Project Summary
The national gas transmission system currently has the ability to pack additional gas into the lines (linepack) in order to provide flexibility and more efficiently manage supply and demand across the network. The amount of energy able to bestored by linepacking in the future may potentially decrease with the addition of blended or 100% hydrogen. This project will explore the feasibility of smaller, intermediate scale storage sites (purpose built geological storage solutions with minimal geographical constraints e.g. lined shafts, engineered rock caverns,underground silos) to supplement linepack capacity and provide system flexibility and network optimisation.
Innovation Justification
Core innovation aspects:
Demonstrating technical understanding and safe operability of hydrogen storage asset to be used for linepack supplementation
Geotechnical analysis and subsurface modelling of a lined rock shaft storage for hydrogen
Thermodynamic modelling of hydrogen gas cycling for lined rock shaft storage
P2G flexibility opportunity energy system modelling for a hydrogen storage asset, considering gas and electricity systems.
Energy network optimisation modelling considering N-1 constraints for technical constraints
Parametric digital design models for system optioneering across geological locations
Digitalised risk mitigation construction planning
H2FlexiStore developed by UK based Gravitricity, is developing lined rock shafts for storage of gaseous hydrogen. This is state of the art technology for hydrogen storage, with the potential to be deployed rapidly and at scale, depending on land and geological suitability, across our entire repurposed transmission system for hydrogen. The solution could provide up to 100tons of safe hydrogen storage per site.
This project aims to be a world first in demonstrating lined rock shaft storage of hydrogen for Linepack supplementation in a 100% hydrogen transmission network to improve system resilience and enable energy ecosystem optimisation opportunities across both electricity and gas networks.
Beyond incremental innovation
This project builds on existing research into intermediate geological storage options done by the University of Edinburgh and SGN in the Storage Upscale project (currently ongoing) with the aim to accelerate the development of a demonstrator for gaseous hydrogen stored in lined rock shafts.
This project will go beyond incremental innovation by developing digital design solutions to accelerate potential rollout, increasing the opportunity for emerging hydrogen hubs and electrolysers to connect to a transmission system, understanding cross-energy vector system optimisation opportunities and developing a pressure regulation strategy to better manage Linepack swing thanconventional methods.
Readiness levels
TRL - 5 -\> 7
IRL - 1 -\> 2
CRL - 1 -\> 3
Size and scale
Estimated size of demonstrator will contain 1-2 tons of hydrogen in a lined rockshaft at 30-80m deep. This will provide a good demonstration of how the technology could be used to bolster linepack.
Business-as-usual
Hydrogen projects can not be funded under BAU funding as hydrogen is not included in the RIIO-2 business plan.
Counterfactuals
Large scale seasonal hydrogen scenario - seasonal scale hydrogen storage facility to hydrogen connected to 'Project Union' phase complementing existing compressor stations capability
Increased hydrogen network length for storage
Gravitricity supplying localised energy storage
Impacts and Benefits
Pre-Innovation Baseline
Compressors are critical assets on the NTS, providing pressures and flows to meet demand for gas and provide flexibility on the network. 64 of 72 compressor units are driven by gas turbines, Compressor stations can be used to manage linepacking (more molecules packed in same volume) capability, acting as network storage for gas system resilience based on supply/demand trends.
100% gaseous hydrogen transmission is a potential solution which can be utilised as a fuel gas in most of the gas turbines to reduce emissions, however, linepacking capability could decrease significantly (~74%) due to the lower volumetric energy density on hydrogen. Therefore, storage and additional pressure regulation strategies may be required for 100% hydrogen.
One commercial B-Linepack+ system, if demonstrated, could be the equivalent to the linepack capability in 14km of 36" diameter NTS pipeline. Extrapolating further, if rolled out along Project Union (~2000km), the system may need \>100 units to provide a pressure regulation strategy and flexible storage asset for system resilience and security of supply.
Forecast Benefits
The discovery phase will develop the business case and the cost benefit analysisfor this project. The benefits that we propose to track are as follows:
Financial - HyNTS linepack supplementation (-/+) & commercial storage potential
Understanding the value of linepacking zones with a hydrogen transmission system and need for pressure regulation strategies with good distribution of injection points across the repurposed transmission system. Additionally, commercial storage value could be preliminary reviewed either being connected to the electricity or gas systems. A CBA will be developed considering counterfactual scenarios.
Environmental - System Emissions
The opportunity to utilise existing pipelines for renewable energy storage through hydrogen is invaluable in supporting the 2050 Net Zero Target. Linepack increases the volume of storage that in turn reduces our dependency on fossil fuels. Whilst this option has some environmental impact in its construction, the long term environmental impact of deploying below ground storage is beneficial over the use of solid/battery storage or the deployment of above ground solutions. Emissions from underground storage are greatly decreased in comparison to above ground options.
Benefit Synergies
A broader understanding of the wider system benefits will be achieved through this project and demonstration of the H2flexiStore technology.
Impacts and benefits
Financial benefits
Network upgrade and connection costs to geographically constrained assets could be in the order of £7,680,000 per salt cavern with new build pipeline costs at £1,200,000 per km and a minimum assumed connection distance of 6.4km, based on a connection to a natural gas storage site in salt caverns near Cheshire. This would be significantly reduced per lined rock shaft with a maximum connection distance <=0.5km per shaft. Significant upfront and ongoing costs are associated with COMAH certification to store \\>5t compressed hydrogen. These costs will be further explored as the project progresses but are in the order of £800k initially followed by an additional £150k/year for ongoing interventions per site. Considering east coast hydrogen only, if each site required operational hydrogen storage that would be 13 sites requiring certification with an upfront cost of £10,400,000 and ongoing costs of £1,950,000 per annum. Regarding permitting, discussions with HSE on if COMAH tiers apply the same for subsurface gaseous hydrogen storage is to be determined in Alpha phase, if this was deemed safe it would result in significant financial benefits. The number of required potential COMAH sites will be determined in Alpha via Power2Gas modelling of the GB system. Due to high variability of gas demand in the integrated electricity and gas test system, OPEX system costs savings of implementing lined rock shafts with higher flow rates of between 5-20%. With hydrogen compression fuel and non-fuel OPEX per annum for a full hydrogen network (7600km) assumed to be £338M (Source: NIA Linepack opportunities), this would be a minimum saving of £16,900,000 per annum to operate a full hydrogen network implementing distributed storage across the network and a minimum saving of £5,000,000 per annum for Project Union (2000km). This will be explored more with modelling of the actual gas transmission system in Alpha to understand the effect of increasing withdrawal/injection flow rates in more detail.
Environmental Benefits
"Linepack+" storage is seen as an enabler to East Coast Hydrogen development which has expected CO2 avoided emissions savings savings per annum of 12Mton. This is with an estimated need for hydrogen storage of 10.7TWh by 2050 detailed in the East Coast Hydrogen delivery plan, this figure does not include the "Linepack+" flexibility capacity required determined in Discovery, which we estimate to be in the order of 4TWh for Project Union. Therefore, potential of further avoided emissions may be feasible.
Revenues
Gasunie implements the Linepack Flexibility Service (LFS) to incentivise end-of-day balancing amongst network users by using the flexibility of the network to settle the networks user’s imbalances at a 0.4% tariff. If the System Balancing Signal (SBS) position is in the dark green zone at the end of the gas day, Gasunie settle the network users’ gas shortage or surplus using the network’s linepack. The use of this is subject to a tariff of 0.4% of the neutral gas price, which is the volume weighted average for all trades executed on the gas exchange during that gas day and the previous two gas days. For example, if a network user is 2 MWh short i.e. has withdrawn 2MWh of gas more than it has injected into the network, it will cost the network user 2 MWh x 0.4% x neutral gas price in €/MWh. A similar service could be implemented utilising capacity of the lined rock shaft storage system.
Based on feedback given on our unsuccessful alpha application around value for money we will look to pursue the project via alternative private/commercial investment routes by creating a new consortium to develop a project utilising existing relationships built in discovery and via previous SIF round 1 funded work such as HyNTS Compression and HyNTS Deblending at the FutureGrid facility in Spadeadam.
It was deemed the technologies LCOS to not be as competitive as alternative subsurface hydrogen storage options such as salt caverns and depleted hydrocarbon fields for long duration hydrogen storage. However, while this is accurate, the value of the project comes with the lower development times of lined rock shafts (2-3years) which we anticipate is worth paying a premium for in comparison to capture the value in the nascent hydrogen market. Operating at intermediate scale (3.3GWh per shaft), the lined rock shaft technology offers superior value for money when compared to alternative geographically flexible storage solutions such as metal hydrides, compressed above ground vessels and dedicated pipeline storage due to the lower material CAPEX and BoP requirement. Hence, why the discovery project partners see it worthwhile exploring via alternative funding options to SIF to develop a technical demonstrator.
