This story is part of CT Mirror Explains, an ongoing effort to distill our wide-ranging reporting into a "what you need to know" format and provide practical information to our readers.

Connecticut is playing a quiet role in powering the global build-out of data centers through the development of fuel cell power stations.

The global fuel cell market is expected to grow to around $30 billion in revenue by 2030, more than ten times the $2.8 billion in revenue reported last year, according to research firm Rystad Energy. Demand is largely coming from data centers, which require the kind of continuous, on-site power generation fuel cells provide.

While Connecticut has yet to experience widespread development of hyperscale data centers, it is home to two of the world’s leading manufacturers of fuel cells: Fuel Cell Energy in Danbury and Torrington and HyAxiom — a division of Doosan Group — located in South Windsor.

But what are fuel cells, and why are they suddenly of interest to data center developers?

How do fuel cells work?

Simply put, fuel cells create energy from a chemical reaction involving air and another fuel, usually hydrogen. The reaction produces water, electricity and heat.

From there, the process works similarly to a battery, with negative (anode) and a positive (cathode) ends surrounding an electrolyte layer. Hydrogen is delivered to the anode while air is sent to the cathode. Electrons travel through a circuit between the two ends, creating electricity.

Unlike a battery, fuel cells can operate around-the-clock without the need to recharge.

Fuels cells powered by natural gas must first break down methane into hydrogen and carbon dioxide, but they emit a lower volume of CO2 than traditional power plants that burn fossil fuels. (Fossil fuel-burning power plants also emit other air pollutants, such as nitrogen oxides and sulfur.)

For this reason, proponents tout fuel cells as an effective way to cut emissions while still providing essential power to homes, businesses, factories and, increasingly, data centers.

“That’s the biggest value piece of where fuel cells bring a real differentiator,” said Eric Strayer, the global head of sales at Fuel Cell Energy. “You don’t have a loud turbine combusting and, you know, vibrating at your site. It’s a quiet, electrochemical conversion of that natural gas into electricity and heat.”

Some critics, however, point out that fuel cells do rely on fossil fuels and related infrastructure, including natural gas pipelines.

How are they used?

The basic technology behind fuel cells has been around since the mid-1800s, a short time after the invention of batteries. A century later, Pratt and Whitney made hydrogen-oxygen fuel cells that were used to power the Service Module on NASA’s Apollo space missions.

Since the 1970s, the development of fuel cell technology has been driven by rising energy prices and the push for cleaner forms of electricity, according to the Los Alamos National Laboratory. In addition to providing electrical power, fuel cells can be used to power vehicles and heavy machinery.

Honda and Toyota both began selling hydrogen-fuel cell vehicles in the early 2000s. However, that technology has not become more widely available due to the high cost and limited availability of hydrogen refueling stations.

There are also different fuel cell designs based on the type of electrolyte used to produce the chemical reaction.

Fuel Cell Energy, for example, manufactures a molten-carbonate system with a minimum output of 1,250 kilowatts. Doosan, the parent company of HyAxiom, produces a 440-kilowatt solid-oxide fuel cell system.

What does the future hold?

Power fuel cells can be built small enough to fit on top of a tractor-trailer, allowing them to be transported and located nearly anywhere.

That’s made them attractive option for energy developers seeking to build in dense, urban communities or on former brownfield sites. Bridgeport, for example, is home to four different fuel cell power stations.

In addition, modular designs allow fuel cells to be scaled to provide much larger quantities of power — one of the principal demands of data centers.

For example, developers behind proposed data center projects in Beacon Falls, Colchester and Cromwell have all pitched using fuel cells to power those facilities instead of relying off the local power grid. So far, none of those projects have received approvals from state or local officials.

Elsewhere, the rush to construct and power new data centers is having local economic effects. At its manufacturing facility in Torrington, Fuel Cell Energy is currently hiring a around 100 workers as part of a ramp-up in production to meet the demand from data center developers. Just a few years ago, Strayer said, the plant’s production capacity was about 40 megawatts of fuel cells annually. The current ramp-up will increase production to 100 megawatts a year.

In addition, the company is investing more than $200 million to expand its manufacturing facility in hopes of producing up to 500 megawatts a year by mid-2028.

In October, South Windsor Town Manager Michael Maniscalco announced at a public meeting that HyAxiom was looking to “double in size” its facility within the town, adding about 200 jobs.