The 34 megawatt solar photovoltaic plant is expected to supply all of Koodaideri's electricity demand during peak solar power generation times and about 65% of the mine's average electricity demand when the 43 million tonne per annum operation comes online late next year.

The plant represents Rio's second solar facility in Australia, but its first company-owned facility.

Aggreko owns and operates a 20MW solar facility that provides power to Rio's Amrun bauxite mine in Queensland.

The Koodaideri plant will comprise an estimated 100,000 panels, covering an area of 105 hectares.

Rio also plans to build a 12MWh battery energy storage system in Tom Price that will provide spinning reserve generating capacity to support a stable and reliable network.

The solar plant and battery are estimated to lower annual carbon dioxide emissions by about 90,000 tonnes compared to conventional gas powered generation, equivalent to taking about 28,000 cars off the road.

"The construction of our first solar plant in the Pilbara is a significant milestone for the business and an important step in reducing our carbon footprint in the region," Rio Iron Ore chief executive Chris Salisbury said.

"We are investigating additional renewable energy options in the Pilbara, as well as other opportunities to reduce emissions across our entire global portfolio, building on the 43% reduction in absolute greenhouse gas emissions since 2008."

Funding for the solar plant and battery sits within Rio Tinto's existing guidance for sustaining capital expenditure for its iron ore business.