Green hydrogen project developers tend to favour proton-exchange-membrane (PEM) technology for their projects over alkaline electrolysis (AE), according to analysis of IEA project data by Hydrogen Economist.
Of the 886 green hydrogen projects registered with the IEA by the end of last year, some 239 projects (27pc) said they were definitely using PEM technology, compared with 159 projects (18pc) that have committed to AE.
The choice of an electrolyser technology involves evaluating a number of factors including cost, volume of rare metals used, technology readiness, the ability to operate in a flexible mode and robustness.
Currently only AE and PEM systems are fully commercialised. AE systems have the advantage of using low-cost components for both electrodes, as well as long operating lifetimes.
PEM facilities are the most promising option for pairing hydrogen production with solar and wind generation as the low level of partial load required by the electrolysers and their ability to rapid cycle makes them suitable for running on intermittent power sources. But they are currently more expensive—partly due to their use of expensive components such as rare metals.
AE costs are currently $1,378/kW, while PEM costs are $2,456/kW, according to research by Australia’s Commonwealth Scientific and Industrial Research Organisation (Csiro).
Both AE and PEM costs are expected to fall as the technologies becomes more commercialised—with PEM falling more sharply to reach parity with AE around 2040, according to modelling by the Csiro.
As a result, many developers of larger, long-term green hydrogen projects are waiting to see how the technologies develop before they commit to one type, further analysis of the IEA project data by Hydrogen Economist reveals.
Just under 25pc of projects that are operational, under construction or have taken FID have specified that they will use AE technology.
But only 13pc of projects that are yet to take FID—meaning they are at a concept, feasibility study or demonstration stage—have specified they will use AE.
Similarly, 37pc of post-FID projects have specified they will use PEM. But only 20pc of projects that are yet to take an FID have specified they will use the technology.
The market for electrolysers will be big enough to accommodate both technologies—and likely the nascent solid-oxide and anion-exchange-membrane (AEM) electrolyser technologies as well, according to a report by the International Renewable Energy Agency, titled Scaling up electrolysers to meet the 1.5°C climate goal.
“AEM [electrolysers] are taking an increasing market share of a burgeoning hydrogen sector. Similarly, solid-oxide is now commercial, offering a more efficient option that can be integrated with hydrogen-derived products,” it says.
One supplier of components to PEM electrolysers told Hydrogen Economist they believe PEM could realistically gain a 30pc share of the global electrolyser market.
Policymakers will do well to avoid over-prescriptiveness on technology in the pursuit of efficiency, according to Matthew Klippenstein, regional manager for the Canadian Hydrogen and Fuel Cell Association, speaking on a recent webinar organised by German hydrogen research organisation Mission Hydrogen.
“It is wiser to offer hydrogen contingencies than try to force efficiency,” he said. “If you maximise the number of options that is a more sustainable path forward.”