## 3 Results  
Prior to commencing the optimization process, the initial solution values are outlined in Table 12. \begin{table}
\begin{tabular}{c c} \hline \hline
**Source of Emission/Sink** & **Annual Carbon Balance (\(\mathrm{tCO_{2}}\))** \\ \hline Existing olive groves in Crete & \(-\)1,310,393 \\ Use of heating oil for heating buildings in Crete & 95,619 \\ Transport & 1,030,188 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Annual carbon emission and absorption in Crete for 2018. The implementation of the methodology produces the values of the decision variables and the system's metrics, as illustrated in Table 13.  
The optimal energy system's annual emissions are estimated at 279,358.2 \(\mathrm{tCO_{2}}\). For the specific solution, the island's energy mix is illustrated in Figure 20:  
The methodology has effectively eradicated imports through the interconnection, rendering the island self-sufficient. The extensive expansion of RES ensures that the majority of the load is met through Direct RES production, with conventional sources minimized to an average hourly contribution equal to 69.1 MW, slightly above their hourly lower technical limits. The utilization of fuel cells is rare, occurring only for a few hours annually when RES production proves insufficient due to weather conditions. On a monthly basis, Figure 21 illustrates the energy mix for the load time series of 2023. The main contribution stems from Direct RES generation, while total conventional production operates mostly at its lower technical limit. This implies that additional conventional reduction would necessitate the shutdown of power plants, facilitating further penetration of RES and leading to a subsequent reduction in \(\mathrm{CO_{2}}\) emissions. The annual RES production is shown in Figure 22 as percentage shares: \begin{table}
\begin{tabular}{c c} \hline \hline
**Variable** & **Value** \\ \hline PV\({}_{\mathrm{cap}}\): & 2.13 GW \\ WT\({}_{\mathrm{cap}}\): & 3.55 GW \\ ELCAP: & 278.83 MW \\ F.C. CAP: & 278.83 MW \\ STCAP: & 69.20 MWh \\ CAPEX: & 6,516,043,003.31 EUR \\ NPV: & 0.49 EUR \\ Net carbon emissions: & 94,772.22 \(\mathrm{tCO_{2}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Optimal solution and results. Figure 20: Optimal energy mix of Crete. In a scenario where RES production is exceptionally high, there is almost zero electrolysis leading to storage (0.05%). Instead, electrolysis serves almost exclusivelyfor conversion to industrial hydrogen, with the majority of the produced energy being rejected, rendering the system inefficient. This underscores a mismatch between energy supply and demand, highlighting the need for achieving the desired goals with means other than the expansion of the installed capacity of RES to this extent. On a monthly basis, Figure 23 shows the monthly production, mostly comprised of rejections of the system. Despite the substantial profits estimated, the optimized system fails to manage the surplus energy produced in a financially viable manner, as production significantly exceeds the island's total consumption. Figure 23: Optimal monthly RES allocation for 2023. Figure 21: Optimal monthly energy mix for 2023. Figure 22: Optimal RES allocation for 2023. The initial capital expenditure for the optimal solution is presented in Figure 24, demonstrating the ratio of RES system expenditure to the hydrogen system cost. The majority of the costs stem from the expansion of RES, primarily due to the high installed capacities and elevated costs in comparison to the components of the hydrogen system. The annual cashflows for the entirety of the investment's lifespan are presented in Figure 25, presenting the most impactful contributors to the business model's operation:  
In a scenario where the income from hydrogen sales surpasses any maintenance or consumable costs, assuming an infinite demand for hydrogen mass, the system appears financially robust. Interestingly, the interconnection plays a negligible role, neither utilized for imports nor serving as a significant source of income.