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June-August 2023

Splitting water in a green hydrogen climate

Almost all of the so-called ‘grey’ industrial hydrogen produced at present comes from fossil fuel feedstocks that contribute directly to the climate warming problem. The future production of green hydrogen must therefore be based on the other possible route, the splitting of water – by either electrolysis or photolysis.

Direct solar splitting of water, or photolysis, uses light energy to split water into hydrogen and oxygen. These photolysis processes are currently at initial stages of development but are expected to provide a long-term source of green hydrogen. The electrochemical method, using electrolysers, is therefore expected to be the preferred route to green hydrogen for the near future. These electrochemical technology systems range in size from small to exceptionally large. Small systems are comparable in dimensions to a ship’s container for adjacent use (e.g. to deliver fuel or to store energy), while large systems, such as those supplied by Siemens Energy, can generate up to 50 000 tonnes of e-methanol formed from renewable hydrogen and biogenic carbon dioxide. This large process can avoid 100 000 tonnes of carbon dioxide emissions annually in shipping, by replacing fossil fuels.

The role of green hydrogen in climate remediation has been covered extensively in the international media. Carbon emission targets across many developed countries will require massive scale up and acceleration of renewable hydrogen production. It is recognised that hydrogen fuel cells in transportation have several advantages over battery-powered electric motors in addition to having zero greenhouse emissions. These advantages include greater power and longer range with no dependence on the critical metal elements for batteries, namely lithium, cobalt etc. The fact that hydrogen is the most common element in the universe is clearly an advantage.

The rapid recent development of commercial large-scale water electrolysers for hydrogen production is a strategic step as the world approaches the economic tipping point of $2/kg of hydrogen. Once this tipping point has been crossed, green hydrogen will become increasingly competitive against fossil fuels. It is important then that Australia is engaged in developing large-scale hydrogen production projects.

Initial offtakers of the CS Energy Kogan hydrogen project near Chinchilla in Queensland’s Western Downs region include Sojitz Corporation, supplying green hydrogen to Nauru to assess replacement of fossil fuels in marine vessels with hydrogen. Other clients are interested in the development of modular hydrogen refuelling stations in the heavy transport and haulage market in southern and western Queensland.

Once commissioned, the ENGIE Yuri electrolysis plant, in a joint venture with Japan’s Mitsui and Co Ltd, will generate renewable hydrogen for use in Yara Australia’s ammonia facility at Karratha in the Pilbara region of Western Australia. Among the largest of its kind in the world, the plant will include a 10-megawatt electrolyser powered by 18 megawatts of solar photovoltaics and supported by eight megawatts of battery storage.

The competitive Townsville Region Hydrogen Hub program will deliver federal government funding towards projects that accelerate the development of a hydrogen industry in North Queensland. This is part of a larger government investment in the North Queensland region in renewable hydrogen as fuel, energy generation and storage, and as chemical feedstock. It will extend the Regional Hydrogen Hubs Program for projects in locations such as Gladstone, the Hunter Valley, the Pilbara, Port Bonython and Bell Bay.

The looming $2/kg economic tipping point will be the effective launch point of the long-awaited green hydrogen economy. The global market size is projected by MarketsandMarkets to increase from US$676 million (A$1000 million) in 2022 to US$7314 million (A$11 000 million) in 2027. The hydrogen market compound annual growth rate is projected to be 63.4% by 2027. Massive investments in the USA are a central driver of this growth. MarketsandMarkets list the several major international companies already involved in green hydrogen technology.

Given the expected massive growth in demand over the coming decades for green hydrogen from electrolysers, a global problem has been identified. The world has a critical shortage of fresh water, which is required for most electrolyser systems. This has led researchers from universities in China and Australia (reported in Nature November 2022) to develop an electrolysis system based on seawater, and the hydrogen produced is called ‘Blue H2’. A demonstration of this system operating over 130 days produced 386 litres of hydrogen. The authors claim that this Blue H2 method is cost efficient and scalable in a comparable way to the existing electrolysis systems using fresh water. A problem with this approach is the production of the toxic and corrosive chlorine gas from chloride at the anode of the electrolysis system. Natural cations in seawater, such as magnesium and calcium, form by-products that reduce the efficiency of the system. The research team has redesigned the membrane system to create a design that maintains a constant flow of clean water to the electrodes while excluding the cations and seawater impurities. The researchers are now improving the efficiency of this pre-cleaning system. They also claim that their seawater system can recover useful by-products, including the critical alkali metal lithium, and may be adaptable to other applications such as cleaning up industrial wastewater.

A more significant issue with hydrogen has been identified in a recent report from the UK Government ( Hydrogen is an indirect greenhouse gas and its reactions with hydroxyl radicals in the atmosphere may offset the advantages of hydrogen as a non-carbon-emitting gas. This impact is being investigated at present, but if proven this observation makes it imperative that hydrogen leakage into the atmosphere from pipelines and other distribution infrastructures are kept to an absolute minimum. This means that the cost and efficiency drive to convert natural gas pipelines into hydrogen pipelines will have to be carefully refined. This problem is exacerbated by the greater ability of the lighter smaller hydrogen molecule to diffuse through junctions, gaskets and linings of the existing natural gas pipelines. It will also tend to favour the deployment of smaller-scale distribution technologies for hydrogen that are adjacent to applications such as refuelling of vehicles, and which minimise the use of pipelines that may leak hydrogen.

An alternative existing strategy is to convert green hydrogen to green ammonia, which circumvents the hydrogen leakage problems and makes transportation of the green fuel more practical. A potential future method to make green ammonia would be by reacting green hydrogen from water electrolysis with nitrogen from the air in a Haber–Bosch process powered by sustainable electricity.

Ralph Cooney ONZM, FRSNZ, FRACI CChem has had a science and innovation career bridging New Zealand and Australia. He was former University of Auckland Pro Vice Chancellor of the Tamaki Innovation Campus, Dean of Science, Head of Chemistry and Science Leader of several major national research programs.

Airbus models hydrogen-powered, zero-emissions engine


A model of the Airbus ZEROe fuel cell engine.

Late last year, Airbus announced that it is developing a hydrogen-powered fuel cell engine. The propulsion system is being considered as one of the potential solutions to equip its zero-emission aircraft that will enter service by 2035.

Airbus will start ground and flight testing this fuel cell engine architecture on board its ZEROe demonstrator aircraft towards the middle of the decade. The A380 MSN1 flight test aircraft for new hydrogen technologies is currently being modified to carry liquid hydrogen tanks and their associated distribution systems.

‘Fuel cells are a potential solution to help us achieve our zero-emission ambition and we are focused on developing and testing this technology to understand if it is feasible and viable for a 2035 entry-into-service of a zero-emission aircraft’, said Glenn Llewellyn, VP Zero-Emission Aircraft, Airbus. ‘At scale, and if the technology targets were achieved, fuel cell engines may be able to power a 100-passenger aircraft with a range of approximately 1000 nautical miles. By continuing to invest in this technology, we are giving ourselves additional options that will inform our decisions on the architecture of our future ZEROe aircraft, the development of which we intend to launch in the 2027–2028 timeframe.’

Airbus identified hydrogen as one of the most promising alternatives to power a zero-emission aircraft, because it emits no carbon dioxide when generated from renewable energy, with water being its most significant by-product.

There are two ways hydrogen can be used as a power source for aircraft propulsion. The first way is by hydrogen combustion in a gas turbine, and the second is by using fuel cells to convert hydrogen into electricity in order to power a propeller engine. A hydrogen gas turbine can also be coupled with fuel cells instead of batteries in a hybrid-electric architecture.

Hydrogen fuel cells, especially when stacked together, increase their power output, allowing scalability. In addition, an engine powered by hydrogen fuel cells produces no NOx emissions or contrails, thereby offering additional decarbonisation benefits.

In 2020, Airbus created Aerostack, a joint venture with ElringKlinger, a fuel cell systems and component supplier, and later that year presented its pod concept, which included six removable fuel cell propeller propulsion systems.


The rapid recent development of commercial large-scale water electrolysers for hydrogen production is a strategic step as the world approaches the economic tipping point of $2/kg of hydrogen.

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