# Hybrid Renewable Systems for Small Energy Communities: What Is the Best Solution?
## 4 Conclusions  
Hybrid energy systems are flexible but complex due to the need to manage multiple energy sources, demands, and constraints. Smart optimization of these systems requires several iterations and restatements to achieve the most efficient configuration for each scenario. In this particular study, the Generalized Reduced Gradient (GRG) was used, but other methods, such as evolutionary algorithms and multi-objective algorithms, such as the NSGA-II, could also be employed to find global solutions. The newly presented model integrates solar, wind, hydropower, and grid electricity to meet energy demands through the following steps: (i) Solar/Wind Energy: Hourly energy production data is analyzed to determine if it can meet all energy demands or if there is surplus energy. (ii) Energy Demand: Unmet energy needs are supplemented by hydropower or grid electricity. (iii) Pumped-storage Hydropower (PSH): Surplus renewable energy is to pump water to \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Configuration** & **Initial Investment [\(\upxi\)]** & **O\&M [\(\upxi\)year]** & **NPV [\(\upxi\)]** & **LCOE [\(\upxi\)kWh]** \\ \hline SA1 = PV + Wind + PHS & 259,177.0 & 3151.8 & \(-\)287,785.7 & 0.039 \\ \hline SA2 = PV + Wind + PHS + BESS & 273,861.0 & 3718.6 & \(-\)307,615.0 & 0.044 \\ \hline GC1 = PV + PHS + Grid & 205,914.0 & 2259.1 & \(-\)262,446.0 & 0.069 \\ \hline GC2 = Wind + PHS + Grid & 157,000.0 & 1965.0 & \(-\)179,287.0 & 0.054 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Energy community: initial investment and O&M costs. store potential energy. (iv) Reservoir Management: Ensures proper volume levels in the reservoir for efficient operation, considering the maximum and minimum previously defined. (v) Water Demand: Must be met fully from the reservoir, maintaining 100% reliability. (vi) Grid Energy: Utilized for buying or selling energy depending on supply and demand, with tariffs affecting profitability. (vii) Off-Grid Solutions: Batteries store excess and supply energy during deficits, ensuring continuous operation without grid reliance. This research work fulfilled the objective of developing advanced smart optimization models in hybridization of the water sector by the definition and design of a mathematical algorithm. The decision variables imposed in this model are the hydropower, grid, and solar factors, each constrained between 0 and 1, for which water-energy needs are fully met. The defined objective function, used equally for each scenario, aims to minimize the total installed power capacity of the system, corresponding to the sum of primary renewable sources, pump and hydropower, and battery capacity, if present. A small community in the north of Portugal, Marruge, was selected as the site for the model implementation as a smart hybrid energy solution. As a model deployment, it was utilized to analyze a microgrid of a small energy community entirely isolated from the national electric grid (i.e., stand-alone) or grid connected. Four solutions were analyzed, two stand-alone and two grid-connected, integrating various renewable sources and storage methods. The stand-alone configuration uses solar and wind energy with pumped-storage hydropower (PSH) for energy storage and production, while also considering battery storage: SA1 (PV + Wind + PSH) and SA2 (PV + Wind + PSH + BESS). SA1 uses solar and wind energy combined with pumped-storage hydropower (PHS) to ensure 100% independence from the grid, resulting in 220 kW of installed power distributed across PV, wind turbines, pumps, and turbines. The optimized system generates excess energy to meet peak demand during winter, ensuring sufficient capacity despite periods of lower demand. The second stand-alone solution, SA2, incorporates a battery energy storage system (BESS) to assess its impact on reducing the required power installations of other energy sources. The optimized power distribution includes 55 kW in PV, 100 kW in wind, 35 kW in pumps, 40 kW in turbines, and 40 kW in batteries, totaling 270 kW.