Cet article fait partie des 112 cas de l’économie bleue.

Cet article fait partie d’une liste de 112 innovations qui façonnent l’économie bleue. Il s’inscrit dans le cadre d’un vaste effort de Gunter Pauli pour stimuler l’esprit d’entreprise, la compétitivité et l’emploi dans les logiciels libres. Pour plus d’informations sur l’origine de ZERI.

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Cas 40 : Electricity from Osmosis

Apr 14, 2022 | 112 Innovations, Energy

The market

The International Energy Agency calculated that $10 trillion in energy investments are needed worldwide between now and 2030. The Chinese Government has already scheduled $1.3 trillion of investments in additional power supply. This ten trillion worldwide is the equivalent of one percent of global GDP over the whole period. However the Russian investment as a proportion of GDP is closer to fiver percent, and Africa tops 4 percent, compared to only half a percent for the OECD member states. Half of all investments for additional electricity capacity in the 27 member states of the European Union is in renewables. However, the challenge of renewables is that wind and solar, the two main sources of green power are unstable and require an investment in baseload supply. When there is no wind, and clouds block the sun across the European continent, then the total supply of electricity from these two core sources that represent by 2030 respectively 138 and 30 GW could drop in one day by as much as 20GW. That is why for each additional unit of renewable energy, the power supply companies calculate that they have to invest in an extra 0.9 unit in baseload supply. Alternatively, they could invest in electricity storage which tends to be more expensive. Baseload electricity operates 365 days without interruption. The preferred energy sources for this stable supply is combined cycle natural gas, at an investment cost of $1,000 KW, coal fired power stations at $3,000 KW and nuclear at $5,000 KW. While hydro and geothermal could also be part of the baseload energy portfolio, their availability is more determined by location. The investment cost in baseload supply is determined by the type of financing. Banks are eager to finance construction of baseload generation facilities with long term sales contracts since these pose a low risk. Still, an investment of one billion dollars in a baseload station includes 65 percent in construction costs, and 35 percent in financial charges and fees. If the financing were based on capital investments, then the returns could increase by at least one third.


Since most baseload power is supplied by coal and nuclear, there is a search for renewable energy that can provide not only intermittent, but also baseload power. Concentrated solar power is one of the promising renewable energy technologies. It can collect and store energy in pressurized steam, molten salt or purified graphite. Wind energy has been combined with a wide variety of storage systems including pumped hydroelectric storage, batteries, regenerative fuel cells, flywheels and magnets. However the most promising seems compressed air energy storage (CAES) which stores air in underground (geological) structures. The challenge remains that these storage facilities require extra investment costs and increased maintenance, further increasing the cost per kilowatt hour. Stein Erik Skilhagen, the Vice-President for Osmotic Power at the Norwegian Statkraft observed the power of a Redwood tree which sucks water up to 100 meters. The tree exploits the difference in concentration, pushing moisture all the way up. When fresh water from the mountains flows into salt seawater, a lot of energy is released through the change of concentration of salt. He observed that the flow of rivers into the ocean is a never ending flow thanks to the natural cycles of evaporation, condensation and precipitation. Therefore, the energy that is released through the difference between higher salinity that has higher pressure, and lower salinity with lower pressure could operate 365 days without any interruption. This is an ideal renewable baseload energy source. The mere exploitation of differences in concentration that generate pressure implies that the source of energy comes from within the realm of physics, the type of innovations proposed by The Blue Economy. This power source is also known as osmotic power or salinity gradient power, exploiting the difference in salt concentration between fresh river or rain water and salt water. The technique to generate electricity out of this gradient has been tested in the Netherlands through reverse electro-dialysis (RED), and has been put into practice in Norway through pressure retarded osmosis (PRO). The membrane that keeps the two water types apart is the key to success. While fresh water migrates to the salt side, it creates a pressure differential. This pressure is used to spin the turbine. Just like reverse osmosis (RO), this PRO generates a by-product. However unlike RO which produces brine with a high salt content, PRO generates brackish water that could be used in the production of algae, permitting the co-location of PRO-based energy plants and algae farms. This clustering of economic activities permits the generation of multiple cash flows, another characteristic of the innovations proposed by the Blue Economy.

The first cash flow

Statkraft decided to invest $8 million in a demonstration unit. One square meter of membranes generates at present 3W of electricity. It is expected that the introduction of a new type of membrane will increase the output to 5W. Experts consider that this is the minimum required to make the PRO technology competitive. The cost of operation has to include filtration. The creation of a biofilm on the membrane, quickly reduces its efficiency. It is here that the vortex, a proven technology from Sweden, and tested in Spain could serve as a low cost solution further decreasing investment and maintenance costs.

The opportunity

The application of osmosis to generate electricity is limited to where you have abundant fresh and salt water. This implies that any estuary reaching out into the sea has a potential. Experts have already established that the potential for osmotic power in Europe is three times the potential of wind and solar combined. The fact that it can operate 24 hours a day, 7 days a week makes it as competitive as gravity. HydroQuebec, the Canadian power company has calculated that the St. Lawrence River estuary has a potential of 12 Gigawatts. Countries with an abundant rainfall and a long shoreline are all expecting to harness this potential. The Tokyo Institute of Technology and Kyowakiden Industrial Co. from Nagasaki have started testing osmosis in Fukuoka. Stein Erik Skilhagen believes that once a few osmosis facilities are on-stream the major membrane suppliers of the world will apply their existing know-how of reverse osmosis membranes for the production of drinking water from salt water, to the osmosis. While Europe, North America and Japan have already engaged in the planning of facilities, the real future is for great river deltas of the world where energy is in short supply and extra baseload supply is urgently needed: The Yellow and Yangtze rivers, Mekong, Ganges, Pearl River, Brahmaputra, Nile, The Gambia, Okovango, Niger, Volta, Zambezi, Orinoco, Amazon, Parana, Lena and Yenisey.

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