a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent - from MSE-HUST k54

1. Seminar: Fuel cells
Class: Materials Science Engineering
Teacher : Phạ m Ngọ c Diệ u Quỳnh
Student: Hoàng Văn Tiế n
Hanoi 6-6-2012

3. What is fuel cell ?
-A fuel cell is a device that converts the
chemical energy from a fuel into electricity
through a chemical reaction with oxygen or
another oxidizing agent.
-Fuels: +Hydrogen ( the most common fuel.)
+Hydrocarbons : natural gas,alcohols ..…..
-Air pollution emissions almost “equal zero”.

4. design
A block diagram of a fuel cell

5. clasification
Based on types of electrolyte:
 polymer electrolyte membrand fuel cell
 alkaline fuel cell
 phosphoric acid fuel cell
 molten carbonat fuel cell
 solid oxides fuel cell

6. Case study: polymer electrolite membran fuel cell (PEMFC)

8. reactions
-Anode : H2 --- 2H+ +2e-
*E =0 VSHE (standard hidrogen electrode)
-Cathode: 1/2O2 +2H+ +2e- --->H2O
*E0=1.229 VSHE
Overall reaction: H2 +1/2O2 -- H2O
*E0=1.229 VSHE

9. Electrochemical Aspects
-The standard free energy change of the fuel cell reaction is
indicated by the equation :
∆G = –nFE-
The value of ∆G corresponding :
*∆G= −229 kJ/mol,
*n = 2,
*F = 96500 C/g.mole electron,
⇒ E = 1.229 V.
The enthalpy change ∆H for a fuel cell reaction:
∆H = –nFEt
-Nernst equation :
E = E0+ (RT/2F) ln [PH2/PH2O] + (RT/2F) ln [PO2 1/2]

10. Thermodynamic Principles
-The maximum electrical work obtainable in a fuel cell
operating at constant temperature and pressure is
given by the change in the Gibbs free energy of the
electrochemical reaction:
W = ∆G = –nFE
-The difference between ∆G and ∆H is proportional to
the change in entropy ∆S:
∆G = ∆H – T∆S

11.  The effect of temperature and pressure on
the cell potential:
− ∆V: change in volume,
∆S : entropy change,
E :cell poten-tial,
T:temperature,
P :reactant gas pressure,
n :the number of electrons transferred,
F: Faraday’s constant.

12. Fuel Cell Efficiency
 the efficiency :
 The ideal efficiency of a fuel cell operating
irreversibly:
 The thermal efficiency of an ideal fuel cell operating
reversibly on pure hydrogen and oxygen at standard
conditions:

13.  The thermal efficiency of the fuel cell ( in
terms of the actual cell voltage):
 Based on the higher heating value of
hydrogen:

14. Advantages and
disadvantages

15. Applicaions
-Power:
Type 212 submarine with fuel cell propulsion of the German Navy in dry dock

18. Other applications
 Providing power for base stations or cell sites
 Distributed generation
 An uninterrupted power supply (UPS)
 Base load power plants
 Fuel cell APU for Refuse Collection Vehicle
 Hybrid vehicles, pairing the fuel cell with either an ICE or a battery.
 Notebook computers for applications where AC charging may not be
readily available.
 Portable charging docks for small electronics (e.g. a belt clip that
charges your cell phones or PDA).
 Smartphones, laptops and tablets.
 Small heating appliances.

19. References
 www.wikipedia.org
 Nice, Karim and Strickland,Jonathan. "How
Fuel Cells Work: Polymer Exchange
Membrane Fuel Cells". How Stuff Works,
accessed August 4, 2011
 www.fuelcells.org
 www.fuelcellenergy.com
 onlinelibrary.wiley.com