Hydrogen gas is increasingly discussed as the “fuel for the future”. The reasoning behind this assertion is that when combusted to produce energy, Hydrogen does not release any greenhouse gasses (GHGs) or harmful polluting emissions. Instead the hydrogen (H2) reacts with oxygen (O2) to form only water (H2O).
Despite being conventionally discussed as a futuristic alternative to current technology, using hydrogen for energy has a long history. It has previously been used as a fuel for industry, for domestic demand and as rocket fuel.
Current interest in hydrogen reflects many of the challenges of today, including the need to decarbonise energy, improve air quality and increase energy security.
Although being the most abundant element in the universe, hydrogen is rarely found in its pure, useable form. Instead it must be produced using energy from another source, making it an energy carrier. However, once produced, it can be stored, giving it an advantage over other energy carriers such as electricity.
Hydrogen can be formed from multiple sources such as water or hydrocarbons and in a variety of ways, adding to energy security.
Steam reforming: the vast majority of hydrogen produced today is through steam reforming. The fossil fuel source (usually methane) mixes with steam at high temperature and pressure and, using a nickel catalyst, it forms hydrogen and carbon dioxide. This process is currently two to three times more expensive than fossil fuels. [i]
Partial oxidation: is similar to steam reforming but also requires oxygen. Partial oxidation can be used for other hydrocarbons including oil and coal. Although the efficiency is lower than with steam reforming the use of this process will depend on what natural reserves a country has – e.g. coal.
Water electrolysis: requires large amounts of electricity to split water molecules. However it may be a way of using surplus renewable power rather than overload the grid. Photoelectrolysis is a new technology that achieves the same results but using a solar cell rather than electricity.
Biological production: many species such as algae and bacteria produce hydrogen naturally through photosynthesis and fermentation but this is yet to become a commercial process.
Hydrogen can be used to provide either heat or electricity through either combustion or a fuel cell. Heat is the largest source of energy demand in the UK and therefore an essential element of energy policy for decarbonisation, security and affordability. Currently 80% of homes run on natural gas but Hydrogen is one alternative fuel that could help meet policy targets. The Hydrogen option is being explored in Leeds where a report[ii] showed the potential for converting the gas grid to hydrogen allowing residents to cook and heat with the gas. If this project successfully progresses it will be an example for other cities to follow. Due to the potential, the Committee on Climate Change has mentioned hydrogen as one of the main options for future heat.
Hydrogen fuel cells are already commercially used in transport for cars and buses. The cells combine hydrogen and oxygen from the air to produce electricity and water as the only bi product. As well as not producing any GHGs or harmful air pollutants, the cells are also silent, as they have no moving parts. Hydrogen can also be burned directly in an internal combustion engine after modification. A number of manufacturers such as MBW have demonstrated the potential of these engines and conversion demonstrations of existing HGVs are also increasing. Due to the great opportunities of Hydrogen transport the Government launched in March 2017, £23 million to boost hydrogen vehicles.
Hydrogen can be stored as compressed gas at pressures of around 200 bar, as liquid hydrogen at very low temperatures of -253°C or as chemicals when certain metal alloys incorporate and store hydrogen in their chemical structure to be released when heated.
Hydrogen is one of many storage options open to dealing with intermittent renewable sources and balancing the grid. However many of these storage options are very energy intense so any use of the hydrogen would have to take the storage energy costs into account. Current efficiency is 30 to 40% but could increase up to 50% if more efficient technologies are developed.[iii]
Fuel cells can also be used for electricity outside of transportation. For example they can power domestic dwellings and businesses, particularly when these are off grid.
There are numerous opportunities that a new hydrogen economy could deliver including:
- Decarbonisation: reducing GHG emissions for transport and heating
- Air pollution: not contributing to transport emissions currently linked to 40,000 deaths annually.[iv]
- Energy security: reduce dependence on imports, as there are many sources of hydrogen for domestic production. This should also reduce variability of fuel bills.
- British industry: a hydrogen economy could rejuvenate industry with production plants in previous industrial areas where Carbon Capture and Storage (CCS) has the most potential (see POSTnote335) and additional industrial options in transport infrastructure.
But a new hydrogen economy would face many challenges including:
- Cost: the cost of hydrogen compared to fossil fuels or other low carbon options is very high. Especially considering the dramatic price reductions in technologies such as solar power.
- Safety: hydrogen is less flammable than other oil products but it does need to be transported and stored at high pressure or very low temperature which poses both a hazard and a technical challenge
- Technical: large infrastructure changes may be required for a hydrogen economy. Although much of the gas grid is made of plastic so can already transport hydrogen, the changes to vehicle fleets are significant as are the infrastructure requirements for production and storage.
- Environmental: limited knowledge of the hydrogen cycle means it is unclear what the result of releases of hydrogen to the atmosphere would mean. In addition, hydrogen production requires CCS to remove the CO2 emissions released in hydrogen production. Without CCS the environmental case for hydrogen diminishes. CCS has been demonstrated around the world but currently lacks political support in the UK.
The hydrogen transition will likely be one part of a wider low-carbon transition instead of a silver bullet. Already underway within the transport sector, expansions into gas grids and storage could dramatically increase decarbonisation and security. To achieve further developments in the hydrogen economy, cost reductions, demonstration projects and infrastructure development are needed before uptake can begin on the mass market.[v] The Government have already highlighted Hydrogen as a Government priority in the 2017 UK green paper ‘Building our Industrial Strategy. Continuing this ambition to the Industrial Strategy and wider policy is key, and could help achieve the coordinated research and development approach needed.
[i] UNEP, The Hydrogen Economy, a non-technical review, 2006. Available at: http://www.globalbioenergy.org/uploads/media/0601_UNEP_-_The_hydrogen_economy.pdf
[ii] Leeds City Gate H21 report. Available at: http://www.northerngasnetworks.co.uk/wp-content/uploads/2016/07/H21-Report-Interactive-PDF-July-2016.pdf
[iii] Energy Storage Association, Hydrogen Energy Storage. Available at: http://energystorage.org/energy-storage/technologies/hydrogen-energy-storage
[iv] Royal College of Physicians, Every Breath we take: the lifelong impact of air pollution, February 2016. Available at: https://www.rcplondon.ac.uk/projects/outputs/every-breath-we-take-lifelong-impact-air-pollution
[v] Sperling, D., & Cannon, J. S. (2004). The hydrogen energy transition: cutting carbon from transportation. Academic Press.