Fuel Cells: What They Are and How They Work
Plug has a long, celebrated history in fuel cell technology — crafting innovative solutions across the energy value supply chain as global businesses work to decarbonize their operations.
As green hydrogen fuel cells become both increasingly viable and vital as an energy choice in the age of climate change, those in sectors ranging from automobile, retail, electric utilities, and agriculture — among others — have all shown increased efforts to green their portfolios and play a part in catapulting climate solutions.
With recent U.S. Congressional action accelerating tax incentives for fuel cell applications, and multiple countries aiming to emulate an energy strategy backing fuel cells’ growth, fuel cells remain top-of-mind for many business leaders and policymakers.
What is a fuel cell anyway? How does a fuel cell work in a car and other power applications? Further, what are the various fuel cell types? And what’s the difference between a battery and a fuel cell?
These questions and their answers speak directly to the core of Plug’s business model and customer offerings in the fuel cells space. Further, they touch upon the inherent advantages in our proton exchange membrane (PEM) fuel cells technology, offering us a sector-wide advantage due to their wide utility in both stationary and mobility power generation.
Here are some answers to often-pondered questions about fuel cell technology.
What is a Fuel Cell?
A fuel cell is an electrochemical power generator. Fuel cells combine hydrogen and oxygen to produce electricity with water and heat generated as byproducts. Fuel cells, like a battery, create energy via an electrochemical process and not combustion. But like an internal combustion engine, fuel cells also intake fuel sources and generate a chemical reaction to produce power, yielding energy in an array of use cases. That fuel resource, in Plug’s case, is hydrogen.
How Do Fuel Cells Work?
Fuel cells, summed up, consist of three main components: An anode, a cathode, and an electrolyte membrane, working akin to batteries in that they don’t need charging. Instead, operating continuously provided fuel is supplied into the mechanism. Those three components interact, in turn, intaking and through putting energy.
Plug’s PEM fuel cells function by passing hydrogen through the anode side of the mechanism mentioned above. Oxygen, from the air around us, is passed through the cathode side. Hydrogen molecules then split into electrons and protons on the anode side. Protons next pass through an electrolyte membrane (hence PEM). From there, electrons move through a circuit, generating current and excess heat. At the cathode side, the protons, electrons, and oxygen combine to produce water.
This video shows how the process works:
For Earth Day 2020, Plug released a more in-depth presentation about fuel cells, how they work, and how they’re used – you can check it out here:
What Are Fuel Cells Used For?
In a 2017 report titled “The Business Case for Fuel Cells,” the Argonne National Laboratory concluded that fuel cells can provide “power to retail stores, data centers, production sites and other company facilities, greatly reducing emissions and doing so at a cost that can be competitive with the local electric grid in some states.”
For Plug, our hydrogen fuel cell fleet is on the rise and on the march — demonstrating clearly the benefits of fuel cells, their growth prospects, and a hunger for greater deployment, having recently passed 1 billion hours of operation in commercial applications. Plug’s hydrogen and fuel cell solutions aren’t limited to American companies. In fact, global companies have adopted Plug’s fuel cell technology. To cater to customer demands, Plug is working rapidly to build its offerings. In South Korea, for example, Plug intends to build a second PEM hydrogen fuel cells gigafactory by 2023 to continue to scale hydrogen fuel cells in a $1.6 billion joint venture with SK Group, announced in February 2021. At that gigafactory, Plug will produce and sell products spanning the hydrogen economy value chain, including but not limited to our GenSure stationary power fuel cells and ProGen fuel cell engines.
At large, Plug has deployed several tens of thousands of fuel cell systems, and the number grows every month, as countries around the world cash in on plans to increase business efficiency and curtail greenhouse gas budgets.
What Are the Fuel Cell Types?
Though Plug uses PEM fuel cells, there are a handful of other fuel cell types, as well. Each one has different use cases. Speaking to that, five main types of fuel cells exist including the PEM genre, detailed in here:
- Proton Exchange Membrane or Polymer Electrolyte Membrane (PEM) Fuel Cells are mainly used for mobility purposes, such as micro-mobility vis-a-vis forklifts and other materials handling machinery of the sort, the marquee market for Plug’s PEM fuel cells. They are also used in e-mobility and stationary power applications.
PEM fuel cells require a low operational temperature, making them the most sensible for vehicles needing short periods of time between ignition and start-up. A PEM fuel cell generally operates at a temperature of 80°C (176°F). This low temperature, the U.S. Department of Energy notes, also “results in less wear on system components, resulting in better durability.”
- Solid Oxide Fuel Cells (SOFCs), more traditional for stationary primary power usages, require a temperature of 1000°C (1,830°F) for usage and energy production. Unlike a PEM fuel cell, SOFCs utilize a solid electrolyte (most times a ceramic) sitting between an anode and cathode. Fuel, generally natural gas, gets delivered to the anode. Oxidant, generally air, gets delivered to the cathode. Combined, this creates a chemical interaction releasing electrons through a circuit producing electricity.
Because of their higher startup temperature, SOFCs exist mostly for energy needed on a longer-lasting basis, often as a source of backup power generation.
- Alkaline Fuel Cells are widely used for outer space voyages, utilizing a potassium hydroxide solution in water as the electrolyte. Several types of metals, in turn, can serve as the catalyst at the anode and cathode. They operate at a temperature of 60-80°C (140-176°F).
- Phosphoric Acid Fuel Cells (PAFCs), operational at 200°C (392°F), utilize liquid phosphoric acid as their electrolyte and electrodes, containing a platinum catalyst material. They are typically used in “hotels, hospitals, grocery stores, and office buildings, where waste heat can also be used,” the U.S. Department of Energy notes.
- Molten Carbonate Fuel Cells, which operate at a temperature of 600°–700°C (1112°F-1292°F), are similar to SOFCs in that they are most useful for stationary purposes due to their mandated high ignition temperature. They primarily function today as a combined heat and power source within natural gas- and coal-based power plants for electricity-generating functionality. Different from the other fuel cell types and due to their high operational temperature, external fuel is not needed as an input and hydrogen can still be yielded as an output via a process called internal reforming.
To read more on all of these fuel cell types, see the U.S. Department of Energy’s explainer on the different types of fuel cells and how they work.
How Do Fuel Cells Work in Cars?
Hydrogen fuel cell vehicles, known as FCEVs or fuel cell electric vehicles, utilize hydrogen within a PEM fuel cell stack webbed into electric vehicles, supplanting standard internal combustion engines or the aforementioned battery-powered engines currently powering electric vehicles. Unlike the internal combustion engine and analogous with electric vehicles, hydrogen fuel cell vehicles do not emit pollutants or greenhouse gasses into the atmosphere and instead only emit water vapor and heat, making them beneficial for combating climate change.
Unlike a battery-powered vehicle, which takes an overnight or whole workday to fully charge, fuel cell vehicles can be fueled up within a matter of minutes at fueling station.
Among its other advantages, a hydrogen fuel cell’s light weight also plays an auspicious role within heavy-duty vehicles compared to their battery-powered competitors traveling a similar number of miles.
“A battery-powered, relatively light-weight family sedan may boast a range of around 400-500 kilometres before it must recharge, however a heavy-duty truck would be lucky to get half that range,” Reuters reported in November 2022. “A larger battery, for longer range, would be bulky, taking away precious cargo space and means an extra payload of as much as five tons for an already heavy, fully loaded vehicle.”
Reuters further points out that some FCEVs, in heavy-duty vehicles, enjoy a range of up to 1,000 kilometers (621 miles). At-large, hydrogen cell vehicles average 300 to 400 miles of range, according to the California Air Resources Board.
On the other end of the continuum of vehicular size, Plug’s PEM hydrogen fuel technology can bolster warehouse productivity by up to 15% in utilizing fuel cell forklifts for materials handling. Outside of material handling, Plug and Renault have launched Hyvia to commercialize fleet vehicles — or delivery vans — powered by hydrogen.
The Hydrogen Fuel Cell Partnership, a trade association of which Plug is a part, points out that “many automakers of passenger cars aim for a fuel cell stack lifespan of at least 5,000 hours or approximately 150,000-200,000 miles.” Additively, the Partnership further elucidates that “the heavy-duty category, many bus fuel cell stacks (power plant) have reached lifetimes of 20,000 hours and more, with a goal of 30,000 hours by 2030.”
California, a state on the cutting edge of hydrogen fuel cell vehicles policy, has committed $20 million per year to develop hydrogen fueling stations statewide with a goal of having 200 stations by 2025. And China, one of the world’s largest economies, has a policy goal of deploying over one million FCEVs to market by 2030, as pointed out by the German trade association National Organization Hydrogen and Fuel Cell Technology.
What Are the Advantages of Fuel Cells?
The advantages of fuel cells, which create energy via an electrochemical process and not combustion, are many compared to combustion engines.
Most importantly from a climate change perspective, fuel cells are non-emitting and can have a nearly nil greenhouse gas footprint when utilizing green hydrogen — or hydrogen made from renewable energy resources — which is the central focus for Plug as an industry leader.
In particular, PEM fuel cells have unique advantages over other fuel cell types due to the fact the power production market is currently more focused on growth in renewable energy over fossil fuel-using ones utilized by the other fuel cell types. Other fuel cell types, as of now, maintain a heavy dependence on fossil fuels. Read more about the advantages of fuel cells here.
How Do Batteries Differ from Fuel Cells?
Batteries compare to fuel cells in the way that cousins relate to one another: Similar in their metaphorical genetic makeup, but also far different in terms of their final mechanism for providing power and thus how they end up looking and functioning overall.
On the similar side of the ledger, both rely on electrochemical reactions and not combustion to induce energy, involving an anode and cathode. But the differences are also fundamental: while a battery stores electricity charged into it (think of purchased mini batteries for home appliances or a car), fuel cells create their own electricity via the electrochemical process used by the fuel cells to create electricity.
This means a fuel cell system, by definition, is an open power production loop that can be fed as long as fuel exists to do so, much like a traditional power generator. Battery systems, by contrast, are closed loops in need of either intermittent recharging sessions or eventual discarding. Because of that, as of now, fuel cells have a greater usage longevity.
In a 2019 research paper with lead researchers from the University of Waterloo, it was concluded that PEM hydrogen fuel cells could stand to become even more of a force to be reckoned with going forward from a longevity vantage point. The paper concluded that, with some spelled out tinkering, the ability exists to manifest a “new fuel cell that lasts at least 10 times longer than current technology, an improvement that would make them economically practical, if mass-produced, to power vehicles.”
Further, circling back to an earlier point and as Plug has pointed out before, while batteries contain toxic chemicals in need of disposal after their use, hydrogen fuel cells produce only warm water as their by-product. Relatedly, while hydrogen is among the world’s most abundant natural resources, batteries rely on lithium, a natural resource on the decline and currently subject to global discussions over the rare earth mineral’s depletion.
Looking at the big picture, the Argonne National Laboratory pointed out in the previously cited report titled “The Business Case for Fuel Cells” that “companies [are] finding value in improved operational efficiency and cost savings using fuel cells in forklifts and other vehicles over battery units – eliminating the need for, and space dedicated to, battery charging and swapping.”
Additionally, the report posits that “Fuel cells also allow for quicker refueling, which saves time, and full power operation throughout the shift, without any voltage sag or challenges when operating in refrigerated warehouse environments.”