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(250 MW of peaking power generation over an 8-hour period). The power generated will be sold directly into the NEM. A concrete-lined pressure tunnel will connect the upper reservoir to the underground generation powerhouse. A concrete-lined tailrace tunnel will, in turn, connect the powerhouse to the lower reservoir. A shaft from the surface will connect the underground infrastructure to a surface power control room, which will be connected to a transformer station located on an existing pit bench. The Kidston Pumped Storage Hydro Project (250 MW) is a closed-loop system, which will involve the transfer of water from the upper reservoir to the lower reservoir. This will ensure minimal environmental impact during operation, on what is an already disturbed former mining site. 3.5. CULTANA PUMPED HYDRO PROJECT Energy Australia is the developer of a potential seawater pumped storage project on the Eyre Peninsula in South Australia. A lack of freshwater resources in inland South Australia means sites adjacent to the coastline are worthy of consideration for pumped hydro projects. The Cultana site was selected based on the elevation, proximity to the coast, proximity to grid connection and minimal environmental and cultural impacts [10]. There are many precedents for freshwater pumped storage projects globally; however, there is only one international precedent for large-scale seawater pumped storage projects – a 30 MW facility in Okinawa, Japan, which was decommissioned in 2016 [11]. The prefeasibility study for the project considered a capacity envelope of between 100 MW and 250 MW. Below 100 MW it was expected that the fixed costs of large civil construction would be too high to yield a viable project due to lack of economies of scale. Beyond the upper limit of 250 MW there is a risk that the storage capacity would be too large for the South Australian market. The larger the capacity, the lower the expected market revenue per unit of capacity. Within this range, the proposed 225 MW nameplate capacity of the Cultana Pumped Hydro Project was determined based on the maximum scale that could be achieved while avoiding any significant incremental changes in cost [10]. 4. CHANGING USE OF EXISTING HYDRO STORAGES 4.1. EXISTING HYDRO IN AUSTRALIA The two largest hydro generation companies in Australia are Snowy Hydro and Hydro Tasmania. 206