DYNA JOURNAL ENGINEERING

In addition, with the increasing installation of offshore wind turbines, the electricity produced is incorporated into the network in coastal locations and if it is desired to use the surplus to produce hydrogen, it seems that it would be practical to do so with sea water, which is widely available.

However, this possibility has been ruled out so far because of the requirement of current electrolyzers to desalinate seawater, which makes such an operation uneconomical. In spite of this, this is the means that will be applied in the new city of Neom, on the coast of the northern end of the Red Sea (Saudi Arabia), which intends to equip itself with 4 GW of renewable generation (solar and wind) and the necessary capacity to desalinate the water, both for consumption and for a hydrogen production plant that is expected to amount to 650 T/day, part for own consumption in vehicles and part to be exported in the form of ammonia.

Trying to overcome the need for desalination, a team of researchers from the University of Pennsylvania presented in Energy & Environmental Science their work "Using reverse osmosis membranes to control ion transport during water electrolysis. In it, they propose to locate an inexpensive commercial membrane used for reverse osmosis to separate the inert perchlorate anolite from the catholite, seawater. The hydrogen and hydroxide ions flow through the membrane, but not the sodium ions, and the cathode completes the electrolysis. If the membrane used was the usual one in electrolyzers, the ion exchange membrane (CEM), not only would be much more expensive, but would allow the sodium ions to pass and the chlorine ions released would cause harmful effects to the installation and toxicity to the environment. In addition, the current density required for dissociation, between 10 and 40 mA/cm2, is comparable to that applied in freshwater electrolysers.