How Does a Hydrogen Fuel Cell Work?
There is a lot of buzz around hydrogen. Hydrogen fuel cell electric vehicles are a compelling option, particularly for heavy-duty, public, and commercial transport vehicle use. But how does a hydrogen fuel cell work? What are its applications? What are the pros and cons? Read on to find out.
What is a Hydrogen Fuel Cell and How Does it Work?
Simply put, a fuel cell is a power source. Similar to a battery, it is a device that uses electrochemical reaction to convert energy stored in molecules into electricity. In its simplest form, a hydrogen fuel cell combines oxygen and hydrogen to form water and create electricity. The electricity that is produced is then used to power electric vehicles or is stored in batteries. Warm air, clean water, and electricity are the only by-products of a hydrogen fuel cell, making it a zero-emission and sustainable power source.
The Fuel Cell Process
Composed of two electrodes (a cathode and an anode) separated by an electrolyte membrane, a hydrogen fuel cells works in the following way:
- Hydrogen gas enters the fuel cell through the anode. In the anode, the atoms of hydrogen create a chemical reaction with a catalyst, splitting into protons and electrons. At the same time, oxygen from the atmosphere enters the fuel cell via the cathode. (The catalyst, typically made of platinum particles, facilitates the chemical reaction).
- There is a porous electrolyte membrane between anode and cathode. The protons pass through it. From the other side, the electrons flow out of the cells, creating electricity. This electricity can then be used to run an electric propulsion system.
- In the cathode, the oxygen and protons then combine to produce water.
Types of Fuel Cells
There are several types of fuel cells, each of which is generally defined by the type of electrolyte they use as well as their operating temperature. The choice of which type to use is often based on the fuel cell’s targeted application. The principle all fuel cells work on is the same: splitting hydrogen atoms and using the newly created electrons to create electricity.
Alkaline Fuel Cells (AFC)
Alkaline fuel cells use liquid potassium hydroxide electrolyte. Because of this, it is possible to use non-precious metals as a catalyst, which is its one of the most significant advantages. However, CO2 can easily poison the catalysts. So, oxygen and hydrogen used in an alkaline fuel cell need to be purified, which is a very costly process.
Phosphoric Acid Fuel Cells (PAFC)
As the name suggests, phosphoric acid fuel cells utilize phosphoric acid as an electrolyte. Since it is an acid, it requires a very high temperature to start the reaction. Furthermore, PAFC uses platinum as a catalyst, which is costly. However, this type of fuel cell is relatively more tolerant to impurities and it is very efficient at producing heat and electricity, making PAFC ideal for power plants.
Proton Exchange Membrane Fuel Cells (PEMFC)
Proton Exchange Membrane fuel cells feature platinum coated solid polymer and require only oxygen and hydrogen to generate electricity. The primary advantages of this type of fuel cell are that it is low in weight and has a high-power density. It also operates in low temperatures which allows it to start quickly.
Direct Methanol Fuel Cells (DMFC)
DMFC are Proton Exchange Membrane based fuel cells that utilize methanol rather than pure hydrogen. Because of this, this type of fuel cell shares many of the same advantages of a PEM fuel cell. Some additional advantages of methanol are also available, e.g. it is safer and much easier fuel for storage and transportation.
Also Read: What are Solar Panels Made Of?
Applications of Hydrogen Fuel Cells
Now that you know the answer to “how does a hydrogen fuel cell work?” and you are also familiar with various fuel cell types, it might pique your interest to learn about their applications. The primary applications for hydrogen fuel cells are in hydrogen fuel cell vehicles and stationary power sources. They are used in both motive and stationary power applications for:
- Cars, buses, trucks, and recreational vehicles.
- Generating power on-site.
- Material handling equipment.
- Backup power source to critical communications and computer networks.
- Act as a primary power source for residential, commercial, and industrial buildings or high-volume data centers.
How Does a Hydrogen Fuel Cell Work in Motor Vehicles?
The process of using hydrogen fuel cells to generate electricity in order to power a motor vehicle is the same as the general fuel cell process. Here are the steps:
- Hydrogen is supplied to the negative or anode side of the fuel cell.
- Anode catalyst activates hydrogen molecules, releasing electrons.
- The electrons then travel from anode to cathode, creating an electrical current.
- The hydrogen molecules responsible for releasing electrons become hydrogen ions. These hydrogen ions also move to the cathode side of the fuel cells but they have to go through the polymer electrolyte membrane. During that process, they bond with electrons and ambient oxygen to form water.
- Electricity produced by the fuel cell is directed to an electric motor that powers the vehicle.
- Excess energy is stored in a secondary battery that provides auxiliary power to the electric motor.
Advantages and Disadvantages of Hydrogen Fuel Cells
Fuel cells are a clean source of power as they produce electricity through an electrochemical reaction. Following are some key advantages:
- Fuel cells do not require a recharge like batteries. They can continue to produce electric current as long as the fuel source is available.
- Since there are no moving parts, fuel cells are silent and very reliable.
- Individual fuel cells can be “stacked” to generate more power. A single fuel cell can generate enough voltage to power small applications. On the other hand, stacked fuel cells can be combined to create multi-megawatt, large-scale installations.
There are certain disadvantages of hydrogen fuel cells. First, hydrogen is very reactive so it can easily erode other material. Not to mention it is also highly flammable. These two factors make hydrogen fuel cells costly and difficult to transport. The high cost and lack of building hydrogen infrastructure is another major problem. Hydrogen fuel cells are costly to manufacture as their production involves manual processes and it is still small in scale. Another key cost component is the hydrogen tank that takes up a lot of space because of its huge size.
Although hydrogen is in its infancy as a fuel source, the future of hydrogen fuel cells is bright. This technology is improving on a daily basis and it is only a matter of time before it becomes a viable replacement to other sources of power generation on a large scale.