Transcript Proton Exchange Membrane Fuel cell

Proton Exchange Membrane
Fuel cell
History
 Invented in early 1960’s at General
electric
 First used by NASA to provide power
for gemini space project
Operation
 In PEMFC, the electrolyte used is a
thin polymer membrane (such as
poly[perfluorosulphonic] acid, which
are permeable to protons but does
not conduct electrons
 Hydrogen flows into the fuel cell onto
the anode and is split into hydrogen
ions and electrons
Cont..
 Hydrogen ions permeate across the
electrolyte to the cathode
 Electrons flow through an external
circuit and provide power
 Oxygen is supplied to the cathode
and this combines with electrons and
hydrogen ions to produce water
 PEMFC operate at a temperature of
around 80°C
Cont..
Cont..
 Electrolyte is sandwiched between
two field flow plates to create a fuel
cell
 Each cell produces around 0.7 volts,
about enough power to run a light
bulb
 To generate high voltage, a number
of individual cells are combined in
series
Advantages
 Operate at low temperatures which allows
them to start up rapidly from cold
 High power density which makes them
really compact and lightweight
 PEMFC work at high efficiencies, producing
around 40-50 percent of the maximum
voltage, and can vary their output quickly
to meet shifts in power demand
Disadvantages
 Needs pure hydrogen to operate as
they are very susceptible to poisoning
by carbon monoxide and other
impurities
Current research
 At present, demonstration units capable of
producing 50kw are in operation and units
producing 200kw are under development
 Still number of barriers need to be
overcome
 The main issue is that the cost of
membrane and catalysts are expensive but
the ongoing research and development is
constantly reducing the cost.
Applications
 In 1995,Ballard systems tested PEM
cells in buses in Chicago and later in
experimental vehicles made by
Daimler Chrysler
 In 2000,AeroVironments selected PEM
technology to provide night time
power for its solar powered Helios
long duration aircraft
Q&A
1.What is the operating temperature for
PEMFC?
 1000°C
 500°C
 250°C
 80°C
Cont..
2.What is the electrolyte used in
PEMFC?
 Lithium sodium carbonate salts
 Liquid phosphoric acid
 Potassium hydroxide
 Perfluorosulphonic acid
Cont..
3.What is the amount of voltage
produced by each cell in PEMFC?
 10 V
 20 V
 5.5 V
 0.7 V
Cont..
4.Which of the following matches the
needs and characteristics of PEMFC?
 Pure hydrogen
 Feedstocks free from carbon-dioxide
 Membrane materials and catalysts are
inexpensive
 Capable of producing output
equivalent to 50kw
Cont..
5.Which of the following are susceptible
to CO?
 PEM fuel cell
 Alkaline fuel cell
 Solid oxide fuel cell
 Molten carbonate fuel cell
Storage medium for
Hydrogen
Storage methods
 Hydrogen can be stored as
compressed gas or as a cooled liquid
 Despite these methods storing
hydrogen to power a car requires a
large tank
Obstacle
 With the current technology, the
compressed hydrogen tank size
required to contain 6.8 kg hydrogen
for a 1500 kg vehicle with a driving
range of 560km is 340 litres.
 A typical gasoline tank for such a
vehicle is 70 litres
Current trend
 Currently the hydrogen is injected
directly into the cell
 There is a tank which holds methanol
 Methanol and water vaporize forming
hydrogen