Ammonia Engine Development by Toyota and Daihatsu Tackles Hydrogen Range Limits
Automotive engineering teams are testing liquid ammonia to solve the low energy density that hobbles hydrogen fuel cells. Ammonia offers a carbon-free alternative to gasoline because its chemical formula, NH3, contains no carbon atoms to emit during combustion. Guangzhou Automobile Group pioneered a four-cylinder ammonia engine in 2023, and Toyota divisions are now expanding the technology with co-firing concepts.
Daihatsu Exhibits Co-Firing Concept at Japan Mobility Show
Daihatsu exhibited an Ammonia/Hydrogen Co-firing Engine built into a 658cc three-cylinder Kei-car mill at the Japan Mobility Show. The system converts stored ammonia back into hydrogen on the spot before ignition, which solves the poor ignition properties of liquid ammonia while avoiding the severe storage pressure required for pure hydrogen. Toyota Industries Corporation has also developed an ammonia-fueled motor designed to operate as a stationary or vehicular generator, with public demonstrations scheduled to begin.
Engineering Hurdles Facing Liquid Ammonia Fuel
Ammonia is only half as energy dense as gasoline, though it remains denser than compressed hydrogen. Liquid ammonia requires continuous refrigeration below -28 degrees Fahrenheit and sustained pressure to remain in liquid form at gas stations and inside storage tanks. Raw ammonia is highly corrosive to metals containing copper, brass, and iron, requiring engine bays and fuel lines constructed entirely of steel. According to the U.S. Centers for Disease Control and Prevention, ammonia exposure also presents severe chemical hazards, including skin blistering and chemical burns.
Frequently Asked Questions About Ammonia Combustion
Why do ammonia engines require a secondary fuel or conversion step?
Ammonia does not readily ignite at normal ambient temperatures and requires cooling below -28 degrees Fahrenheit to stay liquid. Manufacturers like GAC initially added gasoline to assist combustion, while newer concepts from Daihatsu and Toyota convert the ammonia back into hydrogen on the spot to achieve smooth running.
What are the primary emissions challenges of burning ammonia?
Combustion of ammonia creates nitrogen emissions that cause toxic air pollution harmful to human respiration.
How does ammonia energy density compare to traditional fuels?
Ammonia has roughly half the energy density of gasoline, making it less efficient for long-range passenger cars. However, it surpasses compressed hydrogen in energy density and eliminates the need for heavy battery packs found in standard electric vehicles.
Worth a look