Hydrogen: somewhere over the rainbow?
the exception of the PEMFC (O'Hayre, et al., 2016). This makes them incredibly expensive to both manufacture and run, so they are only economically viable in niche markets, for example space exploration. Even though the PEMFC is the most viable fuel cell, it has issues as well, specifically in water management (Ijaodola, et al., 2019). The water must be produced faster than it evaporates, as the ionomer is only functional when hydrated. Too much water can result in the gas diffusion layer pores and the active catalyst sites being flooded, ultimately stopping the electrochemical reaction. This combined with a constant in-flow of reactants creates an increasingly complex and finely balanced system in which the failure of only one of many variables results in the malfunction of the whole machine.
New technologies for fuel cells
There are various methods to improve water management of PEMFCs. One approach is to humidify the gases entering the fuel cell. A basic way to do this is to introduce cooling water pipes between cells in a stack. Alternatively, self-humidifying membranes can be made by integrating silicon dioxide into Nafion (Yafei, et al., 2018). A different approach is to weaken specific areas of the gas diffusion layers via laser perforation. A perforation is simply a gap in the wall of a substance. A study by University College London concluded that cone-like perforations are better than cylinder shaped ‘ due to their large lateral area and little water clustering ’ (Yang, et al., 2019). By minimizing pore flooding, this method could also improve a PEMFC’s power density. Another possible sol ution to increasing its efficiency is using cerium salt in the ionomer. This makes thinner electrolyte membranes more stable, thus greatening the speed of transport of ions between the electrodes (Jiao, et al., 2021).
Difficulties with handling hydrogen
Then there are also difficulties with transporting and storing hydrogen. Being the lightest element in the periodic table means it has very low energy density. Therefore, it would take up a huge amount of space uncompressed if it were to produce the same amount of energy as petrol, which is in liquid state at room temperature. A cubic metre of hydrogen contains only a third of the energy of an equivalent volume of natural gas (Alverà, 2021). To solve this issue, it can be compressed or condensed into liquid form. However, maintaining high pressures or the extremely low temperatures required is expensive. The best way of storing hydrogen is underground, for example in salt caverns, and using existing pipes and infrastructure to transfer it. It turns out the petrochemical industry in Texas has been doing this since the 1980s, yet many people are still against the idea due to the notorious volatility of hydrogen and the infamous Hindenburg disaster in 1937. Despite these challenges the future of hydrogen is bright. A pioneering project in the UK, H21, recently completed phase one successfully in May 2021. The pan-industry collaborative project aimed ‘ to deliver quantified safety evidence ’ needed for government approval of the use of hydrogen in the existing gas network (H21, 2022). The H21 social science research suggested public interest in converting from natural gas to hydrogen. These are two big steps forward for the UK’ s 2050 pledge. Tests by the Energy Research Centre of The Netherlands concludes that the best way of implementing fuel cells into the household energy industry is via a PEMFC-based micro-combined heat and power system (CHP) (Smit, et al., 2007). This means the electricity generated by the PEMFC can be used for domestic appliances, while the heat energy created as a by-product can be pumped through a heat recovery unit to heat water used for heating, for example
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