Two-thirds of the Earth is covered in water and 97% is, without the help of very nascent and expensive technology, undrinkable because of salt. However, something magical happens when freshwater and seawater are mixed, which some say could play a sizable role in the clean energy transition. Now, one French startup, Sweetch Energy claims they are the first company to have developed a system suitable for large-scale osmotic power, and as announced on December 18, 2023, the team raised €25 million ($27.38 million) to do it.
When freshwater flows into the ocean, like via a river or estuary, a tsunami of energy is released. This is the process of osmosis, where water moves from a diluted to a concentrated solution, and a chemical shock occurs. This change in “osmotic pressure” was first theorized by British engineer, R. E. Pattle, in 1954, and it wasn’t until the ‘70s that osmosis power was realized and developed by Sidney Loeb, as the world's energy crisis prompted further research into energy supply alternatives.
Also known as blue energy, 2009 marked the year the world’s first osmotic prototype power plant was built in Norway. Named ‘Salto’ and developed by Norwegian state-owned renewable energy supplier, Statkraf, the plant remains one of the handful of osmotic energy projects in the world.
However, Sweetch Energy thinks it can change that.
The global energy crisis of the 1970s catalyzed research into osmotic energy — as well as many other moonshot renewables like nuclear fusion — however as the modern-day climate crisis demands more diversified power sources, Sweetch aspires to create the world’s first large-scale osmosis power station, OsmoRhône 1, in the Rhône Delta in southern France, this year.
“The world desperately needs new sources of renewable energy to make the energy transition and fight climate change,” Nicolas Heuzé, co-founder and CEO of Sweetch Energy said in French in a video on the company’s website.
“We know that in the future we are facing, [there will be a] significant demand for energy, and we will have to massively electrify the planet,” his co-founder and the company’s chairman, Pascal Le Melinaire added.
According to the French renewable energy provider, this burgeoning saltwater power has the potential to build upon intermittent renewables, like solar and wind, and increase optimistic projections of renewables providing 50% of the world’s power by 2050 to 65%.
And they only need salt, water, and Sweetch’s INOD nanotechnology to do it. Sweetch claims that, with INOD, it can achieve the traditionally location-dependent, and largely untapped, process anywhere in the world.
This is how it works. The chemical shock that occurs when freshwater meets seawater happens when the water passes through what’s known as a membrane. These can be thought of as filters like those used in water filtration processes like desalination, or in Sweetch’s case, nanofiltration.
Taking inspiration from the natural process that occurs in deltas and estuaries, Sweetch created nano-scale membranes that, when paired with its electrode system, transports the water’s ions, which in turn, generates electricity.
“We rely on a technology that uses eco-friendly materials locally available,” Heuzé explained in the video, adding that it's not noisy, doesn’t emit smoke, nor rely on heavy machinery. “So in that respect, it ticks all the boxes to be part of the future generation of renewable energies.”
The company’s nano approach began with a paper published by Professor Lydéric Bocquet who heads the nanofluids research lab at ENS Paris and CNRS. Based on his claims of the unprecedented power of osmotic energy and decades of nanotechnology research to generate ionic currents, Sweetch created “selective membranes” with nanoscale pores which they named INON to stand for Ionic Nano Osmosic Diffusion.
“Instead of having a solid membrane with very slow chemical reactions, we have pores that are very large relative to chemical species, with nonetheless, selectivity across the pore that allows ions to circulate extremely rapidly,” cofounder and chief science officer, Burno Mottet, explains in the video, which transforms the ionic current into an electric current.
Gradually installed and distributed along the Rhône over the next decade in collaboration with Compagnie Nationale du Rhône (CNR), Sweetch says the plant, which is currently under development, will provide up to 500 megawatts (MW) of power.
That’s just a fraction of what Sweetch estimates to be a potential 30,000 terawatt-hours of energy that come from the world’s estuaries every year. If harnessed, this would avoid the emissions of 4 gigatons of planet-warming CO2 annually, the company says.
Sweetch isn’t the only company working to deploy osmotic energy. Dutch startup, REDstack, is developing osmotic power through a process called “reverse electrodialysis,” (RED). This process retrieves osmotic energy using a heat engine invented by Loeb and his partners in the ‘70s. REDstack pairs it with its desalination process, a growing technology that removes salt from water to make it drinkable.
Most recently, the company received €1.2 million (about $1.3 million) for its pilot project from the Dutch province of Friesland last June. REDstack is part of a coalition launched by Sweetch — along with two other European blue energy companies, Denmark’s Saltpower and Sweetch’s partner CNR, together, they all aim to scale the energy across the continent.
Nevertheless, one reason osmotic energy has not scaled is the potential impact on marine life and natural landscapes. But, as Heuzé explains in the video, Sweetch systems aren’t massive and could even be put underground. Instead of a giant powerplant in the middle of a river like a dam, Sweetch claims their plants are more like small buildings on the edge of an estuary or delta, with freshwater on one side, and seawater on the other. Water flows through the generator, and returns to the body, continuously harvesting energy.
The Series A financing round was led by Révolution Environnementale et Solidaire, a fund managed by Crédit Mutuel Impact, with participation from Sweetch Energy’s past investors, Demeter Investment Managers, Go Capital, and Positive Future Capital, and its industrial partner CNR, bringing its total funding to nearly €40 million.
Sweetch intends to use the funding to expand research and development for the plant, deploy the first industrial assembly lines, and support its expansion across Europe and overseas to North America. Continuously, they are also working to reduce the cost of generation to align with other renewables.
“Producing clean, 24/7, competitive electricity is one of the main challenges toward a true energy transition,” Heuzé said in a statement, adding that the financing will allow the company to “take another decisive step towards deploying osmotic energy globally.”