The clean energy replacement of Australia’s antiquated generation fleet is a focused effort by a multitude of participants. It’s easy to miss the wood for the trees sometimes, with progress and fresh hurdles announced day after day, but for the renewables workers it’s busy, busy, busy. Especially about 200km northwest of Melbourne, where the Bulgana Green Power Hub is taking shape.
The hybrid wind-and-battery-storage project near Stawell is tipped to power the country’s biggest vegetable glasshouse, owned by Nectar Farms. The $350 million, 194MW facility will generate over 740,000MWh a year, says French renewables developer Neoen, still buoyed by the naked success of its Hornsdale Wind farm and associated Hornsdale Power Reserve in South Australia.
Bulgana is due for completion in August. Until then, there’s plenty to do.
Testing the foundations
Harrison Meehan, a project engineer for civil contractor Fulton Hogan, has been working on the project since February last year. It was all office work for the first few months but by May he was on site. He’s still there a year later. This is Meehan’s first wind farm. “The last project I worked on was a mine site, so I was interested in seeing the more renewable side of things, which has been quite fun.”
With a wind farm, it isn’t just a case of digging holes and plugging turbines into the ground. “First of all we sent out geotechnical engineers to do bore holes and confirm what type of foundations would be required for the project.” Foundation depth depends on what type of rock is lurking beneath the ground cover, Meehan tells EcoGeneration. Generally, there are two options: a concrete base with a dirt cover, or drill straight into rock and secure the tower using piles. “The only problem with that is it’s about four to five times more expensive,” he says. “So it’s not a preferred option.” A mass concrete foundation can be laid on soil or rock, he says, but rock is preferred for stability and lower risk of settling unevenly.
On solid ground
The Bulgana project will host 56 turbines and more than 40 of the foundations have been built on rock. “We’ve had very few soil foundations, which is good for us.” Foundations in soil are wider and bigger than on flat rock. A foundation on rock will take about 440-450 cubic metres of concrete, he reckons. First, the rock foundation has to be levelled and prepared, with all loose rock removed and the surface built up with blinding concrete to make a uniformly flat surface.
The team is working off a map of turbine sites delivered by a wind modelling consultancy, but some of the locations weren’t optimal from an engineering vantage. “Some of the locations weren’t really doable,” Meehan says, “so we micro-sited them – which is moving them by 30 or 50 metres just to get it into a more friendly location to build.”
For example, one turbine had been proposed for a small valley on the side of a hill, but by moving it 30 metres to the top of a ridge the crew could get the turbine in place with far less earthwork. “It was a lot easier to build; just all-round better.”
Blades were delivered first, with delivery organised by Siemens using the only two trailers available at the time from haulage company Rex Andrews. “The plan was to get two blades to site every day possible,” he says. “Each morning we’d like to get two blades in and then they’d head home in the afternoon. As long as they managed to make it back and get loaded up, they’d drive up again the next day.”
Downer worked on transmission at the site. “They’re very competent. Once they hit their start date, they were just flying through it.” Local companies were used as much as possible for the earthworks, along with companies from as far away as Melbourne and Ballarat. “We’ve had some really good contractors, especially earthworks,” he says.
The local residents like turbines, he says, and the ones who don’t like them are the ones who don’t have them on their properties. One resident wanted nothing to do with them, so an arm of the wind farm planned for a neighbouring property was scratched and that landowner missed out on revenue from hosting turbines.
Nine landowners of seven properties are hosting the project, and sheep farming and cropping will continue as before when the project is commissioned. Twenty turbines are complete.
Neoen also owns and operates the 315MW Hornsdale Wind Farm in South Australia, which is connected to the biggest array of Tesla batteries in the world, the Hornsdale Power Reserve.
“The Bulgana Green Power Hub builds on the knowledge gained through Hornsdale, and our work at Degrussa in Western Australia,” says Neoen Australia head of development Garth Heron. “It’s important to gain a good understanding of your end customer, whether they are a mine, an agribusiness or a network, and design your storage and control system around them.”
This year and last have seen a wave of construction of renewables projects, which has tested the resources of the networks and the Australian Energy Market Operator as developers seek connection to the grid. Much of projected supply of the Bulgana project is already accounted for, with the Nectar Farms hydroponic greenhouse agreeing to take about 15% of generation and the Victorian government signing a 15-year power purchase agreement for some of the output.
“Australia has one of the world’s most complex and dynamic electricity networks, due to its size and relatively low population density,” Heron says. “We put in a lot of work at Bulgana in collaboration with AEMO and our transmission network company, Ausnet, to make sure the connection and control design was both robust and optimised.”
Heron concedes marginal loss factors are a challenge for all new power generation units as the grid shifts from a hub-and-spoke electricity supply model to a far more integrated format where load flows can reverse at different times of the day.
It helps that Bulgana will be backed up by a 20MW/34MWh Tesla battery storage facility, he says.
“Neoen has invested $2 billion since entering the Australian market with a view to expand this investment over the next four to five years,” he says. “We hope to see new generation construction ramping up as power stations are retired over the next two decades.”