The results of our survey are shown in Figure 2. Most regions of the world have large numbers of potential sites nearby.PHES is mature off-the-shelf technology and is much cheaper than alternatives for large-scale. An approximate guide to storage requirements for 100% renewable electricity, based on analysis for Australia, is 1 Gigawatt (GW) of. Legacy fossil fuels can support and balance an electrical grid with a large proportion of variable renewable energy (solar PV and wind). Potential sites for off-river PHES are identified using GIS algorithms with defined search criteria. The surveyed latitude range is up to 60 degrees north and 56 degrees south. The following aspects (amongst others) are being worked on: 1. Brownfield sites (existing reservoirs, mine sites) are poorly handled at present due to.