Genex has announced it has optimized the design of the 250MW Kidston Stage 2 (K2) pumped storage project to increase its storage capacity by 25%, and will adopt more efficient speed turbines to meet the needs of its energy offtake partner and meet the demands of future energy markets. The new design will replace the ‘Turkey’s Nest’ design suggested in the project’s original technical feasibility study (TFS).

The K2-Hydro project is part of the overall Kidston Stage 2 (K2) project, which includes a co-located 270MW solar PV project (K2-Solar) at Kidston, North Queensland. Genex completed the TFS for the project in November 2016 which was managed by power and water consulting firm, Entura, in conjunction with project partner, HydroChina. The TFS concluded that the K2 was technically feasible, and that all the key risks identified would be appropriately addressed through detailed design augmentation and optimisation.

Genex has recently been working with engineering firm Mott MacDonald on the optimisation of the K2 project design (TFS Optimisation). The optimisation process focused on taking into account recent shifts in the energy market dynamics as well as feedback from potential energy offtake parties.

Following a detailed review of the studies undertaken to date, it was concluded that an augmented design utilising the two existing mine pits as the upper (Wises pit) and lower (Eldridge pit) reservoirs, was the optimal choice for 250MW of installed capacity, in place of the Turkey’s Nest design under the TFS. In a statement, Genex said it had decided to delete the Turkey’s Nest design because it’s proposal was premised upon a larger storage requirement, given the initial preferred project configuration of 450MW for five hours – with the new optimised design of 250MW, the Wises pit can now be utilised as the upper reservoir for lower capital cost; and with minor excavation and dam works, the TFS Optimisation design provides for a channel connecting the modified Wises pit to the existing proposed location for the underground power station cavern, which was subject to detailed drilling and geotechnical studies as part of the original TFS.

In addition to the deletion of the Turkey’s Nest design, the TFS Optimisation determined several other key changes to the original TFS design:

  • Increased upper reservoir volume from 6 hours to over 8 hours of continuous generation;
  • Proposed adoption of variable speed pump-generator turbines which provide significant operational flexibility, including: Fast generation ramping via speed adjustment; The ability to better match the hydro pumping profile to generation from the co-located K2-Solar project; Better pumping efficiency across the head range; and Overall suitability in the ancillary service market with increased operation flexibility;
  • Reduced excavation and civil works requirements; and
  • Construction estimated to take less than 3 years.

The TFS Optimisation concluded that the K2-Hydro project was feasible based on a capital cost estimate of approximately $330 million (including contingency). Following completion of the TFS Optimisation, Genex is now focused on confirming the final capital cost estimates for the K2-Hydro project via an early contractor involvement (ECI) process. This process will involve the appointment of a preferred EPC contractor, who will work with Genex and its advisers to complete the final design optimisation and the full EPC and O&M contracting process for the K2-Hydro project. Genex said it will provide further updates on the ECI selection process in due course.