2020.06.12 Hyundai Motor Company
[Hydrogen Society] What Moves an FCEV
How does a fuel cell vehicle work? Here’s how fuel cells generate power.
Inside an FCEV, hydrogen travels from tanks to a fuel cell stack. Once in the fuel cell stack, hydrogen goes through an electrochemical reaction with the oxygen collected from the air intake. This reaction creates electricity, which then powers the vehicle's motor. That's easier said than done, though. Let's see how the system actually works.
Hydrogen As Fuel
Gaseous hydrogen is liquefied by cooling it to below -252.78°C. It can be stored in large tanks once hydrogen is liquefied. Storage of hydrogen as gas would require much more space and it would be much less efficient. This is why FCEVs use compressed hydrogen in hydrogen tanks at 700 bar.
Instantly lowering the high pressure within the hydrogen fuel tanks is a challenge, so through the hydrogen fuel feed system connecting into the fuel cell stack, the pressure is curtailed over a two-stage process. An FCEV hydrogen tank’s inner lining is made of a polyamide liner that minimizes hydrogen permeation. The outer lining is made from carbon-fiber composite plastics that maintain integrity against high pressures of up to 700 bars.
FCEVs use the air drawn from the atmosphere
FCEV is powered by electricity generated from the electrochemical reactions between hydrogen and oxygen. For oxygen supply, FCEVs purify the air intake over multiple steps. The first step involves an air filter that collects particulate matter and chemicals. The second step further purifies the air by passing it through a membrane humidifier. The last step scrubs air through a GDL (gas diffusion layer, passes air to the fuel-cell). This air purification system delivers pollutant-free oxygen to the electrolyte membrane.
The oxygen necessary to react with hydrogen is drawn from the atmosphere. Such air drawn into the FCEV passes through an air purification system that cleans it of particulates and other unwanted matter, leaving the air cleaner. This is necessary for keeping the cell stack from pollutants. In a way, it has an atmospheric 'scrubbing’ effect.
Electrochemical reactions between hydrogen and oxygen
A fuel cell stack of an FCEV is one of the most essential compartments because FCEVs need to generate their own electricity using a fuel cell stack system that uses a chemical reaction between stored hydrogen and atmospheric oxygen. Fuel cell stacks consist of hundreds of cells - Nexo has 440 of these, for example - and each cell consists of an electrolyte membrane and catalyst, a fuel electrode (hydrogen), and an air electrode (oxygen).
Electrical Energy Converts to Kinetic Energy
Just as EVs, FCEVs carry several components for electric power: the motor, the Electric Power Control Unit(EPCU), and the reducer that reduce the RPM to an appropriate level.
An energy-saving idea applies when the car is reducing its speed, culminating in the so-called “regenerative braking system.” Some of the Hyundai Motor Group’s EVs are equipped with a mechanism that can control the levels of regenerative braking through paddle shifters on the steering wheel, which improves the fuel economy.
The Only Byproduct: Water
Just like EVs, FCEVs also are eco-friendly and use motors that use electricity. But FCEVs are capable of generating its own electricity using a fuel cell stack system that uses a chemical reaction between stored hydrogen and atmospheric oxygen. Refueling with hydrogen rather than electrical outlets, using atmospheric oxygen, using filtered dust-free air to generate a byproduct of only pure water, are some of the key differences between FCEVs and EVs.
Among many other ways to produce hydrogen, experts expect that we would be able to use renewable energy sources to separate hydrogen from water and again converting the harvested hydrogen back into electricity.
Such a fuel cell system has got a lot of potentials. The system can be supplied to other transportation manufacturers of vehicles, drones, or vessels. The demand for fuel-cell systems from sectors beyond transportation such as power generation and storage systems is also expected to emerge quickly.
