Salinity Gradient

Salinity gradient or osmotic power

When rivers meet the sea, fresh water mixes with salt. This can be harnesses. A membrane between the two can use osmotic pressure to force the fresh water up into salt water.

Blue Power Plant, Deltares

Osmotic pressure could be used to pump fresh water up into the sea.

Norway - osmotic power

Norway has built the word’s first osmotic power plant in 2009.  It is at the mouth of a river.

It works like a desalination plant, but in reverse. Instead of using energy to separate fresh water from salt, it mixes fresh and salt, and get energy from it.


Electro dialysis versus osmosis

An entirely different approach to making energy from mixing salty and fresh water is Revers Electro Dialysis,- RED.

A membrane separates th eions of sodium and chlorine, then generates electricity from the charge difference.

Redstack is world's first to produce blue energy based on reverse electro dialysis (RED). Electricity is generated directly from the membranes in one process step.

Theoretically, with 1m3/sec river water and an equal amount of sea water will generate approximately 1 MW of electricity.

An exploration of suitable rivers in the world shows that there is a potential electricity production of 1,600 TWh annually.

Blue Energy has the advantage that it can be generated continually, contrary to solar and wind energy, which are both dependent on availability and the weather.

The expectation is that Blue Energy will succeed in generating energy for 8 eurocents per kilowatt-hour. More