It is important to understand the design of the infrastructure required to allow blending into the NTS. There are multiple scenarios where hydrogen may be blended into the NTS which need to be considered:
1. High flow industrial blue hydrogen injection
2. Medium flow injection, such as from a large electrolyser site
3. Low flow injection, such as from a wind farm
Each of these connection scenarios should be considered as direct green field feeder connections, along with injecting at existing NTS sites.
The effect that the different flow rates have on the design of the infrastructure should be considered, along with the location of injection.
The findings of the project should also be applied to a specific test case: the design of a temporary hydrogen connection acting as a pilot for hydrogen blending into the NTS.
Benefits
Increase understanding of the connections process for hydrogen blending
Understand the behaviour of hydrogen when blending at NTS pressures
Determine the need for pre-blending or otherwise
Understanding of infrastructure, engineering design and costs of blended hydrogen connections of different types
Learnings
Outcomes
The project focused on understanding the design and infrastructure required for blending hydrogen into the National Transmission System (NTS). It aimed to address technical challenges and assess the feasibility of various hydrogen injection scenarios.
Key Outcomes
Infrastructure Requirements
Designs Developed: Detailed designs for hydrogen blending infrastructure were created, covering various connection scenarios including high, medium, and low flow rates.
Modifications Identified: Necessary modifications to existing infrastructure were identified to enable hydrogen blending.
Work Package 1 of this project provided a comprehensive Literature Review on the various infrastructure elements that would be required for various blending scenarios such as direct and indirect blending options. Various equipment was identified as possible solutions including tee blenders, various meters, injection probes, etc. Based on this output CFD (Computational Fluid Dynamics) modelling scenarios for Work Package 2 were devised and agreed.
Technical Assessments
CFD Simulation Models: Computational fluid dynamics (CFD) models were used to assess blending technologies, ensuring a homogeneous blend at required percentages.
Safety Assessments: Overpressure and thermal radiation consequence modelling were conducted to ensure safe operations.
Work Package 2 showed expected results for direct blending.
Using a simple probe design with bi-directional flow, homogenous hydrogen blending can be achieved within approximately 40 pipe diameters.
The results show that good blending could be achieved within 40D in either direction of the injection probe, irrespective of flow direction. Despite the hydrogen “carrying” along the bottom of the pipework when hydrogen is injected with the natural gas flow (reverse flow).
The pipeline wall local to the probe could be exposed to concentrations of hydrogen above 20% for long periods with the modelled geometry for both flow directions but more so when injecting in the flow direction.
Work Package 2 showed expected results for indirect blending.
A chosen device identified in WP1 was not sufficient to achieve the required induced natural gas flow around the blending loop, resulting in blends greater than 20%.
By incorporating an electro/mechanical gas pumping device to induce flow in the blending loop, the flow can be controlled to obtain a 20% hydrogen blend. In addition, the return blending branch connection can be sized to increase the gas velocity and plume the blended gas into the flowing pipeline gas for efficient secondary blending within an expected 20 pipe diameters.
For larger scale production it is recommended to revisit the option of installing block valves on the Feeder pipe work to generate a flow in a blending loop.
Engineering Drawings
Conceptual Drawings: High-level conceptual engineering drawings were produced for six different connection scenarios, including both existing Above Ground Installations (AGIs) and greenfield pipeline connections. The BoDD was amended following the completion of WP2 to reflect the results of the CFD modelling and update the large-scale production capacity.
8 scenarios have been considered within this project, drawings for 6 of which have been produced.
Direct blending is applicable at existing above ground installations, including at existing industrial offtakes and Multi-junctions (depending on pipe size and above ground lengths). This is most suitable for small-medium scale production facilities up to 100MWth.
Direct injection is not applicable for greenfield locations on pipelines as this would result in protrusions into the pipeline which would impede a PIG. Retractable probes have been considered but due to the pipeline being buried, four large pits would be required for access at the injection and sample locations and for pipeline metering.
For large scale injection, indirect injection is therefore the preferred solution.
For large scale (600MWth) this indirect injection requires diverting the entire pipeline flow around the blending loop which eliminates the requirement for a compressor but does require a full-bore loop.
For small and medium scenarios, the blending loop can be smaller but will require a compressor to induce a flow around the loop.
Pilot Temporary Connection
Design and Demonstration: A bespoke detailed design for a pilot temporary hydrogen connection was developed, aiming to inject 2% hydrogen into the NTS at an existing power station offtake for 4-7 hours during a single day.
Cost-Benefit Analysis
Economic Viability: A comprehensive cost-benefit analysis was conducted for the chosen design scenarios, supporting RIIO-3 costs and evaluating the economic viability of the proposed infrastructure.
Reporting and Governance
NIA Reporting: Ensured governance requirements were followed, and all project activities were logged and disseminated accordingly.
Lessons Learnt
Lessons learnt for future projects include:
- When reviewing and comparing multiple technologies, allow for some contingency time if the technology is critical to be incorporated in future design studies to allow for development of the product to ensure applicability to design scenario.
- Ensure Christmas holidays are incorporated in project Gannt chart in future to avoid delays in project execution.
- Enabling a longer duration in the project timeline to manage feedback and SME input during and at the end of work packages. It is critical that the correct stakeholders are involved in all of our projects. Due to the nature of this project impacting a significant number of teams around the business, it has made it difficult to get the resource time and capacity to support the demonstration.
- Utilise an external SharePoint with supplier(s) to ensure all documentation is accounted for in a single shared area to avoid searching for documents in email inboxes.
Data gathering can be time consuming and require specific design information therefore more time should be allocated to engaging with external parties and parties to engage with should be engaged with as early as possible in the project pre-work packages kicking off if feasible.
- Consistently refer to project schedule to ensure project is continuing to time and have foresight to prepare for next phases of work. Keep internal monthly reporting up to date to support in case project stakeholders change to ensure smooth continuation of project.
- This project encompassed many elements including aligning it to National Gas Transmissions first blending demonstration on the NTS. This resulted in many challenges to overcome due to the innovative nature of the project. The lesson learnt would be to do a smaller discovery type project to prepare a more detailed design and enable the correct suppliers to be onboarded and involved at the correct stages. This project was able to complete the detailed design studies as required but more refinement is needed on a larger scale which has been taken outside the scope.
