Battery-electric vehicles (BEVs) dominate the talk about zero-emission vehidcles, and cars like the Chevrolet Bolt EV and Tesla Model 3 are well-known examples of BEV technology. But another type of electric vehicle — the fuel cell electric vehicle (FCEV) — also produces virtually no harmful exhaust emissions and has virtually all of the other advantages of a BEV.
Furthermore, an FCEV offers quick refueling in a process that mimics filling the gasoline tank of a conventional car. Thus, a fuel cell car regains its full driving range in a matter of five or 10 minutes versus the lengthy charge times of current BEVs.
While all of this sounds exceptionally promising, FCEVs have limitations. One is that until recently fuel cells compact enough to power an automobile have been expensive to manufacture. That issue should resolve itself as the production of fuel cell vehicles scales up.
But an even bigger issue is the availability of hydrogen, the element that, when combined with oxygen, creates the electricity that powers the FCEV. Hydrogen is a common element, but in nature it is rarely found in its isolated state as a highly flammable gas. Most often it combines with other elements in compounds including hydrocarbons like oil and natural gas and with oxygen as water. Because of this, hydrogen must be manufactured, a process that requires energy, and it must be transported to refueling stations. In some instances, it is made at refueling stations by deriving it from water.
No matter how the hydrogen fuel is created, another issue is that the United States has only a tiny number of hydrogen refueling stations open to the public, nearly all of them located in the larger urban areas of California. This creates a chicken-and-egg conundrum. Should society build a hydrogen delivery infrastructure to serve fuel cell vehicles in the anticipation that more FCEVs will hit the road in the future? Or should the hydrogen infrastructure wait until there are enough FCEVs on the road to justify the investment?
In the latter case, there might never be enough fuel cell vehicles in use to spur the construction of hydrogen infrastructure because few people will buy a FCEV if they believe they will have a difficult time filling its tank.
How Does a Fuel Cell Work?
A fuel cell generates electricity through an electrochemical reaction of hydrogen and oxygen that occurs within the vehicle itself. In contrast, the electricity for a BEV is generated outside the vehicle and stored in the vehicle’s battery pack. So, a big advantage of FCEVs versus BEVs is fuel cells don’t require recharging like batteries. Instead, they continue to produce electricity as long as hydrogen and oxygen are available to the car’s fuel cell.
A fuel cell has an anode, cathode, and an electrolyte membrane. It creates an electric current by passing hydrogen through the anode and oxygen through the cathode. At the anode, a catalyst splits the hydrogen molecules into electrons and protons. The protons pass through the porous electrolyte membrane, while the electrons are forced to a circuit as an electric current. At the cathode, the protons, electrons, and oxygen combine to produce water molecules.
Byproducts of this process are water, typically in vapor form, and heat. With no moving parts, fuel cells operate silently and reliably. The fuel cell’s waste heat can be used for heating or cooling.
How Does a Fuel Cell Vehicle Work?
Like battery-electric vehicles, fuel cell vehicles use electricity to power one or more electric motors that drive the wheels. In an FCEV, the electricity comes directly from the fuel cell or from an onboard battery pack that stores both excess electricity and electricity generated by regenerative braking. That process, also used in BEVs and hybrids, saves energy that would otherwise be lost as heat during braking. The amount of energy available to drive an FCEV is the sum of the electricity produced by the hydrogen stored in a tank onboard and the energy stored in the battery pack.
During driving, a simple transmission delivers electricity from the fuel cell and/or from the battery pack to the electric drive motor(s) powering the vehicle. An electronics controller manages the flow of electricity, thus controlling the speed and torque of the electric drive motor. Additionally, an FCEV also has a cooling system that maintains the proper operating temperature range of the fuel cell, electric motor, power electronics, and other components.
The hydrogen fuel is stored in a pressurized tank designed specifically for that use, and the fuel filler is significantly more high-tech than the nozzle on a gasoline pump at the local gas station. Though more complicated, hydrogen refueling is only slightly more difficult than putting gas in a conventional car, and the process takes a comparable amount of time.
Why Aren’t There More Fuel Cell Vehicles?
Fuel cell vehicles offer several advantages over battery electric vehicles, most notably when comparing refueling versus recharging times. Furthermore, in an FCEV, electricity is generated onboard producing only heat and water vapor while a BEV operates on electricity produced elsewhere, typically by fossil-fuel-powered generating plants. However, the process of manufacturing the hydrogen fuel used to power an FCEV is not always clean, either.
The biggest tripping point to widespread FCEV use is the lack of hydrogen fueling stations. Nearly all hydrogen stations open to the public are located in California, where the state is investing in a hydrogen refueling station infrastructure. No surprise, but that’s where the three FCEVs available in the United States are on sale (with a single exception). They include the Honda Clarity Fuel Cell, the Hyundai Nexo, and the Toyota Mirai. The Mirai is also available in Hawaii.
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