Learnings

Outcomes

CONCLUSIONS

·       Hydrogen injection at the NTS offtake offers a means of achieving conveyance of a natural gas blend containing up to 20% hydrogen within the existing regulatory framework of the GCOTER  and within the GSMR, providing the existing maximum limit on hydrogen content can be modified to allow conveyance from 0.1% to up to 20% hydrogen.

·       Capping of FWACV is the principal constraint on the proportion of hydrogen than can be accommodated. The proportion of hydrogen that can be blended varies from around 4% when a relatively small proportion of LDZ energy is supplied as blend, to up to 20% when around 80% or more of LDZ energy is supplied as blend. As a general rule therefore, blend should dominate the amount of energy supplied to a given LDZ. This can be achieved through supplying blend through multiple offtakes or though one large offtake.

·       Adding a significant proportion of LDZ energy as blend reduces the FWACV and hence reduces risk of capping. For this assessment, the energy flows into both LDZs were for those in 2020 and so were not optimised for hydrogen production. Optimising NTS offtake flows is likely to result in a significant increase in hydrogen injection capacity of LDZs.

·       FWACV capping is more of a constraint if the CV of natural gas supplies into an LDZ vary significantly. In such situations, the reduction of FWACV is not so great particularly if hydrogen is blended with lower CV supplies. This is seen with EM LDZ, where the range of CV is greater than with NW LDZ. As a general rule hydrogen injection is more effective if added to the highest CV source.

·       The lower Wobbe index (WI) limit of the GSMR can constrain the proportion of hydrogen that can be injected to less than 20%, even if blend is supplying in excess of 80% of LDZ demand. Such GSMR constraints occur if the WI of the natural gas in the LDZ is closer to the GSMR lower limit and occurs more frequently with NW LDZ than with EM LDZ. A future proposed reduction in the lower WI limit in the GSMR would reduce the incidence of this constraint in the NW LDZ.

·       Because hydrogen injection at the NTS offtakes reduces the FWACV, the enrichment requirements for existing and future biomethane injection projects are likely to be reduced. However, it is unlikely that the need for enrichment would be removed  completely, so although operating cost can be reduced, the capital investment for enrichment plant for future projects is unlikely to be avoided.

·       In principle, existing metering systems at the NTS offtakes are not likely to be compromised by injection of hydrogen, although upgrade of equipment will be required. Future plans for upgrading such sites will need to be designed to accommodate hydrogen injection.
Hydrogen injection adds an additional layer of complexity to network control and operation and better tools are likely to be required. The gas transporter will need to exercise more control over balancing of when, where and how much hydrogen  is injected against FWACV and GASM constraints. This will need significant discussion and agreement within the industry.      

Lessons Learnt

·       When assessing blending hydrogen with natural gas within the bounds the regulations, the natural gas composition is critical to how much hydrogen can be added, so analysis needs to be undertaken using specific natural gas compositions, which can vary depending on the source.

·       Data extracts from GDN gas quality data can be take a long time, so should be defined and extracted early.