Harnessing the energy-storage power of green hydrogen

The potential of offshore wind to turn Ireland into a net energy exporter may be well understood but it could also be harnessed to support the manufacture and export of far more valuable products. This will be made possible by the use of excess power generated by offshore wind farms to produce green hydrogen.

Green hydrogen is created from electrolysis using renewable electricity and produces low or even zero carbon emissions. It offers an elegant solution to the intermittent nature of wind energy. Instead of shutting down wind turbines or dumping electricity at times of low demand, the surplus can be used in electrolysis plants to split water molecules into hydrogen and oxygen. The hydrogen can then be stored and used as a fuel for conventional electricity generating plants which can be pressed into service at times when demand exceeds the available supply of renewable power.

“The stored green hydrogen could be used to power the grid for several hours or even days if required,” says Science Foundation Ireland (SFI) deputy director general Ciarán Seoighe.

It can also be used in fuel cells. “Hydrogen fuel cells use the chemical energy of hydrogen to produce electricity,” Seoighe explains. “In essence it’s the reverse of the electrolysis process. The only byproducts are electricity, water and some heat. This is a green and effectively zero-emissions technology when green hydrogen is used. Fuel cells are very efficient in terms of conversion of energy and are suitable for high-energy requirements like long distance haulage, shipping and even short-haul airlines.”

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But this is just the beginning. “Once generated, the hydrogen molecules themselves can be used as a base for other chemicals as we move towards net zero,” he continues. “One of the main uses will be in the formation of ammonia [NH3], of which about 150 million tonnes are produced each year to satisfy world demand. About 70 to 80 per cent of that is used as fertiliser in agriculture. We could make green fertiliser from green ammonia which in turn comes from green hydrogen. The next most important chemical would be methanol [CH3OH], of which about 110 million tonnes are produced a year. Methanol is used in a variety of products such as textiles and plastics, and green methanol can be used as an alternative, green fuel source.”

Instead of exporting raw electrons, Ireland can sell these high-value products to customers around the world. “We can move up the electron value chain. By manufacturing them here we are not importing them from countries in Asia. That makes them even more sustainable.”

There are some challenges to be overcome if this potential is to be realised. The first and most obvious is the development of the wind energy sector at the scale required to produce the hydrogen. Another is the nature of the gas itself.

“Hydrogen is very voluminous and flammable, so it is difficult to transport and manage,” says Seoighe. “This is why converting it to ammonia or methanol is preferable as they are easier and safer to transport. There are also questions in relation to the infrastructure required to manufacture, store and transport it – where should this be located? How can it be made more cost effective?”

SFI is already supporting a number of research projects aimed at overcoming these challenges.

Dr Mohammad Ali Ekhtiari of the UCD Engineering and Materials Science Centre is researching end-user considerations in the transition to a green gas network. The research will further develop advanced models to evaluate scenarios for the inclusion of green hydrogen to assess the ability of different end users for accepting hydrogen.

In a project co-funded by the Sustainable Energy Authority of Ireland (SEAI), Dr Suresh Pillai of Atlantic Technological University in Sligo and Prof Paula Colavita of Trinity College Dublin are developing low-cost materials to allow commercial hydrogen production from renewable sources.

In addition, the HyLight project at the SFI MaREI centre for energy, climate and marine in UCC aims to provide the knowledge, data and the necessary tools to facilitate the delivery of hydrogen to all energy sectors – heat, transport and electricity, as well as to where it is needed in industry – in a safe and cost-effective manner for energy consumers.

“Hydrogen is the highest-energy molecule in nature,” Seoighe concludes. “But not at the volumes that it normally exists. When you cool it and turn it into liquid it’s got phenomenal energy density. But in its natural state it occupies a vast space. We need to find better ways of storing, managing, moving it about and making it safer to use. We need to research those things. We also need to look at converting hydrogen into higher-value products which will be much more useful to us in future.”