How do hydrogen cars work?

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Are hydrogen cars really the future of motoring? Let’s explore the differences between hydrogen and traditional propulsion systems and find out to what extent they are environmentally friendly.

Why should we even think about moving away from traditional drives?

The complicated design of traditional fuel-powered engines makes these cars unreliable and expensive to operate. They burn fuel with high energy losses and require intensive lubrication and cooling. It is estimated that internal combustion engines use only 33 percent of the energy, releasing huge amounts of exhaust into the atmosphere

Compared to traditional fuel-powered models, the engine design of a hydrogen car is simple and reliable. The refueling time for a hydrogen car is equally short and the range is nearly identical to a gasoline or oil car. And torque is available over the full speed range

Where does the energy for a hydrogen car come from?

Hydrogen car engines, like electric car engines, are powered by electricity. The key difference between these technologies is the source of the energy used. An electric car uses cells to power its engine. A hydrogen car uses energy generated while driving. So let’s explain how a hydrogen car engine works and whether this technology really is the future of motoring.

Energy production in a hydrogen powered car occurs during a chemical reaction that bonds oxygen and hydrogen in fuel cells. A single cell consists of two electrodes separated by a polymer membrane: a negative electrode (anode) and a positive electrode (cathode). Hydrogen supplied from the tank to the negative electrode is oxidized. As a consequence, positive protons and negative electrons are formed. On the other hand, oxygen coming from the air reaches the positive electrode and reacts with the electrons, turning into negative oxide ions

The polymer membrane lets through only the positive protons, which combine with the oxygen anions to form water. Meanwhile, the electrons travel through an external electrical circuit, producing an electric current to power the motor. A simple chemical reaction takes place between oxygen and water, producing electricity. The byproduct of this reaction is water, released as steam

The designers of the Toyota Mirai have used some of the electricity created in the fuel cells to charge the batteries in the rear of the vehicle. In this way, the stored energy can be used to increase the range of the car and can also be used in moments of increased demand for power, e.g. during overtaking.

Are hydrogen-powered cars safe?

Hydrogen is a flammable gas, and when stored under high pressure, it can pose a danger to travelers. A fuel leak or car accident could lead to a gas explosion. The experiments conducted proved that these fears were unfounded

Shooting a cylinder filled with hydrogen with a bullet showed that the hydrogen, which is much lighter than air, was released from the tank quickly and without sudden pressure changes or explosions. An arson test showed that the hydrogen burned in a controlled manner, not occupying the entire car as it would with internal combustion engine fuel. The threat of explosion proved virtually impossible

Hydrogen technology is not without its drawbacks

Like any technological solution, hydrogen propulsion also has its drawbacks. Obtaining pure hydrogen in an environmentally friendly manner requires a significant amount of energy to produce. The most efficient process for producing hydrogen from commonly available chemicals (steam reforming) has a negative energy balance. The amount of energy needed to produce hydrogen is greater than the amount of energy obtained from the resulting hydrogen, and significant amounts of carbon monoxide are emitted into the atmosphere

Better efficiency and and lower carbon footprint of obtaining hydrogen can be achieved using electrolysis which allows water to be broken down into oxygen and hydrogen using electricity. In this case, the negative energy balance is 20 percent, so we achieve an efficiency of 80 percent in global energy terms. So we have to put in 20 percent more energy than we get from combining hydrogen with oxygen in fuel cells.

The extremely low density of hydrogen requires compressing the gas and increasing its density for further storage. Another 13 percent of the energy is lost in the process, relative to what we recover later. Another method of increasing the density of hydrogen for further storage is to liquefy the gas to the state of water. According to calculations, the process of cooling hydrogen to -253 degrees Celsius and storing it at such a low temperature involves a loss of 40 percent of energy

Transporting the hydrogen from the gas producing stations is a logistical problem that generates another 10 percent of the energy cost. The total negative energy cost occurring during production, gas storage and transportation is 43 percent. This compares to an energy loss of only 6 percent for traditional electric cars

As you can see, this technology is far from being revolutionary and will change the face of the automobile. Perhaps in a few years, manufacturers seeking widespread use of hydrogen fuel technology will improve its efficiency.

Main article photo: Designed by Freepik

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