# Hybrid Renewable Systems for Small Energy Communities: What Is the Best Solution?
## 4 Conclusions
While BESS slightly decreases solar and wind installations, the total power increases due to higher pump power needs for using excess solar energy. The BESS has a limited impact, even with a hypothetical increase to 1 MWh storage capacity. On the other hand, the grid-connected setup combines solar or wind with PHS, aiming for at least 80% yearly grid independence and a positive grid balance: GC1 (PV + PSH + Grid) and GC2 (Wind + PSH + Grid). The GC1 configuration requires 95 kW of PV, 65 kW of pump, and 40 kW of turbine power to meet the criteria. Achieving full independence would require significantly higher PV and pump capacities, doubling the initial investment. The grid-connected setup with solar power (GC1) is more efficient in meeting the total load demand compared to stand-alone configurations, producing 134 MWh for an annual consumption of 97 MWh, while grid energy imports are limited to peak winter months. The second grid-connected configuration (GC2) requires 65 kW of wind power and achieves 91.7% grid independence with energy exports twice the imports. Full independence would require a significant increase in wind and pump power, doubling the initial investment. GC2 is optimal for balancing installed power with energy needs, producing 123 MWh annually with only 9.5 MWh of grid energy required. The economic analysis reveals that the grid-connected configurations, GC1 and GC2, offer stable cash flows of \(-\)C2956.3 and \(-\)C123.2 annually, respectively, with GC2 being more economical. The CO\({}_{2}\) costs for GC1 and GC2 are \(\upxi\)1012.6 and \(\upxi\)367.2, respectively. GC2, which integrates wind energy and pumped hydropower storage, has the lowest NPV and installed power requirement of 125 kW, making it the most suitable for sites with existing grid infrastructure. If grid integration is not feasible, the stand-alone solution SA1 would be preferred. The integration of pumped hydropower storage enhances energy independence and offers a storage capacity of 2.17 MWh, supporting peak loads for up to two days. GC presented lower initial investment (between 157 to 205 k\(\epsilon\)), while SA had lower LCOE (between 0.039 and 0.044 \(\epsilon\)/kWh). Conceptualization, J.S.T.C. and H.M.R. ; methodology, J.S.T.C. and H.M.R. ; software and calculus, J.S.T.C. ; writing--original draft preparation, J.S.T.C., H.M.R. and M.P.-S.; review, J.S.T.C., H.M.R., M.P.-S., O.E.C.-H. and F.-J.-S.-R.; supervision, H.M.R., A.M. and M.P.-S.; editing and final preparation, all authors. All authors have read and agreed to the published version of the manuscript. This work was supported by FCT, to UIDB/04625/2020 CERIS, in the Hydraulic Laboratory, for experiments on pumped storage performance, and the project HY4 RES (Hybrid Solutions for Renewable Energy Systems) EAPA\({}_{-}\)0001/2022 from INTERREG ATLANTIC AREA PROGRAMME. This research was carried out during [PERSON]'s stay at the CERIS-IST research center, called \"INCORPORATION OF NEW WATER RESOURCES IN IRRIGATION SYSTEMS THROUGH THE USE OF SUSTAINABLE TECHNOLOGIES AND COMPUTATIONAL TOOLS TO MITIGATE WATER SCARCITY\". Not applicable. The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author. The authors are grateful for the project HY4 RES (Hybrid Solutions for Renewable Energy Systems) EAPA\({}_{-}\)0001/2022 from INTERREG ATLANTIC AREA PROGRAMME 2021-2027, as well as the Foundation for Science and Technology's support to UIDB/04625/2020, the research unit CERIS. The authors declare no conflicts of interest.