Over the last few decades, clean and renewable energy technologies have come a long way. The UK recently experienced its first full day of power with no contribution from coal since the industrial revolution, while globally, 26% of all power is on track to be generated by renewable sources by 2020.
However, while low-emission electricity has improved in leaps and bounds, heating systems have lagged behind. Heating and cooling of buildings and in industrial activities account for almost half of all energy demand in the EU, and yet the decarbonisation of the heating system has seen little progress.
This is finally changing as cleaner heating continues to be discussed and researched. One popular suggested solution is switching the heating network from natural gas to hydrogen. This was the key topic of conversation at a recent event run by DNV GL. The seminar, entitled ‘Developing and Operating a Safe Hydrogen Network’, brought together around 100 professionals from gas distribution networks and other interested parties to discuss hydrogen’s potential.
“The purpose of the event and what we were doing was looking at hydrogen as the fuel gas, and the risks and consequences that it presents,” says DNV GL head of department at Spadeadam Testing and Research, Gary Tomlin.
But what are the risks and benefits?
A cleaner heating system
The main reason hydrogen is being considered as an alternative fuel is its green credentials. When burned, hydrogen produces no CO2 emissions, creating just water vapour and heat. Hydrogen also contains a large amount of energy, making it relatively efficient, as in 1kg of hydrogen, there is the same amount of energy as you would find in 2.8kg of gasoline.
The majority of domestic heating systems run off natural gas – in the UK, 90% of all homes use it –while natural gas produces the least emissions of any fossil fuel, it still contributes to global warming. For every million British thermal units (Btu) of energy, natural gas emits 117lbs of CO2, while coal (anthracite) is the highest emitter, producing 228.6lbs. In the UK, 30% of CO2 emissions come from domestic heating and cooking. If the country’s entire gas system was converted from natural gas to hydrogen, it would cut heat emissions by a minimum of 73%, going a long way to meeting the UK’s decarbonisation targets.
Hydrogen’s green qualities are just one of the pros of using it as a fuel. In eastern Germany, the Hydrogen Power Storage and Solutions project (HYPOS) has begun a series of research initiatives to investigate the potential use of hydrogen as a power source. HYPOS emphasised the easy ability to store hydrogen as a major benefit. As a gas it can be contained in a number of ways: compressed, stored in salt caverns, liquefied or stored as ammonia.
“[Hydrogen is] the only energy carrier with the possibility of long-term storage,” says HYPOS project manager Alexander Spieß, “So we always have in mind that we need to meet Germany’s goals of gaining over 80% of our energy from renewable sources. But if you look at the new results of the climate change commitment, it will, more or less, have to be closer to 100%. For this, we will have to use long-term storage options.”
A further benefit is the potential to use current infrastructure. Electrification of the heating system has been suggested by many as a possible way to decarbonise; however, this would involve substantial infrastructural change. Studies are currently being undertaken by a number of groups, including the Northern Gas Network (NGN) in the UK, as to whether natural gas pipes are the right size and capacity to be simply converted to hydrogen. So far, it seems likely that it will be possible in the UK to use current gas infrastructure to distribute hydrogen, vastly easing the infrastructural challenges and costs of decarbonising the network.
“One of the big possibilities is to use the existing infrastructure, the gas infrastructure instead of building a new one,” says Spieß, adding that, “There are studies that have looked at that and say that the infrastructure cost would be cheaper than implementing an electric grid, or extending the electric grid everywhere.”
Too hot to handle
Switching heating systems would be a colossal project even with the use of existing infrastructure, and it would bring with it a number of challenges, for instance, making it safe to use hydrogen in a domestic setting was expressly discussed at DNV GL’s seminar, and an issue which must be guaranteed if it is to become more widely used.
Hydrogen is generally considered hazardous due to its high flammability, as it will burn in air in a concentration of anywhere between 4% and 75%. But, “hydrogen has a very small molecule size so if there is a release of hydrogen it’s quite possible that it will be less likely to become flammable than natural gas,” says Tomlin, explaining that, “Conversely the flammable range is much wider, so that's something that needs to be considered.
“You've got this balance between it's probably less likely to become flammable, but if it does become flammable, it's more likely to be ignited and the consequences could be pretty serious.” This balance of risk must be taken into account, with alterations made to the gas network to ensure a hydrogen supply is as safe as possible.
One of the more practical concerns is that, while hydrogen emits zero emissions at the point of use, the creation of hydrogen itself produces carbon. “What you have to do is produce the hydrogen in such a way that you're not moving the problem from individual homes producing CO2 to producing lots of CO2 at source, so you have the challenge of capturing that CO2 at source and sequestering it, or actually producing hydrogen without producing CO2,” says Tomlin.
Currently, around 90% of the world’s hydrogen is produced in steam methane reformers. This combines natural gas with high temperature steam, which separates the hydrogen and the carbon, the latter of which is then sequestered, captured and stored. This must be done effectively so that carbon is not leaked and released into the atmosphere; without this, it is not a clean fuel.
Taking hydrogen to the next level
The NGN is currently pioneering a project called H21, which would see the city of Leeds’s gas network entirely converted to hydrogen. This would be a massive step forwards for hydrogen technology, and the report H21 has released is already drawing international attention. Potential gas conversion would cost an estimated £2bn and would be financed through regulatory business plans, an economic system previously used to switch the UK gas network from town gas to natural gas in the late 1960s. NGN hopes that if the project is successful in Leeds, it can be rolled out across the rest of the UK and beyond.
In addition to trial projects, a number of technological advancements are making hydrogen fuel increasingly appealing worldwide. For instance, Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) has developed a thin metal membrane that would allow hydrogen to be easily transported as ammonia, then separated at the point of use. Currently, transporting hydrogen is complex and relatively expensive; CSIRO’s membrane could significantly ease these costs as ammonia is already being traded and transported globally. The project has received $1.7m from the Science and Industry Endowment Fund to continue development as it moves into the final stages.
While hydrogen is the most abundant element on earth, it can be incredibly energy-intensive to obtain. Hydrogen has clear environmental advantages over pure methane or other natural gases from which it can be isolated, but to do so still emits carbon. Research into splitting water into hydrogen and oxygen is ongoing, with hopes that a catalyst can be found that would allow hydrogen fuel to be cleanly produced through electrolysis, removing the reliance on hydrocarbons.
The potential of using hydrogen as a fuel is only just beginning to be realised. As a greater focus falls on decarbonisation of the gas distribution network in particular, it seems certain that hydrogen will have an important part to play.