Osmotic power

Design News magazine article claims that Osmotic Power Using Salt Water Is Newest Form of Alternative Energy. According to the article, alternative energies like solar, wind, and hydropower are poised to get some powerful new company, thanks in part to researchers in Switzerland. The power comes through the transfer of salt ions between two types of salt water when they make contact through a membrane – the new research has created a new a new osmotic-power generation system using a membrane a mere three atoms thick to separate water with different salination levels — such as salt water and fresh water, according to researchers. According to their calculations, a 1m^² membrane with 30% of its surface covered by nanopores should be able to produce 1 megaWatt of electricity. The key limitations of this process are the efficiency and cost of the membrane.

This is not the first time this idea is tested. 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). The technologies have been confirmed in laboratory conditions. They are being developed into commercial use in the Netherlands (RED) and Norway (PRO). The cost of the membrane has been an obstacle. For introduction take a look at Statkraft – Osmotic Power Plant – Free energy – How it works  video below.

The Statkraft osmotic power plant at Tofte, Norway, was the world’s first osmotic power or salinity gradient power generation plant. The prototype plant built in 2009 has a designed capacity to generate 10kW of electricity (produced 2 kW to 4 kW). At the time technology was seen as promising for the solving energy needs- it has been claimed to be it’s the cleanest, most reliable source of renewable energy on the planet.

This test was not success. In 2014 Norwegian power company Statkraft has shelved its much-watched effort to harness energy from pressure-retarded osmosis (PRO). The challenge had been to make the technology efficient enough to achieve energy production costs on par with competing technologies. The PRO technology has not been completely forgotten as for example MIT has studied improvements to it.