Whilst this is a challenging target there is a lot that could be done. This blog post explores one possible option. Energy generated by renewables in the UK is increasing all the time, however they are not consistent throughout the day and the year. To combat this, a method is needed to store excess renewable energy for times when little is produced, therefore helping to stabilise their contribution. This is where hydrogen comes into it all.
Here are two ways to produce hydrogen: either via steam reforming or via electrolysis.
Put in simple terms, during the steam reforming a molecule of methane reacts with water, generating hydrogen and carbon dioxide. Hydrogen can then be stored and CO2 is captured and then stored in the deep waters of the sea.
In a nutshell, we’re trying to replace natural gas (methane) with hydrogen…which in turn requires methane to be produced. It seems a paradox, but the advantage is that there is no combustion throughout the process, and the CO2 is captured, instead of being released in to the atmosphere.
If we started the process from water instead of from natural gas, the molecule could be split into its basic components, hydrogen and oxygen, via electrolysis in the presence of a direct current. This is a much cleaner version, as carbon is not involved, but it’s a less efficient process.
Hydrogen can be stored and then combined again with oxygen from atmosphere when the energy is required, producing water as a product. This process occurs in devices called “fuel cells”, which contain an electrolytic element (the cations are usually sodium or lithium, and the anions are often sulfates) and so generates electricity.
First of all, hydrogen is a similar gas to methane and so can be routed almost straight away through the existing gas network – ten cities of northern England are in fact already planning for this with the ‘H21 Leeds Citygate’ project.
Among the advantages for its use, there is certainly the absence of pollutants such NOx and SOx, as there is no combustion occurring in this process, without affecting safety, which can be reasonably managed.
It can be stored for long periods of time, and therefore could also replace diesel generators as backup power.
However, on the downsides, producing hydrogen requires more energy than it can release, so its use would only really make sense if excess energy from renewables was used for the production.
As with many technologies, the cost is currently quite high, but it is expected that it will drop considerably in the next five years, as the demand increases to meet the “net zero carbon” target.
There are other barriers such as installers not being prepared to liaise with this technology, and a lot of plant space would be required to house the fuel cells (about 30kW could be stored in fuel cells in circa the same volume of a 1 MW boiler). UK legislation also needs to catch up quickly, to avoid poor installation and potential risks.
Finally, the life cost analysis for fuel cells must be carefully considered, to have a realistic comparison with other types of energy storage.
As we face the climate crisis, different technologies are required to break the use of carbon emitting fossil fuels. Hydrogen could be a good technology for the future, however its production would really make sense in terms of energy balance when considered alongside renewables.