Photovoltaics (PV) and wind constitute approximately half of the world’s new generation capacity installed in 2014–۱۶٫ At the end of 2016, the global installations of PV and wind were beyond 300 gigawatts (GW) and 480 GW respectively [1,2]. Rapid growth of PV and wind energy in the electricity sector is expected to continue, driven by a broad range of issues associated with climate change, energy security and economics. High shares of intermittent PV and wind energy in electricity grids bring significant challenges to the economics and security of the system as is the case in South Australia (SA), where nearly half of the state’s electricity production come from rooftop PV and wind farms [3]. SA has a low level of interconnection with the rest of the Australian National Electricity Market (NEM) and there is no existing hydroelectric or pumped hydro facility established within the region. This brings significant challenges to power system operation and the state’s energy security due to supply intermittency and lack of sufficient inertial energy to support PV and wind electricity, especially in light of continuing rapid growth of PV and wind energy investment. In July 2016, when upgrades to the Heywood interconnector coincided with low wind generation at peak times, the average wholesale electricity prices in SA surged to $229/MWh (Australian dollars per megawatt-hour) with 3 extreme price events on 7, 13 and 14 July beyond $5000/MWh [4]. By contrast, the long-term average price in SA when the interconnector is available to import brown coal electricity from Victoria is $50/MWh. Additionally, a range of system events such as load shedding and islanding occasionally occurred in 2016–۱۷ [۵,۶]. This included a state-wide blackout on 28 September 2016, when three 275 kilovolts (kV) backbone transmission lines were damaged by a major storm event [7]. Pumped hydro energy storage (PHES) is capable of large-scale energy time shifting and a range of ancillary services such as frequency regulation, which can facilitate high levels of photovoltaics and wind integration in electricity systems. Developments of PHES began in the 1890s and surged through the 1960s, 70s and 80s in Europe, the United States and Japan where the rapid growth of nuclear energy and coalfired units continued. These large thermal steam plants lack sufficient operational flexibility to accommodate changing demand and required the capability of load levelling. PHES was also regarded as a more economical alternative to oil and natural gas-fired plants for peak shaving, especially during the post-periods of energy crisis in the 1970s [8,9]. In recent years, the prosperity of PV and wind developments has led to a resurgence of interest in PHES. Open-loop PHES, which is continuously connected to a naturally flowing water feature [10], dominates the deployment of existing PHES. However, developments of conventional river-based hydroelectric including PHES are usually constrained by the availability of water resources and a variety of environmental concerns such as the interactions with ecology and natural systems [11]. Consequently, expansions of pumped hydro were generally not included in many high renewables future studies such as [12–۱۴]. By contrast, short-term off-river PHES, which incorporates closed-loop pumped hydro systems, consumes modest amounts of water and has little impacts on the environment and natural landscape.