Fuel cell cars, 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 development.
What is a Fuel Cell Car?
Like electric cars, fuel cell cars use electricity to power motors located near the vehicle’s wheels. In contrast to electric vehicles, fuel cell vehicles produce their primary electricity using a fuel cell. The fuel cell is powered by filling the fuel tank with hydrogen.
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 to the cathode. The hydrogen molecules travel through the membrane to the cathode but not before the membrane strips the electrons off the hydrogen molecules.
Honda FCX Hydrogen Fuel Cell Vehicle
The electrons are forced to travel through an external circuit to recombine with the hydrogen ions on the cathode side, where the hydrogen ions, electrons, and oxygen molecules combine to form water. The flow of electrons through the external circuit forms the electrical current needed to power a vehicle.
Fuel cell cars can be fueled with pure hydrogen gas stored directly on the vehicle or extracted from a secondary fuel – such as methanol, ethanol, or natural gas – that carries hydrogen. These secondary fuels must first be converted into hydrogen gas by an onboard device called a reformer. Fuel cell cars fueled with pure hydrogen emit no pollutants, only water and heat. Vehicles that use secondary fuels and a reformer produce only small amounts of air pollutants.
This Hydrogen, Fuel Cells and Infrastructure Technologies Program animation shows how polymer electrolyte membrane (PEM) fuel cells work.
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 large battery.
Fuel Cell Vehicle and Infrastructure Development
Because fuel cell cars require a completely new vehicle propulsion system and new fueling infrastructure, many deployment issues can only be addressed by integrating and evaluating the components in complete systems. The U.S. Department of Energy (DOE) is developing and testing complete system solutions that address all elements of infrastructure and vehicle technology, validating integrated hydrogen and fuel cell technologies for transportation, infrastructure, and electric generation in a systems context under real-world operating conditions.
Schematic of a fuel cell vehicle