Electric and hybrid cars are gaining in popularity, in part because they help lower the amount of carbon emissions that are released into the atmosphere. But they're not the only option for more environmentally friendly driving. Hydrogen fuel cell electric cars sound like something out of science fiction, but these vehicles have been around for longer than you might think. If you're interested in another alternative to the combustion engine, here's how they work.
How a Hydrogen Fuel Cell Works
Hydrogen vehicles are a type of electric car that use fuel cells to power the motor instead of relying primarily on a lithium-ion battery pack; they don’t burn fuel like gasoline cars. As with EVs, hydrogen cars don’t generate harmful emissions—the only by-product is water vapor. Since they’re EVs, you’ll also hear them called fuel cell electric vehicles (FCEVs).
The fuel cells are similar in design to a lithium-ion battery: they have an anode, a cathode, and a catalyst that triggers the separation of electrons and protons from hydrogen gas pumped inside. Like the lithium-ion cells in an EV battery, hydrogen cars have multiple fuel cells working at once to generate electricity. That collection of cells is called the hydrogen fuel cell stack.
Hydrogen from the car’s onboard fuel tanks combines with oxygen inside the fuel cell stack to generate electricity via a process called reverse electrolysis. The electrons are removed from the hydrogen gas, sent through the circuit to power the motor, and combine with oxygen on the other side of the circuit to form water vapor, which is vented via the car’s exhaust.
The electricity that is generated from the hydrogen fuel cells can take two paths, depending on the situation. The energy either powers the electric motor directly or charges a small lithium-ion battery that helps power the motor and can store the energy for later use. This battery also captures power from the vehicle’s regenerative braking system for later use and stores excess power from the fuel cell stack during low-energy driving. If more demand is placed on the engine, the battery kicks in to help.
Refueling and Range
Refueling an FCEV’s hydrogen tanks is about as fast as filling up a gas car, one serious advantage that hydrogen cars have over battery EVs. You just pull up to the fueling station, connect the hose, and the tank is full in around five minutes.
An FCEV can have multiple hydrogen gas tanks on board. Since hydrogen can be highly flammable if handled improperly, those fuel tanks are thick-walled, pressurized, and tested to ensure crash safety. Failsafes are also built into the vehicle that ensure the hydrogen is dispersed and released if, for example, the fuel cell is removed or overheats.
Another advantage hydrogen cars have over battery EVs at the time of this writing is their longer range. FCEVs can get between 300 and 400 miles before they need to be refueled, according to California’s Drive Clean initiative. All-battery EVs, on the other hand, have an average EV range of around 250 miles at the time of this writing.
The Challenges of Fuel Cell Vehicles
Fast refueling, electric power, and the only byproduct is water—sounds like the perfect green vehicle, right? Well, it could be, but unlike electric vehicles, FCEVs just aren’t there yet.
For starters, while they have a greater range than EVs, FCEVs are more expensive to refuel, in part because hydrogen is so expensive to produce. It may be the most abundant element on the planet, but refining it into a form that can power a vehicle takes effort, and that effort is reflected in the cost per tank.
FCEV refueling infrastructure is also severely lacking at the moment. There are fewer than 400 FCEV fueling stations worldwide, though there are efforts to build more stations; the US aims to have 1,000 online by 2030. Still, that's a lot fewer hydrogen refueling stations than EV charging ports, which numbered around 110,000 in the US as of September 2021.
Another challenge facing FCEVs is that while they may run emission-free themselves, the plants that create their hydrogen fuel often do so by burning fossil fuels in a process called steam reforming. If that continues, FCEVs won’t be doing as much for the environment as they could, and they can’t really be called zero-emission vehicles.
Alternative processes being explored include water electrolysis, which uses a renewable source like solar to generate electricity that can be used to separate the hydrogen from water.
FCEV vs. EV
Hydrogen vehicles have a lot in common with battery-powered cars such as the Ford Mustang Mach-E (above) and the Tesla Model 3. Both battery EVs and FCEVs use electricity instead of combustible fuel, they both have electric motors and onboard batteries, and neither one emits harmful gasses. The differences come down to infrastructure, fuel, and availability.
Battery EVs have a more robust infrastructure for public recharging than hydrogen vehicles. While still not as prevalent as gas stations, there are now thousands of EV recharging locations across the US. Meanwhile, all of the hydrogen refueling stations in the US are located in California, so long road trips are out of the question.
The cost of refueling is also worth considering. Since it's more costly to produce hydrogen gas for FCEVs at the moment, filling up your FCEV is more expensive than it is for an electric car. However, a hydrogen vehicle can be refueled many times faster than an EV and can store excess electrical energy in its battery, allowing it to recharge while driving. Battery EVs, by contrast, need to be plugged into the grid to regain most of their power.
Of course, the biggest issue is that FCEVs aren’t widely available in the US yet. Only a few manufacturers are selling them to the public; the Toyota Mirai and Hyundai Nexo are the most prevalent names in the race currently.
Despite hydrogen's limitations, countries around the world are seeing it as a viable alternative energy source for everything from cars and buses to airplanes. If we can find a cost-effective way to make hydrogen production more environmentally friendly and build out the necessary refueling infrastructure, FCEVs could mean a huge leap forward for green transportation.