Fuel cells
A fuel cell is a device that produces electricity through a chemical reaction between a source fuel and an oxidant. The source fuel could be almost anything that can be oxidized, including hydrogen, methane, propane, methanol, diesel fuel or gasoline. The only byproducts are water and a small amount of nitrous oxide if air is used as the oxidizer.
The first fuel cells were invented in 1838. The first commercial use of fuel cells came more than a century later in NASA space programs to generate power for satellites and space capsules. Since then, fuel cells have been used in many other applications.
Fuel cells are used for primary and backup power for commercial, industrial and residential buildings and in remote or inaccessible areas. They are also used to power fuel cell vehicles, including forklifts, automobiles, buses, boats, motorcycles and submarines.
Types of fuel cells
Fuel cells come in many varieties; however, they all work in the same general manner. They are made up of three adjacent segments: the anode, the electrolyte, and thecathode. Two chemical reactions occur at the interfaces of the three different segments.
The net result of the two reactions is that fuel is consumed, water or carbon dioxide is created, and an electric current is created, which can be used to power electrical devices, normally referred to as the load.
The most important design features in a fuel cell are:
A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load. Voltage decreases as current increases, due to several factors:
Some types are as follows:
Polymer Electrolyte Membrane (PEM) Fuel Cell also known as proton exchange membrane fuel cells (PEMFCs).
Phosphoric Acid Fuel Cell using the phosphoric acid as an electrolyte in order to channel the H+
Solid Acid Fuel Cell using solid acid material as the electrolyte in these fuel cells.
Alkaline Fuel Cell used as the primary source of electricity in the Apollo space program.
Solid Oxide Fuel Cell using solid oxide or a ceramic electrolyte (yttria-stabilized zirconia).
Molten Carbonate Fuel Cell using lithium potassium carbonate salt as electrolyte, this salt becomes liquid at high temperatures and enabling the movement of carbonate ions.
How do fuel cells work?
A fuel cell does not actually burn its fuel. The oxidation process occurs at a far lower temperature than that produced by active combustion. A fuel cell can be recharged by filling a tank or from a continuously available external supply of fuel. In a common form of hydrogen fuel cell, known as the proton exchange membrane (PEM), hydrogen is delivered to a positive electrode called the anode.
At the anode, hydrogen atoms are broken down or ionized into their constituent protons and electrons. The protons permeate through an electrolyte membrane to a negative electrode called the cathode. Electrons travel from the cathode to the anode through an external load, which converts the resulting current to useful power.
(Fuel cell diagram)
Applications of fuel cell
Fuel cell electric vehicles(FCEVs) uses clean fuels and are more eco-friendly than internal combustion engine-based vehicles.
The fuel cells have been used to power space expeditions including the space program.
The fuel cells may be extremely useful in some of military applications.
The electrochemical cells can also be used to power several electronic devices and used as primary or backup sources of electricity in remote areas.
Disadvantages of fuel cells
Use of fuel cells in cars has disadvantage as hydrogen is in the gas state at room temperature and pressure it is difficult to store in the car.
The fuel cells and electric motors are less durable than petrol/diesel engines.
The fuel cells are very expensive.