# Optimizing Sustainable Energy Transitions in Small Isolated Grids Using Multi-Criteria Approaches
## 4 Results and Discussion
### Discussion and Major Findings
#### 4.5.2 Fundamental Insights for Improving Renewable Generation Integration  
After modeling the scenarios examined and analyzing the results, different key issues that were discussed in previous points have been reviewed, addressed and considered in depth. Accordingly, these analyses lead to a number of main points at a more global level that can help to enhance the integration of renewable energies:  
* Decarbonization challenges: Transitioning to renewable energy faces challenges due to the current heavy reliance on fossil fuels. Wind and solar are intermittent, which makes it difficult to ensure a stable energy supply, particularly in isolated regions without connections to larger grids.
* Isolated regions' issues: Islands and remote regions face additional difficulties because they must be self-sufficient. They rely on fossil fuels for their stability, as renewables alone cannot always meet their energy needs.
* Renewable energy and storage needs: To support decarbonization, large-scale renewable energy generation is necessary, but storage is essential to bridge gaps during times of low renewable generation, ensuring a reliable power supply.
* EnergyPLAN Tool: The EnergyPLAN software was used to simulate various renewable energy system scenarios. It helps analyze different configurations by modeling energy systems' performance in terms of energy balance, reliability, and economic impact.
* Optimization technique: A multi-objective optimization technique was employed to balance system costs and GHG emissions, taking into account system constraints such as technology capacities and storage. This approach optimizes the energy system for both cost-effectiveness and environmental impact. The NSGA-II algorithm was selected for the optimization process, as it has demonstrated strong performance and yielded results comparable to those of other commonly used algorithms [43].
* El Hierro case study: The optimization technique was applied to El Hierro, which has an existing renewable energy system. This case study highlights the system's performance and the potential for improvement, showing a hybrid hydro-wind system with significant diesel reliance.
* Adverse conditions and system design: in years with poor renewable resource conditions (e.g., 2023), the renewable system could only cover 35% of the demand, indicating that system designs must account for low generation periods, still relying on diesel generation.
* Excess generation in favorable years: while renewable energy systems show surplus generation during favorable years (30-50%), this excess energy represents inefficiencies. A 100% renewable system would require significant over-sizing of both generation and storage.
* Renewable backup alternatives: To fully eliminate diesel, alternatives like biomass or geothermal would be necessary. However, their availability is limited, especially on islands like El Hierro, where imports would be required, adding complexity and cost.
* Optimized system design: the proposed optimized system reduces diesel use, adds more solar capacity, and increases storage, cutting emissions by 75% and reducing costs by one-third compared to the current system.
* Pathway to decarbonization: Achieving full decarbonization requires careful system planning and optimization. Without it, oversizing systems could lead to wasted resources, making it crucial to select the right path to reach sustainable energy goals, especially in isolated regions.  
The findings emphasize the complexity of achieving a fully renewable energy system, particularly in isolated regions like El Hierro. Balancing renewable generation with storage and backup systems, while minimizing reliance on fossil fuels, is key to both reducing costs and achieving environmental goals. The use of advanced optimization tools and real-world case studies highlights the need for careful planning to ensure energy independence, grid stability, and decarbonization in challenging conditions.