Comparison of electrical energy efficiency of atmospheric and high-pressure electrolysers

Amitava Roy, Simon Watson, D.G. Infield

Research output: Contribution to journalArticlepeer-review

112 Citations (Scopus)


Efforts are being made to produce highly pressurised electrolysers to increase the overall energy efficiency by eliminating mechanical compression. However, in-depth modelling of electrolysers suggests that electrolysis at atmospheric pressure is electrically more energy efficient if parasitic energy consumption and gas losses are incorporated in both cases. The reversible cell voltage increases with increasing pressures. The electrode activation and Ohmic losses, leakage current and inevitable heat losses increase the electrolysis voltage beyond the thermoneutral voltage and consequently heat removal from the stack becomes essential. The expected gas loss at various operating pressures is incorporated to reveal the energy consumption that would occur in practice. Comparison of total energy consumption at various operating pressure up to 700 atm is performed and atmospheric electrolysers are found more efficient at all levels. Practical considerations such as corrosion, hydrogen embrittlement, operational complexity, dynamic response and cost are less favourable for pressurised electrolysers.
Original languageEnglish
Pages (from-to)1964-1979
Number of pages16
JournalInternational Journal of Hydrogen Energy
Issue number14
Early online date3 Apr 2006
Publication statusPublished - Nov 2006


  • atmospheric electrolysers
  • pressurised electrolysers
  • thermodynamic analysis
  • gas loss
  • energy efficiency
  • practical considerations


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