What is Osmotic Energy ?


Besides the “classical” renewable energy sources like tidal or wind energy, salinity gradient power generation is striving to get its place and mention in the RES (Renewable Energy Sources) plan to be explored by the member states. The theoretical potential of MW/h is quite high and the technique ensures a constant production, as regular and powerful as the flow of a river to the sea.

Salinity Gradient Power generation is not a “new” principle. The concept of extracting energy by using the difference of salinity between two water bodies has been discovered in the Early 70’s by Sydney Loeb [1].

“Salinity power” exploits the chemical differences between salt and fresh water, and this project only hints at the technology’s potential: from the mouth of the Ganges to theMississippidelta, almost every large estuary could make green electricity, day and night, rain or shine, without damaging sensitive ecosystems or threatening fisheries. One estimate has it that salinity power could eventually provide as much as seven per cent of today’s global energy needs. Experts evaluated the potential energy yield at 1MW/m3 of fresh water / second.

At this stage it’s important to make a clear distinction between the two techniques that were presented during the workshop: The Reverse Electro Dialysis (RED) and the Pressure Retarded Osmosis (PRO).

Simplified, the RED technique uses ionic exchange between fresh and salt water. In the device the water bodies are separated with membranes allowing only ions to cross. Anions and cations are crossing different membranes and this phenomenon generates energy (picture below).


The PRO technique is more closely linked to the osmosis principle: it uses the difference of density between the water bodies. When separated by a special membrane, the water bodies tend to equilibrate, thus generating a huge pressure. This pressure is then used to generate energy (picture below).


What is the INES project about?

Based on the conclusions of the meeting held in Brussels on the 27th of April 2010, this initiative was created in order to enhance the development of salinity gradient power and the visibility of this innovative renewable energy production technique.

INES’s purpose is to try to find and develop solutions to the common problems identified as crucial to the sector at the April meeting, including bio-fouling, financing of demonstration projects and pilots, water quality, ecological aspects and permitting. Additionally, it is intended to contribute to the further development of the sector and to bring membrane producers, developers, investors, and other potential funding organizations, together with EU, national and regional authorities aiming at a better mutual co-operation.

Regarding the European authorities, this exercise is also aimed at bringing salinity gradient to the attention of the new European Innovation Agency, the relevant European Topic Centres (for example DG Research, DG Region, DG Environment), as well as to International Bodies. INES will help making this invention more known by co-operating with key international agencies. This is important for the transmission of information to key decision makers on Energy and innovation funds, including the relevant OECD directorates, the IEA, the New European Agency on Innovation, the European Topic Centre and The European Investment Bank.

Additionally, INES gives the opportunity to reach out to transatlantic international centres developing salinity gradient power, including theUnitesStatesand Canadian actors. Contacts with Canadian and US Parties are on-going. Also, contacts are being established with Japanese and other Asian parties.

The collaborative network approach (in which IMI has more than 10 years of experience) significantly reduces the research costs and helps its member in finding quick and accurate information.


Nano Tech

First developments in utilizing nano structures to improve the energy yield of salinity gradient-technologies were made in 2013. In their Article “Giant osmotic energy conversion measured in a single transmembrane boron nitride nanotube”, Alessandro Siiria et aldetailed the results of inserting a single boron nanotube into a hole drilled into an impermeable, electrically insulating membrane, a modification of the Reverse Electrodialysis process.

Through this modification, power densities were increased by three orders of magnitude over that of conventional RED methods (power densities were 1000 times greater than conventional RED). These results are still in the context of laboratory conditions, with ideal settings. Currently, Nano-based Salinity gradient power generation is being investigated by IMIEU-partnered start-ups such as Blue Energy Leap (Lausanne, Switzerland), and by France-based Sweetch Energy.

Also, global demand for Lithium has been on the rise, with new battery technologies being developed for electronics applications, energy storage, electrification of transport, etc. Terrestrial lithium reserves are mainly concentrated in granite pegmatite type deposits (spodumene and petalite ores), salt lake brines, seawater and geothermal waste water streams. Among them, the reserves of lithium resources in salt lake brine, seawater and geothermal water are 70–80% of the total. One of the other applications of Salinity Gradient Technologies could be in the extraction of lithium from seawater. Projects such as the SEArcular MINE project in Europe have been initiated to develop methods to extract lithium, magnesium, and other critical elements from the sea, while preserving the broad aims of circularity, and the circular economy.


The INES project would match the needs of Salinity Gradient development projects:


The Content

Firstly, exploration of innovative salinity gradient energy production that involves identification of both RED and PRO opportunities, feasibility studies for selection of appropriate sites, exploration of EU funding options and exchange of information regarding site selection and/or demonstration of hardware installation.

Secondly, supply chain and industry involvement and assessment of effects on ecological and environmental values in the perspective of large scale plant implementation. Considering barrage opening, brackish water release, water pumping, biofouling of membranes, monitoring of ecological and environmental effects; this theme focuses both on PRO and RED techniques. Important point under this theme includes the operationalisation of the use of the principle `Building with Nature´ in relation to other renewable energy plant solutions.

The contribution from the partners in this phase is particularly, a (if desired) participation in the two seminars per year and participation in the orientation board for the special actions and products held in the INES Group. All other organisational aspects, as preparation of the meetings, reporting etcetera, are being provided by IMI.

In the INES project, the research areas will be oriented on the following topics:


  • Exchange of information on technical aspects and solutions for energy generation and water pretreatment, biofouling of membranes and their cleaning.
  • Exchange of information on anticipated environmental issues and their mitigation measures (brackish water release, fish impingement…), -In focus at seminar in Brussels, Belgium
  • Exchange of information on feasibility studies, methodology for site selection and EU regulation related to protection of water and estuaries;
  • Financial aspects relating to the construction and operation of a salinity gradient power plant, return on investment rates and regional incentives for installing salinity gradient: feed in tariffs and sources of financing.


How to join?

If you are interested to join the project, please contact us via info@imieu.eu or by WhatsApp on +31 61 543 822 5 and we will happily answer all your questions.


[1] Sidney Loeb (1917–2008),[1] chemical engineer, made reverse osmosis (ro) practical by developing, together with Srinivasa Sourirajan, semi-permeable anisotropic membranes. Loeb invented the power generating process pressure retarded osmosis (pro) and the method of producing power by reverse electrodialysis, among other inventions in related areas.