Hydrogen’s role in the UK’s 2050 Net Zero scenario
The Net Zero system includes a potentially substantial role for hydrogen as fuel for heating, industry and transport. This could consist of up to 270 TWh of hydrogen production, based on a progression from steam methane reforming (SMR), to advanced gas reforming (AGR) alongside electrolysis.
This will require:
- 10x increase in UK hydrogen production.
- 30% of the UK’s total energy.
- Extensive storage and transmission rebuilding
- Repurposing of existing natural gas distribution infrastructure to accommodate the physical properties of hydrogen.
The use of hydrogen presents few fundamental engineering problems, however there are numerous issues that cumulatively raise doubts about the extent of its use and associated costs.
Net Zero suggests that the least-cost method of producing hydrogen is steam Methane Reforming (MR), however, this is based on cost-at-production source and does not account for the whole-system costs of delivering hydrogen-based energy.
Steam MR is effectively pre-combustion carbon removal from methane, with the disposal of the resulting CO2 through CCS. The proposed Net Zero scenario depends on hydrogen produced in this way, 80% of total production, and as such, the technical risks associated with the production, storage and distribution of hydrogen are compounded by its dependence on CCS and the risks inherent in that technology.
Hydrogen’s dependence on CCS could be eliminated by using alternative production methods such as electrolysis, and large-scale hydrogen production by electrolysis would have a significant impact on power generation mix and could help smooth peak power demand. However, that process is significantly more costly than the projected cost of MR with CCS and is considered unaffordable, unless technologies can be developed to bring costs down.
As electrolysis becomes more efficient at higher temperatures, one potential route is to link hydrogen production to nuclear generation by leveraging the waste heat from nuclear plants. At higher temperatures reached in gas-cooled reactors, production of hydrogen by thermochemical processes is feasible, but the required technology is far from mature. Co-generation of hydrogen by using excess renewables electricity is also being considered, especially in the situations where renewable generation exceeds grid demand.
The substitution of natural gas by hydrogen to decarbonise domestic heating is clearly an attractive proposition, so long as existing infrastructure can be repurposed cost effectively. Hydrogen has a significantly lower energy density than natural gas on a volume basis and in gaseous form it’s approximately one-tenth the density of methane.
The transportation of hydrogen also presents issues relating to its small molecular size and ability to penetrate other materials. The UK’s national gas transmission grid is built from steel pipe, which would be unsuitable to carry hydrogen. As noted in BEIS Hydrogen Supply Chain Study, an entirely new high-pressure transmission pipeline network may be needed to transport hydrogen to local distribution networks. Whilst this doesn’t represent a major technical risk, its undertaking would be significant in cost and scale, and would face regulatory challenges.
At distribution level, most gas pipelines are now plastic and better suited to carrying hydrogen, depending on the pressure, however, the transition from natural gas to hydrogen is not a small logistical undertaking.
Gas storage in the UK is currently managed through either ‘linepack’ (management of the total volume of gas in the system to anticipate daily variations in demand) or subsurface (for large-scale storage management, such as the seasonal energy demand in the winter vs. the summer). As hydrogen is being considered as part of solution for decarbonising domestic heating, the storage requirements will need to match the seasonal demands, and will therefore require the large-scale option.
Large-scale hydrogen storage is likely to utilise the large underground salt caverns in the UK regions where we store natural gas today. Salt cavern storage currently has a fairly limited capacity, so a major programme of works to increase storage capacity would be required, but the opportunity is there to add capacity in many of the regions with salt caverns.
Integrating the hydrogen system
Out of all of the Net Zero system components, hydrogen may well present the biggest challenge around its successful integration.
In an interconnected hydrogen system with an emphasis on MR, we would need to deliver large volumes of natural gas; convert it to hydrogen and capture, transport and sequester the CO2; and either store or transport the converted hydrogen. The extent of hydrogen production and storage and the deployment timing to successfully integrate this into a Net Zero system will require significant coordination.
As a starting point, the government has initiated a series of research projects to identify and assess the opportunities and technical issues associated with hydrogen use, including the Hy4Heat programme, which is paving the way for a large-scale community trial to fully evaluate the option to replace natural gas with hydrogen, resolve technical issues and demonstrate safety.