‘Net zero’: Unlocking the potential of green hydrogen

One cool thing about hydrogen: it has an inherently high specific energy density of up to 40,000 watt-hours per kilogram (Wh/kg) vs 250 Wh/kg for the best electric vehicle (EV) batteries.

That means hydrogen has up to 160 times the energy of the most efficient batteries available today. Liquid hydrogen's high specific impulse, achieved when it's cooled below 33°K, can make rockets go farther and faster while using less fuel, compared to other propellants.

Challenge, opportunity

There’s just one problem: There is no free H2 on this planet. You can’t find hydrogen apart from other elements (like oxygen). You need energy to separate them, one is via a process called “electrolysis”. This requires energy, and cost.

Today, 95 per cent of the world’s supply of hydrogen is produced by “steam methane reforming” (SMR), a super-cheap method, but also produces greenhouse gases, and wastes 50 per cent of the gas.

The remaining 5 per cent of hydrogen is produced from water by electrolysis, wasting 40-50 per cent of electricity in the process.

But things are changing.

Now, new ways exist to produce “green hydrogen”, adding excitement to the mix. Companies and nations are running the race to usher in a “hydrogen century”.

What is hydrogen?

Hydrogen — the colourless, odourless, highly combustible element — is most abundant chemical element in the universe, represented by the chemical symbol “H”. This super element is forms the basic building blocs of life.

What makes hydrogen cool?

For one, it is a versatile energy source, is super-abundant. Henry Cavendish, an English scientist who discovered hydrogen in 1766, dubbed it as the "inflammable air".

As the element that powers stars, hydrogen has high energy content, and is remakably lightweight. Being highly flammable, it’s a top choice for “clean combustion”.

Liquid hydrogen's high specific impulse, achieved when it's cooled below 33°K, can make rockets go farther and faster while using less fuel, compared to other propellants.

Uses of green hydrogen

Green hydrogen can have a variety of uses in industries such as steelmaking, concrete production and manufacturing chemicals and fertilisers. It can also be used to generate electricity, as a fuel for transport and to heat homes and offices.

So why not use hydrogen to its fullest potential?

It's been used for the last 200 or so years, including in 1807, with the world’s first internal combustion engine (ICE), which ran on hydrogen gas.

However, pure hydrogen is hard to come by on Earth. Hydrogen is relatively rare in its pure molecular form (H2) — as it readily combines with other elements. It needs to be "extracted", a process that currently costs $14 per kg.

This makes hydrogen a no-go as fuel for everyday household or personal use. Still, most scientists recognise that as both a fuel form and a power source, hydrogen offers an unmatched potential to significantly reduce the climate impact of industries.

How is hydrogen produced?

Hydrogen is produced by separating that element from others in molecules where hydrogen occurs. For example, water — well known by its chemical symbol of H20, or two hydrogen atoms and one oxygen atom — can be split into those component atoms through electrolysis.

Besides water, it can also be produced from other sources, such as natural gas, and biomass.

“Gray” vs “blue” vs “green” hydrogen:

Gray hydrogen is a type of hydrogen produced from fossil fuels, primarily natural gas, through a process called steam methane reforming (SMR). It is the most common and traditional method of hydrogen production but is associated with significant carbon dioxide (CO2) emissions, making it environmentally unsustainable in terms of greenhouse gas emissions.

Blue hydrogen is a form of hydrogen produced using a process called steam methane reforming (SMR) or auto-thermal reforming (ATR) of natural gas, followed by carbon capture and storage (CCS) to reduce carbon dioxide (CO2) emissions. It is less carbon-intensive than traditional gray hydrogen.

Green hydrogen, in general refers to producing H2 using wind, solar or water (WSW), or without generating greenhouse gases.

What’s driving demand for 'green hydrogen'?

Demand for green hydrogen is set to “skyrocket”, according to the National Engineering Policy Centre and Grandview Research as companies and economies seek to "decarbonise", in line with the Paris Agreement, a legally-binding international treaty on climate change.

It was adopted by 196 Parties at the UN Climate Change Conference (COP21). The UAE is hosting the highly-anticipated COP28 next month.

How big is the green hydrogen economy?

The hydrogen generation market size was valued at $155.35 billion in 2022 — of which only $4.47 billion was green hydrogen.

While total hydrogen market (gray, blue and green) is expected to expand at a compound annual growth rate (CAGR) of 9.3 per cent from 2023 to 2030, the global green hydrogen market and is predicted to surpass around $134.38 billion by 2032, growing at a remarkable CAGR of 40.6 per cent from 2023 to 2032, according to Grandview Research.

Major industrial countries, including those in the European Union, are making huge bets on hydrogen.

What’s new?

Researchers believe that green hydrogen will play a key role in the energy transition towards a low-carbon future. Many countries are keen to usher in a hydrogen economy.

Technology keeps improving, espcially in the following areas:

Bubble-free electrolysis: 


A team lead by Aaron Hodges and Anh Linh Hoang of the Intelligent Polymer Research Institute, at the University of Wollongong, published their work in March 2022 in Nature Communications introducing a unique water electrolysis method.

Interestingly, the researchers said utilising their bubble-free alkaline capillary-fed electrolysis cell demonstrates water electrolysis exceeding commercial electrolysis cells — delivering a 98 per cent energy efficiency, with an energy consumption of 40.4 kWh/kg of hydrogen (vs. ~47.5 kWh/kg in current commercial electrolysis cells).


Advanced electrolyser:

Other research into next-generation electrolysers is also advancing. For example, Shell has started up Europe’s largest hydrogen electrolyser of its kind at in Rheinland, Germany. Auto supplier Schaeffler has also shown a solution in which waste heat from the electrolysis process is used to distill the salt water.

Saltwater-to-hydrogen via wind turbines:


This is the new frontier — using seawater to produce “green hydrogen”. The Harvard China Project found that using wind power to produce hydrogen could provide a cost-competitive alternative to coal-dominated hydrogen manufacturing systems in the mainland. Europeans are also rapidly advancing this technique.

 

Nano technology:

University of Central Florida researchers have recently designed a “nanomaterial” that can split seawater and extract hydrogen. This could provide "electrolysis on an industrial scale”.

Forward Osmosis:


In March 2021, Chemistry World reported a method of saltwater-to-hydrogen conversion combining electrochemical water splitting with “forward osmosis”. This technique could allow a massive up-scaling of hydrogen fuel production using salty natural water without pre-treatment or purification, the journal reported.


Developments in high-energy efficiency in electrolysis, wind, solar and hydro-electricity could bring the cost-competitive renewable hydrogen closer to reality.

If scaled up, the use hydrogen for aeroplanes, cars and ships can prove more viable. The switch to hydrogen is pivotal in helping ease climate change.

Can hydrogen really power planes?

Hydrogen-powered aeroplanes are already flying, from as early as 2008 — though mostly as small, experimental aircraft.

Airbus has also announced it will use the A380 as “test bed” for hydrogen propulsion, and has also signed up Delta Airlines in its drive to develop hydrogen-powered aeroplane.

ZeroAvia, a leader in zero-emission aviation, flew a test aircraft on hydrogen in January, and is focussing on hydrogen-electric propulsion, initially targeting a 300-mile range in 9–19 seat aircraft by 2025, with up to 700-mile range in 40–80 seat aircraft by 2027.

As of 2023, the largest hydrogen-powered aircraft, is the adapted ATR 72 aircraft, fitted with a large liquid-hydrogen tank and sits around 40 people. The company claims that the plane is by far the largest aircraft to cruise principally using hydrogen power.

When produced from sustainable sources such as green hydrogen, sustainable aviation fuel (SAF) can reduce carbon emissions over the fuel’s lifecycle by up to 85 per cent compared to fossil-based jet fuel.

Those planes could eventually pave the way for a next-generation aviation fuel from the same abundant element that keeps the sun shining, at a cost that won't blow a hole in your pocket.