1 15 integration, and regional flexibility services. The RM-GES and CB-GES concepts represent economically promising, durable storage solutions tailored to the technical and spatial characteristics of post-mining regions. Preliminary comparison of costs with other storage technologies Gravity energy storage (GES) is a relatively new alternative in this field, but cost comparisons can be made with other mature storage technologies. To compare energy storage technologies from this perspective, the levelized cost of storage (LCOS) is used, which accounts for capital costs (CAPEX), operating costs (OPEX), loading costs, end-of-life costs, and total discharged capacity over the technology's lifetime [28]. In principle, the capital costs (CAPEX) of GES can be considered medium to high, while the costs of Li-Ion technology are medium (decreasing), those of PHS technology are very high, and those of Redox Flow batteries are high. Furthermore, the capital costs of GES implemented in post-mining areas are much lower due to existing transport and electrical infrastructure. The operational costs (OPEX) are also lower than those of other storage technologies, given that existing transport systems (rail-mounted or belt-mounted) are mature and have low long-term maintenance costs, and the use of local materials such as sand, gravel, or mine tailings as storage mass further reduces OPEX. Thus, with a lifetime of 30-50 years and a round-trip efficiency of 75-85%, the levelized cost of storage (LCOS) of GES is comparable to that of PHS and much lower than that of the other two technologies considered (Li-Ion and Redox Flow). Social and environmental impact Considering social and environmental factors in the siting of gravitational energy storage systems is crucial to the long-term viability and acceptance of this technology. Postmining areas, owing to their existing transformation and socio-economic conditions, are particularly promising sites for GES development, combining infrastructure and revitalisation functions. Such investments can reduce pressure on greenfield areas, create jobs, and support the energy transition of former mining regions. However, the final assessment of their impacts should be based on the results of the planned technology demonstration at the PGE Turów Mine in the second half of 2026. 6. REFERENCES [1] International Energy Agency (IEA). (2023) Energy Storage Tracking Report. International Energy Agency, Paris. [2] International Energy Agency (IEA). (2021) Net Zero by 2050: A Roadmap for the Global Energy Sector. International Energy Agency, Paris. [3] European Commission. (2021) European Climate Law. Regulation (EU) 2021/1119, Official Journal of the European Union. [4] Eurostat. (2024) Renewable energy statistics. European Commission, Luxembourg. [5] Evans, S., Gabbatiss, J. (2023). Wind and solar were the EU’s top electricity source for the first time ever. Carbon Brief. [6] NWEUROPE. (2021) State of the Art Report on Storage Technologies, Opportunities and Trends. Interreg North-West Europe Programme, Lille.
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