Evaluation of performance influencing parameters on alkaline water electrolysis systems
Date
2016
Authors
Gillespie, Malcolm Ivor
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Abstract
Alkaline Water Electrolysis (AWE) has shown to be an effective method of producing
hydrogen from renewable sources of energy. However this process accounts for only 4-5% of
the global hydrogen production. Challenges abound for water electrolysis technologies that
presents the traditional methods as comparably favourable.
This research focuses on investigating the relevant performance influencing parameters for
alkaline water electrolysers, their contribution to compromising or enhancing cell
performance and the various interdependencies that exist between variables. Hydrox
Holdings Ltd., in partnership with Demcotech Engineering, provided permission to analyse
the performance of a membraneless alkaline water electrolysis pilot plant.
Using pure nickel for the anode and cathode electrodes yielded current densities of 51.9
mA.cm-2 (at 1.8VDC, 82% HHV efficiency) and 242.9mA.cm-2 (at 2 VDC, 73% HHV
efficiency) at an electrode gap of 2.5mm, temperature of 70°C and a flow velocity of
0.075m.s-1. At these same experimental conditions, employing Ir-RuO2 on a Ti substrate for
the anode and Pt on a Ti substrate for the hydrogen evolution reaction, current densities of
220 mA.cm-2 (at 1.765VDC) and 474 mA.cm-2 (at 2 VDC) was achieved.
Marini et al., (2012), notes that performance for conventional alkaline water electrolysers
should be in the order of > 100 mA.cm-2 when operating at a cell potential of 2 VDC. The
performance of the membraneless technology has therefore exceeded this benchmark by
more than 2 times with the use of basic nickel electrodes and being more than 4 times with
the use of PGM catalytic materials, and hence could be described to very comparable as
advanced methods of alkaline water electrolysis. The ability to obtain high current density
thresholds implies that the membrane less technology has potential for a substantial reduction
in scale and hence, in the total capital cost of the technology.