Microgrid reduces mine diesel use by almost half

It has been just over two years since the country’s biggest hybrid renewable energy microgrid opened at a remote gold mine in Western Australia.

At the time, the Agnew Hybrid Renewable Microgrid at Gold Field’s Agnew Gold Mine 1000km north-east of Perth was described as a “guinea pig” project. 

Gold Fields Executive Vice President Australasia Stuart Mathews said at the opening the Agnew microgrid was “groundbreaking”.

“… This project has provided a framework to take innovative energy solutions further across Gold Fields’ mine sites both in Australia and around the world,” Mathews said.

The project was built with the support of $13.5 million in funding by the Australian Renewable Energy Agency (ARENA) under the Advancing Renewables Program.

So just how has this microgrid, owned and operated by EDL, performed so far?

While the microgrid officially opened in November 2021, it actually began operations in mid-2020. It was the first mine in Australia to be predominantly powered by wind-generated electricity.

The microgrid includes five energy technologies: five wind turbines delivering 18MW; a 4MW solar farm; a 13MW/4MWh battery energy storage system; an off-grid 21MW gas/diesel engine power plant; and advanced microgrid control systems.

Chief Executive Officer at EDL, James Harman, says “the Agnew project has exceeded expectations, providing 55-60% of the mine’s energy requirements daily, and more than 80% in optimum weather conditions.”

Diesel and electricity emissions at the site have reduced by 42%.

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An alternative power source?

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At the time of commissioning, the grid emissions factor (the amount of CO₂ emissions intensity per unit of electricity generation in the system) more than halved from approximately 0.59 to 0.27tCO₂-e/MWh, according to the Knowledge Sharing Final Report prepared for ARENA by Gold Fields.

But General Manager Remote Energy at EDL, Geoff Hobley, said the project did not come without its share of challenges.

Aside from the obvious logistical nightmare of transporting huge equipment, including the 70m long turbine blades for five turbines cross-country to the outback town of Leinster, this venture into renewables straddled global turmoil.

“Agnew was commissioned during the early stages of the COVID-19 pandemic, which meant dealing with travel restrictions to, from and within Western Australia,” Hobley says.

“Specialised team members and equipment were required from interstate and overseas, adding complexity to the commissioning process and placing additional pressure on our people.”

Hobley says the pioneering aspect of the project in integrating wind, solar, a battery system, a control system to manage power delivery and an underlying thermal power station (gas or diesel-powered) for continuity of power added to the complexity.

“Operationally, the thermal generators in a hybrid power solution are required to work differently from their usual application in a traditional ‘thermal only’ solution,” he says.

“This can place additional stress on the thermal generators as they often operate at lower loads. Interestingly, the renewable generation assets are often the easiest to manage, as they operate most closely to their intended design.”

Sometimes, Hobley says, issues only become apparent after the system is operational. At Agnew, there have been some challenges in meshing the variable wind resource with the thermal station operations.

Agnew currently only has predictive solar technology, but has committed to day-ahead wind forecasting by June 2024.

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Another micropower solution

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EDL’s Operations Manager Remote Energy WA, Paul White, adds finding employees with microgrid experience has also been a challenge, particularly in a tight jobs market. So EDL has developed on-site microgrid training to help overcome this.

On the whole, Hobley says, any issues have been relatively minor.

“Most of these are now resolved and other solutions are under development,” he says. “These lessons are incorporated to optimise performance and inform future projects.”

Agnew is still the largest hybrid renewable microgrid in Australia. Hobley says EDL will use what they have learnt for future projects.

While Agnew has been designed to run with some thermal generators running at any time, EDL also operates a number of other hybrid renewable projects that can operate for periods on 100% renewable energy.

The Coober Pedy Hybrid Renewable Power Station, which powers the remote mining town of Coober Pedy in South Australia, has at times reached 100% renewable energy, and the Jabiru Hybrid Renewable Power Station in the Northern Territory draws on 100% solar energy during the day, with excess stored in a battery.

The Jabiru station has led to a 1.7 million litre reduction in diesel consumption each year.

Hobley says EDL also has other projects under development with mining companies in regional and remote Australia, some of them existing mine operators looking to decarbonise their operations, and others seeking to “set new world benchmarks for low-carbon mining operations”.

“It is an exciting time to be working in this industry, delivering world-leading solutions to a market that demands low-carbon energy,” he says.

And Agnew has played a role in that innovation, Gold Fields’  Knowledge Sharing Final Report says.

“Since completion, the publicity and awareness around the success of the project has reached far and wide…” the report says.

“This awareness has given industry a measure of confidence that projects of this nature are viable and that the ‘guinea pig’ for high-penetration microgrids has survived.”

A live feed of the renewable energy penetration can be viewed at Agnew’s Hybrid Renewable Microgrid page.

To take a look at the construction of Agnew