# Optimizing Sustainable Energy Transitions in Small Isolated Grids Using Multi-Criteria Approaches
## 4 Results and Discussion
### Collapsing on a Single Optimization Metric
\begin{table}
\begin{tabular}{c c} \hline
**Technology** & **Results for Optimal Setup** \\ \hline \hline \multicolumn{2}{l}{Diesel power plant} \\ \hline \multicolumn{2}{l}{Installed diesel power} & 9 MW \\ Generation & 7.35 GWh \\ Average CF & 9.33\% \\ Peak CF & 85.67\% \\ \hline \multicolumn{2}{l}{Annual costs} & 1.187 M EUR 1 \\ Fixed operation costs & 0.180 M EUR & 20.58\% \\ Variable costs & 1.007 M EUR & 79.42\% \\ Annual investment costs & 0 M EUR & -\% \\ \hline \multicolumn{2}{l}{Wind–hydro plant} \\ \hline \multicolumn{2}{l}{Installed wind power} & 11.50 MW \\ Generation & 25.48 GWh \\ Average CF & 24.65\% \\ Peak CF & 65.34\% \\ \hline \multicolumn{2}{l}{Annual costs} & 1.51 M EUR 1 \\ Fixed operation costs & 0.463 M EUR & 30.66\% \\ Annual investment costs 1 & 1.047 M EUR & 69.34\% \\ \hline \multicolumn{2}{l}{Hydro storage} \\ \hline \multicolumn{2}{l}{Installed pump power} & 7.2 MW \\ Installed turbine power & 11.3 MW \\ Storage capacity & 500 MWh \\ Energy pumped & 16.64 GWh \\ Hydro pump average CF & 26.38\% \\ Hydro pump peak CF & 100\% \\ Energy turbinated & 8.37 GWh \\ Turbine average CF & 8.10\% \\ Turbine peak CF & 65.34\% \\ \hline \multicolumn{2}{l}{Annual costs} & 2.628 M EUR 1 \\ Fixed operation costs & 0.749 M EUR & 28.50\% \\ Annual investment costs 1 & 1.879 M EUR & 71.50\% \\ \hline \multicolumn{2}{l}{Solar PV} \\ \hline \multicolumn{2}{l}{Installed Power} & 13.30 MW \\ Generation & 27.36 GWh \\ Average CF & 23.48\% \\ Peak CF & 57.97\% \\ \hline \multicolumn{2}{l}{Annual costs} & 1.266 M EUR 1 \\ Fixed operation costs & 0.104 M EUR & 8.21\% \\ Annual investment costs 1 & 1.162 M EUR & 91.79\% \\ \hline \multicolumn{2}{l}{Total annual costs} & 6.591 M EUR \\ \hline \multicolumn{2}{l}{GHG emissions} & 6.26 kt \\ \hline \end{tabular} 1  
\end{table} 
Table 6: Overview of the main features of the optimal generating system for 2023.  
mix by 2023 to just over 7 GWh in the proposed mix. It should also be noted that in the optimized system, wind generation has been maintained at the current level (in all probability, it has not been reduced since it has been considered appropriate to maintain the existing renewable equipment as a restriction), incorporating solar PV generation with an appreciable contribution, an installed power of more than 13 MW, given its greater cost competitiveness, despite its lack of dispatchability and generation concentration in the central day hours. It should also be noted that the use of storage has increased appreciably with respect to the current case, from just under 8 GWh in the current scenario to almost 17 GWh in the proposed mix. In summary, it can be said that the proposed mix achieves a very significant reduction in emissions while also reducing costs. The reduction in emissions is 75% compared to the figures of the 2023 scenario, 24 kt compared to slightly more than 6 kt in the proposed scenario. On the other hand, the reduction in costs is over 30%, from around 10 M EUR to just under 7 M EUR. In Figure 12, the monthly performance of different generation technologies and the demand are summarized (it is important to note that the actual balances were calculated in hourly intervals, with the monthly representation provided for better visual synthesis). As shown, during the summer months, the generation is significantly greater despite higher demands, leading to more significant surpluses. July and August, followed by May, exhibit the best system performance. Conversely, the winter months, particularly December and February, show considerably lower generation, and then, despite lower demands, the system experiences critical performance moments. January, along with October and November, occupies an intermediate position in these energy balances. Specifically, January has the lowest energy demand and low generation, allowing for balanced generation and demand. In October and November, higher demand is accompanied by higher generation, also leading to a balance of generation and demand.