ABB Explains: Hydrogen rainbow

You may have heard of green hydrogen - or maybe pink? But do you know what turquoise or blue hydrogen is? What do all these colors mean? ABB Explains is here to find out.

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3min

2025-04-02

The hydrogen rainbow: A guide to the different types of hydrogen

As the world searches for sustainable energy solutions, hydrogen has emerged as a key player in the transition to cleaner fuels. But not all hydrogen is created equal. Its production method determines its environmental impact. This is where the "hydrogen rainbow" comes in, categorizing different types of hydrogen by color based on how they are produced.

Black and Brown Hydrogen

Black and brown hydrogen are produced by gasifying coal. Black hydrogen is made from lignite or bituminous coal, whereas brown hydrogen is derived from lignite. Both methods generate significant carbon emissions, making them the least environmentally friendly options.

Gray Hydrogen

Currently the most common form of hydrogen in use, gray hydrogen is produced from natural gas through a process called steam methane reforming. This method releases large amounts of carbon dioxide into the atmosphere, contributing to greenhouse gas emissions.

Blue Hydrogen

Blue hydrogen is made using the same process as grey hydrogen, but with one key difference: the carbon emissions are captured and stored using carbon capture and storage technology. Blue hydrogen is a lower-emission alternative to its gray counterpart, but not completely emissions-free.

Pink Hydrogen

Pink hydrogen is produced through electrolysis powered by nuclear energy. It is a low-emission source of hydrogen suited for regions with established nuclear infrastructure.

Red, and Purple Hydrogen

These variations of hydrogen production from nuclear energy. Rather than using electrolysis, this hydrogen is made using thermochemical processes, tapping heat from a nuclear plant rather than going through the intermediary of electricity.

Green Hydrogen

Often considered the cleanest and most promising form, green hydrogen is produced using renewable energy sources like wind, solar, and geothermal power.

Yellow Hydrogen

This term is used to describe hydrogen generated specifically from solar power, rather than a mix of renewables. While similar to green hydrogen, its distinction lies in the exclusive use of solar energy.

Turquoise Hydrogen

A more niche category, turquoise hydrogen is made from methane through a process called methane pyrolysis. Instead of emitting carbon dioxide, this method produces solid carbon, which can be stored or repurposed, making it a potentially low-emission solution.

White Hydrogen

White hydrogen is naturally occurring and found in underground deposits. Unlike other forms, it is not produced through industrial processes but extracted directly from the Earth. However, its commercial viability remains under exploration.

The future of hydrogen

Understanding the hydrogen rainbow is crucial for making informed decisions about which types of hydrogen can best support a sustainable future. The race is now on to scale up production of green and other low-emission hydrogen sources to make this vision a reality.

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Hydrogen production: The pros and cons behind electrolyzer power supplies configurations

Considering that it is the world’s cleanest energy source, hydrogen is set to play a key role in the decarbonization of several industrial sectors. Crucial to this rapidly developing process is the development of electrolyzer power supplies, which must be capable of managing unregulated low DC voltage under megawatt-scale power levels. This article presents an overview of state-of-the-art power supplies for electrolyzers, while examining the pros and cons behind each configuration.

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