Blue is the New Green

Generating energy from the difference in salt concentration between sea water and river water sounds like magic, yet it really works! Blue energy, as this rather obscure form of sustainable power is commonly known, has huge potential. In theory, an average river could produce as much blue energy as a hydropower plant generating power using a waterfall 142 meters in height! PhD researcher Diego Pintossi has developed new ways of understanding and solving the problem of dirt clogging up the membranes used in generating blue energy. He will defend his thesis on Friday June 11th at TU/e.

[tue.nl] – Tapping the magical power contained in water
[tue.nl] – Fouling in reverse electrodialysis, PhD thesis

Blue Energy Update

Dutch language video

“Blue energy” is tapped from places where river water reaches the sea. The key to this form of energy generation is difference in concentration of dissolved salts.

One very suitable location is the Aflsuitdijk in the Netherlands, where a dike of 32 km separates fresh from salt water. The ultimate potential here is 3 GW, based on a flow of 3300 m³/sec. Currently, a demonstration project is in place that provides more than 160 households with blue electricity (“blue” refers to water).

The key challenge is to develop suitable membranes.

Once the engineers get this to work, the method can be applied everywhere where rivers flow into the sea. And that’s a lot of places, thousands.

Related to blue energy is the possibility of storing energy in salinated water. Rule of thumb: 1 m3 salt water has an energy content of 1 kWh, as compared to fresh water. This is about the same as a conventional car battery, except with salt water, one can work with volumes the size of a lake. The company AquaBattery in Leiden is working on this topic.

[wikipedia.org] – Osmotic power
[deepresource] – Blue Energy (2012)
[deepresource] – Blue Energy Pilot Plant Operational in the Netherlands (2014)
[deafsluitdijk.nl] – De 9 meest gestelde vragen over Blue Energy

Generating Electricity From Fresh-Salt Water Interfaces

Dutch language video, English subs

Prof. Kitty Nijmeijer (University Twente, the Netherlands) explains how it is possible to generate electricity from membranes, separating fresh and salt water. This has great implications for the Dutch energy situation and the dike called the Afsluitdijk in particular:

Pictures of the closure of the Afsluitdijk in 1932.

[wikipedia.org] – Afsluitdijk
[deepresource] – Blue Energy
[deepresource] – Blue Energy Pilot Plant Operational in the Netherlands

Blue Energy Pilot Plant Operational in the Netherlands

Power pilot installation: 50 kW. Current gain of 2,6 W/m2 membrane, should be lifted towards 5 W/m2. Potential for Dutch electricity generation: 200 MW. Estimated global potential: 5% of total energy consumption. Key technological challenge: combat pollution membranes.

Osmotic power or salinity gradient power is the energy available from the difference in the salt concentration between seawater and river water. Two practical methods for this are reverse electrodialysis (RED) and pressure retarded osmosis (PRO). Both processes rely on osmosis with ion specific membranes. The key waste product is brackish water. This byproduct is the result of natural forces that are being harnessed: the flow of fresh water into seas that are made up of salt water.

[wikipedia.org] – Osmotic power
[DeeprResource] – Blue Energy

Zout=salt, zoet=sweet (fresh), brak=mixed (brackish). Blue energy=electricity generated from mixing salt and fresh water (osmosis)

The King Willem-Alexander opens the installation (that is already operational for a year).

[rt.com] – New research to turn salty oceans into a renewable energy source

Osmotic Power Plant In Norway

Youtube text: Osmotic Power – The energy is based on the natural phenomenon osmosis, defined as being the transport of water through a semi-permeable membrane. This is how plants can absorb moisture through their leaves — and retain it. When fresh water meets salt water, for instance where a river runs into the sea, enormous amounts of energy are released. This energy can be utilized for the generation of power through osmosis. At the osmotic power plant, fresh water and salt water are guided into separate chambers, divided by an artificial membrane. The salt molecules in the sea water pulls the freshwater through the membrane, increasing the pressure on the sea water side. The pressure equals a 120 metre water column, or a significant waterfall, and be utilized in a power generating turbine.

Statkraft prototype Tofte/Norway

A 10 kW prototype was realized in 2008. A commercial scale implementation is expected to become operational in 2015. This is expensive technology.

[power-technology.com]

[wikipedia.org] – Prototype Tofte/Hurum, Norway (10 kW)

Blue Energy

Reverse Electro Dialysis is the most promising technique method for extracting energy from the salt difference between sea and river water. The method is inherently sustainable and clean. In theory the Rhine river can deliver 6000 megawatt energy on mixing with the Northsea. Assuming an ideal process, there is no overall energy effect and the process is balanced by cooling the effluent 0.2 degrees or so. Extraction of a part of this 6000 MWatt is an exciting idea.

[wikipedia – osmotic power]
[newscientist.com]

According to a Dutch government source a 50 kilowatt pilot project will be realised and financed with 8 million euro. The potential for the Afsluitdijk is estimated to be 200 MW, but is not expected to be implemented before 2030.

[helpdeskwater.nl]