Reducing the cost impact of hydrogen leakage: four ways to address fugitive emissions

Overcoming hydrogen containment challenges

However, an overlooked solution for driving down the cost of low-carbon hydrogen for end-users is through minimising hydrogen leakage, both at production facilities and throughout hydrogen distribution infrastructure.

Hydrogen presents a significant set of containment challenges, due to the molecule’s small size, high diffusivity and low weight, and the phenomenon of hydrogen embrittlement, where metals become brittle as a result of the penetration of hydrogen into the material.³ As a result, the gas leaks from infrastructure and equipment across the entire value chain and typically at a faster rate than methane.^{4 5} Given its low volumetric energy density, hydrogen is typically compressed to high pressures which exacerbates leakage risk, or liquified, leading to boil-off losses due to a boiling point temperature of -253 °C.

Two recent studies have compiled estimates of rates of fugitive hydrogen emissions (see table 1) across many potential processes in a 2050 hydrogen economy, including deliberate venting and unintended leaks across the value chain. ^{6 7}

Table 1: Compiled Hydrogen Leakage Rates Estimates (Frazer-Nash Consultancy, 2022; Fan et al., 2022).

Note: leakage rates listed for ‘Storage, transmission and distribution’ highly dependent on assumed duration. Among the estimate ranges used for calculating hydrogen leakage, the highest relative dispersions (i.e. greatest uncertainties) were for pipeline transport, above-ground storage and road transport.

Whilst hydrogen leakage has long been identified as a potential safety issue, there is a lack of quantitative data on small, persistent leakage across the hydrogen value chain.⁸ Table 1 highlights that combining certain production and distribution pathways can exhibit leakage rates in excess of five percent in high case estimates. Assuming a levelised cost of hydrogen of USD 5/kgH2LHV, this would equate to over USD 0.25/kgH2 in additional cost as a result of losses before delivery to end-users. Combined with inadequate leakage management at end-use or a high-leakage application, such as hydrogen refuelling stations and fuel cell vehicles, the cost of leakage could rise further still.

Figure 1: Simplified depiction of hydrogen value chain, highlighting stages with high leakage risk. This diagram is non-exhaustive and does not include hydrogen carriers.

Alongside the financial costs of leakage, recent research indicates that the indirect Global Warming Potential (GWP) of hydrogen itself is consequential. ^{9 10 11} Warwick et al. (2022), adopting a new method to account for indirect radiative forcing and for changes in stratospheric chemistry more accurately, estimate that hydrogen’s GWP for a 100-year time horizon is 11 ± 5; over 100 percent larger than previously published calculations. Since hydrogen does not absorb infrared radiation, it is not a direct greenhouse gas (GHG). If it escapes into the atmosphere in significant quantities however, it increases the lifespans and therefore concentrations of direct GHGs, particularly methane.⁷ Hydrogen molecules have a short atmospheric lifespan, exerting a warming effect that is substantial in the near-term. Leakage of hydrogen into the atmosphere, or ‘fugitive hydrogen emissions’, will therefore offset some climate benefits of a hydrogen economy.¹²

Four areas to help address fugitive hydrogen emissions

Minimisation of leaks, through new technologies and procedures, are a priority. Indeed, now is the opportunity for companies in the emerging hydrogen value chain to get ahead of this issue before hydrogen projects, infrastructure, and systems are widely deployed, since it is simpler to address fugitive emissions in design phases than retrofitting.

We propose four interlinked areas for addressing fugitive hydrogen emissions:

1. Manage commercial implications of unavoidable leakage

Procedural and technological interventions will minimise, but not eliminate, hydrogen leakage. The residual rates of hydrogen leakage will have important implications for all commercial hydrogen projects in terms of pricing, profitability and financing. A key first step is to accurately estimate a tolerance level for these acceptable losses, which can be incorporated into commercial contracts. Through use of benchmarks and historical data, this tolerance range may be reduced. Additionally, digital platforms can play a key role in monitoring hydrogen volumes throughout the value chain in real-time (see point 4). Such platforms may also support the billing process, enabling transparency between counterparties and therefore mitigating risks of disputes.

2. Reduce the levelised cost of hydrogen by designing for leakage minimisation

Decisions made during the Front-End Engineering Design (FEED) study significantly impact the realised levelised cost of hydrogen. This includes interventions to minimise leakage. For example, sites can design-out leakage through optimising the specification, capacity, and surrounding environmental conditions of electrolysers, compressors, and storage tanks. For UK-based hydrogen producers, undertaking these steps will also support compliance with the Low Carbon Hydrogen Standard. This standard requires producers to develop a ‘Risk Reduction Plan’ demonstrating how the hydrogen production plant will be designed and operated to ensure that fugitive hydrogen emissions are kept as low as reasonably practical.

3. Factor in leakage risks when calculating a site’s most cost-efficient operating philosophy

To achieve cost optimisation, the operating philosophy of hydrogen production and distribution systems should consider minimisation of leakage risks. Steps to reduce leakage on a day-to-day basis include reducing start/stops for electrolysers, avoiding high pressure and long-duration tank storage, and minimising routine purging. A challenge for site operators is balancing these operating principles with other priorities, namely health and safety, and optimising cost efficiencies across production and distribution.

4. Invest in advanced detection and monitoring equipment

Companies can invest to save by incorporating advanced leakage monitoring throughout production facilities, distribution networks, and end-uses. Sites must think beyond mass balance approaches or direct monitoring of pipeline pressures if they are to pinpoint the small, persistent leaks in their systems. Alongside these measures, sites should procure permanent hydrogen sensors at locations where hydrogen is assessed to be likely to accumulate, such as around electrolysers, compressor units, and refuelling stations. The required precision is at the parts per billion level, well below the threshold for hydrogen gas flammability, but necessary to characterise leakage in the open.

To unlock the true value of hydrogen, partnering is key

The challenges surrounding hydrogen leakage coexist alongside uncertainties around technology readiness, optimal system designs, business models, policy and regulatory frameworks, among other factors. For these reasons, collaboration is key throughout the hydrogen value chain; partnerships can bring together the scientific, engineering, innovation, commercial, and regulatory expertise that will be necessary to make the needed interventions at scale. This will enable participants in the emerging hydrogen value chain to tackle leakage challenges before projects, infrastructure, and systems are widely deployed, thereby reducing the cost of low-carbon hydrogen for end-users and ensuring that the climate benefits of a hydrogen economy are not lessened.

References

¹ A ‘levelised cost’ is the average cost over the lifetime of the plant per MWh of hydrogen produced. It reflects the cost of building and operating a generic plant for each technology.
² IEA Global Hydrogen Review 2022
³ Ocko and Hamburg, 2022
⁴ Mejia et al., 2020
⁵ Swain and Swain, 1992
⁶ Frazer-Nash Consultancy, 2022
⁷ Fan et al., 2022
⁸ Mejia et al., 2020
⁹ Derwent et al., 2020
¹⁰ Paulot et al., 2021
¹¹ Warwick et al. 2022
¹² Fan et al., 2022