# Optimizing Sustainable Energy Transitions in Small Isolated Grids Using Multi-Criteria Approaches
## 4 Results and Discussion
### Scenarios Pre- and Post-Full Operation of the Hydro-Wind Power Plant
Finally, when analyzing the data, it was observed that the year 2023 is abnormally low in its wind resource, while for the solar resource, it is a typical year. Hence, in general, 2023 is a very adverse year in terms of climatic conditions for power generation. Therefore, by using this data, a conservative approach is taken, i.e., the system's performance will be better for any other year with more favorable conditions. Additionally, in the subsequent process of optimizing the sizing of the energy system, a conservative approach is also taken, so that in those years with more favorable climatic conditions, there will be higher electricity generation, thus comfortably covering the demands under any situation. However, it is true that the system's excesses will be greater than those presented. For this reason, it is considered a good option with this optimized model to see its performance when introducing favorable conditions of solar and wind resources, thereby quantifying the minimum and maximum values of both the associated emissions and the excesses for the optimized system. To confirm this proper code performance, the attached figure shows the hourly values of the four generation technologies' contributions along with the demand for a representative week in every main group of the year, both for the results provided by the code and \begin{table}
\begin{tabular}{c c c} \hline \hline
**Variable** & **Results for 2023** & \\ \hline Installed power & 13.04 MW & \\ Generation & 50.50 GWh & \\ Average CF & 43.97\% & \\ Peak CF & & 59.13\% & \\ \hline Total annual costs & \multicolumn{2}{c}{6.835 M EUR} & \\ Fixed operation costs & 0.377 M EUR & 5.52\% \\ Variable costs & 6.458 M EUR & 94.48\% \\ Annual investment costs & 0 M EUR & \multicolumn{2}{c}{——} \\ \hline GHG emissions & \multicolumn{2}{c}{40.16 kt} & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Main characteristics of El Hierro’s all-diesel generation system used to meet the 2023 demand. for the actual system data. As shown in Figure 9b, during a typical summer week, there is a clear predominance of renewable technologies. This situation is completely opposite to what is observed during the winter months (Figure 9c), specifically the weeks near the winter solstice, where demand is almost entirely met by diesel generation. An intermediate situation is observed for the rest of the year, as illustrated in Figure 9a. During these periods, diesel generation made a notable contribution, although renewable generation also played a significant role. When comparing the actual values from the plants (Figure 9-1) with the calculations made by the software (Figure 9-2), it is obvious that, in general, both show similar behavior. While analyzing specific moments may reveal certain differences, the overall behavior is quite similar. For example, a more detailed analysis of Figure 9a shows that the general performance is quite similar. However, there are five major periods of reversible pumping recharge in both cases, although the simulation shows sharpest recharges but with lower durations. As also observed, the areas dominated by diesel and wind generation are very similar, and the simulation presents a slightly lower diesel dependency, since the valley values of the diesel generation are lower in the EnergyPlan simulation. Even the turbine use of the reverse pumping facility is quite similar (red color in the figures). Regarding the summer and winter performance of both systems, comments, which are likely to be those made for Figure 9a, can be made. Then, the overall performance of both systems, real data and simulation results, is similar in general terms, but if the specific performance in a particular time period is analyzed, it may present appreciable differences. The incorporation of the wind-hydro plant completely changed the technical performance of the island. This hybrid system, which combines wind turbines with a pumped hydro storage facility, was designed to maximize the use of renewable energy and minimize reliance on diesel generation.