| Green hydrogen
Dynamic alkaline water electrolysis: the path to parity
Dynamic AWE electrolysers combine the reliability, robustness and low materials costs of traditional AWE systems with the fast responsiveness and wider dynamic range of PEM systems, while designing out the disadvantages of both. As described in a recent white paper* from Verdagy, summarised here, they promise a route for green hydrogen to achieve fossil fuel cost parity
Kevin Cole PhD, Senior Scientist, Verdagy
Electrolysis of water to produce hydrogen using conventional equipment today is expensive, which limits its adoption and economic attractiveness. Conventional hydrogen electrolysis technology revolves around proton exchange membrane (PEM) and traditional liquid alkaline water electrolysis (AWE), with neither being ideally suited to cost effectively and safely scaling up hydrogen production.
Dynamic AWE systems, such as Verdagy’s eDynamic®, are a breakthrough technology drawing upon decades of successful chlor-alkali electrolysis experience and innovated to be perfectly suited to capitalise on the increase in renewable energy. Dynamic AWE systems seamlessly integrate with renewable energy to provide a safe and low-cost pathway for scaling up hydrogen without the drawbacks of traditional AWE and PEM. Traditional AWE was the first water electrolyser technology to see commercialisation, in the 1930s. A traditional AWE system is characterised by two electrodes submerged in a liquid alkaline solution and separated by a porous diaphragm. The electrolyte is commonly potassium hydroxide (KOH) or sodium hydroxide (NaOH) with concentrations ranging from 20 to 40 wt.%. Traditional AWE electrolysers have been used for several decades and are generally considered mature, reliable and low cost. They also do not typically use precious metals such as platinum or iridium, which are required in PEM electrolysers. However, traditional AWE electrolysers still suffer from several disadvantages:
), resulting in lower productivity, ie, lower quantities of hydrogen produced per unit area. Low current densities also necessitate very large systems, increasing materials usage, real estate, and construction costs.
They exhibit low current densities (0.2 – 0.6 A/ cm2
Traditional AWE electrolysers suffer from high leakage or shunt currents from centralised manifolds with highly conductive electrolyte, which lowers their conversion efficiencies and
increases operational costs. Depending on the stack size and load, shunt currents can reduce efficiencies by as much as 10 – 80% (see Figure 1).1
Traditional filter-pressed AWE electrolysers also have limited dynamic operating range because of high gas crossovers, which limits their utilisation when paired with intermittent renewable energy sources.
In addition, they are also susceptible to rapid degradation requiring expensive stack replacements and significant productivity losses. The inability to digitally monitor degradation on a component level leads to sporadic maintenance.
PEM water electrolysis is an acidic system developed in the 1960s that offers dynamic and high current density operation in a compact footprint. Even after decades of innovation, operation has largely remained the same with the acidic environment necessitating the use of precious materials, such as platinum, iridium, and ruthenium, which are often applied as catalysts to internal flow field components, such as porous transport layers (PTLs) and gas diffusion
layers (GDLs). These flow field components assist with control of liquid and protons (H+) and the improved transport within the system allows a PEM electrolyser to be operated with a dry cathode (electrolyte only flows to the anode chamber). The dry cathode enables easier pressurised operation along with higher current densities, greater dynamic range, and more compact footprints than traditional AWE electrolysers.
However, PEM electrolysers have their own set of disadvantages:
PEM electrolysers typically have relatively small membrane areas, which results in significantly more cells and components needed to match the same total equivalent area of a dynamic AWE cell system. This renders PEM substantially more expensive and uneconomic for most hydrogen electrolysis applications. In addition to their higher initial costs, they also require precious metal catalysts that are expensive and scarce, increasing operational costs. Suppliers are attempting to reduce the use of platinum group metals (PGMs) by using thinner MEAs (membrane electrode
*
https://verdagy.com/wp-content/uploads/2025/03/20250311-Dynamic-AWE-White-Paper.pdf
www.modernpowersystems.com | April 2025 | 31
Render of 20 MW Verdagy Dynamic AWE electrolyser (image: Verdagy)
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