Opportunity
The pumped-storage element of the project repurposes two former mine pits as reservoirs. Cheap surplus electricity will be used to pump water from the lower to the upper reservoir. When demand for electricity surges or renewable output falls, water will be released. The pumps will be reversed, turning them into turbines and generating 250 megawatts of electricity.
Solution
The outline design had set out to use the lower of the two pits as a reservoir, but envisaged excavating a new top-level reservoir. We saw the chance to simplify construction and save costs by reusing the mine’s existing upper pit.
We also made the case for reducing the project’s installed capacity from 450 megawatts to 250 megawatts and using two reversible pumps instead of one. We showed that connecting the reversible pumps to the lower and upper reservoirs via smaller-diameter twin tunnels instead of a single large-diameter bore would be easier to build and more efficient to operate.
Our optimization study turned the design concept into an economically viable solution for owner Genex Power, helping to secure the project’s financial backing. With further design efficiencies, we saved more than $15 million (AUS$21 million) and reduced construction by six months.
Our cost-saving design optimization was the product of global expertise in pumped-storage and large hydropower projects. Our team knew where to start looking for efficiencies.
We’re now in a joint venture with the consulting firm GHD to deliver the detailed design for Kidston pumped storage and all design services to the engineering, procurement, and construction contractor, a joint venture between McConnell Dowell and John Holland.
Our detailed design is being delivered using Building Information Modeling, which includes geotechnical and geological models, as well as the project arrangements. BIM enables real-time review of the design as it develops. The model will be an important asset for the future operation and maintenance of the facility.
Outcome
Construction began in May 2021 and is expected to be completed in 2024, with power flowing to the national electricity market in early 2025.
The pumped storage hydropower plant will produce enough electricity to power 143,000 homes for at least six hours. The project will create about 400 direct jobs, stabilize the local grid, and unlock the renewable energy potential of North Queensland. The state is aiming to generate half its electricity from renewable sources by 2030.
A 50-megawatt solar array located started generating power at the end of 2017, providing more than 26,000 homes with electricity and offsetting about 120,000 metric tons of CO2 a year. A 270-megawatt solar array will be added.
The Kidston project is forecast to deliver $238 million (AUS$343 million) in net public benefit. The project’s lifespan is at least 75 years, which is five times that of most of today’s batteries. The scale and long lifespan of pumped-storage hydro means its production and storage in terms of cost per kilowatt-hour are lower than for other technologies.