## 2 Materials and Methods
### Methodology  
Minimizing CO\({}_{2}\) emissions on an electrically interconnected island represents an integral and challenging campaign to enhance the sustainability and efficiency of the energy system. With the coexistence of conventional power plants and renewable energy sources on the island, flexibility and optimal use of the energy produced is vital. An innovative approach involves the use of a hydrogen tank to store excess energy produced from RES sources. Additionally, the sustainability and independence of the island's grid are also pursued, utilizing the interconnection only for power export to the mainland for financial gain. Therefore, the methodology's pursuits are the achievement of the following grid properties:  
* Independence;
* Sustainability;
* Carbon neutrality. Hydrogen storage is a central element in the mechanism for storing the energy produced, allowing it to be converted into electricity during periods of peak demand. This enhances the reliability of the energy grid, allowing excess energy to be sold either as electricity to other regions through the interconnection or as compressed hydrogen gas for industrial use. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Energy Source** & **Technology** & **Current Use in Crete** \\ \hline Solar energy & Photovoltaic cells & Yes \\ Solar energy & Solar thermal power & Planned \\ Wind power (on-shore) & Wind turbines & Yes \\ Wind power (off-shore) & Wind turbines & Planned \\ Biogas & Burning & Yes \\ Solid Biomass & Burning & No \\ Hydro energy & Hydro turbines & Yes \\ Electrolytic hydrogen & Fuel cells & No \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Sustainable Energy Technologies can be applied in Crete for electricity generation. The combination of conventional and renewable energy sources with the use of hydrogen storage allows for flexible and more efficient management of energy demand and supply. With the help of algorithms and computing systems solutions, it is feasible to determine the optimal combination of RES, conventional production units, and interconnection usage in collaboration with hydrogen production and storage in order to achieve a minimum environmental impact from CO2 emissions. * Creating a precise mathematical model to compute the parameters outlined in this study is intricate and heavily reliant on the unique conditions and attributes of the energy grid of the specific island under consideration. Based on aforementioned data, a simplified model has been devised to estimate the optimal performance of a hydrogen energy storage system, which follows these steps:
* Simulation of Crete's network as proposed. * Calculation of annual values based on key parameters. * Estimation of environmental and financial metrics based on real data. * Development of an optimization model to reach the desired goals under certain constraints. The power dispatch strategy prioritizes grid stability and minimizes reliance on conventional fuels by employing a tiered approach. The priority chain commences by activating only the minimum essential load coverage from conventional power plants, ensuring stable operation while conserving conventional fuel resources. Subsequently, available energy from locally produced RES is directly utilized to meet demand, maximizing the use of clean and sustainable energy. If real-time RES production proves insufficient, the strategy incorporates stored energy, potentially captured from prior periods of high-RES production through electrolysis. This stored energy can be converted for use through fuel cells. In scenarios where demand surpasses both real-time RES production and stored energy capacity, conventional generation is proportionally increased up to their technical limits or until the hourly load is satisfied. As a final resort, if all previous stages are inadequate, a controlled import of energy from the external grid can be implemented, though this option is used sparingly due to potential dependence on external energy sources.