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Gold Fields, one of the world’s largest gold miners, plans to deploy a hybrid microgrid at a mine in Western Australia with an eye toward applying lessons learned to its other operations.
The South African company has signed a deal with Aggreko, UK-based off-grid and remote power systems specialist, to design, build and operate the microgrid, which will use natural gas generation, 8 MW of solar power and a 2 MW/1 MWh lithium-ion battery energy storage system. The project will be installed at the Granny Smith mine east of the town of Laverton in Western Australia’s Goldfields region.
Aggreko will deliver electricity to the mine under a power purchase, microgrid-as-a-service agreement, spokesperson Philip Hiersemenzel told Microgrid Knowledge.
The solar-storage system is expected to produce 18 GWh per year of emissions-free energy and reduce fuel consumption at Granny Smith 10-13 percent per year. It will be integrated with natural gas-fueled generation that Aggreko and Gold Fields installed at the mine in 2016 and upgraded in 2017. The natural-gas power generation will be increased to 24.2 MW, according to Gold Fields.
Powering underground mining and ore processing
The expanded, hybrid microgrid will independently power Granny Smith’s Wallaby underground mine (12.2 MW) and the facility’s processing plant (12 MW).
The microgrid “is part of our overall sustainability strategy, particularly in Australia where we’re reliant on a single supplier for natural gas. In Australia’s outback the obvious solution is solar,” Gold Fields’ spokesperson Sven Lunsche told Microgrid Knowledge. “We’re trying to be more energy efficient, and make use of renewables to reduce carbon emissions and the impact on climate.”
Cost, energy security and climate change considerations were key factors that led Gold Fields to choose the hybrid microgrid, Lunsche said in an interview. “Those are our three overriding criteria when we look at energy strategies. The microgrid certainly fits in with all three of them…It’s a big breakthrough for us, one that we’ve been working on a long time.”
Mines use electricity in processing plants that crush, treat and refine ore. “At Granny Smith, we also need to provide power underground. We’re extending the underground mine, which will require about half the microgrid’s power output, including the solar and storage,” he said.
Adding solar-storage capacity turned out to be roughly cost-competitive with adding more natural gas-fueled generation capacity. Then there are the additional environmental and climate-related benefits, Lunsche said. “And we don’t need to be concerned about getting fuel there, which made it [solar-storage] an obvious choice.”
More sustainable mining
Government policy also factored into Gold Fields’ decision to invest in the hybrid microgrid. “If you can show that you’re reducing emissions, you can get ERF (Emissions Reduction Fund) credits. We used some of those to fund the feasibility study and do some of the basic groundwork for the plant,” Lunsche said.
Gold Fields is considering investing in hybrid microgrids at Agnew and St. Ives, its two other mines in Western Australia. “We’ve studied using both solar and wind at our other mines, as well as including an independent supply of natural gas. Hopefully, we’ll make an announcement soon,” Lunsche said.
The miner is looking to apply lessons learned in Western Australia to its mines in Ghana and South Africa, as well. “Ghana now has regulations that require that roughly 10 percent of the energy used to power mining operations should be from renewables,” Lunsche pointed out.
The regulatory environment and energy market conditions in South Africa are more complicated, in part due to state-owned utility Eskom’s financial troubles and its status as sole electricity distributor.
“The weather and climate conditions for solar are good, but there is a whole range of regulations tied in with Eskom as sole distributor that make for a complex environment. We’ve been looking to invest in a 14 MW solar PV plant for three years now. We’ve gone a long way, even signing a contract with an IPP (independent power producer) for delivery. But at this point regulatory considerations have prevented us from moving forward,” Lunsche said.
Aggreko expects to begin construction on the Granny Smith microgrid in May and complete it by year-end.