How do Hydrogen Fuel Cell Vehicles Function?

Electric Vehicles are the hot topic in the automotive world today and have been for some time as people started realizing their benefits over fossil fuel powered vehicles in tackling climate change. But, when people refer to electric vehicles (EVs), they are mostly talking about Battery Electric Vehicles (BEVs) such as Teslas. However, most people don’t realize that hydrogen fuel cell powered vehicles are also electric vehicles. They are commonly known as Fuel Cell Electric Vehicles or FCEVs.

EVs in general, draw an electric current from a source which could either be a battery or a fuel cell, to power an electric motor. The main difference between an EV and a traditional car is that EVs use an electric motor instead of an internal combustion engine. This is the case with both BEVs and FCEVs.

What is a Fuel Cell Electric Vehicle (FCEV)?

With BEVs, the source of electric current given to the motor is a series of many battery cells and uses the electrical energy stored in these cells. In an FCEV, the electrical current is a production of an electrochemical reaction within the fuel cell between a fuel (most commonly hydrogen) and oxygen in the air. The chemical reaction between hydrogen and oxygen produces electrical current and water. In BEVs, there are no waste products.

A similar process is powers rockets, which use the reaction of hydrogen fuel to create an explosive thrust. However, with an FCEV, the energy is more controllable and containable within the fuel cell without producing an explosion.

The chemical reaction is reversible, so, you can break down water in a chemical reaction called electrolysis to produce hydrogen and oxygen. On an industrial scale, however, natural gas is used for hydrogen fuel production. The process of deriving hydrogen from natural gas produces some CO2 emissions itself, so hydrogen fuel cell vehicles aren’t completely clean when it comes to air pollution.

However, their CO2 emissions are still surprisingly lower than traditional vehicles and even that of BEVs.

Why aren’t there more FCEVs in the market?

FCEVs were once regarded as the future of the automotive industry, in providing a clean source of fuel for transport and tackling climate change. This was because FCEVs are more powerful than battery electric vehicles and can cover more mileage. If they can power rockets, then they can’t be that bad!

Another benefit of FCEVs over BEVs is that they can refuel faster. BEVs can take hours to charge, whereas an FCEV can refuel quicker than that.  BEVs take so long to charge because, although electric motors are efficient, the batteries aren’t very energy dense. Energy density is the primary reason petrol and diesel vehicles rule the market today.

When fully fuelled, they can also cover more mileage than a typical BEV. For example, the Toyota Mirai has the shortest range for a commercial FCEV, covering about 317 miles at full tank. Comparatively, the base model of a Tesla 3 can only cover 220 miles when fully charged, so the Mirai can cover almost 50% more than the Tesla.

Why aren’t there more Electric Vehicles?

So, they have a higher energy density, can refuel faster and have a greater mileage than a BEV. They also don’t have the emissions problem plaguing traditional cars, so why aren’t there more FCEVs out in the market? It all boils down to two reasons: Cost and Convenience.

Currently, FCEVs are more expensive than BEVs and certainly more than traditional gasoline cars. And also, there’s the additional cost of fuel. For one kilogram of hydrogen fuel, it can cost as much a $14 whereas the equivalent cost of gasoline would cost around $5.80.

The other problem is that of convenience. Gas stations and even EV charging stations for BEVs are quite common and convenient. However, hydrogen refuelling stations are far less common.

There are also safety concerns about storing that amount of hydrogen in one place. Any storage tanks of hydrogen would need to very secure and strong to avoid potential hazards.

Basics of a Hydrogen Fuel Cell

To understand how a hydrogen fuel cell car works, it is important to understand what a fuel cell is.  So, the reaction within the fuel cell is essentially an “electrochemical” reaction. This is because chemical reaction produces the electrical energy.

Similar to a battery, a fuel cell has three key components. It has a positively charged cathode) and a negatively charged anode. These terminals are separated by a chemical known as an electrolyte.

Hydrogen Fuel Cells – How do they Work?

In a hydrogen fuel cell, the cathode (positive terminal) receives the hydrogen gasg through a series of pipes from the hydrogen storage tank. The anode (negative terminal) receives oxygen from the air through another series of pipes.

The cathode is usually made from metals like platinum. This acts as chemical catalysts to speed up the chemical reaction. At the cathode, hydrogen atoms split up into simpler, more unstable particles known as ions. Ions are basically atoms with their electrons stripped away, this makes them quite unstable.

Due to the lack of electrons, the hydrogen ions have a positive charge. So, they naturally attract to the anode with the negative charge. They will hence travel through the electrolyte from the cathode to the anode.

The electrolyte is a thin layer of material, usually made from a type of polymer, that only lets through protons.

The electrons that were separated from the hydrogen atoms at the cathode, now flow through an external electrical circuit towards the anode. Any flow of electrons will produce a current, so this movement of electrons in the external circuit will power the motor.

At the negatively charged anode, the protons and electrons will join with oxygen to form H20, also known as water. This water elimination happens through an exhaust pipe as steam or vapour.

This type of fuel cell is commonly referred to as a PEM, a proton exchange membrane, since it selectively allows protons to pass through.

The amount of hydrogen is the only limiting factor in an FCEV, because there is readily available oxygen in the air. FCEV technology are constantly evolving, and only time can tell if they could overtake gasoline vehicles or BEVs in the future.

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