Scientists from the Australian National University (ANU) have identified 616,818 locations throughout the world that could be suitable sites for 23.1 million GWh of pumped-hydro storage capacity.
The sites relate exclusively to closed-loop pumped-hydro energy storage projects with little environmental impact due to their location away from rivers and can be found through an open-source online platform managed by the Australian government.
The identified sites are all located at altitudes of less than 100 m above sea level and have sufficient height differences to enable potential energy storage between two water reservoirs. “The upper reservoir can be located near a hilltop rather than in a river valley, which substantially increases the height difference (‘head') between the reservoirs and hence the available potential energy,” the research team said, adding that a large head varying from 100 m to 800 m is usually preferable.
“Off-river” pumped-hydro projects are also said to overcome the typical topographical issues of conventional pumped-hydro, as the size of reservoirs is relatively small, ranging from tens to hundreds of hectares. This limited size also reduces the need to manage large flood events and ensures considerably lower construction costs.
The enormous storage potential identified in the research should be mostly used for medium-term storage of intermittent PV and wind power generation. “The pumped hydro resource is well distributed at a regional and sub-regional level to support variable renewable energy deployment,” the academics explained. “The total global storage capacity of 23 million GWh is 300 times larger than the world’s average electricity production of 0.07 million GWh per day.”
Using just 1% of the identified sites in the atlas for pumped-hydro storage would be enough to support a global electricity system powered by 100% of renewables, according to the researchers. Currently, there are over 180 GW of pumped-hydro storage systems in operation around the world.
The Australian group also emphasized that the levelized cost of storage (LCOS) for closed-loop, off-river pumped hydro is currently the lowest for storage of hours to days. ” The lowest energy storage cost is achieved in reservoir pairs with large head and large water-to-rock (V/R) ratios for the target storage capacity,” it stressed.
The findings of the research were presented in the study Global Atlas of Closed-Loop Pumped Hydro Energy Storage, published in Joule.
In a previous work published in April 2019, the same research group had identified 530,000 locations for 22 million GWh of pumped-hydro storage capacity. In this research, as well as in the latest paper, the scientists identified the sites through a global audit that relied on geographic information system (GIS) algorithms.
The algorithms helped to identify dry-gully or turkey’s nest sites, which include upper and lower reservoirs with hypothetical tunnels between them. The researchers were able to look at data such as latitude, longitude, altitude, water volume, energy storage potential and approximate relative cost. “There is an increase in the number of sites relative to the earlier release due to modification of the filtering,” research co-author Matt Stocks told pv magazine.
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