Increasing reliance on intermittent renewable electricity sources makes balancing supply to demand difficult. This will become increasingly challenging as the proportion of renewables increases into the future. One solution is the large-scale geological storage of energy in the form of hydrogen. Electricity generation from stored hydrogen can balance summer to winter seasonal energy demands, with the added potential for hydrogen to repurpose the gas grid and replace methane for heating. This is significant as the heating of buildings is currently the largest source of carbon emissions in the UK, exceeding those for electricity generation.

However, the underground storage of hydrogen in porous rocks has not yet been demonstrated commercially. This project hence uses state-of-the-art laboratory experiments to address questions which require insight before commercial trials occur, focusing on the geological (underground) storage of hydrogen in geographically-widespread porous rocks. Storage of hydrogen underground is well established in caverns of halite (salt). However, in the UK this type of geology is restricted only to Teesside, Northern Ireland and Cheshire, with long and costly transport to consumers elsewhere. Methane gas in the UK is already stored underground onshore in porous reservoirs and offshore in re-purposed natural gas fields, and that provides insight to operational designs and challenges. The project partners have expertise in hydrocarbon reservoirs, geological assessment of CO2 storage, and compressed air energy storage using porous rocks.

WP1 Hydrogen reactivity examines whether the hydrogen could react chemically with the rocks into which it is injected or the overlying seal rock, which could prevent the gas from being recovered and used. Controlled laboratory experiments with hydrogen injection into porous rock at subsurface temperatures and pressures will identify and quantify likely chemical reactions.

WP2 Petrophysics assesses how effectively hydrogen migrates through water-filled porous media, and how much of the injected hydrogen can actually be recovered from the rock. Because the rock is made of solid grains with a network of pore spaces between, capillary forces naturally trap some of the hydrogen. How much is trapped affects the commercial viability of the whole process. Laboratory-based experimentation will inject hydrogen into rock samples to help answer this question. CT scanning provides live 3D images of the hydrogen retention in the rock pores.

WP3 Flow simulation uses digital computer models of fluid flow adapted from hydrocarbon simulation to scale up from laboratory experiments to an underground storage site. Hydrogen reactive flow properties from WP1 and WP2 will be used to calibrate numerical fluid flow software codes. These models can calculate how efficiently the hydrogen can be injected, and predict how much of the hydrogen can be recovered during operation. Volumes and types of cushion gas to be left in the reservoir as a precaution to maintain operation pressure and minimise water encroachment during withdrawal periods will also be assessed.

WP4 Public perception considers how societal familiarity with hydrogen may be much lower compared to natural gas. A key objective of the project is to ascertain at an early stage how citizens and key opinion shapers feel about hydrogen storage underground, and to engage civil society with the research and development process to ensure that hydrogen storage develops in a way that is both technically feasible and socially acceptable.

WP5 Project management, industry advisory board, communication and outreach are essential in this type of project. Digital updates will be posted on a dedicated project website and social media channels, with presentations made at academic and industry events. Public project reports and, eventually, peer reviewed publications will provide an open access record of project progress.

Potential Impact:
The HyStorPor project will have significant impact during and after its completion as it lays the fundamental scientific foundations for commercial hydrogen storage in the subsurface. Large-scale geological storage of hydrogen offers the potential to balance inter-seasonal discrepancies between demand and supply; and decouple energy generation from energy demand and decarbonise the energy system. If burned for heating, hydrogen could reduce the carbon emissions of the largest source of carbon emissions in the UK. Hydrogen generated from renewable electricity has the potential to accelerate the UK towards a low-carbon energy system and provide a substantial improvement in energy security. The project will increase understanding of the whole hydrogen system, from fundamental processes to social acceptability. The outputs and ongoing dialogue will be coordinated through a new multidisciplinary research centre and information hub on hydrogen usage and storage, based at the University of Edinburgh.

The project outcomes will enable policy makers and commercial developers to appreciate the likelihood and nature of the geological storage of hydrogen by increasing the UK-relevant evidence base. The improved understanding of the processes, capacity and integrity of storage sites will assist regulators in managing the environmental risks arising from the geological storage of hydrogen, delivering effective industry regulation and environmental protection. A backdrop of ethical and cultural factors informs societal perception of future energy technologies, such as hydrogen storage, and as such, it is vital to avoid assumptions about public concern and to engage early on to understand what shapes perception of alternative energy options. Iterative dialogue and accessible information presented in a straightforward way from the beginning of the project will inform industry and the public.

The project will engage opinion-shaping citizens in dialogue on how hydrogen storage may affect daily living, both in terms of immediate effect of technologies on the built environment, and also its fit into a future low-carbon society for the beginning of the project. The outcome of this will be a "socially acceptable" consultation processes and proposed regulations for assessment and integration of societal concerns for future hydrogen storage deployment, in order to ensure it is governed in a way that respects and is responsive to societal concern. Independent of industry and regulators, we will feed into the public debate on what needs to be done to achieve "safe and responsible" geological hydrogen storage.

This proposal will assist the nascent hydrogen energy industry by providing developers with scientific understanding of commercial hydrogen storage in the subsurface that will enable them to both understand the science associated with their activities and to communicate the benefits to the regulators and to the public. We expect that early industry benefiters to be those involved with currently proposed hydrogen schemes, such as the H21 Leeds City Gate project and the H100 project, and collaboration with our advisory board will ensure dissemination directly to industry, enabling our early-stage research a pathway to market within the UK.

The scientific outputs of the proposal will benefit the international academic community by furthering scientific understanding of geological hydrogen storage in the areas of reactivity and multiphase flow based on experimental benchmarking and integrated modelling. This multi-disciplinary project will be the first of its kind and the results from HyStorPor will be integrated into Masters-level teaching, ensuring that the next generation of energy and industrial professionals have a sound understanding of the viability and significance of geological hydrogen storage.

Outputs will be made available using metadata portals for data and by giving the datasets "doi" labels to facilitate referencing.