As society strives to reduce our carbon emissions, many companies, governments, and other organizations are quick to point to hydrogen as a solution. But it’s a divisive subject, with different opinions on hydrogen’s importance in the drive to net zero.

What we can say with certainty is that hydrogen has a role to play in delivering power with zero emissions at the point of use, including as part of mission-critical and backup power systems.

In this article, we’ll cover the background of hydrogen, its usage, and its production and then look at how it can be used in fuel cells for power delivery.

History and usage of hydrogen

Although people were actually producing and observing it at least a couple of hundred years earlier, hydrogen was first recognized as a distinct substance in 1766 by the English scientist Henry Cavendish. But, for a lot of us, when we think of hydrogen, the image that springs to mind is the great airships of the 20^th century, given lift by hydrogen’s low density.

Of course, this era ended badly, with the destruction by fire of the Hindenburg in 1937, but hydrogen continued to find applications. And while the concept of the fuel cell had long been known, its first commercial use came recently in 1965, in NASA’s Gemini spaceflight program.

There are two ways to release the energy stored in hydrogen: You can burn it through a process, like combustion in an engine, or you can use it in a fuel cell. Using hydrogen can greatly reduce greenhouse gas emissions compared to traditional fossil fuels, which are made of hydrocarbons and release CO₂ when burned. Importantly, hydrogen’s waste product is only water when it is used in a fuel cell system.

Hydrogen by the colors

We’ve said that hydrogen has zero emissions at the point of use, but what about its production?

Not all hydrogen is created equal. Typically, hydrogen is defined with a color that indicates both its source and the technology used to make it. There are a lot of colors used today, including black, brown, gray, purple, pink, blue, white, and green.

Black or brown hydrogen are the least attractive options from an emissions perspective. They use a gasification technology to create the hydrogen, typically using coal, which leads to a very high carbon footprint.

At the opposite end of the spectrum, that's where we have green hydrogen, which is the cleanest option. Green hydrogen is defined as using electrolysis to produce the hydrogen by separating water molecules, with the electricity required coming from renewable energies, such as wind, solar, and hydropower. This means it has a minimal carbon footprint, so it’s the best choice to reduce emissions.

Challenges of hydrogen

Hydrogen is a challenge to work with at scale — but the promise of clean power means that it's worth it.
 
 When we compare it to traditional fuels, hydrogen's energy density is very low. This means you have to store a lot of it to get the same kind of power output that you'd expect from fossil fuels. Storage is, therefore, a challenge, and it requires high pressure to compress the hydrogen to occupy a reasonable space.

We also need to consider that hydrogen is 14 times lighter than air. This means it likes to escape through the smallest gap or defect. So, we have to consider what types of materials we're using for the compression vessel. Also, when we make connections with pipes and connectors, we must make sure they're all effectively sealed.

We have defined green hydrogen as the most appealing option with the lowest emissions, but it presents its own challenges, especially as we look at more broadly scaling up production. To make green hydrogen, we need renewables in place, and these are still constrained in terms of the capacity of operational power generation. We're going to see hydrogen production, therefore, scale at the same speed, or maybe slightly behind, the pace of the adoptions of renewables.

The other challenge with hydrogen is that, once it’s been produced, it, of course, needs to be transported to where it will be consumed. To limit your emissions footprint as much as possible, you need the locations of production and consumption to be physically close together, which may not be practical.

These challenges mean that, today, we're not yet seeing high adoption rates of hydrogen, but the potential is there. As we have increasingly broader adoptions of renewable energy sources, we're going to see hydrogen availability grow in parallel.

Hydrogen fuel cells

Today, hydrogen is used in a wide range of industrial processes, such as fertilizer production and petroleum refining. It’s also used as a rocket propellant, and in fuel cells in vehicles and electricity generation.

Fuel cells are more energy-efficient than combustion engines and hold the promise of zero carbon emissions. Figure 1 shows a conceptual overview of how a fuel cell works. Hydrogen molecules (H₂) enter at the anode, and oxygen molecules (O₂) enter at the cathode. The hydrogen atoms in the hydrogen molecules split into electrons and positively charged hydrogen protons.

The electrolyte membrane allows only hydrogen protons to pass through. The electrons are forced through an external circuit, thus generating an electric current. This flow of electrons reaches the cathode, where the negatively charged electrons combine with the positively charged hydrogen protons and oxygen from the air to form water (H₂O). This process also dissipates heat.

Different materials can be used as the electrolyte, leading to different characteristics of the fuel cell, and making it suitable for different applications. For example, polymer electrolyte membrane (PEM) fuel cells use an acid membrane and a solid polymer as an electrolyte, with porous carbon electrodes containing a platinum or platinum alloy catalyst. PEM fuel cells offer a quick startup time, low operating temperatures, and electrical efficiency of around 45% to 65%, in addition to being smaller and lighter than other fuel cells.

Hydrogen fuel cells are starting to be used to power cars, but it’s still early — and there are still very few hydrogen fueling stations. It’s not readily available yet, but it’s much faster to fill up with hydrogen than to wait for your electric car to recharge. Infrastructure is key.

Hydrogen systems for mission-critical settings

To help meet the goal of sustainable energy resilience, hydrogen can provide reliable power with zero carbon emissions at the point of use. A modular and scalable hydrogen fuel cell system enables mission-critical power users, such as data centers, utilities, ports, airports, and wastewater treatment plants, to rapidly deploy a sustainable energy solution. These systems can be used as a prime or backup power source, for peak shaving, or as part of a distributed energy network.

Hydrogen fuel cell technology for power generation will enable businesses to achieve the emissions reductions they need without compromising their mission-critical power supplies.