# Hybrid Renewable Systems for Small Energy Communities: What Is the Best Solution?
## 2 Methods and Developments
### Model Deployment
#### 2.2.2 Microgrid System  
As a model deployment, it was utilized to analyze a microgrid of a small energy community as a microgrid may be entirely isolated from the national electric grid (i.e.,  
Figure 6: Marruge as a future eco-village: location in country (**a**); place (**b**); small community village (**c**). stand-alone) or grid-connected (Figure 7). In the latter case, synchronization is required to enable imports/exports between the microgrid and the outside grid network. The **stand-alone (SA)** configuration employs solar and wind energy as the primary renewable energy source, integrating PHS as an energy storage and production mechanism. Furthermore, a scenario with a battery energy storage system (BESS) is presented. The **grid-connected (GC)** setup implements solar or wind with PHS. The grid-connected solutions were validated based on two criteria: a minimum yearly grid independence of 80%, i.e., only 20% is allowed as a maximum dependence, and a positive grid balance, defined as energy exports minus imports. The cash flow corresponds to the difference between revenue (selling excess energy to the grid) and costs (buying energy from the grid). The primary objective is to develop a reliable and cost-effective solution for a small-scale energy community. Accordingly, the evaluation encompasses a range of energy source configurations and installed capacities in both the stand-alone and the grid-connected setups. In this case study, the subsidies are not considered, nor are the costs associated with the hydraulic circuit of the pump-storage hydropower (PSH), including reservoirs, pipelines, and valves, which already exist to satisfy the existent irrigation system. The economic parameters defined for this small-scale analysis are summarized in Table 1. \begin{table}
\begin{tabular}{l l} \hline \hline
**Solar Energy**[32; 51] \\ \hline C\({}_{inv}\)\_PV & 850 \(\,\mathrm{\upxi}\,\mathrm{kW}\) \\ \hline O\&M\_PV & 8.5 \(\,\mathrm{\upxi}\,\mathrm{kW}\)/year \\ \hline Inverter (DC/AC)—100 kW & \\ \hline Inverter (DC/AC)—40 kW & \\ \hline Inverter (DC/AC)—50 kW & \\ \hline C\({}_{inv}\)\_Inv.100/40/50 & 3414 \(\,\mathrm{\upxi}\,\mathrm{\upxi}\,\mathrm{2177}\,\mathrm{\upxi}\,\mathrm{ \upxi}\,\mathrm{1861}\,\mathrm{\upxi}\) \\ \hline O\&M inverter & 1\% \\ \hline
**Wind Energy Parameters**[52; 53; 54] & \\ \hline Efficiency & 98\% \\ \hline C\({}_{inv}\)\_WT & 1200 \(\,\mathrm{\upxi}\,\mathrm{kW}\) \\ \hline O\&M\_WT & 15 \(\,\mathrm{\upxi}\,\mathrm{kW}\)/year \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Economic parameters of this small energy community. Figure 7: Microgrid definition: can include photovoltaic, PV, wind, pumped-storage hydropower (PSH), battery energy storage system (BESS), and GRID support. The grid balance cash flow for the grid-connected setup is constant throughout its entire lifetime due to the absence of state subsidies. The hybrid system can be independent of the grid according to certain water-energy allocation values. Nowadays, most EU countries tax these emissions, which increases the costs, thus requiring them to be taken into account when analyzing the economic parameters during a lifetime. The cost derivative from CO2 emissions can be computed as follows, by Equation (8) defined in [53]. \[EC_{\text{CO2}}=Grid\ Energy\cdot CO_{2}factor\cdot Emissions\ Tax \tag{8}\]  
where ECCO2 corresponds to the annual costs derivative from CO2 emissions, in \(\epsilon\); grid energy is the total annual energy consumed by the system, in kWh; the CO2 factor is the relation value between energy and kilograms of carbon dioxide emitted, equal to 0.331 kgCO2/kWh; and the emissions tax corresponds to the value defined by the government/authorities to penalize the emissions associated with the system operation, equal to 0.1162 \(\epsilon\)/kgCO2 [53]. Once the results for different water-energy needs have been obtained and optimized, the yearly energy and economic balance can be evaluated. In this case study, a lifetime analysis of 25 years is defined.