PEM Fuel cell refers to Proton exchange membrane fuel cells. They are also known as Polymer Electrolyte Membrane (PEM) fuel cells.
The PEM cells were recently in news for the reason that they are the leading candidate to replace the aging alkaline fuel cell technology, which was used in the Space Shuttle.
In India also, the CSIR’s chemical arm is doing research on generating electricity from polymer electrolyte fuel cell. A major programme on energy is underway at Council of Scientific and Industrial Research (CSIR) and its affiliate National Chemical Laboratory (NCL) here with a focus on search for novel materials and turning them into devices for affordable technologies. The CSIR-NCL which has identified Solar energy and Fuel Cell as two major “thrust areas” of its research, is working on harnessing solar energy to produce thermal and electric power, in particular “organic photovoltaic and dye-sensitised solar cells”, the important components of the country’s Solar Mission project to add a 500 MW of power availability.
Different Types of Fuel Cells
The fuel cells are mainly classified by the type of electrolyte they use, and their operating temperature. The main types of fuel cells are:
- Polymer Exchange Membrane Fuel Cell (PEMFC): It is also known as proton exchange membrane fuel cell, and has a high power density. This cell uses a solid polymer as an electrolyte, and porous carbon electrodes, containing a platinum catalyst. PEM fuel cell is light in weight, and has an operating temperature ranging from 60°C to 80°C, or 140°F to 176°F. It is mainly used in transportation applications, like vehicles, cars, buses, etc
- Solid Oxide Fuel Cell (SOFC): This fuel cell uses a hard, non-porous ceramic compound as its electrolyte. Solid oxide fuel cell is suitable for large-scale stationary power generators, and operates at very high temperatures between 700°C and 1,000°C. Due to its high operating temperatures, it produces more steam which in turn generates more electricity and hence, improves the overall efficiency of the system
- Alkaline Fuel Cell (AFC): It is known as Bacon fuel cell, and is one of the oldest and reliable fuel cell technology. It uses a solution of potassium hydroxide in water as an electrolyte, and operates at low temperatures between 100ºC to 250ºC, or 212ºF to 482ºF. As alkaline fuel cell gets contaminated by carbon dioxide (CO2), it requires pure hydrogen and oxygen. It is a high performance cell, and has an efficiency up to 60% in space applications
- Molten Carbonate Fuel Cell (MCFC): This fuel cell is best suited for natural gas and coal-based power plants, and operates at 600ºC. This cell uses an electrolyte, composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminium oxide (LiAlO2) matrix
- Phosphoric Acid Fuel Cell (PAFC): Phosphoric acid fuel cell uses an electrolyte, composed of liquid phosphoric acid and porous carbon electrodes, containing a platinum catalyst. This cell is used in small stationary power-generation systems. It operates at high temperature and so, it is unsuitable for cars
- Direct Methanol Fuel Cell (DMFC): It is supplied with pure methanol, mixed with steam and fed directly to the anode. It has a same operating temperature as PEMFC. This fuel cell is expensive and uses large amount of platinum as a catalyst. It has no fuel storage problem and is portable. (buzzle.com)