Bench Talk

Source: Phennapha/stock.adobe.com; generated with AI

Hydrogen fuel cells are quietly transforming the way we power everything from electric vehicles to backup systems for hospitals and data centers. These compact, efficient devices generate electricity through a clean electrochemical process, producing only water and heat as byproducts. For electrical engineers, they represent a compelling alternative to traditional power sources—offering high energy density, rapid response times, and the potential for seamless integration with renewable energy systems.

As the demand for sustainable energy solutions grows, hydrogen fuel cells are emerging as a key technology in the global shift toward cleaner, more resilient power infrastructure. Whether it’s stabilizing microgrids, supporting mission-critical electronics, or enabling zero-emission transportation, fuel cells are proving their value across a wide range of applications.^[1],^[2] In particular, proton exchange membrane (PEM) fuel cells are offering ideal solutions for integrating renewable energy.

But what exactly makes PEM fuel cells so special? And how do they work? Let’s dive into the science and engineering behind this transformative technology.

The Hydrogen Journey from Water to Watts

Hydrogen doesn’t exist freely in nature—it must be extracted (Figure 1). Engineers use several methods to produce hydrogen, each with its own trade-offs.

Figure 1: Generating electricity from hydrogen fuel cells requires an extraction process, of which there are several different techniques. (Source: VectorMine/stock.adobe.com)

The most common method today is steam methane reforming (SMR), which is efficient and cost-effective but relies on fossil fuels and emits carbon dioxide. A cleaner alternative is electrolysis, where electricity splits water into hydrogen and oxygen. When powered by renewable energy, this method produces zero emissions. Other emerging techniques include photoelectrochemical water splitting and biological production using microorganisms, though these are still in the early stages of development.

For electrical engineers, electrolysis is particularly exciting. This method is where electrical expertise meets green innovation. Designing systems that efficiently convert renewable electricity into hydrogen involves optimizing electrolyzers, improving membrane technologies, and developing better catalysts.

Inside the Electrolyzer: Modern Tech at Work

Electrolysis may sound simple, but today’s systems are anything but. There are three main types:

• Alkaline electrolyzers: Cost-effective and scalable, but slow to respond to changes in power supply.
• PEM Electrolyzers: Fast, efficient, and ideal for pairing with solar or wind power, though more expensive due to their use of precious metals.
• Solid oxide electrolyzers: Highly efficient and flexible, but still under development.

PEM systems are currently the front-runners, especially as costs continue to fall. They’re also the foundation for PEM fuel cells, which reverse the electrolysis process to generate electricity.

How PEM Fuel Cells Work

At the core of a PEM fuel cell is a deceptively simple yet powerful process—converting hydrogen and oxygen into electricity, heat, and water. The cell itself is structured like a sandwich, with layers that each play a critical role.^[3]

Hydrogen gas enters the anode side of the cell, where it meets a platinum catalyst. This catalyst splits the hydrogen molecules into protons and electrons. The protons pass through the proton exchange membrane—an ultra-thin, selectively permeable layer—while the electrons are forced to travel through an external circuit. This flow of electrons is what generates usable electric current.

On the other side, at the cathode, oxygen molecules combine with the returning electrons and the protons that passed through the membrane. The result? Water—clean, harmless, and the only byproduct of this reaction.

This elegant process is repeated across multiple cells stacked together, forming a fuel cell stack. These stacks are then integrated into systems that manage fuel, air, water, and temperature—each a critical component in ensuring reliable and efficient operation.

Why PEM Fuel Cells Matter

PEM fuel cells are particularly well-suited for applications that demand quick response times and high efficiency. Unlike other types of fuel cells, PEM systems operate at relatively low temperatures (50–80°C), making them ideal for mobile and distributed power applications.^[4]

For electrical engineers, PEM fuel cells present a unique design challenge. The electrochemical reaction is just the beginning. Turning that reaction into usable power requires sophisticated electronics and system-level integration.

The Electronics Behind the Energy

The electricity generated by a PEM fuel cell is low-voltage and high-current—great for chemistry, but not so great for powering your home or car. That’s where power electronics come in.

DC-DC boost converters step up the voltage to usable levels. These converters often use wide-bandgap semiconductors like silicon carbide (SiC) and gallium nitride (GaN), which offer higher efficiency and better thermal performance than traditional silicon. In systems that need alternating current (AC), such as electric vehicles or grid-tied applications, engineers add an inverter stage to convert the boosted DC into AC.

For applications that require AC, such as grid connections or electric motors, a two-stage conversion is used: first boosting the voltage, then inverting it to AC. These systems must be finely tuned to match grid standards and handle fluctuations.

But it’s not just about conversion. Engineers must also manage transient loads, prevent reverse currents, and minimize electromagnetic interference (EMI). Energy storage—via batteries or supercapacitors—adds another layer of complexity. Advanced control algorithms, some even using machine learning, manage the flow of energy between the fuel cell, storage, and the load, ensuring smooth operation and extending component life.

Building the Whole System

Designing a PEM fuel cell system isn’t just about the stack or the electronics. It’s about orchestrating a symphony of subsystems—thermal, fluid, mechanical, and electrical—to work in harmony.

Temperature control is critical. Too hot, and the membrane dries out; too cold, and performance drops. Cooling systems must respond dynamically to changing loads. Hydrogen delivery must be precise in pressure and purity. For example, automotive systems store hydrogen at 700 bar, but the fuel cell stack operates best at just 1–2 bar.^[5] Even trace contaminants can degrade the platinum catalyst.

Then there’s the balance of plant (BOP)—the collection of auxiliary components like air compressors, humidifiers, and sensors. These often account for more than half the system’s cost.^[6] Proper sizing and integration of BOP components are essential to minimize energy losses and ensure long-term reliability.

Modern systems even use machine learning to predict maintenance needs and prevent failures, from membrane drying to catalyst degradation.

Looking Ahead to Widespread Adoption

Hydrogen fuel cells are evolving fast. Researchers are finding ways to reduce reliance on expensive materials, while digital tools are improving performance and reliability, as well as system diagnostics and control. As costs drop and efficiency rises, fuel cells are expanding into new areas.

When it comes to PEM fuel cells, they are more than just a clean energy alternative—they’re a showcase of what happens when chemistry, materials science, and electrical engineering converge. As hydrogen infrastructure expands, we’ll see PEM fuel cells powering more than just cars. Think data centers, telecom towers, and even ships. For electrical engineers, this is a golden opportunity to shape the next generation of clean energy systems by designing smarter electronics, optimizing integration, and pushing the boundaries of what’s possible.

For a deeper dive into this topic, read the full article, “Designing Efficient Hydrogen Fuel Cell Systems.”

This blog was generated with assistance from Copilot for Microsoft 365.

[1] https://www.airbus.com/en/innovation/energy-transition/hydrogen
[2] https://www.energy.gov/eere/fuelcells/articles/h2iq-hour-integrating-hydrogen-tech-and-grid-enable-efficient-and-stable
[3] https://www.fuelcellbuses.eu/wiki/fuel-cells-hydrogen-and-fuel-cells/4-components-pem-fuel-cell
[4] https://www.energy.gov/eere/fuelcells/types-fuel-cells
[5] https://www.energy.gov/eere/fuelcells/hydrogen-storage
[6] https://www.nrel.gov/docs/fy24osti/87625.pdf