Learnings

Outcomes

Key findings from the HG2V Project can be summarised as follows:

·        There is a strong case for UK distribution of hydrogen via the natural gas grid: Either as a blend of hydrogen and natural gas (for downstream separation), or as 100% hydrogen, which will promote a low carbon hydrogen economy.

·        The gas grid could be used to supply FCEV hydrogen refuelling stations across the UK, assuming the hydrogen produced meets the ISO 14687:2019 hydrogen fuel quality product specification, and that there are no impurity issues which degrade the final delivered product  

·        The most likely method of centralised large-scale hydrogen production for injection into the gas grid is thermochemical natural gas treatment, such as SMR, due to its maturity, lower costs and increased efficiency compared with biological and electrolytic processes.

·        Technical exemptions or a change to GMSR 1996, which covers the whole network, must be in effect before sustainable quantities of hydrogen suitable for transport applications can be injected into the gas grids. 

·        Bulk natural gas contains Sulphur-based odorants. These also have a critical impact on fuel cells and need to be removed or replaced with a new non- Sulphur-based odorant, to comply with the total Sulphur limit in the ISO 14687:2019 hydrogen fuel quality product specification. 

·        Contaminant levels in the samples representing the two repurposed grid scenarios (hydrogen enriched natural gas and 100% hydrogen) are not compliant with the ISO 14687:2019 hydrogen fuel quality product specification. Therefore, purification is necessary before supply to the hydrogen refuelling stations (and FCEVs). 

·        For the new gas grid scenario, contaminants sourced from the polyethylene pipe sample are not identified. There is mostly an increase of CO2, CO, potential particulates and water. Therefore, purification requirements for a new gas grid using 100% hydrogen are significantly less than those for a repurposed gas grid. 

·        The method chosen for deblending (separation of hydrogen from a mixture with natural gas) should use similar pressures for the reject gas and hydrogen product. This avoids a recompression energy penalty which would compromise the HG2V strategy. 

·        The challenge of deblending (i.e., downstream separation of hydrogen from the natural gas) is to understand: 

o   The fraction of contaminants in the deblended hydrogen

o   The consequent purification required to obtain hydrogen that could be supplied to hydrogen refuelling stations (i.e., FCEV users). 

·        It is suggested that hydrogen enriched natural gas grids should become less of a focus for the project. Their potential to provide FCEV-ready hydrogen is an attractive concept in the context of other projects such as HyDeploy. However, the benefits are far outweighed by the hydrogen recovery/ deblending difficulties and associated cost.

·        Testing of five selected contaminants identified in the Cadent Gas network - on the short- term performance and initial cell voltage degradation rates of PEM fuel cells - indicates the absence of any major concerns for FCEV use of grid-supplied hydrogen. 

·        More sophisticated analysis is required to establish the optimum locations for grid connected refuelling stations. This should be linked to the UK areas with the largest anticipated FCEV market growth. 

·        There is no clear guide in the study sources to indicate the future share of grid-supplied transport hydrogen. This therefore necessitates further work to anticipate the future proportion of grid-supplied hydrogen requiring purification. 

·        The variation in hydrogen purity across the network and its impact on separation/purification technology is a key area for future research. 

·        There is the potential to deliver 100% hydrogen through the existing gas grid and purify it to FECV-readiness at a cost that can allow commercial viability. 

·        GHG emissions associated with separation (i.e., hydrogen deblended from a grid-supplied natural gas mixture) and purification are relatively small but not insignificant. The emissions can be minimised through appropriate design choices, which may include: 

o   The use of low carbon energy to power purification/separation energy demands. 

o   Improving efficiency by taking advantage of available pressure reductions and energy sources. 

o   Reducing any direct emissions of natural gas or hydrogen.

Recommendations for future work:

·        More sophisticated analysis is required to establish optimum locations for grid connected refuelling stations. This should be linked to the UK areas with the largest anticipated FCEV market growth. 

·        Action is required to refine the technology choices suitable for large scale roll-out. In future research, the implications of separation and purification, using PSA, at a significantly smaller scale should be explored to highlight any potential methods of downscaling economically. 

·        Materials and operating conditions need to be optimised for all areas of hydrogen purification technology, considering different options for membranes, adsorbents, etc. 

·        A mix of technological solutions is required for purification. This may include purification in stages targeting the removal of individual contaminants rather than achieving the removal in one step. The laboratory testing work in later project phases should therefore focus on testing these technologies to target problematic contaminants. 

·        Fine tuning the cost estimates is necessary in order to provide an accurate price per kg for hydrogen at the pump. Further examination of how costs might also vary with geographical location would also be informative. 

·        Additional study is required to indicate the future share of grid-supplied transport hydrogen and therefore the anticipated proportion of grid-supplied hydrogen requiring purification. 

·        The variation in hydrogen purity across the network and its impact on separation/purification technology is a key area for future research. This suggests that there will be cleaner areas of the network which would make a better choice for the siting of hydrogen refuelling stations. So identification of ‘clean spots’ on the network is recommended.

·        The possibility that 100% hydrogen through the existing network may eventually flush out inherent grid contaminants should be investigated. 

·        If ATR processes become more widely available across the UK, they ought to be explored in future phases of this project. 

·        A key area for future investigation is in testing the impact of new non-sulphur odorants, as sulphur-based compounds (which adversely affect PEM fuel cells) in existing odorants must be removed to very low levels. 

·        It would be helpful to review the existing GSMR 1996 as they relate to the need for management or control of certain grid gas contaminants. This is particularly applicable to the intended use of a new non-sulphur based odorant, as the current natural gas (sulphur- based) odorant adversely affects fuel cell function. Note that any new non-sulphur odorant needs to be GSMR-compliant. 

·        Further long-term testing of hydrogen exposure to polyethylene may be required. 

·        Development of a new online analyser is necessary to monitor contaminants in the deblending and purification process and ensure compliant quality before supply to the hydrogen refuelling stations. 

·        Technical exemptions or a change to GMSR 1996, which covers the whole network, must be in effect before sustainable quantities of hydrogen suitable for transport

Lessons Learnt

·        Phases 1-3 and the first deliverable in phase 4 was delivered as set out in the original scope of the project, although delivery timescales were challenging. 

·        Delays at the start of the project needed to be reflected on the end date and the budget. A need to not wanting financial payments to move into the next financial year meant that there was often no contingency to complete the work required for the deliverables, in particular time for the reports to be reviewed and approved.

·        HG2V project was an ambitious project from the offset; achieving clarity and agreement of the objectives between all the partners proved challenging, although consensus was delivered through regular project meetings.

·        The complexity of putting a test RIG in Teddington, the planning permission that was required and who would pay needed to be built into the plans. 

·        Communication was good, the meetings with the partners were very useful, provided the opportunity for clear discussion and they were solution driven and focused.

·        Would recommend Cadent use a project manager independent of the partners, there was often a conflict of interest when it came to who the PM was working for. 
Building in the project breakpoint to assess the test rig and decide whether to proceed with the project as planned or terminate activity was necessary, it enabled the partners to look at all the findings from the project and showed that the original plan going into phase 4 was not viable and brought about the discussion of what was needed. The partners have since been working on the Hy4Transport proposal.