Fuel Cell Electric Vehicles
Fuel cell electric vehicles, powered by hydrogen, have the potential to revolutionize our transportation system. They are more efficient than conventional internal combustion engine vehicles and produce no harmful tailpipe exhaust—their only emission is water. Fuel cell vehicles and the hydrogen infrastructure to fuel them are in an early stage of deployment. The U.S. Department of Energy is leading government and industry efforts to make hydrogen-powered vehicles an affordable, environmentally friendly, and safe transportation option. Hydrogen is considered an alternative fuel under the Energy Policy Act of 1992 and qualifies for alternative fuel vehicle tax credits.
What is a fuel cell electric vehicle?
Fuel cell electric vehicles use a completely different propulsion system than conventional vehicles, which can be two to three times more efficient. Unlike conventional vehicles, they produce no harmful exhaust emissions. Other benefits include increasing U.S. energy security and strengthening the economy.
Fuel cell electric vehicles are fueled with pure hydrogen gas stored directly on the vehicle. Fuel cell electric vehicles fueled with pure hydrogen emit no pollutants, only water and heat. These vehicles have the capability to refuel in as little as three minutes and can achieve a range of more than 300 miles on a single tank.
Fuel cell vehicles can be equipped with other advanced technologies to increase efficiency, such as regenerative braking systems, which capture the energy lost during braking and store it in a battery. These vehicles are nearing commercial readiness and many major auto original equipment manufacturers have announced plans to begin selling and leasing vehicles to the public starting in 2014.
How Fuel Cell Vehicles Work
Like battery electric vehicles, fuel cell electric vehicles use electricity to power a motor located near the vehicle's wheels. In contrast to other electric vehicles, fuel cell vehicles produce their primary electricity using a fuel cell powered by hydrogen, rather than a battery. During the vehicle design process, the vehicle manufacturer controls the power of the vehicle by changing the fuel cell size and controls the amount of energy stored on board by changing the fuel tank size. This is different than a battery electric vehicle where the amount of power and energy available are both closely tied to the battery size.
The most common type of fuel cell for vehicle applications is the polymer electrolyte membrane (PEM) fuel cell. In a PEM fuel cell, an electrolyte membrane is sandwiched between a positive electrode (cathode) and a negative electrode (anode). Hydrogen is introduced to the anode and oxygen (usually from air) to the cathode. The hydrogen molecules break apart into protons and electrons because of an electrochemical reaction in the fuel cell catalyst. Protons, travel through the membrane to the cathode.
The electrons are forced to travel through an external circuit to perform work (providing power to the car) then recombine with the protons on the cathode side, where the protons, electrons, and oxygen molecules combine to form water. See the fuel cell animation to learn more about the process.