A potentially vital part of the low carbon economy, decarbonising the hard-to tame-sectors.
What it is
Hydrogen (H 2 ) has three principal functions: a fuel; a chemical feedstock; and an energy carrier. It thereby has many applications in industry, and the power, transport, and heating sectors.
How it works
Hydrogen occurs naturally, but not in usable form. It is generated in two principal ways:1
- Conversion of fossil fuels into H 2 and CO 2 via coal gasification and (primarily) methane reformation. 2 Termed ‘grey hydrogen’ this represents ~ 96% of global H 2 production of ~ 70m tonnes. If the CO 2 produced is captured and stored the hydrogen is termed ‘blue hydrogen’. 3
- Electrolysis, whereby electricity is passed through water, splitting it into its two constituents, H 2 and O 2. 4 If the electricity is generated from a renewable source, the hydrogen is termed ‘green hydrogen’. 5 So far this represents only ~ 4% of global production.
Hydrogen is used principally in the chemical industry and fossil fuel refining. 6 However, it has potential applications in decarbonsing other industries, 7 primarily due to its energy density, 8 application in high temperature processes, and relative ease of transportation. 9
- Heavy Industry. H 2 could be used to decarbonise sectors with difficult-to reduce-emissions, notably the chemical and steel industries, 10 the main users of H 2 and high temperatures. Switching to green H 2 would reduce emissions significantly. 11
- Energy. The cost of green hydrogen is tied to that of renewables. It could play a complementary role in grid balancing and energy storage particularly where renewable electricity is abundant. 12 It may also have a role in decarbonising the existing gas infrastructure. 13
- Transport. The applicability of H 2 differs by sector, but those that involve long distances, heavy loads, and require low down-time and rapid refuelling, such as logistics and mass-transit, stand to benefit particularly. 14 Shipping 15 and aviation 16 may be others.
Implications and issues
Many countries, accounting for ~ 70% of the world’s economy, have published hydrogen strategies. 17 Although momentum is increasing given increased governmental support, the hydrogen economy faces numerous obstacles to widespread adoption:
a. Cost. Green hydrogen is presently too expensive to compete with fossil fuels in most contexts, unless: CO 2 emissions are priced appropriately; governments subsidise; or scale economies prove substantial. Improvements in technology and decreasing renewable costs will likely help, but whether that will suffice to achieve competitiveness is debatable. 18
b. Lack of Infrastructure. The most immediate obstacle facing an H 2 economy is a lack of infrastructure, from fuelling stations 19 to electrolysers, 20 access to renewable power, and storage and transport facilities. These will also require standardisation and certification. 21
c. Safety. H 2 is highly flammable, and when pressurised needs very careful handling. 22 As the smallest atom, it leaks through the tiniest holes, and metals exposed to H 2 can develop cracks. 23
d. Storage. This requires compression; refrigeration; or combination with an organic chemical or metal hydride. This is expensive in terms of energy used but enables renewable energy to be transported without the need for a shared electric grid. 24
e. Policy. Rigorous policies and stringent regulations would be needed to integrate H 2 into energy networks and manage supply at an acceptable level of safety.
f. Pollution. The creation and use of green hydrogen produces no harmful emissions. The same can be true of blue hydrogen, but fugitive CO 2 emissions are an issue. 25
Green hydrogen is recognised in most of the world’s major economies as an important part of their future energy mix. That said, its precise contribution will depend on a ready supply of renewable electricity, early support for infrastructure, and a constructive policy environment. Technologies-series-Hydrogen-December-2020