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Figure 39: Layout of a Solid Oxide Electrolysis System
d. SOE Electrolysis (SOEL)
SOEL performs electrolysis of water vapour at high temperatures, which has a higher efficiency compared with liquid water electrolysis. It could use waste heat also for supplying the heat required for part of the electrolysis. SOEL operates at high temperatures of 700–900 °C, which would give higher efficiencies than AEL or PEMEL, but its material stability is a challenge to solve. The high efficiency is the result of improved kinetics, favourable thermodynamics for internal heat utilisation at higher temperature and higher conversion of steam. Despite this, SOEL is not ready to be commercialised because of durability problems due to severe conditions. A simplified process layout of a SOEL system is shown in Figure 39. The reactions at the electrodes are:
H2O + 2e_ → H2 + O2_ Cathode
O2_ → ½O2 + 2e_ Anode
Figure 39: Layout of a Solid Oxide Electrolysis System
Photoelectrochemical water splitting
46 46 Photoelectrochemical (PEC) water splitting is a very promising green method to produce hydrogen. In contrast to the conventional photovoltaic panel and electrolyzer combo to produce hydrogen from water electrolysis, PEC technology merges the two separated equipment into a simple single device. It has a huge potential to be a cost-effective and efficient method to generate clean and sustainable hydrogen.
