Hydrogen Vehicles & Fuel Cells Practice

A fuel-cell electric vehicle (FCEV) makes electricity onboard and drives its wheels with a motor. A hydrogen combustion engine burns fuel to move pistons. These are different systems. Burning hydrogen in air can create nitrogen oxides; a pure-hydrogen fuel cell does not use combustion.

PEM means proton exchange membrane. Hydrogen enters one side and oxygen arrives in air on the other. At the catalyst, hydrogen separates into protons and electrons. Protons cross the membrane while electrons travel through an outside circuit, supplying current. Their reaction with oxygen forms water and releases heat. Multiple cells form a stack.

Stored hydrogen supplies the stack; electrical power reaches the traction motor through power electronics. A traction battery buffers energy and captures some braking energy. The motor turns the wheels through the drivetrain. Cooling controls component temperatures. A DC/DC converter supplies lower-voltage accessories. Exact layouts vary by vehicle.

Hydrogen carries energy; producing it also takes energy. Electrolysis uses electricity to separate water into hydrogen and oxygen. Other processes obtain hydrogen from fuels such as natural gas. Production, electricity supply and delivery affect the overall environmental result. Water at the vehicle exhaust does not mean the entire supply chain has no emissions.

Vehicle hydrogen storage uses specialized equipment. Hydrogen can ignite readily and its flame can be difficult to see. Ventilation and engineered detection matter. High-voltage components also require trained service. Do not open tanks, loosen hydrogen fittings, bypass protective controls or attempt energized electrical work. For a suspected leak or damaged vehicle, keep away and contact emergency responders or qualified service as appropriate.

Use this module to learn the principles and vocabulary. Refueling and service instructions must come from the vehicle manufacturer and station operator. Check current station access before planning a journey. APG wrote these lessons and practice questions for independent learning; they are not manufacturer training, certification or an official exam. References below support the technical facts and provide further reading.