10-12-2012, 01:59 PM
Fuel Cells
Fuel Cells.ppt (Size: 1.2 MB / Downloads: 38)
What is a Fuel Cell ?
A fuel cell is a device that uses hydrogen (or hydrogen rich fuel) and oxygen to create electricity by an electrochemical process.
If pure hydrogen is used as a fuel, fuel cells emit only heat and water as a byproduct.
Current applications: power passenger vehicles, commercial buildings, homes, and laptop computers.
Fuel Cell Systems
Most fuel cell systems consist of FOUR basic components:
Fuel Stack :
The fuel cell stack is the heart of a fuel cell power system. It generates electricity in the form of direct current (DC) from chemical reactions that take place in the fuel cell. A typical fuel cell stack may consist of hundreds of fuel cells. The amount of power produced by a fuel cell depends upon several factors, such as fuel cell type, cell size, the temperature at which it operates,
Fuel Processor :
It converts fuel into a form useable by the fuel cell. If hydrogen is fed to the system, a processor may not be required or it may only be needed to filter impurities out of the hydrogen gas. If the system is powered by a hydrogen-rich conventional fuel such as methanol, gasoline, diesel, or gasified coal, a reformer is typically used to convert hydrocarbons into a gas mixture of hydrogen and carbon compounds called “reformate”.
Benefits of Using Fuel Cells
They produce much small quantities of greenhouse gases that contribute to global warming.
None of the air pollutants that create smog and cause health problems.
If pure hydrogen is used as a fuel, ONLY heat and water are emitted.
Fuel Cell Technology Challenges
Cost. The cost of fuel cell power systems must be reduced before they can be competitive with conventional technologies.
Durability and Reliability. The durability of fuel cell systems has not been established. For transportation applications, fuel cell power systems will be required to achieve the same level of durability and reliability of current automotive engines.
System Size. The size and weight of current fuel cell systems must be further reduced to meet the packaging requirements for automobiles.
Air, Thermal, and Water Management. Air management for fuel cell systems is a challenge because today's compressor technologies are not suitable for automotive fuel cell applications. In addition, thermal and water management for fuel cells are issues because the small difference between the operating and ambient temperatures necessitates large heat exchangers.