Energy From Hydrogen

Green hydrogen has traditionally been more expensive than blue hydrogen primarily due to the high investment cost of the electrolysers, as well as the availability of renewable energy to power the process. But We could soon see a change with the ongoing cost reduction of wind and solar power, as well as electrolyser technologies.

Scaling-Up Hydrogen Production

Hydrogen has an amazing potential as a zero-carbon fuel. It is expected that in the coming years, hydrogen will be helping to replace traditional fossil fuels in order to tackle climate change and air pollution.

However, there are barriers to making this a reality. There needs to be a simultaneous demand and supply for new hydrogen technologies, with infrastructure investments and large-scale production needed.

Hydrogen is typically produced via the steam methane reforming process, which creates hydrogen from natural gas and steam. This is the tried-and-tested method for hydrogen production that has been used for many decades. However, this method emits a large amount of carbon dioxide into the atmosphere. Carbon capture and storage technology can be used to negate this; but with the storage space and capital needed, this is not an ideal solution.

Hydrogen can also be produced through electrolysis. This method involves using electricity to separate water into its individual elements, hydrogen and oxygen. Hydrogen produced via electrolysis is ‘pure’ hydrogen, making it ideal for fuel cell electric cars. Electrolysis is highly efficient, but its current production facilities are small. With falling costs of renewable electricity, electrolysis has a high potential for ‘scaling up’ and becoming the dominant form of green hydrogen production.

There are two other groups of technologies that can be used for hydrogen production. Biological methods are available using anaerobic digestion with microbes that convert biomass energy to hydrogen instead of methane. New biotechnologies can ensure a greater yield of hydrogen. This method is only being developed at laboratory and demonstration scale, so it can only make a small (but nonetheless valuable) contribution to a green hydrogen economy.

energy conversion systems

The final technology group used for hydrogen production is known as ‘solar to fuels’, using sunlight to split water molecules into hydrogen and oxygen. This technique has been dubbed ‘artificial photosynthesis’. This technology is still in the early stages of development, with questions still remaining over its long-term efficiency.

Ammonia – An Efficient Way to Store and Transport Hydrogen

Currently, more than half of all hydrogen produced is used to create ammonia, a chemical typically used in fertiliser production. The Haber-Bosch process uses hydrogen from steam methane reforming, reacting it with nitrogen in an energy-intensive industrial procedure, requiring approximately 27 GJ of energy per tonne of ammonia.

With around 170 million tons of ammonia being produced every year, its production is associated with around 2% of all global carbon emissions. With the advent of green hydrogen, these emissions can be significantly reduced.

Ammonia as an energy carrier

Additionally to its applications as a fertiliser, ammonia is a favourable way in which hydrogen can be transported and stored, given its safe and stable nature. Ammonia has 40% of the calorific value of hydrocarbon fuels.

Ammonia combustion produces nitrogen and water, making it a far less polluting option than fossil fuels. It can be used directly in high-temperature solid oxide fuel cells. It can be partially cracked for combustion in turbines, and in internal combustion engines.

Expanding Green Hydrogen

Currently, around 95% of global hydrogen production uses fossil fuels – primarily, natural gas, used in steam methane reforming. This method has been tried-and-tested for decades, and is likely to continue, at least on a small scale.

Steam methane reforming, as well as other thermochemical methods for hydrogen production, emits carbon dioxide into our atmosphere. If we are to achieve a zero-carbon world in the coming decades, these methods are to be phased out, or, paired with carbon capture technology.

With the UK aiming to reach carbon neutrality by 2050, energy authorities are proposing new infrastructure based around a green hydrogen economy. The H21 Leeds City Gate suggests that the entire UK gas grid could be converted to hydrogen, over natural gas. This would be achieved incrementally over the next thirty years, with appliances converted to work with hydrogen. Studies are still underway, but this report asserts that hydrogen conversion is an achievable scenario.

The most viable way to achieve low-carbon mass-production of hydrogen is through electrolytic routes. There are a range of electrolyser technologies available.

Alkaline electrolysers are the furthest along in technological development. However, they are not ideal for use with intermittent green energy sources. The largest electrolyser plant in the world was 135MW, in Glomfjord, Norway. It was operational from 1953 until 1991, when the low cost of natural gas rendered it uneconomic. With the falling cost of renewable electricity, it is possible that plants like this can become a reality again.

Other technologies available include polymer electrolyte membrane electrolysers (PEM), which are being developed rapidly by companies such as Siemens and ITM Power (based in Sheffield, UK), working in cooperation with Shell.

Another technology possible for electrolysis is solid oxide electrolysers. This technology is less mature in its development, but it could potentially provide the highest efficiency of all the technology options. This method requires a sustainable source of heat, ideally from zero-carbon means.

production of hydrogen and oxygen by electrolysis

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