Multi-objective optimization of hydro-wind-solar generation: A path towards total economy decarbonization with external energy independence in small stand-alone grids
C. Berna, Lucas Álvarez-Piñeiro, David Blanco, Yago Rivera
Abstract
However, integrating renewable sources such as wind and solar photovoltaics presents significant challenges due to their intermittent and unpredictable nature, particularly pronounced in isolated territories and islands with limited grids. El Hierro, a small island in the Spanish Canary Islands Archipelago, hosts a pioneering hydro-wind power plant that covers a substantial portion of its electricity demand. Despite its success, the system's reliance on diesel generators and over-installed hydropower capacity has economic and environmental drawbacks. This study aims to optimize El Hierro's renewable energy system to enhance cost-efficiency, reduce CO 2 emissions, and minimize energy excesses , providing insights for sustainable renewable energy integration in similar isolated systems. A multi-objective optimization problem approach was employed using EnergyPLAN and EPLANopt, a genetic algorithm-based tool. The study focused on minimizing annual costs, CO 2 emissions, and energy excesses, generating a Pareto front of optimal solutions under various generation and storage technology constraints. The previously conflicting objectives are converted into a unified cost function . Emissions and surpluses are monetized to evaluate the overall economic impact, allowing a direct comparison of different configurations. The single solution yielding the lowest combined cost provides an optimal system design that balances environmental sustainability , cost-efficiency, and grid reliability. Renewable energy capacities of 8–10 MW for solar, 11–13 MW for wind, and 7–9 MW for pumping power, with storage capacities of 400–450 MWh, are optimal. Lifecycle CO 2 emissions were reduced to 6–13 % compared to an entirely fossil fuel-based system, while system costs ranged from 6.2 to 6.7 million euros. Diesel backup, although minimized, remains the most viable dispatchable technology in the absence of geothermal or biomass alternatives. The study highlights that pumped hydro systems play a critical role in optimized configurations, contributing significantly to overall costs, while wind and solar generation provide balanced contributions. Incorporating multiple objectives offers a balanced and sustainable system design that aligns with the economic, environmental, and reliability goals of El Hierro and other isolated renewable systems.