The 2021 UN Climate Change Conference in Glasgow saw more than 40 countries, including Australia, sign the Breakthrough Agenda. These nations, as part of the Breakthrough pledge, had committed to ensuring that affordable, renewable and low carbon hydrogen would be globally available by 2030, leading to a reduction in CO2 emissions.

Given its versatility as an energy storage solution, Green Hydrogen has a major role to play in the transition to a net-zero world.

The ARC Training Centre for The Global Hydrogen Economy (GlobH2E), co-directed by UNSW Sydney Scientia Professor Rose Amal and the University of Sydney's Prof Kondo-Francois Aguey-Zinsou, is leading the development of innovative approaches to efficient, cost-effective hydrogen energy generation, storage and utilisation.

Prof Amal and her UNSW colleagues, Prof Iain MacGill (project lead), Prof Sami Kara and Dr Rahman Daiyan, along with the University of Sydney's Prof Aguey-Zinsou, are leading the Australian consortium for the HySupply Project, which explores the feasibility of an Australia-Germany hydrogen value chain.

Recently, Prof Amal and Dr Daiyan have delivered the NSW Power-to-X prefeasibility study for the NSW government, which offers a roadmap for creating NSW hydrogen jobs for the future.

What is Green Hydrogen?

Hydrogen is extracted from water via a process called electrolysis. Electric current is passed through water (H2O) to break it down to its component parts – hydrogen and oxygen. When this electric current is drawn from a renewable source such as solar or wind energy, you get Green Hydrogen.

Since Green Hydrogen is produced without any CO2 emissions, it can play an important role in global campaigns for net zero.

Green Hydrogen for energy storage

Hydrogen can be used to ‘store’ energy created by renewable sources, providing a more efficient alternative to traditional lithium batteries, which have limited storage capacities, a shorter lifespan and greater sensitivity to environmental conditions.

Hydrogen can store larger amounts of energy over a longer period of time, and can also be transported safely over long distances. Hydrogen can also be used as a fuel to heat homes or power vehicles.

Limitations in use of hydrogen as a fuel

Historically, hydrogen has been relatively expensive to produce due to electricity costs; however, this could be offset to a certain level once renewable energy gets cheaper. Hydrogen is also difficult to store as a gas (which requires very high pressures of up to 750 bar) or a liquid (which requires very low temperatures of -250 degrees Celsius), both of which significantly increase the cost.

Green Hydrogen currently costs around US$5-6 per kg to produce from renewable energy, compared to around US$2 per kg for hydrogen from fossil fuels.

The NSW Hydrogen Strategy, announced in October 2021, has set a goal for the state to produce 110,000 tonnes a year of Green Hydrogen for less than US$2.10 per kg (AU$2.80) by 2030.

The safety factor

In the gaseous form, hydrogen is lighter than air and will rise at almost 20 metres per second. In the event of a leak, it will disperse very quickly into a non-flammable concentration. Even if hydrogen gas does ignite, it does not produce any hot ash and burns out very quickly.

Unlike conventional fuels, hydrogen gas is non-toxic and therefore does not contaminate the environment or threaten the health of humans or wildlife.

The use of hydrogen is also strictly regulated, adding to its safety.

Green Hydrogen as an energy source

Hydrogen can be stored and transported in different ways. Hydrogen has a very high energy density per weight, but very low energy density per volume. Therefore, it needs to be compressed up to 750 bar for storage as a gas. A 150-200 litre fuel tank is currently required to store around 5kg of hydrogen, which is sufficient to power a car for a 300-mile journey. The size of the tank is three to four times bigger than that required for a petrol tank in a conventional vehicle, so a key challenge in hydrogen-powered vehicle development is the space needed to store the fuel.

For hydrogen to be stored as a liquid, it needs to be cooled to -250 degrees Celsius. This requires a large amount of energy, and represents a significant barrier to large-scale production.

There are different potential options with advantages and disadvantages. More research is required to eliminate these barriers and make Green Hydrogen a viable component in the drive to net zero emissions.

Source: UNSW Sydney

Image: Shutterstock

Architecture News & Editorial Desk

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