July 24, 2023
By Kathryn Porter

Hydrogen, blue or green or beyond, cannot prevent the looming renewable energy disaster

Probably history's most famous hydrogen explosion CREDIT: AP

The Royal Society of Chemistry describes hydrogen as “a colourless, odourless gas”. It’s up there at the top if the Periodic Table: Group 1, Period 1. It is the most abundant gas in the universe, but on Earth it is mostly found bound with oxygen in the form of water – very little hydrogen gas is present in the atmosphere as it quickly escapes the Earth’s gravity and floats away into outer space.

Yet this ephemeral gas is touted as the solution to the great looming problem of renewable power – carbon free energy storage at scale. The obvious issues with relying on intermittent wind and solar energy can be solved by using excess renewable energy on sunny, windy days to produce hydrogen gas. This can then be stored for use on less windy days, whether that be by direct combustion to generate heat, or to generate electricity, or in other industrial uses.

The different ways in which this invisible element can be produced have been assigned different colours: green, blue, brown, yellow, turquoise and pink hydrogen. Also, white hydrogen. Helpfully, there is no universal naming convention so hydrogen colour definitions may change over time, or between countries.

Green hydrogen is the “best” hydrogen, made by using that surplus renewable energy to electrolyse water, splitting it into its components of hydrogen and oxygen, emitting zero carbon dioxide. Some say yellow hydrogen if solar power is used. This is currently a very expensive way to make hydrogen and represents less than 0.4 percent of current hydrogen production.

Blue hydrogen is produced from methane – the “natural gas” currently piped to our homes for heating and cooking – using a process called steam reforming, which combines the methane with steam to produce hydrogen but also carbon dioxide which then needs to be captured and stored. The carbon capture part is the difficulty, with only one percent of existing projects including this capability.

Grey hydrogen is essentially blue hydrogen but without the carbon capture part. Almost all the hydrogen currently produced is made by this method.

Black and brown hydrogen are made from coal (black) or lignite (brown) and these methods emit even more carbon dioxide than grey hydrogen. This type of hydrogen is obviously not going to form part of the net zero pathway.

Pink hydrogen is generated through electrolysis powered by nuclear energy – this is also referred to as purple or red hydrogen. Like green hydrogen, this is zero-carbon but expensive.

Turquoise hydrogen is made using a process called methane pyrolysis to turn natural gas into hydrogen and solid carbon. This relatively new process is yet to be proven at scale, but the production of solid carbon would obviously reduce the challenges associated with carbon capture and storage.

Finally, white hydrogen is naturally occurring hydrogen, found in underground deposits. It might perhaps be extracted through fracking, a process already effectively banned in many places. It has been talked up for decades but, according to the National Grid, there are still “no strategies to exploit this hydrogen at present”.

Apart from the black and brown hydrogen this all sounds lovely. Quite literally, one can picture a gleaming future where horrible, sooty, carbon dioxide (because we all picture it as being sooty despite the fact it’s also colourless and odourless) is replaced with a beautiful rainbow of lovely, clean hydrogen, whose only byproduct on combustion with oxygen is water.

However, it is far from being that simple, or that clean. To begin with, hydrogen is one of the most explosive and flammable gases – the airship Hindenburg was filled with it – but its real challenges relate to the fact its molecules are very small and as a gas it has very low density. This means that hydrogen is hard to contain and large volumes of it are needed to generate much energy. You need around three times the volume of hydrogen as compared to methane to get the same amount of energy.

Tiny hydrogen molecules fit through tiny gaps, so structures designed to contain methane such as pipes, joints, boilers and cookers, and gas storage facilities such as tanks or geological formations (salt caverns or depleted gas fields) allow hydrogen molecules to escape where methane molecules would not. Tests suggest that the safety concerns this creates are mitigated by the lightness of hydrogen which means it quickly dissipates, but leakage also worsens the economics of using hydrogen as an energy store.

Hydrogen is also hard to move around. To get gas to move through pipes it has to be compressed and pushed along using compressors. This process requires energy: the losses in moving hydrogen through pipes are ten times greater for hydrogen than for methane: up to thirty percent. In other words, you need to use up almost a third of your gas just moving it from A to B.

Hydrogen can also cause the metals in pipes and storage equipment to become brittle leading to material degradation and potential safety issues. Special materials or coatings may mitigate these effects, but they add further complexity and cost to an already complex and expensive system.

In fact, all of this is expensive. The infrastructure for hydrogen storage does not yet exist, neither for the most part do the production facilities and they will cost billions of pounds to build. Then the underlying cost of storing hydrogen is probably at least four times that of storing methane. Huge amounts of energy are lost in each stage of the process due to the fundamental properties of hydrogen.

Quite simply hydrogen is one of the worst substances you could choose for this purpose, but, because you can burn it in air without creating carbon dioxide, it has been hailed as the answer to net zero dreams.

Like its cousin, carbon capture, hydrogen energy storage is a backfill technology – a silver bullet that will enable the otherwise unlikely net zero target to be met, but neither actually exists yet. Both are square pegs which people are desperately trying to force into round holes.

Hydrogen of whatever colour is a hypothetical solution to the challenge of net zero, and an extremely expensive one at that. And this goes to the heart of the net zero problem: it relies on developing a range of solutions that are easy to say but difficult and expensive to do.

Who will be left to pay for all of this? We will.

Kathryn Porter is an independent energy consultant. She holds a Master’s degree in Physics and an MBA, and is an associate member of the All-Party Parliamentary Group for Energy Studies executive council