Eco Friendly Actions Alternative Energy Sources Compositions alternative energy sources ebook | Page 35

Potential osmotic energy or salinity gradient energy is the available energy from the
salt concentration difference between sea water and river water. It is renewable
energy. Two practical methods for this are reverse electrodialysis (EDC) and delayed
pressure osmosis (OHP).
Both processes are based on osmosis with
ion-specific membranes. The key residual
product is salty water. This by-product is
the result of the natural forces that are
exploited: the flow of fresh water into the
seas, which consist of salt water.
The procedures have been confirmed
under laboratory conditions. They are
developed in commercial use in the
Netherlands (EDC) and Norway (OPH). The cost of the membrane was an obstacle.
New, low-cost, high-density polyethylene films made suitable for potential commercial
use.
Other methods have been
proposed and are currently
under development. Among
them, a method based on
dual-layer
capacitor
technology [2] and a method
based on the difference of
vapor pressure.
In the world, Statkraft opened
the first osmotic plant with
installed 4 kW power on November 24, 2009 in Tofte, Norway. This plant uses a
polyimide membrane and is capable of producing 1W / m² of membrane. This power
is obtained at 10 liters per second of water flowing through the membrane at a pressure
of 10 bar. Both the increase in pressure and the water flow would allow to increase the
power obtained.
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