The conversion of the NTS into a hydrogen transmission network has been widely discussed and extensive work is underway to prove the technical capability and commercial viability of a 100% hydrogen network. However, it is recognised that blending of hydrogen and natural gas in the network is an important intermediary step towards that goal.
It is therefore important to understand the technical effects that blended gases will have on the NTS and determine the “worst case” conditions for testing purposes and safety considerations.
Consideration should also be given to the effects different blend concentrations have on current recompression technologies and in-line inspection technologies.
This work will be a combination of desktop literature review, modelling and physical testing.
Benefits
Show that demonstrating network capability with 100% hydrogen can provide evidence for network capability at hydrogen/natural gas blends
To gain a better understanding of how hydrogen / natural gas blends may affect the NTS and ensure the appropriate testing is conducted to demonstrate safety and resilience at “worst case” scenarios.
To determine if testing asset capability at 100% hydrogen is the “worst case” scenario for impact or if alternative blends have a greater negative impact on asset capability and lifetime.
Learnings
Outcomes
Phase 1: Identification of key parameters impacting the NTS
Process and CFD calculations indicate that most of the current configuration on the NTS can handle up to 20% H2 blend. However, uncertainties around impact of hydrogen on materials needs to be further studied to establish the most likely blending scenario.
The most likely blending scenarios identified are less than 20% hydrogen by volume, with further study needed on pipeline materials to establish safe limits. A study conducted in 2019 showed that NTS pipelines can handle up to 2% H2 blend without any issues: SGN Feasibility study into 2% hydrogen blending at St Fergus and H2 pipeline and hub at Aberdeen, Project Ref: NIA_SGN0134 (Ena Smarter Energy Portal)
Current study findings align with existing literature, however, the velocity criteria used for hydrogen seem too conservative. The key properties such as density, speed of sound, cp and cv of gas can be predicted for hydrogen blended gas within +/- 1% accuracy using the GERG EoS. Limited literature is available on the impact of blended gas on compressors. The addition of 0.5 or 1 bara (0.7 to 1.4% H2 at 70 bara design pressure) causes a sharp fall in cracking resistance (toughness) with further pressure increases causing a more gradual reduction.
Phase 2: Hydrogen Modelling & Simulation
Key Parameters assessed in modelling study: Miscibility of hydrogen & natural gas under relevant conditions, dissipation of blend when added to 100% natural gas flow, pressure, flow characteristics, flow speed, temperature and compression duty requirements.
The high-level impact of the hydrogen blending ratio on key parameters is listed below:
Pressure & Temperature – Marginal impact on network pressure and temperature profile when assessed for peak energy demands Velocity – Significant increase in gas velocity, however pipelines should be able to handle up to 20% blending ratio
Flow stability & Mixing Lengths – Lower blending ratios require greater mixing lengths, while once the fluids were mixed, the blend was found to be stable in the pipeline. A minor change in the concentration of hydrogen was observed radially across the pipeline. Compression – Manageable up to 20% H2 blend ratio, additional compressors may be required if 100% H2 is required on the NTS.
Phase 3: Concept Validation
Key properties of a blended mixture such as density, speed of sound and cp, cv values were selected for physical testing as they are critical for modelling analysis. Properties of gas obtained using fluid modelling software using GERG EoS were within +/- 1% error margin when compared to experimental data.
Key parameters identified for gas physical testing – Density & Speed of Sound Key parameters identified for materials testing – Fracture Toughness Test. Test methodologies proposed by third parties were reviewed by SMEs from Wood and NGT. Three runs were carried out for single test data and average values were detailed in the report. Similar testing methodologies have been used in past to determine the properties of natural gas and hydrogen. A test plan was developed early in the project and laboratory vendors were selected for study soon after the project kick-off. Selected laboratory vendors demonstrated previous experience in conducting such tests. The requirements were informed to vendors along with the detailed case matrix prepared by Wood after consultation with NGT.
Value tracking
Data Point
Maturity
TRL2-3
Research Project. Set the baseline for understanding how our gas properties will interact with the network and pipeline materials.
Opportunity
>50% or multiple asset classes
This project has created additional knowledge and understanding of how the characteristics of hydrogen will impact our network operations and significantly highlight key recommendations and next steps to ensure we fill additional gaps identified through the project.
Deployment costs
£0
No. Deployment not fully understood yet, as this was a project to define what we need to focus on.
Innovation cost
£ 445,845
Cost of innovation project
Financial Saving
£0
Financial savings are not currently identified due to early TRL level. It is projected that curtailed energy is economic for hydrogen production in 2030.
Safety
5%
This is difficult to define. But progress has been made within this project to identify parameters that we need to get a deeper understanding of on how we apply it to our future network for best management of safety for our consumers.
Environmental
0
No direct environmental benefit, albeit there is the potential of associated CO2 savings by enabling blending in the future.
Compliance
Support Compliance
Identified key parameters to support our policy and compliance areas to be aware of and consider.
Skills & Competencies
Individuals
Key SMEs and project stakeholders have gained understanding of the blending implications on the NTS, including our modelling teams, asset strategy and commercial teams.
Future proof
Indicated on business strategy.
Supports adding information and direction for our business strategies and net zero future.
This project has created additional knowledge and understanding of how the characteristics of hydrogen will impact our network operations and significantly highlight key recommendations and next steps to ensure we fill additional gaps identified through the project.
Lessons Learnt
The main lessons learnt from this project are listed below:
- Project information management needs standardising. There were some handovers of Project Leads due to unforeseen circumstances within this project in NGT. NGT have developed a standardised reporting pack to be used by suppliers reporting on progress throughout projects, and have improved the internal handover processes for projects.
- There is a need to highlight what data is required early in projects and be clear on what is needed and when. A data collection summary sheet has been collated in response to this and will be used in early stages of future projects for clarity.
- Clear conclusions and ‘So what’ statements are needed at closing stages of projects, so there is an understanding of what the main messages to disseminate are. A summary table was created within the final report to clearly state what occurred and what the key recommendations and ‘so what’ statements were for each work package. These are summarised in Section 7 below.
