When AEM is not the answer: three kinds of project we turn down

The question we are asked most often is whether a project should use PEM or AEM. We have written the technology comparison elsewhere. This article answers from the other side, starting with the enquiries where our own products are the wrong choice.

We already answer those enquiries that way. Saying no in the first reply costs us a quotation and saves the buyer several weeks of evaluation, and the conversation is easier to reopen later if the first one was straight.

There are three kinds of misfit, and they are worth keeping apart because each one fails at a different stage: scale, technology, and operating conditions.

When the scale does not fit

A project looking for tens of megawatts is not ours. We received an enquiry for a 20 MW project and replied that we were not the right supplier.

The reason is that what we sell is specific. Today that is electrodes, test cells, the 2 kW stack, the 2 kW HXB-V1 system, and the 46-cell, 30 kW-class HXS-30 full stack. HXS-30 has completed first operation and is under long-term evaluation, and we report its measured data separately from its design values. A 30 kW finished system is in development with a target launch in the second quarter of 2027. The 250 kW and 1 MW configurations come after that on the roadmap and are not sales specifications.

So a complete system today means one or more 2 kW units in parallel. A larger stack means buying HXS-30 and integrating the balance of plant, power, controls and safety systems yourself. A project that has to order tens of megawatts now belongs with an alkaline or PEM supplier that has commercial plants at that size behind it.

When the technology is already decided

We make AEM electrodes, stacks and systems, and nothing else. Two kinds of project are therefore outside our scope before any number is discussed.

The first is a specification that names PEM. The tender calls for an acidic membrane, or the plant is an extension that has to match existing PEM equipment. Our stacks use an anion exchange membrane and run on an alkaline electrolyte, so they cannot stand in for a PEM specification, and we tell the enquirer to go to a PEM supplier.

The second is a site already running its own alkaline plant, with liquid electrolyte and porous diaphragms, where the aim is to expand it. Extending with the same technology is the sensible answer. The electrolyte handling and operating procedures on that site are already built around it.

None of this is a ranking of technologies. Which one fits is decided by the project, and once a project has decided, we have nothing useful to propose.

When the operating conditions sit outside what we have validated

Scale and technology can both fit and the answer can still be no, because the requested condition lies outside what we have tested. These are the ones that come up most.

Two of those rows need a sentence more. Higher flow is not forbidden, but we have not run and validated it, and it raises the pressure drop through the internal flow field, which widens the pressure difference between anode and cathode. And purity: with a dryer fitted we have confirmed hydrogen at 99.999% or better, but that is with a dryer, and the standard unit does not include one.

Why we answer only inside the validated range

The durability data, pressurised operation data and gas purity data by load that we publish were each measured under stated conditions. Outside them we cannot put a number on performance either.

If we say yes to an unvalidated condition and something goes wrong after installation, the cost falls on the buyer. So an enquiry that does not fit gets told so, and one that is close to the edge starts with whether we can test it. For custom builds we do not carry the published figures across; the quotation states which parts of the scope are validated and which are not.

The range of what we answer is the range of what we have published. Anything past that starts as a test, not a promise.

What is left once those are removed

1. Sites that need between about 1 and 15 kg of hydrogen a day, where cylinder deliveries are the burden or small mobility fuelling needs on-site production. One HXB-V1 or several in parallel.
2. Research that evaluates materials and stacks directly. Electrodes, a 1 to 25 cm² test cell and short stacks take the work from a single cell to a short stack on the same hardware, with our MEAs or other suppliers'.
3. Developers integrating a stack into their own system. The 2 kW stack is supplied for balance-of-plant integration, with the connection specification and design inputs in a published integration guide.
4. Demonstrations run without staff on site. The desktop app can be reached through remote access to its computer, and the built-in pump tops up feed water; whether unattended running is acceptable is a site risk assessment.

On renewable-coupled sites, the fit is narrower than it sounds. HXB-V1 is a steady-operation machine and not a load-following product; a varying supply is matched by switching units on and off and keeping the running ones at a load we have measured data for.

One more criterion for some buyers. The anode is a nickel-iron catalyst with no iridium or other precious metal. The cathode does use platinum-group metal, a low-loading platinum-based catalyst, so the claim is independence from iridium, not from precious metals altogether. If you are still deciding whether your project is in this list, send us the required quantity, pressure and site conditions, and we will tell you which side of it you are on.