Project Summary

This project supports Innovation Challenge 4: Heat by allowing the gas distribution networks to safely minimize the costs of re-purposing existing transmission and distribution assets to carry hydrogen-natural gas blends and 100% hydrogen.

Gas network designers will be challenged to safely repurpose networks to low carbon heating gas with minimum costs while maintaining energy delivery. The energy delivered by hydrogen is one third of that delivered by natural gas per unit so, under many of the likely demand scenarios in the zero-carbon future, the flow rate of gas in re-purposed gas networks will need to increase.

Gas network designers need to know the safe design velocity limits so they can reduce to a minimum any need to increase pipe sizes to accommodate zero-carbon heating.

The network innovation involved is to design a suitably rigorous test campaign (to be executed in the Beta Phase) that will produce a new safe design velocity limit for hydrogen-natural gas blends and 100% hydrogen in the UK gas networks.

The Discovery phase concluded:

1. Hydrogen could enhance erosion rates due to a synergistic hydrogen embrittlement/erosion mechanism. This mechanism could be a credible risk to network integrity.
2. Particle (debris) transportation would be significantly different in hydrogen with a possible increased likelihood of pipe wall erosion.
3. Initial investigation found a range of erosion rates expected, depending on the gas pressure and composition.
4. SGN experiences the presence of debris across all pressure tiers and has a significant impact in medium and low-pressure systems.
5. A cost benefit analysis of any velocity limit(s) is required.
6. Noise and vibration modelling has indicated there are differences in hydrogen and natural gas.

The Discovery phase recommendations:

1. The potential for enhanced hydrogen uptake and erosion rates are further investigated to determine the risk to network assets.
2. If synergy between hydrogen embrittlement and erosion is proven, then then current erosion models and velocity limits must be revised.
3. The erosion models require validation in hydrogen and hydrogen blends. Theoretical modelling must be included to ensure a representative full-scale test programme and design of the required facilities.
4. Further investigation is required to understand particle transportation and how this might affect erosion. Validation of existing particle transportation models in hydrogen is required.
5. Initial modelling has suggested differences in hydrogen and natural gas in noise and vibration risk. However, the models have not been specifically validated for hydrogen.

 

The Alpha Phase project should include:

1. Document the GB Gas network experience of network debris.
2. Industry engagement to obtain "buy-in" and direction towards a new industry design standard.
3. Design and cost the full-scale test facility and campaigns to be delivered in the potential Beta phase.
4. Cost-benefit modelling to balance design gas velocity increases against network reinforcement costs.

Addressing the Heat Challenge requires a transition to "business as usual" where UK gas network operators, professional bodies (IGEM) and designers to accept the new design limits as scientifically valid and are assured that the design limits when applied will maintain safety, reliability and affordability of low carbon heating.

Partners:

• SGN (Lead) is one of the four gas distribution network operators in the UK with 74,000 km of high, medium and low pressure pipes supplying gas to 5.9 million consumers.
• DNV is a leading provider of material testing services and operates lab and full-scale gas network test facilities as well as hydraulic modelling software and gas distribution domain expertise.

All UK gas distribution and transmission network designers will use this innovation; experience and data from all UK gas network operators and obtain industry "buy-in" of the outcomes is part of the Alpha scope.

Innovation Justification

The problem to be solved is allowing network gas designers the freedom to safely maximise the flow of low-carbon heating gas in existing networks while minimising the need to increase pipe sizes throughout the energy transition.

The project is innovative because there has been no suitably rigorous physical testing to quantify the entrainment of typical debris present in UK Gas Networks by hydrogen-natural gas blends and 100% hydrogen and to establish design limits so that asset integrity, and environmental, risk is not increased.

The energy sector is challenged to deliver the transition to low and zero carbon heating while keeping costs to consumers to a minimum and maintaining reliability and safety. This project will provide some of the assurance that designers need to deliver these goals.

Our solution will ultimately deliver a valid trusted design velocity limit, for low, and zero, carbon heating gas, that designers can rely on in ensuring the gas distribution networks remain safe and reliable throughout the transition.

Literature surveys reveal that the work on this subject to date has been theoretical using digital hydraulic models, (ENA are currently running a hydraulic modelling project related to this topic - see details here: https://smarter.energynetworks.org/projects/nia_ngn_302/) which can be used as additional input to this project. We have been unable to find any practical physical test work done that can be relied on to establish safe design gas velocity limits using representative conditions, materials and debris in the UK gas distribution networks.

While hydraulic modelling offers some indication of the entrainment capacity and effects of low carbon heating gas, a suitably rigorous physical testing campaign is required to fully evaluate actual behaviours and effects in representative conditions and existing network components.

If the project is not done, UK gas network operators are at risk of:

1. Unnecessary spending on increasing network pipe sizes to maintain the current design velocity limits while delivering increased unit rates of low and zero-carbon heating gas.
2. Increased damage to pipework and components from erosion and vibration or increased environmental impact from noise if the design velocity limits are set too high.

UK gas network operators are required to maintain safe and reliable networks and deliver gas uninterrupted to consumers through-out the energy transition.

Increasing the diameter of pipe in the network costs approximately £250,000.00/kilometre (< 8 inch pipe only); with 290,000 km of gas transmission and distribution pipe in the UK, there is an obvious benefit in minimising any pipe replacement needed to meet gas velocity design limits while distributing increased gas volumes throughout the energy transition.

The UK gas distribution industry has well over 100 years' experience in the safe design of networks and has developed and proven design standards based on this experience. The energy transition, with the change to low and zero-carbon heating gas, presents the network designers with heating gases of which there is no industry experience or practical knowledge of the impact of these gases on:

• Entraining typical debris present in the networks (much of it as a legacy from town gas supply)
• Quantifying the potential for erosion damage and possible interaction with other damage mechanisms (hydrogen embrittlement) to be considered in establishing velocity limits.
• The effects of noise or vibration caused by turbulent low, and zero, carbon gas flow on existing network components
• The velocity and flow regimes in which entrained debris starts to cause unacceptable damage to gas network components.

This project will enable new design standards to be accepted by the industry and become new "business as usual".

Benefits

The project, once the Beta phase is delivered, will deliver net benefits to consumers by:

1. Giving network maximum flexibility in re-purposing the networks to zero-carbon heating
2. Minimising network reinforcement costs
3. Ensure that the design velocity limits for hydrogen and hydrogen-natural gas blends are safe and there is no reduction in integrity standards or increased risk.

A simple financial business case (initially focussing on the on the low-pressure network only) is attached. This shows that with the current broad assumptions about the level of network reinforcement (to increase the pipe diameter and reduce velocity) could cost the consumer between £550 million and £2.75 billion throughout the energy transition if the current velocity limits are maintained. Further costs can be anticipated in reinforcing higher pressure tiers and pressure reducing facilities.

A detailed business case will be developed in the Alpha phase. To do this, a representative network model(s) will be run against likely hydrogen and hydrogen-natural gas blend demand scenarios to quantify the length of network subject to reinforcement. The reduced reinforcement length delivered by incremental gas design velocity increase up to a safe limit can then be quantified.

The business case relies on minimising the cost of replacing gas distribution pipes to maintain velocity design limits under peak flow conditions. Finding this safe limit will offer designers maximum flexibility in repurposing the networks and minimise network reinforcement (pipe size increase) costs required to keep any increased gas flow rates within safe velocity limits.

The Alpha phase will:

1. Gather data and experience from industry including:

• All UK Gas distribution Network Operators.
• The gas National Transmission System (NTS) operator (National Grid Gas).
• The industry body IGEM.
• Relevant regulatory and advisory bodies such as the Network Safety & Impacts Board.

2. Cost and scope a test campaign that is accepted by the industry as valid for the Beta results to be used to amend engineering practice and standards.

3. Build a detailed business case that clearly quantifies the length of UK gas pipe that would be subject to reinforcement at the current limits and demonstrate the savings in reinforcement costs delivered by new, safe, design velocity limits.

The benefits of the project are in several areas

1. To consumers:

• Safe and resilient supply of heating gas is maintained throughout the energy transition.
• The costs of re-purposing the networks will be kept at a minimum.2. Economic benefits:
• Supply of heating gas to UK consumers will be maintained throughout the transition to zero-carbon heating by making maximum use of the existing gas network assets and components.

3. Impact on Government priorities:

• Government can be assured that the conversion and transition priorities set can be suitably structured, and the industry can be assured that the priorities can be met within suitable constraints.

4. Environmental impacts, either positive or negative:

• The environmental impact and risk profile of gas distribution operations in the UK will be improved by better understanding of the implications of re-purposing existing networks.

5. Expected regional or wider energy supply resilience benefits:

• Spreading the knowledge of the outcomes to the industry as "business-as-usual" with incorporation into design standards.
• Maintained or improved integrity risk.
• Knowledge and validation of digital models used in developing network strategy and design.

6. Impacts on consumers of the whole energy system, both individuals and collectively, including those with any vulnerabilities or experiencing fuel poverty

• The resilience of the whole system will be maintained and improved through-out the energy transition.