Firming up renewables in mining

Our Chief Scientist, Nigel Steward, on long-term energy storage

One of the challenges of decarbonising the way materials like iron ore and aluminium are produced is finding ways to store #renewable energy to keep our operations running.

We are deploying a range of wind and solar projects over the next 10 years. However, both forms of renewable energy generate intermittent power that needs to be firmed – or supplemented – with power from another source when the sun isn’t shining or the wind isn’t blowing.

We operate in more than 35 countries, so we need different firming solutions to give us flexibility and certainty of power and to cater for all weather and seasons. They must also be able to store enough energy to power huge operations and be affordable. It’s no small ask.

To overcome this challenge and support the #decarbonisation of our operations, we are looking at a range of long-term storage, including mechanical, electrochemical, chemical and thermal solutions.

Mechanical storage such as pumped storage #hydropower, and liquid or compressed-air energy storage, can provide firm power to high-power processing facilities and large mine sites that require vast amounts of energy to be stored. It is currently prohibitively expensive, but we are working with start-ups on this challenge right now. Until we find a cost-effective solution, firming will have to come from conventional power sources such as hydro or gas turbines. Alternatively, we will need to modulate demand, where we adapt our energy consumption to match renewable production. We are developing this capability in our aluminium smelters.

While lithium-ion battery electrochemical storage is cheaper than mechanical storage, it is still too expensive and it also doesn’t deliver enough storage capacity for our sites.

The good news is that certain thermal storage technologies thermal mass storage, can provide secure, low-cost power to our energy intense alumina refineries and other hydrometallurgical plants that require steam, and we are actively pursuing these technologies.

Beyond 2035, we expect new battery systems will become more cost effective, including vanadium flow batteries and other lower-cost chemistry technologies currently being developed.

We are also monitoring other energy sources, like geothermal, which has been around for decades but is seeing renewed interest, as well as small modular nuclear reactors and nuclear fusion. These technologies would be transformational, but we believe they are at least 20 years away, and fusion beyond 2045.

Technology will bring changes we cannot yet imagine. So in our R&D efforts we are remaining open-minded and looking at a range of solutions to help us tackle decarbonisation challenges like long-term storage.

Our current renewables projects underway

Western Australia

We are progressing work towards 1GW of renewable power in the Pilbara, with Phase 1 planned to deliver 234MW solar and 200MWh storage from 2023–2026. In addition to this, we have built a 34MW solar plant at our Gudai-Darri iron ore mine.

Madagascar

Our renewable energy project in Madagascar consists of an 8MW solar energy facility comprising 14,000 solar panels (phase 1), and a 12MW wind energy facility, comprising up to 19 wind turbines (phase?2).

Queensland, Australia

We have a Request For Proposal in progress to secure 4GW of renewable power to provide a competitive future for our Queensland aluminium assets.

South Africa

We’ve signed a 130MW solar power purchase agreement for Richards Bay Minerals (RBM) in South Africa, with a further 200MW of wind in progress. We have partnerships in progress to have RBM 100% powered by renewables by 2040.

Find out more about our decarbonisation activities in our?Climate Change Report.

Energy storage systems explained

Pumped storage hydropower: Potential energy is stored by pumping water to an uphill reservoir. Energy is then recovered through a hydropower turbine when the water is released downwards. (Source:?US Department of Energy)

Compressed-air energy storage: This works in a similar way to pumped storage hydropower. Air or another gas is compressed and stored under pressure. When electricity is required, the pressurised air is heated and expanded in a turbine that drives a power generator. (Source:?American Clean Power Association)

Liquid air storage: Liquid air energy storage uses electricity to cool air until it liquefies. The liquid air is stored in a tank and is then brought back to a gaseous state by exposure to ambient air or with waste heat from an industrial process. That gas is then used to turn a turbine and generate electricity. (Source:?Energy Storage Association)

Concentrated solar thermal: These systems use mirrors (also called heliostats) to concentrate sunlight into a targeted location, producing high temperatures. This heat is captured using a fluid, such as oil or molten salt, which can then be used to heat water to create steam to power a turbine and produce electricity. The heat can also be used directly to decarbonise some industrial processes. (Source:?Australian Renewable Energy Agency)

Molten salt and thermal mass: These systems use materials like molten salt, concrete or bricks to absorb to store heat energy so it can be used at another time.