Blue Energy

When a river runs into the ocean and fresh water mixes with saltwater, huge amounts of energy are unleashed. Unlike violent torrents in a waterfall or steaming hot geysers, the energy released cannot easily be seen from the banks of the estuary. Nevertheless, the energy is there, and everyone who has tried to separate salt from seawater knows that large amounts of energy are needed.

There are several ways to harvest energy from the entropy of mixing fresh or river water with salt or sea water. The two most important ways, pressure-retarded osmosis (PRO) and reverse electrodialysis (RED), depend heavily on membrane development and a reduction in the price per square meter.

Over the last twenty years, membrane technology has become more and more important in areas such as waste water treatment, desalination and drinking water preparation, resulting in a great reduction in prices. This has strongly supported the breakthrough of saline power, the brand name for PRO developed by Statkraft in Norway in 1998, and Blue Energy, under which name KEMA in the Netherlands started the development of the RED variant in 2002.

Starting with some historical notes, Van’t Hoff’s Nobel Prize in 1899 will be described, including the physical-chemical principles. Then the current technical status and challenges will be discussed. This will include the key topic, membranes, but also other issues such as pump energy, water pre-treatment, etc. Consideration will also be given to the potential energy production in delta areas and industrial sites. This will include the necessary electrical infrastructure for Blue Energy, which generates DC power and low voltage output.

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