# Optimizing Sustainable Energy Transitions in Small Isolated Grids Using Multi-Criteria Approaches
## 3 Materials and Methods
### Definition of Scenarios  
Coverage of electrical demand in El Hierro up to 2014, as previously detailed, was achieved employing diesel-powered generators, a technology that entailed a substantial impact on the environment. This situation significantly improved after that date with the establishment of the fully renewable wind-hydro power plant of Gorona del Viento. Based on this, there are two different options or models for the supply of electrical energy for El Hierro. The first possibility involves continuing to use the current energy generation system, which means using the wind-hydro plant and supplementing it with the thermal power plant during periods when it is necessary (approximately 50% generation from each over these years). The second option aims to evolve the current model towards one with a greater renewable share, with the intention of achieving a 100% renewable system. But in order to have a reference point of the performance of El Hierro's electricity system prior to the installation of the wind-hydro power plant, the analysis of the system completely based on fossil fuels is also presented. Thus, the three models can be summarized as follows:  
* Generation completely based on the diesel thermal power plant (generation systems up to 2014). * Integrated wind generation with energy storage, alongside a diesel thermal power plant (current generation system). * Optimizing the configuration of these renewable systems to achieve generation levels as close as possible to a full renewable energy system while considering existing constraints. Additionally, the accuracy of the software was assessed by evaluating its 2023 simulation outcomes against existing data sources. As the monthly data of the two systems for the current generation system is available, the accuracy of the code forecasts has been tested against that of these facilities. Subsequently, through this approach, the correct performance of the code was assessed, and a code analysis was carried out, which will subsequently be used for detailed analyses of the established scenarios. After validating the software's performance, the first step is to conduct an analysis of the optimum generation system from an integrated energy planning approach. This line of investigation considers the analysis of the electric system's performance with the aim of reaching the point of optimal efficiency over the thorough energy landscape. Once the various possible contributions are taken into account, an hourly analysis of the balances between renewable energy production, storage technologies, and energy demand is carried out, considering the effect produced by the inherently oscillatory nature of this type of energy source with an adequate level of detail. These analyses evaluate the performance of the current energy system. Additionally, an in-depth analysis of the optimized multi-criteria scenario is conducted, so that the main findings related to the effects of the analyzed constraints on the considered factors can be presented and discussed. Within the developed multi-criteria optimization procedure, the prospective use of other sources of extra generation and storage should be explored, i.e., the data gathered from wind generation and storage performance for El Hierro's wind-hydro plant. In the current study, the consideration of solar generation was explored, adding to unavoidable additional storage capacity. This additional storage capacity can be reached by increasing the current facility or by finding other appropriate locations for new plants. Particularly for solar photovoltaic generation, Trina Solar Vertex 550 W+ panels have been used as a reference model, with an initial investment of 1300 EUR/kW and Operating and Maintenance costs (O&M) of 3.5 EUR/kW per year [15,18].