EE-421
Unit 3: Fuel Cell
Dr. Khaliqur Rahman
Department of Electrical Engineering,
AMU Aligarh
Contents
• Fuel cell basics
• Operation of fuel cell
• Classification of fuel cell
Fuel cell
• A fuel cell is an electrochemical device that produces
electricity without combustion by combining hydrogen
and oxygen to produce water and heat.
History
• Discovered German Scientist G H Shoenbein
• First developed by William Grove
-In 1839, Grove was experimenting on electrolysis (the process by which water is split into hydrogen and oxygen by an electric current), when he observed that combining the same elements could also produce an electric current.
• 930s -1950s Francis Thomas Bacon, a British scientist, worked on developing alkaline fuel cells.
• He demonstrated a working stack in 1958.
• The technology was licensed to Pratt and Whitney where it was
utilized for the Apollo spacecraft fuel cells.
Operation of fuel cell
Anode and Cathode:
Materials which have high electron conductivity and zero proton conductivity in the form of porous catalyst (porous catalyst or carbon).
Electrolytic membrane (Catalyst):
Platinum
Electrolyte:
High proton conductivity and zero electron conductivity
Operation of fuel cell
Following reactions take place in fuel cell:
At anode: H
24H
++4e
-At cathode: O
2+4H
++4e
-2H
2O
Overall Reaction: 2H
2+O
22H
2O
Operation of fuel cell
Principle:
• A fuel cell is a device that uses hydrogen (or hydrogen-rich fuel) and oxygen to create electricity by an electrochemical process.
• A single fuel cell consists of an electrolyte sandwiched between two thin electrodes (a porous anode and cathode)
• Hydrogen, or a hydrogen-rich fuel, is fed to the anode where a catalyst separates hydrogen's negatively charged electrons from positively charged ions (protons)
• At the cathode, oxygen combines with electrons and, in some cases, with species such as protons or water, resulting in water or hydroxide ions, respectively
• The electrons from the anode side of the cell cannot pass through the membrane to the positively charged cathode; they must travel around it via an electrical circuit to reach the other side of the cell.
• This movement of electrons is an electrical current.
Operation…
• The amount of power produced by a fuel cell depends upon several factors, such as
-fuel cell type, -cell size,
-temperature at which it operates,
-and the pressure at which the gases are supplied to the cell.
• Still, a single fuel cell produces enough electricity for only the smallest applications.
• Therefore, individual fuel cells are typically combined in series into a fuel cell stack.
• A typical fuel cell stack may consist of hundreds of fuel cells.
Advantages of fuel cell
1. High efficiency of energy conversion (approaching 70%) from chemical to electrical energy 2. Low noise and thermal pollution.
3. Gives excellent method for efficient use of fossil fuels hence saves fossil fuels.
4. The chemical process involved in it is clean.
5. Hydrogen-Oxygen fuel cells produce drinking water of potable quality.
6. The design is modular, therefore the parts are exchangeable.
7. Low maintenance cost.
8. Performance is independent of power plant size.
9. Fast start up time for low temperature system.
10. The heat is cogenerated hence increases efficiency of high temperature system.
11. The demand for variations in power and energy densities is easily met as required.
12. Fuel cells automotive batteries can render electric vehicles, efficient and refillable.
Disadvantages of fuel cell
1. High efficiency of energy conversion (approaching 70%) from chemical to electrical energy 2. Low noise and thermal pollution.
3. Gives excellent method for efficient use of fossil fuels hence saves fossil fuels.
4. The chemical process involved in it is clean.
5. Hydrogen-Oxygen fuel cells produce drinking water of potable quality.
6. The design is modular, therefore the parts are exchangeable.
7. Low maintenance cost.
8. Performance is independent of power plant size.
9. Fast start up time for low temperature system.
10. The heat is cogenerated hence increases efficiency of high temperature system.
11. The demand for variations in power and energy densities is easily met as required.
12. Fuel cells automotive batteries can render electric vehicles, efficient and refillable.
Disadvantages
1. High initial cost
2. Lifetime of the cells are not accurately known.
3. Large weight and volume of gas fuel storage system.
4. High cost of pure hydrogen.
5. Hydrogen can be stored in lesser volume by liquefaction but liquefaction itself require 30% of the stored energy.
6. Lack of infrastructure for distributing hydrogen.
Applications
1. The first commercial use of fuel cell was in NASA space program to generate power for satellites and space capsules.
2. Fuels are used for primary and backup power for commercial, industrial and residential buildings in remote and inaccessible area.
3. They are used to power fuel cell vehicles including automobiles, airplanes, boats and submarines.
