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 250MW of electricity.
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. When we were appointed to carry out a design review, 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 scheme’s installed capacity from 450MW to 250MW, and using two reversible pumps instead of one. And 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 both easier to build and more efficient to operate.
Our optimisation 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 AUS$21M and reduced construction by six months.
Solution
Our cost-saving design optimisation 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 consultancy 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 modelling, which includes geotechnical and geological models, as well as the scheme arrangements. BIM enables real-time review of the design as it develops, and 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, stabilise 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 50MW solar array located started generating power at the end of 2017, providing more than 26,000 homes with electricity and offsetting about 120,000t of CO2 a year. A 270MW solar array will be added.
The Kidston project is forecast to deliver AUS$343M 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/kW are lower than other technologies.