The solar photovoltaic plant, Rio Tinto's first company-owned solar facility, is expected to supply Koodaideri's electricity demand during peak solar generation times and about 65% of the mine's average electricity demand.
It will consist of about 100,000 panels, covering 105 hectares.
Construction is expected to start later this year, subject to government approvals, and is due to be finished in 2021.
Complementing that will be the 12MWhr battery energy storage system that will provide spinning reserve generating capacity to support a stable, reliable network.
The solar plant and battery are expected to lower Rio Tinto's annual carbon dioxide emissions by about 90,000t compared to conventional gas-fired generation.
Rio Tinto Iron Ore chief executive Chris Salisbury said building the company's first solar plant in the Pilbara was a milestone for the business and an important step in reducing its carbon dioxide footprint in the region.
"We are investigation 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," he said.
Rio Tinto is working to define new emissions reduction targets from 2020.
Koodaideri is about 35km northwest of Rio Tinto's Yandicoogina mine and about 110km from the town of Newman.
Funding for the solar plant and battery sits within Rio Tinto's existing guidance for sustaining capital expenditure in its iron ore business.
Rio Tinto's Weipa operation in northern Queensland sources power from an on-site solar facility.