Connected for COP26: Replacing hydrocarbons with hydrogen?
This article was originally published as part of the Geological Society of London Blog.
Professor Mike Stephenson on behalf of the Geological Society.
Geoscience will be critical in the development of hydrogen as a major energy carrier. Hydrogen is already powering buses, trains and cars, but could be harnessed more widely in industry and domestic heating.
Hydrogen – a decarbonised fuel
The term ‘hydrogen economy’ was first coined by the chemist John Bockris, to describe the use of hydrogen as a fuel rather than the oil, gas and coal that form the present hydrocarbon economy. Hydrogen fuel could be used in vehicles and ships, power stations and energy storage feeding from off-peak excess electricity.
A large-scale change from a hydrocarbon to hydrogen economy requires radical change to infrastructure across the UK. The distribution of hydrogen energy infrastructure will be different to that of other energy sources, such as oil, gas and renewables.
There are three kinds of hydrogen energy system: brown, blue and green. A brown hydrogen system extracts hydrogen from fossil fuels such as coal. Blue hydrogen is where high temperature steam (700°C-1000°C) is used to produce hydrogen from a methane source. Green hydrogen is produced through electrolysis, which is powered by renewable energy sources, such as solar. Blue and green hydrogen systems are favoured in the UK. The blue hydrogen model is the most likely to catch on early for large-scale hydrogen deployment because it appears to be cheaper than electrolysis.
The need for underground storage
The drawback of blue hydrogen is that it produces CO2 as a by-product. Carbon dioxide generated by hydrogen production, must be stored or it will be released into the atmosphere. An understanding of geology is vital in order to managing this CO2, such as through geological storage.
All three types of hydrogen fuel systems require storage facilities, to manage fluctuations in consumer demand. In the same way that natural gas needs to be stored, hydrogen must be quickly and easily accessed, whilst remaining secure during storage.
Hydrogen is already stored in a small number of salt caverns in the UK and the USA; to support chemical plants and oil refineries. The extremely low permeability of salt limits any flow of gases and liquids in or out of these caverns. The largest single hydrogen store in the US holds over 100 gigawatt hours (energy equivalent) of hydrogen – this is enough to power one million homes for an hour.
Hydrogen projects in the UK
Plans for regional hydrogen networks are already underway. The H21 Leeds City Gate project aims to convert completely the existing natural gas network in the city to hydrogen. A batch of four steam methane reformers in nearby Teeside could produce the hydrogen needed, while the CO2 by-product could be captured and stored offshore under the North Sea. Since 1996, CO2 from Sleipner gas field in the North Sea has been injected 3km into the underlying rock, proven to be stored safely and securely by long term monitoring of the site.
Salt cavern hydrogen storage in the North East will be needed for ‘intra-day’ and ‘intra-seasonal’ swings in demand as heating is turned on and off by consumers. The availability of low-cost bulk hydrogen in a gas network could help introduce fuel cell hydrogen vehicles in the North East.
The Liverpool-Manchester Hydrogen Cluster is a similar project that aims to decarbonise domestic heating and even major industrial gas users in area. Including supplies to oil refining, glass manufacturing, food and drink and chemicals, pulp and paper sectors. Speculatively, the nearby Liverpool Bay hydrocarbon fields, could be repurposed to provide CO2 storage and these fields are likely to cease production around the time that a hydrogen cluster concept might be reaching maturity.
A hydrogen economy will need geoscientists
In January this year, 100 leading geoscientists gathered at the Geological Society’s Bryan Lovell Meeting to discuss the role of geoscience and the subsurface in delivering decarbonisation. A major focus of the meeting was discussion around the transition to a hydrogen economy and development of industrial-scale carbon capture and storage technologies. The meeting highlighted the importance of geoscience during this energy transition, including regulation that will be needed to manage the subsurface in new ways and investment in the research needed regarding the chemical and physical properties of potential storage sites such as better understanding of the fluid flow of rocks and different methods of CO2 disposal. Fluid flow in the subsurface – a priority research area raised at the Lovell meeting – relates to both hydrogen storage and CO2 storage. Furthermore, storing hydrogen in salt caverns relies on salt being co-located in the in the region of interest; urban or industrial centres are not always located so conveniently.
A key outcome of the Lovell meeting was to communicate the importance of geoscience research and skills in delivering decarbonisation targets but also to raise awareness of the role of geoscience and the subsurface to professionals in other technical sectors. Collaboration between mechanical and chemical engineers, energy systems specialists, and economists will be vital. The geoscience community must also rise to meet this challenge if we are to achieve widespread decarbonisation.
Read the rest of the blog series here.