## 3 Results and Discussion
### Exploitation of a Hypothetical Battery System in Combination with Other Use Cases
Finally, even though the approach is generally applicable, it requires adjustments to suit local conditions, including variations in energy markets, policy environments, and renewable energy potentials. The investigated case was specifically tailored to Slovenia's grid infrastructure and energy policies, which may limit the broader applicability of the findings to regions with different energy mixes or grid configurations. This study contributes to the field of energy flexibility and renewable energy integration in industrial processes by assessing the economic feasibility of using solar energy surpluses in aluminium smelting. Using long-term solar radiation data and varying electricity and aluminium prices, it provides insights into the financial implications of utilising surplus renewable energy in aluminium production over the long term. Furthermore, this study addresses the challenge of energy surplus management by evaluating the installation of a local, large-scale PV power plant. It demonstrates the economic potential of leveraging aluminium smelting as a flexible energy consumer, thereby contributing to sustainable energy strategies and enhancing grid stability through industrial participation. Future research could incorporate the direct impact of existing local PV production on consumption, given the availability of such data. Additionally, it could explore different grid configurations, energy policies, and incentives, simulating policy changes such as carbon taxes or renewable energy mandates to assess their effects on economic feasibility. A life cycle assessment (LCA) of PV systems, battery storage, and aluminium production would provide insights into the overall sustainability and environmental impact of such systems. Further studies could also explore various strategies to maximize both economic and environmental benefits. As global energy demands rise and the shift to sustainable energy sources continues, utilising these surpluses effectively is essential for both environmental and economic benefits. Using the electricity surplus in the presented way can strengthen the energy grid and reduce energy waste. Additionally, directing this energy to industry supports industrial growth and job creation and is a significant step toward a sustainable and green economy. Conceptualization, M.B., P.S., G.S., H.S.H., D.M. ([PERSON]) and S.K. ; methodology, P.S. and M.B. ; software, M.B. and N.L. ; validation, P.S., G.S. and N.L. ; formal analysis, P.S. ; investigation, M.B. and P.S. ; resources, D.M. ([PERSON]); data curation, N.U. ; writing--original draft preparation, M.B. ; writing--review and editing, P.S., G.S. and N.L. ; supervision, N.L. ; project administration, D.M. ([PERSON]); funding acquisition, N.L., D.M. ([PERSON]) and G.S. All authors have read and agreed to the published version of the manuscript. This work was financed by the Slovenian Research Agency (Research Funding Nos. P2-0041 and P2-0115 and research project No. J7-50095). The raw data supporting the conclusions of this article will be made available by the authors on request. The authors thank ELES d.o.o. for providing the electricity power measurements and Talum d.d. for co-financing the study. Conflicts of Interest:Authors [PERSON], [PERSON] and [PERSON] were employed by the company Talum d. d. Kidricevo. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.