What are electrolysers? How is hydrogen produced and how do fuel cells use energy?

After the hydrogen is used up, the process is reversed. In vehicles, hydrogen is recombined with oxygen to produce electricity, heat and water through a fuel cell system.

A typical electrolyzer uses 9 kg of water to produce 1 kg of hydrogen, with the remaining 8 kg released as oxygen. In a standard fuel cell, 9 kg of water is released for every kilogram of hydrogen used. A sustainable water source is a key factor in locating green hydrogen production projects. Another issue is the availability of large amounts of cheap renewable energy.

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Why are electrolysers and fuel cells important for mitigating climate change?

At power plants, a small percentage of green hydrogen can be blended with natural gas without modifying equipment to reduce the plants’ carbon intensity. According to the Finnish company Wartsila, a hydrogen admixture ratio exceeding 50 percent requires equipment modernization.

Energy generation is included 63 percent Globally, fossil fuel energy production accounted for 40% of total energy-related greenhouse gas emissions in 2021, according to the Hong Kong Environment and Ecology Bureau.

In steelworks, hydrogen can be used as an oxidizing agent to produce low-carbon steel. Pilot projects are being developed in many countries.

According to SNE Research, hydrogen fuel cell vehicles have been used in transportation for more than two decades, with approximately 14,500 units sold worldwide last year. Recently, some ships have started using fuel mixed with hydrogen derivatives such as methanol and ammonia to lower emissions.

Ultimately, the climate change mitigation benefits of adopting green hydrogen will depend on the rate of cost reduction and production and supply chain development. These will depend on government policy and technological progress.

China’s supply of green hydrogen is forecast take the rocket from about 350,000 tons last year to 6.8 million tons in 2035 and 71 million tons in 2050, according to Shanghai-based research and consulting firm Integral.

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Is electrolyzer and fuel cell technology new?

The first electrolysers and fuel cells were invented in the 19th century. Commercial use of electrolysis has been rare because for decades hydrogen was produced cheaply from fossil fuels by reacting natural gas or coal with steam, a highly carbon-intensive process.

The industrial use of fuel cells emerged many decades later to generate electricity for off-grid applications such as space exploration and satellites. Then came solutions for emergency power supply for buildings and remote areas, as well as transportation.

According to Assaf Sayada, CEO of the Israeli company Hydro X, which wants to commercialize its know-how in the safe transportation of low-carbon fuel.

“The world understands that there is absolutely no way to achieve the goal of decarbonizing the planet without the significant role that green hydrogen will play,” he said.

Hong Kong start-up Epago has developed a new type of membrane, a core component in hydrogen fuel cell batteries, bringing down production costs and manufacturing time. Photo: Yujie Xue — Hong Kong start-up Epago has developed a new type of membrane, the main element of hydrogen fuel cell batteries, reducing costs and production time. Photo: Yujie Xue

What are the main electrolysis technologies available on the market?

The two main technologies available on the market are alkaline membrane and proton exchange membrane (PEM).

Solid oxide electrolysis (SOEC) is close to commercialization, while anion exchange membrane (AEM) is still in its early stages of development.

Alkaline electrolysers were first used over 100 years ago to produce ammonia – a key fertilizer ingredient – using hydropower. Hydrogen is first produced from natural gas and then mixed with nitrogen to produce ammonia, under conditions of extreme temperature, pressure and in the presence of a catalyst.

PEM electrolysers were developed in the 1960s by General Electric for space applications to produce oxygen to sustain astronauts. They were then used to commercially produce hydrogen for industrial applications such as oil refining, glass and metal production.

What are the advantages and disadvantages of electrolyzers using the two main technologies?

A noble metal such as platinum or iridium must be used as a catalyst in PEM electrolysers, while nickel can be used in alkaline electrolysers.

However, PEM electrolysers can operate efficiently at high current densities – that is, the amount of electrical current flowing per unit cross-sectional area – and can adapt to rapid changes in power levels. This makes them better suited to the use of renewable energy, the supply of which may be intermittent and change depending on the weather.

“China has made great progress in reducing the cost and improving the efficiency of alkaline electrolysers,” said Gao Xiaoping, president and CEO of the company CM Xiageng Hydrogen Energy Technology, a manufacturer of green hydrogen equipment, is backed by the Fujian government and the state-backed conglomerate China Merchants Group. “Still, we need more technological progress to better cope with volatile wind and solar energy production.”

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Which electrolyzer is likely to dominate the green hydrogen market?

According to Amily Guo, a refining and chemicals analyst at UBS in China, alkaline electrolysers are more likely to dominate China’s green hydrogen market than PEM electrolysers, which are more common in Europe and the US.

This is because the cost of alkaline electrolysers in China has fallen to one third of the cost of PEM electrolysers, making them more attractive for large green hydrogen projects being built in the renewable energy-rich northern regions of the country.

However, Guo expects the price gap between the two types of products to narrow after 2030 as the technology continues to develop, allowing PEM products to gain market share in China.

She noted that the current cost of “gray” hydrogen from coal is about 10 yuan ($4.10) per kg. There is still a significant difference from the 30 yuan per kg of green hydrogen produced in alkaline electrolysers and the 25 yuan per kg produced in PEM electrolysers, which means that financial incentives are needed to adopt the green option.