Salt water, new energy source

With the continued exponential growth in our demands for digital computer processing, above all with the advent of AI, global energy consumption is also on a seemingly unstoppable upward trajectory. This ever-increasing need for energy represents a crucial challenge within a context of ongoing and intensifying climate change. An acceleration in the development of de-carbonised energy sources as substitutes for fossil fuels, which remain predominant in the global energy mix, has never been more urgent.

A colossal reservoir of underutilised clean energy

Faced with these energy challenges, the race to implement a new energy source is gaining momentum. Osmotic energy or 'blue energy', exploits the difference in salinity between seawater and freshwater. The principle is as follows: when two bodies of water with different salinity levels are separated by a semi-permeable membrane, fresh water naturally migrates across the barrier towards the salt water, balancing out the differing ionic concentrations. This movement generates hydraulic pressure that can be captured and converted into electricity, thus offering a particularly innovative and renewable energy source. This is what we call the natural phenomenon of osmosis.

By exploiting the many locations across the world where rivers and streams flow into the sea, colossal amounts of energy could be generated. According to the International Energy Agency (IEA), the theoretical global potential of osmotic energy is estimated at approximately 2,000 TWh/year, equivalent to the production of 1,000 nuclear reactors, compared to the current world total of about 440¹. Such immense potential capacity is not the only virtue of this 'blue' energy: it does not suffer from intermittence, unlike solar and wind energy, and is completely carbon-free if produced using bio-based materials.

A French industrial champion of osmotic energy

Despite its promise and having been known about for decades, osmotic energy, remains unexploited on a large scale. In the United States, Japan, Norway and France, many companies are developing the membranes necessary to allow osmotic energy to be produced. However, none has so-far moved beyond research into large-scale production. Currently, costs are still proving to be too high and there are technical and financial challenges in scaling from prototypes to industrial operations. 

However, a new French breakthrough could finally improve the prospects of making such technologies viable. After five years of research, the Rennes-based company, Sweetch Energy, has succeeded in developing a new type of membrane that is more efficient, cost-effective and suitable for industrial-scale production, drawing inspiration from the work of physicist and CNRS Research Director, Lydéric Bocquet. 
Based on nanoscale membranes made from bio-sourced materials, its INOD® technology would multiply membrane performance by 20 and divide material costs by 102. An initial demonstration plant has now been deployed on the River Rhône, near the Barcarin lock, in partnership with the Compagnie nationale du Rhône (CNR) and EDF Hydro. 
This pilot project marks a step-change in the development of osmotic energy, with a targeted power output increase of around 700 MW3 over the next few years. By laying the foundations for a sustainable industrial sector, this project could actively contribute to strengthening national energy sustainability and sovereignty. In the long term, osmotic energy could provide 15% of global electricity needs, avoiding the emission of 4 Gt of CO2 every year.

Discover our feature on "The Race for Innovation to Preserve the Blue Gold" by clicking here.