Learnings
Outcomes
This project represents SGN’s first Pre-FEED end-to-end system transformation infrastructure assessment and has delivered a number of conclusions and recommendations. These are detailed below. More comprehensive outcomes and recommendations will be available in a summary report in the near future.
Hydrogen Transmission - Aberdeen Vision
The project successfully routed and designed a new system of hydrogen transmission pipelines and AGIs. The routing and optioneering assessment of this system, outlined above, proved highly successful in rapidly assessing and ranking millions of AI generated corridor options. This accelerated process enabled increased confidence in refined route options, and, following micro-routing and POI surveys, the final preferred corridor. This approach proved highly successful and is expected to yield significant benefits in a number of future project elements, most notably route justification and environmental impact assessments. The design and material selection of the pipeline has also proved to be robust and instils further confidence in its constructability.
The project has developed a feasible route for a dedicated 36” x 75km Hydrogen Pipeline from St Fergus to south of Aberdeen inclusive of eight injection locations into the existing networks. Two spur lines of approx. 3.5km x 16” (Craibstone) and 9.1km x 12” (City Gate) have been included with the other connections using new connections adjacent to existing facilities.
The project has completed a technoeconomic assessment of the design and has established and selected routes and locations for Pressure Reduction Stations and spur pipelines to connect the new Hydrogen mainline to existing PRS sites at Peterhead, Kinknockie, Ellon, Craibstone and City Gate; the last two being the major connections into Aberdeen. Further connections are proposed to feed Westhill, Peterculter and Maryculter offtakes. The pipeline is sized to allow for further expansion to the South to connect to other systems being considered both to feed Hydrogen further South or connect to other supplies or storage in the future. The pipeline has been analysed for steady state and transient analysis and is capable of supplying the changeable daily winter demand whilst maintaining inlet flows at a constant rate +/- 20%. The impact of further flows to the South have not been modelled as these were not available at the time of the Pre-FEED.
The option to repurpose existing National Gas Feeders located within the same general corridor South-West from St Fergus was investigated using existing take off points and additional spur lines to reach the same locations as the standalone pipelines as an alternative to the main AV trunkline. This option is outlined in the summary report.
Hydrogen Demand Assumptions
The basis of design of the Aberdeen Vision Pipeline was equal to the currently natural gas demands of the offtakes and PRSs the system was to connect into. This was by design to understand the required transmission infrastructure to enable each and every gas customer to convert to 100% hydrogen, should they choose the option to; effectively, this BOD was designed to underpin the infrastructure requirements for a full choice system transformation approach. The market share of natural gas connections, across domestic, industrial and commercial customers, is highly likely to decline as a more varied and competitive downstream technology market emerges, namely through the uptake of heat pumps and the development of heat network zones. As such, a crucial next step in the development of the project will be to refine demand assumptions to ensure a balance is achieved between firm demand in phase 1 and sufficient futureproofing to service the growth of the hydrogen economy; ensuring sufficient transmission capacity is in place will be vital in facilitating primary energy recovery of renewables and minimising curtailment. It should be noted that even if traditional gas network demands decline over time, hydrogen is expected to play an increasing role in multiple other sectors, such as industry, electricity generation, as a feedstock to sustainable fuel production and transport.
It was determined that irrespective of future hydrogen demands from traditional gas network connections and any potential reductions, there is a strong case to progress with the main transmission Aberdeen Vision FEED study. The proposed infrastructure was specifically routed and designed to receive blue hydrogen from St Fergus (via the Acorn Project), with the capacity and potential to receive and transport green hydrogen production from future offshore and onshore hydrogen production development. This provides the optionality to deliver a masterplan integrating the pipeline with follow on Pre-FEED projects, such as the in-flight H2 Caledonia project, which is being designed to facilitate the transportation of hydrogen between known and emerging hydrogen production locations to major potential offtakers, interfaces with Project Union and strategic locations on the gas distribution networks to enable blending and 100% conversion, should heat policy support it. H2 Caledonia and Aberdeen Vision, constructed as one integrated system, will be key in connecting scaled green hydrogen production with the rest of the UK, in particularly Industrial Clusters in the North of England and storage developments in more favourable geologies for the development of hydrogen storage. SGN’s system transformation developments will require careful integration with Project Union, with each development likely key in the success of the other.
The project outputs includes a detailed cost estimate for the future phasing of project development, including, but not limited to; Contractor FEED Engineering & Management costs, SGN FEED Management & Support costs, major crossings costs and land management costs. This information can be utilised to help secure funding for future phasing and provide confidence in further development. Furthermore, overall project cost estimates were determined for the Aberdeen Vision Hydrogen Pipeline and associated Above Ground Installations (AGI) facilities from budgetary inquiries. A project schedule (Level 3) was also established to demonstrate key milestones for Engineering, Procurement and Construction (EPC) for the Aberdeen Vision Hydrogen Pipeline System. It is recommended both these are revisited during the project life cycle to upgrade the accuracy detailing major sections of work – this includes upgrading to an AACE Class 3 level of cost accuracy at the FEED stage.
Below 7 Bar Analysis
A statistically representative approach was adopted by DNV for the below 7 bar analysis of the Aberdeen City distribution network. This analysis estimated the per sector requirements for reinforcements to handle elevated velocities and parallel mains for the sectorisation and conversion of Aberdeen. This approach was selected for efficiency and to derive cost estimates and resource requirements for distribution and downstream conversion costs. Whilst it achieved these outputs, it was recognised that a statistically representative approach was sub-optimal in deriving a credible infrastructure plan; whilst costs may be derived efficiently, a full plan accounting for the complexities and interconnectivity of gas grids and the variance in customer type and distribution was not possible from the selected approach. As such, for future Pre-FEED projects, SGN have adopted a comprehensive conversion analysis approach utilising its in-house below 7 bar modelling team. This has been utilised by the H2 Caledonia and H2 Connect projects and has proved highly successful. Aberdeen has been included in this analysis by SGN’s in house modelling team, who are highly experienced and familiar with each individual gas grid.
Blending
Due to policy decision uncertainties, it is pragmatic to approach the need case develop of hydrogen transmission assets based on a variety of offtakes, including blending into the distribution networks. Alongside hydrogen for industry, storage and electricity generation, hydrogen blending into the existing natural gas supplied grids provides a credible, lower risk offtake assumption for the development of new infrastructure, and as a interim solution preceding a full system transformation to 100% hydrogen. New 100% hydrogen transmission infrastructure has been routed to key national transmission (NTS) offtakes and PRS sites to provide the optionality of an up to 20% blend by volume into the highest-pressure tier system, maximising the potential for hydrogen blending into the system.
This provides the opportunity for early producers/adopters of hydrogen to feed excess hydrogen as a spillover from industrial production and demand into the gas networks. Blending has the potential to initiate the demand for hydrogen and stimulate the development of a hydrogen economy reducing both industrial and gas network associated emissions.
The project did however highlight several gaps and challenges which will require addressing prior to realising a 20% by volume in to the gas distribution networks. There relate in particular to billing and flow weighted average CV. Additional network adaptions will be required to facilitate blending, which would not be required in an end-state hydrogen network.
Conversion Strategy
DNV’s below 7 bar Pre-FEED analysis also included the development of a process to adapt and prepare a gas grid for conversion, followed by a sector-by-sector process to safely and practically manage the transition of a gas grid from natural gas to 100% hydrogen. This masterplan strategy drew on previous approaches developed from other projects such as H21 Leeds City Gate, H21 North of England, Frazer Nash Logistics of Domestic Hydrogen Conversion and a suite of NIA projects to develop a workflow and process of necessary steps and activities 36 months prior to the conversion of a sector inclusive of all downstream customers. This process is outlined in the summary report and provides a highly useful basis for infrastructure and conversion planning. The conversion strategy and process enabled the calculation of resource requirements and associated timescales, and the costing of differing sector’s respective conversions.
This enabled a resource calculation of the number of labour days, costing of domestic sectors, costing of industrial & commercial sectors required to undertake the conversion of the Aberdeen Study Area.
Future Project Cost Estimates
Transmission Costs
The above 7 bar Pre-FEED has returned a Class IV cost estimate for the development and construction of the proposed Aberdeen Vision transmission system. This classification of cost estimate has been informed by cost norms, engineering assumptions and budgetary inquiries, and carries an error of -30%/+50%. The CAPEX estimate for the onshore pipeline and AGIs is £205m, with additional DEVEX and costs covering FEED, land management, surveys, detailed EPC support, SGN support and project management, contractor support and project management, construction mobilisation and demobilisation, and all ancillary services totalling £87.5m. with a 20% contingency, this totals £350.9m for the above 7 bar transmission calculated to a class IV estimate, in 2022 prices. Of these costs, FEED costs are estimated at £13.57m, inclusive of a 20% contingency and major crossing surveys. The estimated level 3 schedule is a total of 4 years, comprising 2 years engineering and procurement and 2 years for construction and commissioning.
The development of new hydrogen transmission infrastructure combined with the repurposing of existing assets will potentially provide a credible and affordable infrastructure plan to enable the transition of the whole energy system to net zero. The need for new hydrogen infrastructure has been highlighted by the National Infrastructure Committee to provide low carbon and green hydrogen to large scale industrial and commercial users with the potential to benefit domestic consumers, should policy support be in place.
Distribution Costs
Using the aforementioned statistically representative approach deployed by DNV in their analysis of Aberdeen City, estimations for the required below 7 bar upgrades and downstream adaptions were derived. Total costs were £464.9m and carry an error of -50%/+50%. With a 20% contingency, this cost totals at £557.9m. FEED costs for the below 7 bar element of Aberdeen Vision are estimated at £13.89m, which increases to £16.67m with a 20% contingency.
A pilot FEED study is recommended to further address uncertainties to further increase the level of confidence within the current cost estimation model. These uncertainties primarily in demand assumptions, I&C customers and downstream technology availability.
Development of this new infrastructure combined with the repurposing of existing assets provides customers with a potential lowest upfront cost pathway to conversion to net-zero. The need for new hydrogen infrastructure has been highlighted by the National Infrastructure Committee to provide low carbon and green hydrogen to large scale industrial and commercial users with the potential to benefit domestic consumers.
Lessons Learnt
This project represents the first pre-FEED phase end-to-end system transformation assessment of gas transmission and distribution infrastructure for a conversion to 100% hydrogen, aiming to design and derive a credible infrastructure plan applying the in-flight portfolio of technical R&D into network and downstream suitability. As the assumptions feeding into this project (particularly in relation to the repurposing of existing infrastructure) as inherently dynamic, this project was expected from the offset to provide significant learning for future similar projects. This project proved successful in delivering against its stated objectives but has also produced a number of highly useful lessons and considerations, which have been utilised in the H2 Connect and H2 Caledonia projects, SGN’s current in-flight Pre-FEED projects.
Hydrogen Transmission Assets - Aberdeen Vision
Multiple lessons learnt can be drawn from the routing and pipeline design exercise. The novel AI driven approach, although demonstrably more efficient and quicker than traditional pipeline routing, did take longer than anticipated due to the complexity of this multifactored exercise; these timelines should be reflected in future project scheduling. However, the AI learning approach adopted should result in greater efficiencies in future projects due to the machine learning of the software as a result of this project.
Deriving a credible route is critical for all project elements, such as flow assurance, mechanical design, material selection and constructability assessments. Another key learning from the above 7 bar pre-FEED was the value of engaging experts in specific fields such as trenchless crossings and those with experience in delivering complex large diameter pipeline projects, which can be a challenge considering the time since similarly scaled projects have been developed (NTS and LTS). Early engagement ensures constructability risk is managed and independent quality assurance is carried out on the selected route corridor options.
Whilst the route corridor optioneering during the project took longer than expected due to additional modifications required to the AI software for hydrogen pipelines, a final report delivered by Continuum Industries outlines the benefits of the approach for future projects, potentially delivering savings in cost and time when applying the software to future work. This has been realised in the in-flight H2 Caledonia and H2 Connect projects which also utilised the same approach, where additional routing work was possible due to the well-established software – these projects have also led to increased refinement of the tool and development of additional features.
The AI approach utilised delivered several options for further refinement (drawn down from millions of theoretical corridors) which were then optimised and narrowed down further during phase 2. Phase 2 was informed by micro-routing and by information gathered during site visits. This approach was crucial in refining the route further and narrowing down route options and in particular, assumed major crossing locations. This exercise further increased routing constructability confidence and is recommended for implementation in future projects. Further re-risking activities such as line walking, drone/helicopter surveys and LIDAR should also be considered during or before FEED. Topographical and geotechnical surveys are also recommended across the route to enable greater confidence in proposed construction techniques. Additionally, for areas where trenchless techniques are proposed, the scope of any survey must provide sufficient geotechnical data and detail of the soil strata, to allow the final crossing method to be determined. Crossing locations and the deliverability of proposed techniques have a significant impact on project cost estimates and scheduling, as such, confidence in deliverability is essential from an early stage.
It is recommended that during the FEED phase of the project, discussions for consenting of the route should be initiated alongside engagement with key stakeholders, to allow careful management of consenting risks associated with large linear infrastructure projects.
NTS repurposing as an alternative to a new pipeline was also considered as part of the project scope (with LTS pipelines proposed as offtakes). Further recommendations of the study include work to assess the suitability of material properties and design parameters, against the requirements of IGEM/TD/1 Edition 6 and the new requirements within IGEM/TD/1 Edition 6 Supplement 2. This information will help to determine the suitability of existing feeders for re-purposing to hydrogen (note much of this work in underway through Project Union and FutureGrid). Should both Feeders 10 and 13 be suitable for re-purposing – the recommendation of the project at the time was for No. 10 Feeder to be repurposed to 100% hydrogen due to a reduced requirement for the construction of new spur lines when compared to No. 13 Feeder. Note this information is now outdated due to the identification of No. 10 Feeder for CO2 repurposing.
It was determined where possible, offtakes should also be located at or near existing facilities to reduce the costs associated with these offtakes, aid in the permitting & consenting processes and minimise the environmental impact of the project. Additionally, the layouts developed as part of the Pre-FEED phase identified major hardware requirements at each of the AGI sites; these will require further definition within the FEED phases to determine the equipment package requirements, electrical power consumption and to identify any long-term leads. It is recommended all risk and hazards are also re-evaluated and a QRA is undertaken to assess risks across the end-to-end transmission system, inclusive of AGIs.
Currently it is recommended that the Aberdeen Vision pipeline adopt an IGEM/TD/1 Supplement 2 Low Stress Design for the pipeline FM analysis design. Cracking resistance of the pipeline will require confirmation by FM analysis (ECA) and FM testing in hydrogen pressure applied to line pipe, butt welds and pipe components (flanges/fittings/valves etc). Procedures and scoping for FM testing will require development which will be subject to specialist review – it is suggested these are started at an early stage within the project schedule to allow for development, refinement, and any re-testing to confirm the cracking resistance of carbon steel.
To progress the project further, extensive stakeholder engagement will be required on a much larger scale for both domestic and industrial & commercial (I&C) users to gather detailed information to improve understanding on future hydrogen demands and end user requirements; confidence in demand assumptions will be key in consenting and engineering justification of line sizing.
Below 7 Bar Analysis
To estimate below 7 bar costs, resourcing and infrastructure requirements for a conversion to 100% hydrogen, a sectorisation methodology based on statistically representative samples was adopted by DNV. Whilst efficient, this approach reduced the accuracy of costing outputs, however, allowed for a full conversion costing of the study area to inform future funding decisions relating to more detailed below 7 bar FEED projects. It is recommended for future project, full sectorisation analysis is carried out to ensure credible infrastructure plans are derived, which will increase confidence in deliverability and constructability.
Additionally, a reduction in line pack capacity was expected when repurposing LTS pipelines for hydrogen compared with natural gas. It was determined the below 7 bar pipeline system would not be able to facilitate any additional storage required. Should hydrogen demands be lower than current natural gas demands, repurposed LTS assets may then have sufficient capacity. It was determined further investigation of seasonal and diurnal storage (including non-pipeline options) will be integral to future flow assurance of new and repurposed hydrogen assets.
