[ efficiency ] electrochemically active catalyst materials and via alterations to the underlying cell architecture intended to minimise electrical resistance .
It is worth noting that since catalyst materials contribute significantly to the overall cost of electrolyser stacks , efficiency benefits from material substitution can also be counterbalanced by increases to project CAPEX . Innovations in this area have therefore focused as much on reducing material costs for electrolyser systems as they have on boosting cell performance . The impact of material changes on other parameters that influence the LCOH , such as cell degradation , also needs to be evaluated prior to adoption .
Beyond the commercially advanced technologies , there has been growing interest in hightemperature electrolysers , principally solid oxide electrolysis ( SOE ). Since the electrochemical reactions within an SOE cell are assisted by the technology ’ s high operating temperature , projects can make use of waste heat from co-located high-temperature processes to offset some of the electricity input requirements . SOE electrolysers supplied with an external heat source can achieve significant improvements in electrical efficiency at the stack level – approaching 85 % relative to the LHV at BoL , which compares to maximum current values of slightly over 70 % for PEM and alkaline electrolysers .
Despite these efficiency benefits , further progress in key performance areas is likely to be required to make SOE a commercially attractive proposition for most project developers . Current disadvantages include high capital costs at the stack level , short lifespans due to thermally induced cell degradation , and lack of responsiveness to variable loads .
There are also some early-stage technologies that promise still greater efficiencies . Australian start-up Hysata and Israeli start-up H2Pro both claim stack efficiencies in excess of 95 % ( relative to the HHV ) with radically different approaches to cell design .
Hysata ’ s technology aims to achieve this via the use of capillaries for water transport within the cell , which prevents bubble formation and inefficiencies from fluid and gas flow interactions . H2Pro ’ s technology separates the hydrogen and oxygen evolution reactions that usually take place within a single cell into distinct electrochemical and thermally activated chemical steps . Both companies also claim simplified BoP requirements . However , it is not yet known whether these advantages will translate into robust and scalable commercial offerings .
Realising efficiency improvements at the system level
The years leading up to 2030 will be a crucial period for scaling up electrolyser capacity . Although new technologies promise substantial efficiency improvements , most projects delivered during this period will use PEM and alkaline stacks with performance characteristics identical or similar to those of currently available systems . Nonetheless , important gains can still be made to achievable system efficiencies by focusing on an electrolyser ’ s operational profile and its BoP .
Measures taken to reduce the frequency of standby and shutdown events will also increase an electrolyser ’ s capacity factor . This is potentially a more important motivation than minimising operational losses since it significantly decreases the capital investment needed for an electrolyser to deliver a set level of hydrogen output . Nonetheless , load smoothing helps to maintain optimal conversion efficiencies as well as limiting stack degradation rates , especially for alkaline electrolysers with limited dynamic capabilities . Various electricity sourcing options have different implications for plant capacity factors and
Hydrogen Tech World | Issue 16 | June 2024 17