Understanding hydrogen: how is it made, how is it scaled, and what challenges does it bring?

The fundamentals of hydrogen and its role in the global energy transition. 

Major momentum behind energy transition, fuelled by pressures to decarbonise, decentralise, and digitalise, has spurred innovation within the energy sector, as we hunt for alternative fuels to secure a more sustainable future.  

Much ado has been made about the role of hydrogen in this energy transition, as organisations worldwide implement new models based around: 

• Electrification. 
• Green hydrogen and biofuels. 
• Hydrogen for thermal engines. 
• Renewable energies for electrolysis. 
• Technologies other than electrolysis, such as biomass thermolysis. 
• Transportation of hydrogen via pipelines, trailers, decentralised energy, and platforms that enable peer-to-peer energy sharing. 

For those in the industry who last discussed chemical elements in a classroom, it’s time to get a firmer grasp on this high potential gas. Here, Francesca Gabriel, Senior Consultant at Capgemini, and Jack Taylor, Associate Consultant at Capgemini, explore the standard generation methods, potential applications, and common challenges for hydrogen. 

What is hydrogen? 

Hydrogen is the lightest of all chemical elements and, at standard conditions, is a colourless, odourless, tasteless, non-toxic, and highly combustible gas. Constituting a staggering 75% of normal matter in the observable universe, serving as the fuel for stars, hydrogen is present in almost all organic matter. Its gravimetric energy density of 120 MJ/kg exceeds that of fossil fuels and Li-ION batteries, which underpins the excitement surrounding hydrogen’s potential as a low-carbon energy source.  

Note: gravimetric energy density refers to the amount of energy stored per unit of mass – it’s often referred to as the specific energy. 

What are the different types of hydrogen and how are they produced?

In juxtaposition to its lack of colour and odour, hydrogen is typically classified due to its production method and carbon intensity as part of a colourful spectrum. This classification for hydrogen has been universally adopted to explain the difference between the various hydrogen production methods as the table below describes.

Green Hydrogen uses electricity generated from low carbon renewable sources (e.g., wind and solar) in electrolysers to produce hydrogen.  

• Varying loads across the day introduces challenges in the efficiencies of connected electrolysers. 
• Green hydrogen is typically the most expensive form of hydrogen at circa $3.2-8.65/kg. 
• Cost of green hydrogen production is heavily linked to the cost of the renewable electricity used in the electrolysis process. 

Purple/Pink Hydrogen is derived from nuclear power. The electricity/heat from the nuclear reactor is used to power electrolysers and produce hydrogen.  

• Unsubsidised prices for pink hydrogen are typically in the range of $2.7-5.4/kg. 
• Electrolysers connected to constant loads typically benefit from efficiency gains, making nuclear a potentially attractive option. 

Blue Hydrogen takes the CO₂ emitted from grey hydrogen production and stores it using Carbon Capture Storage (CCS) technologies – processes generally involving compression/liquidation of CO₂ before transportation by road or by pipeline into underground rock formations. 

• Blue hydrogen prices are generally comparable to grey hydrogen due to the 50-65% dependency on the price of natural gas in the region. 
• Prices of blue hydrogen typically vary from $2.8-3.5/kg. 

Grey Hydrogen is produced through Steam Methane Reforming (SMR), which breaks down methane (CH₄) to release hydrogen using high temperature steam. The carbon released through grey hydrogen production is on average 1.5 times less than black/brown hydrogen. 

• As of 2020, grey hydrogen provided 71% of global demand. 
• During SMR, CO₂ is released as a by-product which takes the carbon intensity of grey hydrogen to the region of 10kg of CO₂ produced per 1kg of grey hydrogen. 
• The cost of grey hydrogen is on average around $3.30/kg. 

Brown/Black Hydrogen is produced through a process called gasification, whereby Lignite or Anthracite (brown/black coal) is loaded into a gasifier alongside pressurised air and steam to produce a syngas from which hydrogen can be extracted. 

• It has the highest carbon intensive of hydrogen production methods, releasing 14-15kg of CO₂ per 1kg of hydrogen produced. 
• Average temperatures required for the gasification process are in the region of 700^oC, potentially increasing its carbon output, dependant on its power source. 
• The cost of brown/black hydrogen is, on average, $1-2/kg. 

The most prominent hydrogen production methods continue to rely on fossil fuels. To solve this problem, the world is currently exploring “low-carbon hydrogen” (such as green hydrogen or pink hydrogen), which has only marginal carbon emissions in the production process and is emerging as a promising tool for emissions reduction and sustainable development. 

A deeper dive into green hydrogen production

There are three ‘generations’ of electrolyser varying in technological maturity, electrolyte, and operating conditions, summarised in Figure 2.

Electrolyser integration and ancillary components 

Typically, electrolysers are incorporated into stacks, forming integral components of broader hydrogen generation systems. These stacks are accompanied by an array of ancillary components, including purifiers and de-ionisers. These elements collectively ensure the purity of reactants, a critical factor in optimising the efficiency of the hydrogen production reaction. This meticulous approach underscores the precision required to achieve optimal results in green hydrogen generation. 

Ultimately, the transition away from high carbon intensity hydrogen production methods (black, brown, grey) and the mass adaption of green hydrogen depends on electrolyser technology becoming more cost effective.  

How diverse are the use cases and applications for hydrogen?

Hydrogen has a plethora of use cases and typically offers the most promise in areas where electrification is not a feasible solution. Figure 3 showcases the key use cases where the integration of hydrogen could result in significantly lower CO₂ emissions.

In summary, hydrogen’s diverse applications hold the potential to drive transformative changes in decarbonising various sectors of the economy, from mitigating emissions in steel production to enabling grid stability and decarbonising transportation.  

What are the challenges in using hydrogen for decarbonisation? 

As well as showing significant promise for decarbonisation, there are still some major hurdles to hydrogen’s application at scale. Two key areas of contention are safety considerations and scalability (although this is by no means an exhaustive list of challenges).  

1. Safety – Hydrogen molecules have a very high diffusivity which means that if leaked, gas levels can quickly reach dangerous levels of combustibility. As such, it’s likely there will be different engineering considerations for hydrogen infrastructure compared to existing gas networks. Hydrogen can also cause embrittlement when stored in an untreated metal container; it will eventually force its way through the gaps with steel being particularly susceptible to this process. Embrittlement increases the likelihood of mechanical failure which could lead to a leak or explosion. The risk of embrittlement can be reduced by lining hydrogen-filled containers via electroplating. The nuanced behavioural characteristics of H₂ molecules require a level of safety standards that the current infrastructure may not meet. If true, that would mean significant investment to make infrastructure safety compliant.   
2. Scaling – Material costs to build electrolysers are one of the key factors driving the cost per kg of hydrogen. Catalysts are the most expensive materials in an electrolyser, with Iridium typically fetching circa £130,000 per kg. Building a 1MW electrolyser system capable of producing 400kg/day can therefore cost between £350,000 and £750,000. This would then produce only enough hydrogen to keep 250 cars on the road for 100 miles. Scaling this system to provide enough hydrogen for a fleet of vehicles might prove costly without incorporating subsidies. Together, the expenditure on ancillary components for an electrolyser system, management of electrolytes, infrastructure, and hydrogen storage all lead to higher costs for hydrogen usage compared to traditional fuels. 

Capgemini and hydrogen. 

Stayed tuned for the next instalment of our ‘Future of Hydrogen’ series, in which we’ll explore the economics of hydrogen and some of the associated scaling challenges. 

In the meantime, our industry experts have authored several in-depth reports on hydrogen and its role in decarbonisation. Download them here: 

• Unlocking the hydrogen age – explore the critical, engineering-specific challenges vital to creating a low-carbon hydrogen value chain, and the innovative concepts to surmount them. 
• Low-carbon hydrogen: A path to a greener future – learn more about how to capitalise on the opportunities green hydrogen creates. 
• The path to low carbon hydrogen – understand the market perspectives and strategies essential to decarbonated production of hydrogen. 

You can also hear some of our global perspectives on the topic, over on our YouTube channel:

• Why low-carbon hydrogen is a sustainable solution  
• Capgemini Invent Talks: The path to a green hydrogen future 
• Creating a hydrogen marketplace 

To see our hydrogen expertise in action, read our relevant case study on how we helped take Hyliko from concept to company to provide freight transportations companies with a more sustainable, carbon-negative alternative. Download it here: https://www.capgemini.com/news/client-stories/hyliko-powers-freight-transport-with-hydrogen/ 

Get in touch with one of the hydrogen team – Francesca Gabriel, Jack Taylor, or Nicole Alley – if you have a specific hydrogen-related challenge or want to explore options for decarbonising your business.  

Explore our ‘Future of Series’ blog page, click here to learn more.