The story of PEM
Over three decades, the technology has developed from compact on-site hydrogen generators for specialised applications to modular, megawatt-scale systems serving customers around the world.
This is the story of where our PEM-technology began, how it developed and where it is heading next.
Origins
It started with an idea
The roots of our PEM technology stretch back to early applications in aerospace and life-support systems. The technology was originally developed by General Electric for aerospace applications. It was later being acquired by Hamilton Sundstrand to produce oxygen for submarine crews.
1994
1996 · The founding
Proton Energy Systems is founded
The ambition was to make hydrogen available where it was needed by producing it directly from water and electricity. The company developed compact, on-site hydrogen generators for customers that required a dependable supply of high-purity hydrogen. What began with a relatively small team in Connecticut would grow into technology used across industries and countries around the world.
1996
1999 · EARLY PRODUCTS
From early prototypes to commercial products
By the end of the 1990s, Proton Energy Systems was turning its PEM technology into commercial products. Among them was the HOGEN 40, an early predecessor to today’s S40, designed to produce high-purity hydrogen directly on site. The system helped demonstrate how compact, scalable PEM technology could serve a growing range of laboratory and industrial applications.
1999
2006–2014 · EARLY CONNECTIONS
Two paths begin to converge
The relationship between Nel and Proton began years before the companies eventually came together. They first explored opportunities to work more closely in 2006, when Proton was looking for new capital, but changes surrounding Nel’s ownership meant the discussions did not progress. The two teams met again in 2014, when representatives from Nel visited Proton’s Wallingford facility. Although the timing was not yet right, the meeting strengthened a connection that would continue to develop in the years ahead.
2006
2017 · Joining Nel
Proton OnSite becomes part of Nel
In June 2017, Nel completed the acquisition of Proton OnSite. The combination brought together two long histories of electrolyser development: Nel’s alkaline technology and Proton OnSite’s PEM expertise. It also connected the Wallingford team to Nel’s wider global organisation and created a broader technology portfolio for customers seeking to produce hydrogen from electricity and water.
2017
A quick guide
What is PEM?
PEM stands for proton exchange membrane. Inside a PEM electrolyser, electricity splits water into hydrogen and oxygen. The membrane allows hydrogen ions to pass through while keeping the produced gases separated. The result is high-purity hydrogen produced on-site and on demand.PEM electrolysers have a compact footprint and can respond rapidly to changes in power input. This makes the technology well suited to applications requiring flexible operation, including energy systems using variable renewable power.
The principle
Water. Electricity. Hydrogen.
A simple principle, developed and improved through decades of engineering.
Scaling up
From specialised applications to a broader hydrogen economy
Early systems were designed to produce hydrogen directly at the point of use for specialised industrial and laboratory applications. Over time, the technology expanded into larger systems and new markets.
Today, Nel’s PEM technology supports applications including industrial hydrogen production, mobility, energy systems, generator cooling and critical life-support systems.
The scale has changed significantly since 1996. The focus on safety, reliability, hydrogen purity and continuous improvement has not.
2024 · A new chapter
A new chapter for Wallingford
In October 2024, Nel officially opened its expanded and automated PEM manufacturing facility in Wallingford. The expansion increased annual production capacity from 50 MW to 500 MW. The new facility was designed to produce ten times as many PEM electrolysers at approximately 30 percent lower cost than the previous manufacturing setup.
It represented more than an increase in capacity. Thirty years after the company was founded, the technology was entering a new industrial chapter.
50 → 500
MW per year
10×
more electrolysers
~30%
lower unit cost
2024
2026 and beyond
Thirty years in.
Still moving forward.
This anniversary is an opportunity to celebrate how far the technology has come and to recognise the people who brought it here. The next chapter will be built on everything we have learned – and on the people who continue to challenge what PEM technology can become.
2026
Looking ahead
The next generation of PEM
This is the story of where our PEM-technology began, how it developed and where it is heading next.
Thirty years of PEM experience are shaping what comes next. At Nel’s facility in Wallingford, Connecticut, our team is developing a new stack designed to produce more hydrogen, use less electricity and cost less to manufacture.
The work builds on years of research and our previous collaboration with General Motors, combining experience in electrolysis, fuel cells and automotive manufacturing.
“Together, we are taking the PEM technology a giant step further,” Kathy Ayers said in an earlier Nel interview.
With the new design, we aim to achieve:
- More hydrogen: Over 1,200 kg per day from a 3 MW stack.
- Lower costs: Around 70% reduction in stack costs.
- Less electricity: 47.5 kWh per kilogram of hydrogen at stack level.
- Fewer parts: More than 50% fewer components, making the stack simpler to manufacture.
These improvements share one purpose: to make hydrogen from electrolysis more affordable.
