At Aiguasol, we’ve had the privilege of contributing to a transformative project in one of the most remote locations on Earth: the island of Saint Helena, a British Overseas Territory located in the South Atlantic. In collaboration with the local utility company Connect Saint Helena Ltd, we led the techno-economic optimization of the island’s electrical system, with the aim of reducing its reliance on diesel and moving towards an energy model based on renewable sources.

An island context full of opportunities

Saint Helena faces many of the typical challenges of island territories: a heavy dependence on fossil fuels, high electricity generation costs, and significant environmental vulnerability. However, it also benefits from abundant and stable solar and wind resources throughout the year, making a transition to a cleaner and more self-sufficient energy system feasible.

To tackle this challenge, we developed a detailed model of the island’s electrical system using hourly simulation tools. Our team worked with real data provided by Connect Saint Helena, climate information gathered through data acquisition systems, and observations collected during an intensive field campaign on the island.

With this information, we evaluated a range of technological and economic scenarios to identify the optimal combination of generation and storage systems that would maximize renewable energy penetration at the lowest possible cost. Beyond technical and economic aspects, the analysis also considered environmental impacts and the local capacity to operate and maintain the system—two key factors for ensuring long-term sustainability.

A hybrid system tailored to local realities

The proposed solution is based on a 6,500 kWp photovoltaic installation combined with a 22 MWh pumped hydro storage (PHS) system. This setup includes two 30,000 m³ reservoirs, 3 MW hydro turbines, and the corresponding pumping infrastructure. To complement this system and ensure grid stability during peak demand, a 0.5 MWh battery is also included, capable of responding to short-term load spikes for up to 10 minutes.

As part of the project, we assessed the feasibility of achieving a 100% renewable energy system. While technically possible, doing so would require significantly oversized infrastructure, with the associated increase in costs. For this reason, we considered it more realistic and efficient to aim for an 80–95% renewable penetration target, retaining the existing diesel generators as backup for exceptional situations.

This project has highlighted that, in isolated environments like Saint Helena, the suitability of a given technology is not determined solely by resource availability, but by the balance between resource potential and associated costs. Although wind is plentiful on the island, photovoltaic systems proved more competitive due to their simplicity, performance, and lower installation and maintenance costs. As for storage, despite the falling costs of batteries, pumped hydro remains the most robust and efficient solution for small to medium-scale island systems.

Advancing the global energy transition

Our work in Saint Helena has been far more than a technical study—it has been an opportunity to contribute to a project deeply committed to sustainability. We applied a comprehensive methodology that integrates local knowledge, environmental criteria, and economic feasibility—one that can serve as a model for many other islands and remote regions striving for a fair and effective energy transition.

At Aiguasol, we’re proud to have been part of this process and remain committed to delivering energy solutions that are efficient, realistic, and sustainable around the world.