Kidston hydro set for construction 22 Aug 2019

The Genex Power Kidston pumped storage project in Australia has secured key debt funding that will enable work to start early next year on the complex underground infrastructure. The developer has secured funding of up to AU$610 million (US$410 million) from the Northern Australia Infrastructure Facility (NAIF). It is now finalising the last pieces of funding, hoping to reach financial close by the end of 2019. Genex is also putting AUS$25 million (US$17 million) equity into the project, in which it will be 50:50 co-owner with Energy Australia, an energy retailer.

Major works at Kidston project

The designer and contractors are already onboard, having been working on project development over the last few years. The Owner’s Engineer on the 250MW scheme is Entura, and the EPC contractor is a JV of McConnell Dowell/John Holland, with hydro machinery by Andritz.

The contractor was appointed late 2017 under Early Contractor Involvement (ECI) procurement, with Norconsult and GHD Australia its technical advisors. After its work on final design optimisation, in February 2019, it was given the green light to start early works on hydraulic design and other turbine activities. Following financial close and the notice to proceed, expected before the end of 2019, the EPC contractor will move on to detailed design. Main activities, including excavation, will commence in early 2020, Simon Kidston, Executive Director of Genex Power, said in an interview with TunnelTalk.

Aerial view of quarries at Kidston energy hub

Reservoir inlet at top of headrace shaft

Headrace shaft links to powerhouse caverns

The underground infrastructure, which is based in an old gold mine, has a drop headrace shaft from the upper reservoir to the power cavern complex from which a tailrace tunnel links to the lower reservoir. Other excavations will include an access tunnel, and cable and ventilation shafts. Kidston briefed TunnelTalk on the scale of the excavations:

• The power cavern complex has two caverns: the main powerhouse is 82.2m long x 17.5m wide x 44m high and the transformer cavern is 31.8m long x 10m wide x 10m high.
• The 1.5km long access tunnel is 6.5m wide x 6.6m high.
• The intake shaft is 240m deep x 4.8m diameter; the cable shaft is 250m deep x 3.3m diameter; and the ventilation shaft is 235m deep x 3.3m diameter.
• The two tailrace tunnels are each 160m long x 6m wide x 6m high.

Geologically, the workings are within a hydrothermal breccia pipe system. The headrace pressure shaft and powerhouse complex caverns will be located within the Einasleigh Metamorphics (gneiss), near the breccia pipe margin, the former being harder than the latter. Most excavation will be by drill+blast, including crown and bench progressive opening of the caverns. Raise boring will be used for all shafts.

While the groundwater level is high, Kidston said “groundwater modelling predicts minimal flows into the underground excavations. Very little grouting is anticipated.” All hydraulic tunnels will be lined: with steel closest to the caverns where water pressures will be highest and with concrete for other conveyance tunnels.

The project is designed to provide about eight hours of generation at constant 250MW output, and then take eight hours pumping water to the upper reservoir at cheaper times for the power grid. The closed-loop hydro scheme reuses the same water, except for occasional top-ups due to evaporation in the dry season.

NAIF is providing the debt funding for the hydro scheme. Its investment is sizeable financially and also a notable share, 12%, of its own resources. Its CEO, Laurie Walker, cited the benefits of the project that attracted its investment, which is subject to government approval, include low emissions, improved energy reliability, reduced transmission losses to supply the local region, and also lower electricity prices.

The pumped storage project is the heart of a renewable energy hub being developed by Genex Power in Queensland, which now includes proposed solar and wind farms. The scheme has received funds from the Australian Renewable Energy Agency and has been designated critical infrastructure by the Queensland Government. It is expected to come online in 2022. Energy Australia will operate the asset.

Other recent hydro developments in Australia include the Snowy 2.0 scheme with contract award to Salini Impregilo.