A hydrogen vehicle is a type of vehicle that uses hydrogen as a source of energy to move. These vehicles can include cars, trains, rockets, forklifts, ships, and planes. Power is created by changing hydrogen's chemical energy into mechanical energy. This is done either by combining hydrogen with oxygen in a fuel cell to power electric motors or, less often, by burning hydrogen in an engine.

Hydrogen burns more cleanly than fuels like gasoline or methane. However, it is harder to store and transport because hydrogen molecules are very small. In the 2020s, hydrogen-powered cars for everyday use, such as passenger vehicles, were sold in limited numbers due to competition with battery-powered electric vehicles. By 2021, two models of hydrogen cars were available in some areas: the Toyota Mirai (2014–), the first mass-produced hydrogen fuel cell electric vehicle (FCEV), and the Hyundai Nexo (2018–). In 2024, the Honda CR-V e:FCEV became available for lease in very limited numbers.

As of 2019, most hydrogen was made using steam methane reforming, a process that releases carbon dioxide. Hydrogen can also be made by splitting water through electrolysis or using renewable resources with other methods, but these processes are expensive. Scientists are working on new technologies to reduce costs and increase production to match hydrogen made from natural gas.

Hydrogen vehicles have the advantage of long travel distances after a single refill. However, they face challenges, such as high carbon emissions when hydrogen is made from natural gas, high costs for building and maintaining infrastructure, and the need for large amounts of energy to produce and transport hydrogen. Hydrogen also has low energy content when stored at normal temperatures and pressures. Additionally, leaked hydrogen is invisible, highly flammable, and has a global warming potential 11.6 times stronger than carbon dioxide.

Vehicles

Hydrogen vehicles are being developed because they can help reduce the use of fossil fuels, lower greenhouse gas emissions, and decrease air pollution from transportation. For this to work, hydrogen must be produced in a clean way, especially in areas where other methods to reduce pollution are not as effective or efficient.

Many large rockets use liquid hydrogen as fuel, paired with liquid oxygen (LH2/LOX). One benefit of hydrogen is that it produces a higher exhaust velocity compared to other rocket fuels like kerosene or UDMH. This means rockets can use less fuel to move faster. Hydrogen also has a higher energy density than other fuels. LH2/LOX is the most efficient rocket fuel in terms of how much propellant is used.

A challenge with LH2/LOX engines is that liquid hydrogen is very cold and has a low density. This requires larger, insulated fuel tanks, which make the rocket heavier compared to using methane. Another issue is that hydrogen can easily evaporate, so rockets using LH2/LOX must be fueled shortly before launch. This makes them unsuitable for rockets that need to be launched quickly, like ICBMs. For first stages of rockets, denser fuels may offer some advantages due to smaller size and less air resistance.

The Space Shuttle used LH2/LOX to power fuel cells that provided electricity for its systems. The fuel cells produced water as a byproduct, which was used for drinking and other needs in space.

As of 2021, two hydrogen cars were available in select markets: the Toyota Mirai and the Hyundai Nexo. The Honda Clarity was also produced from 2016 to 2021. Hydrogen combustion cars are not available for sale. By the end of 2022, about 70,200 fuel cell electric vehicles had been sold worldwide, compared to 26 million plug-in electric vehicles. In 2023, 3,143 hydrogen cars were sold in the U.S., compared to 380,000 battery electric vehicles. As electric vehicles and battery technology grow, hydrogen's role in cars is becoming smaller. Some experts suggest hydrogen might still be used for classic cars or as a feedstock for efuel.

The first hydrogen-powered vehicle was the Chevrolet Electrovan, introduced by General Motors in 1966. The Toyota FCHV and Honda FCX, leased starting in 2002, were the first government-approved commercial hydrogen vehicles. The Honda FCX Clarity, leased in 2008, was the first mass-produced hydrogen vehicle. Honda created the first dealer network for hydrogen vehicles in 2008.

The 2013 Hyundai Tucson FCEV was a modified model offered only for lease. Hyundai claimed it was the first mass-produced hydrogen vehicle, but sales were low due to high costs and lack of infrastructure. The Hyundai Nexo, introduced in 2018, was named the "safest SUV" by Euro NCAP but was recalled in 2024 due to a faulty pressure relief device that could cause fuel leaks and fires.

Toyota launched the Mirai in Japan in 2014 and later sold it in California, Europe, and other regions. The Mirai has a range of 312 miles and can refill its tank in about five minutes. It was initially expensive, and Toyota faced losses on each sale. By 2019, over 10,000 Mirais had been sold, but by 2024, sales had dropped significantly. Many car companies tested hydrogen vehicles but shifted focus to battery electric vehicles. By 2020, most companies had stopped hydrogen car production, except for three.

In California, many public hydrogen stations cannot dispense fuel. In 2024, Mirai owners sued the state over the lack of hydrogen availability, claiming false advertising and broken warranties.

The International Energy Agency's 2022 report suggests hydrogen could meet about 30% of heavy truck energy needs by 2050, mainly for long-distance freight, while batteries might cover 60%.

In 2017, United Parcel Service tested hydrogen delivery trucks. In 2020, Hyundai started producing Xcient fuel cell trucks for Switzerland. In 2022, Australia used hydrogen trucks to transport zinc from a mine to a port.

Some experts suggest hydrogen might be used in shipping or airplanes, but others believe biofuels and batteries will be more successful. Companies like Boeing and the German Aerospace Center are testing hydrogen for planes. In 2008, Boeing tested a hydrogen-powered small aircraft. In 2010, Boeing unveiled the Phantom Eye UAV, powered by hydrogen.

As of 2019, hydrogen fuel cells are not used for large ships but are being studied for smaller electric vessels like ferries. Ammonia made from hydrogen is being explored for long-distance travel.

Fuel-cell buses were tested in Ursus Lublin in 2017. Solaris Bus & Coach introduced hydrogen buses in 2019, with several dozen ordered. The first U.S. city to operate a hydrogen bus fleet was not completed in the text.

Internal combustion vehicle

Hydrogen internal combustion engine cars are different from hydrogen fuel cell cars. A hydrogen internal combustion car is a slightly changed version of a traditional gasoline-powered car. These hydrogen engines burn fuel in the same way as gasoline engines, but the main difference is what comes out of the engine. Gasoline burning produces mostly carbon dioxide and water, along with small amounts of carbon monoxide, NOx, particulates, and unburned hydrocarbons. Hydrogen burning mainly produces water vapor as the exhaust.

In 1807, François Isaac de Rivaz created the first hydrogen-fueled internal combustion engine. In 1965, Roger E. Billings, a high school student, changed a Model A car to run on hydrogen. In 1970, Paul Dieges patented a way to modify internal combustion engines so that gasoline-powered engines could use hydrogen instead.

Mazda developed Wankel engines that use hydrogen, which are used in the Mazda RX-8 Hydrogen RE. The benefit of using internal combustion engines, such as Wankel and piston engines, is that it costs less to change how they are made for production.

Fuel cell

Hydrogen fuel cells cost more money to make because they need rare materials, like platinum, to work as a catalyst. In 2014, Pat Cox, who was the President of the European Parliament, said Toyota would lose about $100,000 for each Mirai car sold at first. In 2020, scientists at the University of Copenhagen's Department of Chemistry created a new type of catalyst to help lower fuel cell costs. This new catalyst uses much less platinum because the platinum particles are placed on durable nanowires instead of being coated on carbon. In traditional fuel cells, the carbon coating keeps the particles in place but makes the catalyst unstable over time, requiring more platinum. The researchers now want to expand their work so the technology can be used in hydrogen-powered vehicles.

Early fuel cell designs had problems at low temperatures, such as limited range and difficulty starting in cold weather. These issues have been solved, so they are no longer major problems. In 2014, users reported that their fuel cell cars could still operate in temperatures below freezing without greatly reducing range. Studies using neutron radiography showed ice forms in the cathode during cold starts, and there are three stages to the cold start process. Nafion ionic conductivity and a measurement called "coulomb of charge" were also studied to evaluate cold start performance.

The lifespan of fuel cells is similar to that of other vehicles. Polymer-electrolyte membrane (PEM) fuel cells can last about 7,300 hours under normal use conditions.

Hydrogen

Hydrogen is not found in easy-to-access sources like fossil fuels or helium. It is made from materials such as natural gas, biomass, or by splitting water using electricity. One benefit of using hydrogen in vehicles on a large scale is that it may reduce emissions of greenhouse gases and substances that contribute to ozone. However, in 2014, 95% of hydrogen was produced from methane. It can also be made using heat-based or high-temperature methods with renewable materials, but this process is costly.

Renewable electricity can be used to convert water into hydrogen. Some projects, like wind-to-hydrogen plants, are testing ways to make hydrogen production cheaper and more efficient. One challenge of using hydrogen in vehicles is storing it safely on the vehicle. In September 2023, hydrogen cost $36 per kilogram at public fueling stations in California, which made it 14 times more expensive per mile for a Mirai compared to a Tesla Model 3.

Hydrogen used in vehicles can be made through various heat-based processes, including using natural gas, coal (through a method called coal gasification), liquefied petroleum gas, biomass (through biomass gasification), a method called thermolysis, or from a microbial waste product called biohydrogen. As of now, 95% of hydrogen is made using natural gas. Hydrogen can be produced from water through electrolysis with an efficiency of 65–70%. It can also be made using chemical hydrides or aluminum. Current methods for making hydrogen use between 25% and 50% of the energy value of the hydrogen fuel for production, compression, liquefaction, and transportation.

Producing hydrogen from fossil fuels leads to greenhouse gas emissions, which would also happen if methanol were converted to hydrogen on a vehicle. Using renewable energy to make hydrogen would avoid these emissions, but renewable energy production would need to expand significantly to meet transportation needs. In some countries, renewable energy is being used more widely to create hydrogen. For example, Iceland uses geothermal power, and Denmark uses wind energy.

Hydrogen is stored in vehicle tanks at pressures of 350 bar (5,000 psi) or 700 bar (10,000 psi) using type IV carbon-composite technology. Hydrogen has a very low energy density compared to gasoline, so it must be stored as a super-cooled liquid or highly compressed gas, which requires extra energy. In 2018, researchers in Australia used a membrane technology to separate hydrogen from ammonia to power a Toyota Mirai and Hyundai Nexo. Ammonia is safer to transport in tankers than pure hydrogen.

To deliver hydrogen fuel to transportation users, significant investments are needed, including building new port infrastructure, buffer storage, pipelines, ships, refueling stations, and facilities to convert hydrogen into easier-to-transport forms. The International Energy Agency (IEA) highlights the need for refueling stations near industrial hubs and airports, as well as major investments for hydrogen use in shipping.

As of 2024, there were 53 publicly accessible hydrogen refueling stations in the U.S., with 52 in California (compared to 65,000 electric charging stations). By 2017, Japan had 91 hydrogen fueling stations. In 2024, Mirai owners in California filed a group lawsuit over the lack of hydrogen availability for fuel cell electric cars, citing claims of false advertising and broken warranties.

Rules and standards for hydrogen safety and storage have slowed the use of hydrogen technologies. To support the use of hydrogen in consumer products, new rules and standards must be created and approved by federal, state, and local governments.

Official support

Fuel cell buses are supported. The New York State Energy Research and Development Authority (NYSERDA) has created incentives for hydrogen fuel cell electric trucks and buses.

Criticism of hydrogen cars

Critics say that using hydrogen in cars on a large scale is unlikely to happen for many years and that hydrogen cars may take attention away from easier ways to reduce fossil fuel use in vehicles. Joseph Romm, a former U.S. Department of Energy official, said that hydrogen cars are one of the least efficient and most expensive ways to reduce greenhouse gases. He explained that building a nationwide network of hydrogen refueling stations would cost too much. Robert Zubrin, the author of Energy Victory, called hydrogen "just about the worst possible vehicle fuel."

As of 2024, more than 95% of hydrogen is made using a process called steam methane reformation, which produces mostly grey hydrogen (about 95%), some blue hydrogen (a small portion), and only about 1% green hydrogen. This process creates carbon emissions similar to those from gasoline cars. Even if more hydrogen were made using renewable energy, experts say it would be easier to use that energy to charge batteries in all-electric or plug-in hybrid vehicles instead. Over their lifetimes, hydrogen vehicles will emit more carbon than gasoline vehicles.

In 2009, The Washington Post asked, "Why store energy as hydrogen and then use it to make electricity for a car when electrical energy is already available to charge car batteries?"

Volkswagen’s Rudolf Krebs said in 2013 that hydrogen mobility only makes sense if green energy is used. However, converting electricity to hydrogen loses about 40% of the energy. Compressing and storing hydrogen also uses more energy. Then, converting hydrogen back to electricity in a fuel cell causes another loss. Krebs said that from 100% of original electric energy, only 30% to 40% remains.

A 2016 study by scientists at Stanford University and the Technical University of Munich found that investing in all-electric battery vehicles is a more economical choice for reducing carbon dioxide emissions.

A 2017 analysis in Green Car Reports said that the best hydrogen-fuel-cell vehicles use more than three times as much electricity per mile as electric vehicles. They also produce more greenhouse gas emissions and have very high fuel costs. Building the infrastructure needed for hydrogen vehicles could cost up to $400 billion. These vehicles are likely to remain a small part of the market with little impact on oil use. The U.S. Department of Energy agrees that hydrogen made from grid electricity via electrolysis is better than other methods, but not for most other production methods.

A 2019 video by Real Engineering said that moving a fuel-cell vehicle one kilometer costs about eight times as much energy as moving an electric vehicle the same distance.

Studies since 2020 show that hydrogen vehicles are only 38% efficient, while battery electric vehicles are 80% to 95% efficient. A 2021 report by CleanTechnica found that most hydrogen is still made from polluting grey hydrogen, and delivering hydrogen would require expensive new infrastructure. The two advantages of fuel-cell vehicles—longer range and fast refueling—are being reduced by improvements in battery and charging technology. A 2022 study in Nature Electronics and an article in Recharge News also supported these findings. A 2022 report by Germany’s Fraunhofer Institute said hydrogen is unlikely to be widely used in road transport.

A 2023 study by the Centre for International Climate and Environmental Research (CICERO) estimated that leaked hydrogen has a global warming effect 11.6 times stronger than carbon dioxide.

Safety and supply

Hydrogen fuel is dangerous because it can catch fire easily with very little energy, burns strongly, and can escape from storage tanks because its molecules are very small. In 2024, Hyundai recalled all 1,600 Nexo vehicles sold in the United States up to that time because a faulty "pressure relief device" could cause fuel leaks and fires. Hydrogen can also weaken the materials used in storage tanks and nearby car parts over time if leaks happen often. Since hydrogen has no smell, leaks are hard to detect without special tools.

Explosions at hydrogen fueling stations have been reported. These stations usually receive hydrogen delivered by trucks from suppliers. If there is a problem at a hydrogen supply facility, it can stop multiple fueling stations from operating.

Comparison with other types of alternative fuel vehicle

Hydrogen vehicles are among the options being considered as replacements for traditional vehicles that use fossil fuels.

Natural gas vehicles (NGVs) use methane, which comes from natural gas or biogas, as fuel. Methane has more energy than hydrogen, and NGVs powered by biogas produce very little carbon emissions. Unlike hydrogen vehicles, natural gas vehicle technology has been used for many years, and there are already filling stations that can refuel both commercial and home vehicles. By the end of 2011, there were 14.8 million natural gas vehicles worldwide, mostly bi-fuel vehicles that can use both natural gas and gasoline. Methane is also used to make hydrogen gas through a process called steam reforming, which is commonly used to power electric cars with fuel cells.

Methane can also be used as fuel for rockets.

Plug-in hybrid electric vehicles (PHEVs) are vehicles that can be charged using electricity from the power grid to recharge their batteries. Unlike traditional hybrid vehicles, which rely on an internal combustion engine to generate electricity, PHEVs use a battery that can be charged externally. This allows them to drive longer distances using only electricity, which improves fuel efficiency. If the battery runs low, a backup engine (usually a turbocharged gasoline engine) can help extend the vehicle’s range.

By 2023, 26 million battery electric vehicles had been sold worldwide. In North America, there were 65,730 public charging stations, and many people also have access to charging at home or work using standard electrical outlets. Long-distance electric trucks require more powerful charging stations to operate efficiently.

Hannah Ritchie has pointed out that there may not be enough land available to produce enough aviation biofuel to meet demand.