Power supply
may incorporate a battery to smooth out the variability and employ a specialised control system – a microgrid controller – to manage the dispatch of each of the sources of energy, ensuring the power supply is reliable and the use of renewable energy is always maximised.
As James Koerting, Gold Fields Australia’s vice- president for energy and technology, explains, this improves the miner’s position in all three parts of the energy trilemma. “On the affordability front, the cost of dispatching renewable energy is cheaper than the marginal cost of thermal generation, particularly where diesel is the fuel,” he says. “Increasing diversity in the electricity supply with alternative forms of power generation ensures security, and the mine becomes more sustainable where renewables displace fossil fuels and reduce the emissions intensity factor of the power supply.” Security of supply is particularly important in the remotest mines, which can be exposed to supply risks when road access is restricted due to inclement weather. If a mining operation relies on diesel for both mining and power generation, and has one week’s supply of diesel fuel, a storm event that cuts off the roads for more than a week could be disastrous. However, a hybrid system that generates a large proportion of electricity from renewables would reduce the mine’s diesel consumption, potentially allowing it to ride through the supply restriction without interrupting production.
Exceed expectations
Owned and operated by global energy producer EDL, the Agnew Hybrid Renewable Project at Gold Fields’ Agnew Mine in Western Australia is Gold Fields’ flagship renewables mine, and a case in point. Its A$113m ($85m) microgrid comprises a 4MW solar farm, 18MW wind and a 13MW/4MWh battery energy storage system, all of which is backed up by 18MW of gas generation.
It is managed by an advanced control system that optimises renewable energy penetration, with components interfacing and reacting swiftly to changes in load requirements – essentially eliminating unplanned outages. The microgrid has already surpassed EDL’s target of supplying over half the mine’s power requirements with renewable energy. This can rise to up to 85% in favourable weather conditions.
“The Agnew Hybrid Renewable Project provides widespread applications for distributed energy across Australia for remote communities or mines,” says EDL CEO James Harman. “A lot of these power stations in the past have been built on fossil fuel technology. We’re proving at Agnew that we can build new energy solutions with hybrid renewables that are more reliable than the grid, more sustainable than using fossil fuels, and at a competitive cost.”
World Mining Frontiers /
www.nsenergybusiness.com
Capable of powering the equivalent of up to 11,500 homes per year, the microgrid is expected to reduce Gold Fields’ carbon footprint by 45,000t carbon dioxide equivalent (CO2
-e) per year. Immense challenges
of concrete, requiring about 85 truckloads of concrete per continuous pour. A 1,600t crane, one of the largest operating in Australia, was transported in sections to site to lift and fit wind turbine segments on each footing. Five weeks of heavy lifting were required to erect all five turbines.
Harman is the first to acknowledge that Agnew has been an immensely challenging project to get up and running. Constructing the wind farm alone involved shipping 55 wind turbine components – including 15 blades measuring 70m each – from China to Geraldton Port and trucking the components over 600km to site. The oversized blades had to be transported in convoys consisting of five vehicles, each requiring ten to 12 hours to travel to site. It took eight days in total to deliver all blades and equipment from port to site. To then install the five 110m-high turbine towers, the supplier’s joint venture partner constructed concrete footings for each turbine base, each reinforced with 50t of steel and consisting of 500m3
The project then experienced additional challenges caused by the bushfires in late 2019 and early 2020, and the Covid-19 pandemic that struck in March 2020. The bushfires caused land transport routes to be closed off, delaying deliveries of critical equipment and forcing the project team to reprogramme their works and seek alternative supplies.
“We can build new energy solutions with hybrid renewables that are more reliable than the grid, more sustainable than using fossil fuels, and at a competitive cost.”
James Harman
Meanwhile, as the wind and control systems were being commissioned, the travel restrictions and mandatory isolation requirements caused by the pandemic prevented key specialist personnel getting to site. The project team was forced to reschedule the wind commissioning and work with the control system supplier to commission the system remotely from Tasmania.
Manage commercial risks
There are also significant technical and commercial risks for miners to consider when making the decision to power their operations with a hybrid plant rather than a more traditional set-up. “Hybridisation means adding variable generation to
49 A$113m
Value of the Agnew Hybrid Renewable Project’s microgrid, which includes a 4MW solar farm, 18MW wind and a 13MW/4MWh battery storage system.
Gold Fields
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