If synthesizing billions of tons of hydrogen from water or natural gas to replace fossil fuels seems like a massive technological undertaking at an enormous cost, that’s because it will be.

Listening to panels of electrochemists and engineers participating in discussions at this week’s Department of Energy “Hydrogen Shot Summit” made that point very clear.

The effort will require developing a new industry from existing niche technologies, many of them unrelated. In contrast to the enthusiasm of DOE officials comparing it to the U.S. drive to land astronauts on the moon within a decade, the engineers and chemists talked of the minutiae that must be dealt with and solved.

Some talked of setting standards, while others noted that the electrolysis technology requires rare minerals and metals that must be mined or pulled from recycling processes, some of which haven’t been developed. They also discussed their efforts to develop new technologies from what now are merely demonstration projects. And they noted that scaling up known technologies to massive operations will likely encounter problems just because of size.

On the positive side, the U.S. is late to the global hydrogen party and will benefit from research already done in Europe or by European companies with operations here, they said.

While not as simple as pushing direct current through water, as might be done in a college chemistry classroom, electrolysis uses components and engineering involved in fuel cell technology, though on an industrial scale.

In other words, researchers competing for the billions of dollars in DOE funding will already have had experience, for example, with polymer electrolyte membranes (PEM) used in fuel cells, assuming Congress approves the bipartisan infrastructure package.

“We’ve got a lot of things … in the R&D docket,” Andrew Park, an engineer with The Chemours Company (NYSE:CC), said when discussing the company’s work with polymers in one of the sessions.

“And we think these new materials that we’re developing are going to be critically enabling as we try to get down to $1/kg of hydrogen. And toward that end, we are leading and or participating in three Department of Energy projects right now in the hydrogen economy space. We’re working with Los Alamos National Lab, [the National Renewable Energy Laboratory] and Lawrence Berkeley [National Laboratory] on developing the next generation of membranes for PEM water electrolysis,” he said.

An industrial-scale electrolyzer can start with a PEM cell or use competing systems. A full-sized electrolyzer includes a number of equally complicated components, from a water purification system, to systems that add chemicals (electrolytes), to outside components that take the moisture out of the hydrogen and purify it before another component collects and stores the gas. All of these systems must be controlled by power electronics. And the machine must be built tough enough to last for many years.

Another complicating issue: Electrolyzers are designed to run continuously, not intermittently, as they might be asked to do if the source of the electricity flowing through them is from wind or solar. In one session, the engineers looked at what might have to be changed to deal with running intermittently.

“There’s just definitely some physical limitations that we have from a desiccant [drying agent], from a bad design perspective. … We just cannot go against the physics unless we evolve in our knowledge,” said Blanca Ramirez, an engineer with Lectrodryer, a Kentucky-based company that specializes in the drying and conditioning of gases and liquids. The company’s first drying system was for natural gas in 1932.

Ramirez also pointed out that standards must be developed for just how pure hydrogen used, for example, as a fuel must be. “What we really need to know is, how pure do you need this? The fact that it can be done [ultra pure] doesn’t mean that it needs to be used.”

Sasha Dass, director of engineering program management at Analog Devices, a multinational semiconductor company, also noted that using an intermittent power supply presents a real problem.

“You have to be able to run continuously in order to get the output that you want and in order to realize the depreciation and amortization of your equipment,” she said. “That is key and, again, coming from semiconductors where your expected uptime is in the 95% range, you can’t afford to turn your equipment off in times of waning sunlight or when the wind dies down.

“We have to design these stacks intelligently in order to run continuously, albeit at a reduced output. … And that’s one of the ideas that we’re trying to vet.”