With approximately 70% of the Earth’s surface covered in water, the oceans hold about 96.5% of all Earth’s water.
As the human population continues to increase at an alarming rate there is international recognition that planet Earth is in the midst of a climate crisis. With so much water surrounding us, is there not a way of harnessing energy directly from the oceans?
Offshore wind farms have been growing in numbers globally and filling our oceanic views with vast wind turbines for years. These sizeable offshore farms produce approximately 60,008 MW of energy globally, going some way to supplying the ever-increasing energy needs of Earths growing population.
Offshore wind is not the only energy production in the oceans. Hydropower also tops up global energy supplies but is only responsible for an estimated 15% of global energy production.
With an ever-increasing need for alternative energy production to reduce global climate temperatures, another recent development is how seawater can be used to generate Green Hydrogen.
The process of splitting H2O into hydrogen and oxygen by electrolysis, usually requires purified water to ensure the electrodes are not contaminated. When seawater is used in Hydrogen production, desalination equipment is usually factored into projects which need to source their water from the sea.
However, China have recently announced that they plan to build a 6,000km hydrogen pipeline network to transport green H2 from renewables-rich regions, tapping into the oceans as their primary source of base material.
The Chinese floating platform which includes in-built electrolysis, as well as “intelligent energy conversion management”, safety detection and control systems; was said to have produced hydrogen in a “stable” fashion for more than 240 hours at the Xinghua Bay offshore wind farm, off Fujian province. (1)
While the new technology could remove the need for desalination, the removal of salt and other substances and microorganisms from seawater by reverse osmosis is relatively inexpensive, costing about 0.035kWh of electricity per kilogram of hydrogen — a fraction of the 50-65kWh/kgH2 needed by electrolysers. (1)
The ability to produce sustainable green hydrogen from seawater, the most abundant base material on Earth, could be a game changer for international energy requirements. Furthermore, the use of Hydrogen across industry, automotive and energy production could be transformed if the Chinese system could be upscaled and deployed internationally.
However, this is not the first example of how seawater has been used to generate hydrogen. The innovative ‘Energy Observer’ was the first hydrogen-powered, zero-emission vessel to be self-sufficient in energy. (2)
The Energy Observer is a 100% energy self-sufficient boat, sailing around the world to prove the usefulness of cutting-edge technologies, including a hydrogen fuel cell made with help from Toyota (3)
The Energy Observer uses a patchwork of different cutting-edge technologies to generate enough energy to power nine homes each day. During the day, 200 square meters of solar panels charge up the boat’s lithium-ion batteries. Any extra energy is stored as hydrogen, thanks to a special fuel cell which goes by the name Rex H2 (short for Range Extender H2).
The Rex H2 was made by Toyota, using components from Toyota’s hydrogen-powered Mirai vehicle line. The fuel cell brings in seawater, removes the salt and then separates the H from the pure H20 with electricity. (3)
Seawater has also been used by researchers at The University of Adelaide, Australia to generate hydrogen.
To overcome the need for desalinisation and to avoid corrosion in the electrodes, scientists introduced a Lewis acid layer (chromium oxide), on a transition metal oxide catalyst, which promotes water splitting to H and OH. (4)
Captured hydroxyl anions can then be oxidised into oxygen molecules with anodic potential, and as the process produces large amounts of OH−, it reduces the amount of Cl− that is formed. “These results demonstrate that the harmful Cl− chemistry in direct seawater electrolysis can indeed be avoided by preferentially enriching OH− on the electrode surface,” University of Adelaide (4)
Furthermore, scientists only filtered the seawater to remove solids and microorganisms, but did not purify it beforehand, which is a step that is normally needed when using conventional electrolysers. (4)
These three examples of how seawater can be used in the production of green sustainable hydrogen, could see the green hydrogen economy boom. With vast investment globally in the production of hydrogen, the necessity to produce more green hydrogen is vastly important in the global efforts to tackle advancing climate change and reduce global emissions and temperatures.
Written by Katy Mason for and on behalf of Dolphin N2.