2 April, 2024 Member article

Rutten NES’ innovative hydropneumatics storage technology project in São Tomé and Príncipe

One of the problems often encountered with off-grid systems is the premature ageing and failure of the electrochemical storage unit (batteries). Because of the high and often unfunded cost of replacement, these systems often stop working properly within a few years and end up being abandoned, depriving users of electrical service.

Willing to provide a more reliable and sustainable energy storage solution, ARE Member Rutten NES has created the NES-Store, an innovative, environmentally friendly and sustainable storage system inspired by pumped hydro, but which does away with any topographical constraints.

The energy is stored in the form of air compressed by water and is released through a specifically and in-house designed hydroelectric turbine. The whole system is containerised and modular. According to the chosen community’s needs, a given number of containers can be grouped together to achieve the required power and storage capacity.

This technology is internationally patented by Rutten NES and offers several advantages, such as insensitivity to deep discharges, with no deterioration in storage capacity over time; reliability and ease of maintenance; and is particularly well suited to sites where high ambient temperatures can be challenging.  From an environmental point of view, the system, which uses mainly steel, air and water, is easily recyclable and is not classified as a dangerous good for transport. It consumes no water, oil or fuel, and produces no gas or waste, so the risks of fire, short-circuits or explosion are very low.

In collaboration with the General Directorate of Natural Resources and Energy of São Tomé and Príncipe, and with financial support from Belgium and Wallonia, Rutten NES is currently carrying out a project aiming at complete electrification of an isolated community of around 300 inhabitants, located in the heart of the island of São Tomé. The company will install a photovoltaic power plant with a capacity of around 50 kWp, coupled with one of its hydropneumatic storage units, as well as a low-voltage distribution network incorporating intelligent energy management for the entire village (homes, community centre, multifunction platform, public lighting, etc.). To ensure the sustainability of the system and the safety of residents, these will be trained in the rational use of energy as well as in electrical risk management, which until now has been non-existent in the village. A power plant management structure will also be set up in collaboration with the local authorities, and its members will receive training specifically dedicated to the operation and maintenance of the power plant.

With commissioning scheduled for the second half of 2024, this emblematic project will enable the development of educational and economic activities through the productive use of energy within the community. The project will help to support the country’s renewable energy and sustainable development goals (SDG7), which are of vital importance for small island developing states such as São Tomé and Príncipe.