Securing a Safe Future for Gas

Hydrogen: a way to provide safe, sustainable and clean energy to satisfy rising demand and meet carbon emission reduction targets?

RIGHT now, energy is a hot topic. Globally, energy demand is expected to increase by 35% before 2030. In the UK, the energy sector is rapidly changing as technologies across power, heat and transport evolve to address the need to reduce carbon emissions and conserve fossil fuels. It is clear that safe, clean and sustainable energy solutions need to be found if this continuing growth in demand and targets for cutting carbon emissions are to be met.

According to the CCC, the Committee on Climate Change (http://bit.ly/2BYsMMM), which undertakes an annual assessment of whether the UK is on course to meet its carbon budgets and reports this progress to parliament, “meeting future carbon budgets and the UK’s 2050 target to reduce emissions by at least 80% of 1990 levels will require reducing domestic emissions by at least 3% per year. This will require existing progress to be supplemented by more challenging measures”.

Natural gas has significantly lower emissions on combustion per unit of energy delivered than either coal or oil, but higher emissions than nuclear or most renewable energy sources. That said, the UK’s heat system is accountable for around one third of our carbon emissions. The obvious way to address this issue would be to de-carbonise our gas network by either partially or completely replacing natural gas with a cleaner, sustainable alternative.

Hydrogen: the fuel of the future?

HSE’s Centre for Energy Innovation is keeping pace with the UK’s changing energy sector. By bringing scientific expertise to discussions around the use of alternative fuels, it is both helping to prevent work-related death, injury and ill health and facilitating progress.

One viable solution is to replace natural gas with hydrogen. Today, hydrogen is produced by steam methane reforming of natural gas. In addition, hydrogen can be sustainably produced using any surplus electricity produced by renewable energy sources such as wind or solar farms. This excess electricity can be used to power electrolysers. The process of electrolysis separates water into its component hydrogen and oxygen. The hydrogen produced can then be injected directly into the natural gas system or alternatively stored in liquid or gas form for later use.

Meeting future carbon budgets and the UK’s 2050 target to reduce emissions by at least 80% of 1990 levels will require reducing domestic emissions by at least 3% per year. This will require existing progress to be supplemented by more challenging measures

Unlike methane and other fossil fuels, as hydrogen contains no carbon it can’t release carbon dioxide when it is burnt; it actually releases water as a by-product of burning. Consequently, the CCC believes that “hydrogen has the potential to make a significant contribution to future decarbonisation”, and scale trials using discrete private gas networks are already underway.

But, as with the introduction of any new technology, there are questions to be answered and challenges to be overcome before the widespread adoption of hydrogen as an alternative to natural gas can take place. The transition from natural gas to hydrogen on a national scale has implications for everyone in the energy supply and distribution chain, from technology innovators and appliance manufacturers to gas engineers and end consumers. It is vital that hydrogen’s properties and behaviours have been fully researched, tested and understood both by those who will work with and those who will use it. A scenario in which, for example, domestic gas appliances suddenly begin exploding due to their incompatibility with hydrogen use is clearly best avoided. One area that is a priority around the world involves the potential to move to hydrogen-powered vehicles and how associated safety challenges are addressed. Work is ongoing in relation to managing potential risks associated with the increased presence of hydrogen in transport applications and its safe transportation and storage, either as compressed gas or cryogenic liquid.

For the energy sector this will mean acquiring and transfering new knowledge and new ways of working, but this is not a situation without precedent.

In the 19th century, and for most of the 20^th, so-called “town gas” (a dangerously toxic gaseous mixture produced when bituminous coal is subjected to high temperatures in the absence of oxygen) was distributed for industrial and domestic use via the local gas network. The discovery of significant reserves of cleaner, safer natural gas in the North Sea in the mid-20th century meant that the manufacture of town gas was no longer necessary. However, because the properties of North Sea gas differed significantly from those of town gas, this led to the development of Great Britain’s national transmission system and the adaptation of other delivery systems and appliances for its use between 1967 and 1977.

This time around, exchanging one gas for another (in this case 100% hydrogen) would require the replacement of all existing gas appliances. Routine maintenance and upgrading of Britain’s regional gas network means that they are already likely to be capable of handling the transition from natural gas to hydrogen. Logistically, and from a climate-change perspective, the arguments generally seem to be in favour of turning to hydrogen as a suitable alternative to natural gas, but one key question must be answered before we can proceed.

How can we ensure that hydrogen is safe to use?

Identifying, understanding and managing all of the risks associated with using hydrogen as an alternative energy solution is absolutely fundamental to its successful adoption. Inevitably, industry operators are likely to want to work with hydrogen in as similar a way as possible to natural gas. Yet they need to know exactly what they are dealing with, what the differences are and whether the introduction of hydrogen brings any new hazards that must be addressed. Hydrogen is a small molecule, and extra effort is required to prevent hydrogen systems from leaking. Pipework deemed “leak tight” when pressure-tested with nitrogen will often be found to leak with hydrogen. Extra attention needs to be paid to welds, flanges, seals, and gaskets, etc in design and operation for hydrogen systems. When hydrogen forms an explosive mixture with air the energy needed to initiate a hydrogen/air explosion is small in comparison with other fuels such as methane, LPG or petrol. Even very small sparks, such as those produced by wearing certain types of clothing, are capable of igniting hydrogen/air mixtures.

Scientists at the Health and Safety Executive (HSE), Great Britain’s national regulator for workplace health and safety, have been conducting hydrogen research and experimentation for more than 15 years, as a result of their involvement with a  number of EU projects that investigated the use of hydrogen in fuel cells. Focussing on the safety aspects, HSE’s role was to undertake exploratory research on the behaviour of hydrogen. Pre-normative research led by HSE found, for example, that under certain conditions when released from high pressures hydrogen can self-ignite in the absence of any ignition source.