Hydrogen - an overview
Hydrogen will play a duel role in the transition to cleaner fuels: storage and source. The excess energy from renewable sources could be expended in electrolysis to produce hydrogen. This can either power fuel cells or be stored as cryogenic liquid for later use. The versatility of hydrogen's utility makes it one of the key players within the energy revolution. Moreover, hydrogen fuel cells could help reduce the anthropogenic greenhouse emissions from passenger vehicles and further diversify our transportation energy options. Fuel cells will also be grid independent and hence potentially provide a viable opportunity to extend energy access to remote areas.
Despite the promising future for hydrogen, there are numerous technical challenges that have hindered its commercialisation. Its explosive nature combined with its tendency to leak in gaseous form pose a set of challenges for transportation and storage. Moreover, it has a lower volumetric energy density as compared to other fuels such as gasoline. As such, hydrogen needs to be compressed under high pressures to store it efficiently. To make the fuel cells viable, the energy extracted from the hydrogen must be significantly more than the energy required to compress and decompress it.
In terms of storage, hydrogen could be stored within nanomaterials by physisorption. Graphene is one of the most promising adsorbents for this application . Japanese researchers have discovered that illuminating borophane with UV light at room temperature and pressure can release high amounts of hydrogen . Further research could indicate whether something similar could be accomplished with visible light. Such a breakthrough will revolutionise the hydrogen economy. However, it is necessary to conduct focused research to optimise the production of these nanomaterials to make this a viable strategy.
By adapting the natural gas transportation infrastructure, it is possible to streamline the transition to hydrogen. Hydrogen transportation capacity through the current pipelines is almost 20-30% lower than natural gas . Blending natural gas with hydrogen for transportation purposes could significantly accelerate the modifications necessary to the current system. Fibre-reinforced polymers could be added to the pipes in order to make them suitable for the higher pressures. This combined with the fact that graphene can reduce the cure times for FRP production is very promising. Current gas stations could also be adapted to become “hydrogen stations”. This could pave the way for hydrogen fuel cells to infiltrate the trucks and buses market easily.
It is also possible to exploit other methods of hydrogen energy production which will reduce the costs significantly. It is possible to use graphene-based proton exchange membranes to extract hydrogen from humid air . This could reduce the necessity for fuelling stations. However, this process will require electric currents which will utilise some energy. This could come from either solar sources or hydrogen fuel cells. By increasing the production efficiency, this could transform mobile energy generation.
To produce 175 billion kWh energy, fuel cells operating at 50% LHV efficiency would require about 10.5 million tons of hydrogen . If this was produced using non-carbon sources, it could displace up to 27.5 million tons of carbon . However, production of hydrogen in a carbon neutral way has been a technical challenge. Electrolysis combined with turbine energy generation could be an efficient method to produce hydrogen in coastal areas. It is also possible to produce hydrogen through acidogenesis - recycling food and animal waste through anaerobic digestion. This will also reduce the necessity for biodegradable waste removal. To make this transition practical, there will need to be large-scale shift to volume production of hydrogen. This will lower the costs and hence make it economically viable.
Ultimately, hydrogen will be an immense part of the energy transition. Available abundantly through sea water, it could help increase the reliability of renewable sources by storing excess energy. With a focused drive to revolutionise the infrastructure, it has the potential to transform our transportation energy sources. Without compromising the driveability of vehicles, fuel cells could lead the way to greener transport systems. By using hydrogen based auxiliary power units in vehicles, it could be possible to make transportation carbon neutral in the near future.
Click here for the bibliography.