Fuel Cells: How They Work and How They're Used (Text Alternative Version)
This is the text alternative transcript for the U.S. Hydrogen Program podcast titled: Fuel Cells: How They Work and How They're Used. The media files can be accessed on the DOE Hydrogen Program Media Files page.
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Welcome to The Hydrogen Report. I'm Mike Weiner.
In this episode we're going to talk about fuel cells — what they are, how they work, and how they're used. Let's get started...
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Fuel cells are not mysterious devices that magically make energy. In fact, despite their modern high-tech aura, fuel cells actually have been around since the early 19th century. Although they were generally considered a curiosity in the 1800s, greater understanding of fuel cell science has fostered further research and development to make practical fuel cells.
In the 1960s, NASA — the National Aeronautics and Space Administration — needed to power its manned space flights. Batteries were too heavy, solar energy was too expensive, and nuclear power was too risky. NASA awarded a number of research contracts to develop a practical working design for a fuel cell. This research led to the development of the first Polymer Electrolyte Membrane, the essential building block of the modern fuel cell.
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As you may already know, hydrogen is a versatile energy carrier that can be used to power nearly every end-use energy need. A fuel cell is an energy conversion device that can efficiently capture and use the power of hydrogen.
Fuel cells can generate a wide range of power and are well suited for a variety of applications. Stationary fuel cells can be used for emergency backup power to supplement the grid, power for remote locations, distributed power generation, and cogeneration, in which excess heat released during electricity generation is used for other applications. Fuel cells can power almost any device that uses batteries, from video cameras to laptops and forklifts. And fuel cells can also provide primary and auxiliary power for transportation, including personal vehicles, trucks, buses, and marine vessels.
So what exactly is a fuel cell and what are the advantages to using one?
Well, fuel cells convert the chemical energy in hydrogen to electricity and heat. It doesn't happen through combustion, like in our car's engine; it happens electrochemically. In a fuel cell, hydrogen combines with oxygen from the air to create electricity, with pure water and heat as the only byproducts.
Creating electricity through an electrochemical process sounds complicated, so we asked Dr. Nancy Garland of the U.S. Department of Energy, to simplify it for us:
"Picture a sandwich — two thin pieces of bread with a big slice of cheese in the middle. That's your fuel cell — two electrodes (the bread) and a membrane (the cheese)...only much thinner. The membrane is the consistency of plastic wrap and thinner than a single sheet of paper. The electrodes are carbon spheres covered with tiny platinum particles embedded in plastic material, and even thinner than the electrodes.
So hydrogen enters on one side of the cell, where it splits into protons and electrons. The membrane only allows the protons to pass through it — the electrons must pass around the membrane in an outside circuit. This circuit is electricity that can be used to do work. On the other side of the membrane, the protons and electrons combine with oxygen, drawn from the air, to create water. This is an exothermic reaction, releasing heat."
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A single fuel cell produces about one volt, which is not high enough to power even the smallest applications. To increase their power, fuel cells are stacked in series. That's why you'll often hear the term, "fuel cell stack." A fuel cell stack can range from a few individual cells to hundreds, allowing the flexibility to run laptop computers — which need 50 to 100 watts of power — to homes that need 1 to 5 kilowatts of power — to vehicles that need 50 to 125 kilowatts — and even industrial applications requiring megawatts of power.
Not only are they pollution-free, but compared to internal combustion engines, fuel cells also have fewer moving parts requiring less maintenance, operate much more quietly, and can be two to three times more efficient.
Take vehicles, for example. Under normal driving conditions, the gasoline engine in a conventional car is less than 20% efficient in converting the chemical energy in gasoline into the power that actually moves your car. Hydrogen fuel cell vehicles, which use electric motors, are much more efficient and use up to 60% of the fuel's energy — this can mean more than a 50% reduction in fuel consumption compared to a conventional vehicle with a gasoline engine.
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So, what does the future hold for fuel cells? There are some challenges to overcome before they'll be as commonplace as batteries or combustion engines.
"Reducing cost and improving durability are the top challenges. Our research at DOE is focused on identifying and developing new materials that will reduce the cost and extend the life of fuel cell stack components. These components operate over a wide range of conditions, including temperature and humidity. Low cost, high volume manufacturing processes will also help to make fuel cell systems cost competitive with traditional technologies."
It'll be a while before we see fuel cell vehicles in every dealer showroom, but fuel cells for certain specialty applications are commercially available today. Concerns over air quality and the effect of battery change downtime on warehouse productivity are driving users to consider fuel cells over internal combustion engines and batteries for forklifts. For emergency back up power, fuel cells offer longer, continuous runtime and are more durable in harsh environments than batteries. And compared to generators, fuel cells have lower maintenance requirements, can be monitored remotely, and have lower emissions.
The added value of these features makes fuel cells an excellent alternative in these niche markets. In turn, early deployment will help to pave the way for future commercialization by improving and reducing the cost of the technology and building the domestic manufacturing infrastructure needed for the successful integration of hydrogen into our nation's energy portfolio.
Thanks for listening. If you'd like to learn more about hydrogen — and increase your H2IQ — visit hydrogen.energy.gov. And be sure to listen for future episodes of The Hydrogen Report.