and water. The state has 2500MW of hydroelectric capacity developed since the 1960's but is now looking to enhance this with around 1000MW of wind-generated electricity, and export electricity to the mainland via Basslink, a proposed cable running under Bass Strait to Victoria. Completion of this link is expected by early 2004.
The Woolnorth wind farm at Bluff Point is a three-stage Hydro Tasmania project on 3000 acres of former farmland that will eventually have 79 turbines producing a total output of 138MW. (The last stage is dependent upon approval being given for Basslink.)
Each 100t 60m tower is constructed in three sections, and topped with a 63t 1.75MW Vestas V66 nacelle (generating unit) coupled to an 18.5t blade assembly. Each of the three blades per assembly is 33m long and weighs 5t. The blades are made of a proprietary Vestas composite mixture that makes them 30-40 percent lighter than any other blade on the market, but with their huge sail area this also means that they can only be assembled when the wind is below 8m/sec.
Alstom Power Ltd in Hobart manufactured the tower sections (the largest section is 25m long, weighs 45t and has a 4.1m base diameter), which were transported to Launceston by Elliott Bros. for painting by Metal Protection Services, then transported to site. The nacelles are landed in Burnie from Denmark, and transported to site by Hazell Bros. The blades are transported to site as a set of three in a container 34m long.
From the second stage (to be known as Bluff Point Wind Farm) fibreglass nacelle housings will be made in Tasmania, and the nacelle, with all its internal components, will be assembled there, as part of a long term agreement between Hydro Tasmania and Vestas to develop the local wind energy industry, with further wind farms planned for Musselroe and Heemskirk. The blades could also be manufactured locally.
The wind conditions that make Woolnorth an ideal site for a wind farm make it a less than ideal site for heavy lifting. Project manager for the Hydro Tasmania Mike Gilmore states that it takes about two hours for each heavy lift. Vestas International, which has a supply and erect contract, has engaged the 600t Demag CC2800 crawler crane of National Cranes (Melbourne) to do the job. This crane is being used with a 78m boom.
The major lifts can only take place safely in less than 10m/sec winds, and complicating this is the need for the top tower section and the nacelle to be erected at the same time, as the tower at full height without a load can develop an oscillation effect that could compromise its structural integrity. A full wind monitoring station is set up on site, and each tower has its own anemometer.
By late July four of the six towers that form the first stage had been erected, and the remaining two are scheduled for erection by the end of August. The heavy lift crew (three Danish wind turbine specialists from Vestas, four local riggers and four crane crew from National Cranes) are on standby around the clock, to take advantage of any window of opportunity for lifting. Floodlights are stationed permanently on site.
The Demag is transported between lift sites on a special multi-axle heavy haulage trailer, and self-dismantles for travel between sites. Tower sites are 250-400m apart. As the ground conditions are undulating peat bog, considerable preparation is required for the roadways on site, and the crane lifts from bog mats.
The Demag is supplemented on site by a range of cranes from local firm Tas Crane Service, including 70t and 150t pin jib cranes, some Tadano truck cranes and a 12t Linmac.
At $200m the Woolnorth Wind Farm project is one of the largest projects currently being undertaken in Australia, and uses the largest and highest output towers to be seen in this country.
Wind farms will provide significant heavy lift opportunities in Australia for a number of years to come, as some of the most suitable sites in the world exist in Australia, with a number of them in Tasmania.