Given that the supply of many renewables – e.g. solar and wind – is intermittent, there is still the need for alternative generation methods to help fill the gaps as the network evolves.
Currently, gas turbines are the most efficient option for the network to meet any shortfalls in grid demand. However, the use of these is in direct contrast to the goals of Net Zero.
Hydrogen has long been seen as a potential solution to this problem, and its wide range of applications mean that it holds the possibility of meeting a number of needs.
We will look to explore some of this in further detail, and hopefully answer a few of the common questions surrounding the use of hydrogen.
How is Hydrogen produced?
Steam Methane Reforming (SMR) is the most common method of hydrogen production. It involves reacting methane (natural gas) with high-temperature steam to produce hydrogen and carbon monoxide. The resulting mixture is then further processed in order to separate the hydrogen.
Unfortunately, whilst the resulting hydrogen can be used to produce energy with low or zero carbon emissions, the SMR process itself still emits a substantial amount of carbon dioxide.
Alternatively, hydrogen can be produced through Electrolysis, a process in which electricity is used to split water into hydrogen and oxygen. When carried out using renewable electricity, this results in zero carbon emissions.
The downside to electrolysis is that the process is only 40% efficient. Given that, the question becomes whether it is practical to use renewable energy to create relatively little hydrogen, if that hydrogen will only be cycled back and used to generate zero-carbon energy itself?
What role does Hydrogen play in electricity production?
Whilst the production methods of hydrogen mean it is largely unsuitable as a primary method of electricity generation, it can still play an extremely useful role in the energy fuel mix, and in balancing grid demand.
Currently, battery storage can only be used on a short-term basis, whereas hydrogen can function as a long-term storage option.
When produced by electrolysis, hydrogen offers the potential for zero-carbon energy to be stored in large volumes for extended periods of time. When there is the need for the network to produce additional electricity at times of high demand, it can then be released for use in a hydrogen-powered power station. Hydrogen also has the added bonus of being transportable, which allows for the gas to be produced in one location, and then taken to local grids where renewables may be more scarce.
Longer-term chemical storage aligns well with the more seasonal renewable generation methods – excess solar energy (which is typically generated during summer) can be stored for months before being released at a later date, when the amount of available solar energy may be insufficient to meet demand.
Hydrogen-fired power stations might also be seen as a preferred lower-carbon alternative to traditional natural gas power stations, even in situations where the former uses “blue” hydrogen (that which is manufactured using the SMR process) due to carbon-capture and storage methods.
Capturing carbon at the pre-combustion stage i.e. when it is created during the intense SMR process, as opposed to being produced later on when the fuel is being burned, is posited as being easier and therefore more cost-effective. This could make hydrogen potentially more attractive as a production source for generators (who will have their own emissions obligations to adhere to) especially if existing gas-fired power stations can be converted to make use of hydrogen.
Can Hydrogen replace Natural Gas?
During the transition period, heavy industry is likely to retain a high appetite for gas consumption. Given that burning hydrogen produces zero emissions, what is limiting its adoption as a like-for-like replacement for natural gas?
In order to be a feasible substitute for natural gas, hydrogen would need to be produced efficiently and in high quantities. As outlined, the SMR production process carries a substantial carbon impact of its own, which mitigates some of the benefits of its end product.
And although hydrogen produces more energy (on a pound-for-pound basis) than natural gas, because it is much lighter and less dense than natural gas, the need to increase the pressure or volume of hydrogen used in the heating process can offset the energy value that it offers.
Additionally, hydrogen’s highly flammable nature makes the combustion process more difficult to control, which in turn increases some of the logistical and safety challenges.
Various trials have taken place across the UK and Europe, using gas blends of between 30%-100% hydrogen (in the case of the latter, the hydrogen is typically generated using electrolysis from local renewable sources), though its viability in the fuel mix as a large-scale alternative to natural gas remains subject to further review.
How is Hydrogen used in Transport?
Hydrogen can be consumed by vehicles through the use of fuel cells. The hydrogen gas is stored in a high pressure tank and fed into the fuel cells, where a chemical reaction in the presence of a catalyst creates an electrical current which powers the vehicle.
Since the only byproduct of the hydrogen fuel cell reaction is water vapor, hydrogen vehicles produce zero exhaust emissions, making them an environmentally friendly alternative to traditional internal combustion engine vehicles.
The drawbacks remain the same as in other applications – namely that the production of the hydrogen may be inefficient or involve notable carbon emissions – though the benefits mean that in certain cases the use of hydrogen vehicles is advantageous. For example, its higher energy density makes hydrogen more suitable for many larger heavy-duty vehicles, whereas traditional lithium-batteries are more favourable for smaller-scale use.
What is the future of Hydrogen?
It has been demonstrated that hydrogen has much to offer in the transition to Net-Zero, though its future in the energy industry is likely linked to the pace and growth of technology.
As renewable energy options continue to advance and reduce in cost, the level to which hydrogen technology is embraced will be dictated by its own improvements in scale and efficiency.
