Fuel cells: Future of energy source

What is fuel cell?
A fuel cell is nothing but an electrochemical energy conversion device that converts hydrogen and oxygen into water, producing electricity and heat in the process. Every fuel cell has two electrodes, one positive termed as cathode and one negative called anode. The production of electricity takes place at the electrodes. A fuel cell has an electrolyte that carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes. It is just like a battery that can be recharged while you are drawing power from it. It can be recharged using electricity; however, a fuel cell uses hydrogen and oxygen.

In an ordinary combustion reaction, as in a flame or an internal combustion engine, essentially all of the energy released in the reaction is converted to heat. In a fuel cell, the reaction is done electrochemically, meaning that in the anode compartment the fuel is oxidized and in the cathode compartment, oxygen from the air is reduced to water. The two compartments are connected by an electrolyte that allows hydrogen ions (protons) to move from the anode to the cathode. A single fuel cell can generate very small amount of direct current (DC) electricity. Generally fuel cells are assembled into a stack.

Application:

Fuel-Cell-Powered Electric Car
A fuel cell using pure hydrogen has the potential to be up to 80-percent efficient. But hydrogen is difficult to store in a car. Adding a reformer to convert methanol to hydrogen drops the overall efficiency to about 30 to 40 percent.
To convert the electrical energy into mechanical works the electric motor and inverter are required. The motor/inverter is about 80 percent efficient. Converting methanol to electricity is about 30 to 40 percent efficiency at and converting electricity to mechanical power is 80-percent efficient. This gives an overall efficiency of about 24 to 32 percent. Fuel cell provides a direct current voltage that can be used to power motors, lights or any number of electrical appliances.

Classification of fuel cells :
Different types of fuel cells exist each using a different chemistry. They are usually classified by the type of electrolyte they use. While are useful for small portable applications or for powering cars. Some of the important fuel cell technologies are described below:

PEM Fuel Cell Technology:

The technology of PEM was invented at General Electric in the early 1960s, through the work of Thomas Grubb and Leonard Niedrach. This company announced an initial success in mid-1960 when the company developed a small fuel cell for a program with the U.S. Navy's Bureau of Ships (Electronics Division) and the U.S. Army Signal Corps. The Proton exchange membrane fuel cells work with a polymer electrolyte in the form of a thin, permeable sheet. Thomas Grubb and Leonard Niedrach of this company ran a fan with a small diesel powered PEM fuel cell in April 1963. The PEM technology served as part of NASA's Project Gemini.

Alkali Fuel Cell Technology
The alkali fuel cells work on compressed hydrogen and oxygen and generally use a solution of potassium hydroxide in water as their electrolyte. The working
temperature inside alkali cells are around 150 to 200 degrees C. NASA preferred alkali fuel cells for the Space Shuttle fleet, as well as the Apollo program, mainly because of power generating efficiencies that approach 70 percent. These cells also provide drinking water for the astronauts.

Solid Oxide Fuel Cells Technology
A solid oxide fuel cell makes use of a hard ceramic electrolyte instead of a liquid and operates at temperatures up to 1,000 degrees C. The solid oxide and molten carbonate fuel cells are high temperature devices. During recent years the climbing energy prices and advances in materials technology have reinvigorated work on SOFCs, and a recent report noted about 40 companies working on these fuel cells.

Recent research has proved that using readily available hydrocarbon fuels like methane would avoid the logistical problems of storing and refueling with hydrogen. Such fuel cell cars will start to replace gas and diesel engine cars in coming 2 to 3 years. It will be very similar to an electric car but with a fuel cell and reformer instead of batteries.
In future you will fill your fuel-cell car up with methanol, but some companies are working on gasoline reformers. Some companies hope to do away with the reformer completely by designing advanced storage devices for hydrogen. The fuel cell will fight with many other types of energy conversion devices, including the gas turbine in our city's power plant, the gasoline engine in our car and the battery in our laptop and will prove superior.