Transcript Fuel cells - The University of Toledo

Fuel cells
Fuel cell history
 First demonstrated in principle by British Scientist
Sir Willliam Robert Grove in 1839.
 Grove’s invention was based on idea of reverse
electrolysis.
What is a fuel cell
 Creates electricity through
electrochemical process
 Operates like a battery
 Emits heat and water only
Parts of fuel cells
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There are 4 main parts
Anode
Cathode
Catalyst
Proton exchange membrane
Fuel cell theory
 A fuel cell consists of two electrodes - Anode and Cathode.
 Hydrogen and Oxygen are fed into the cell.
 Catalyst at Anode causes hydrogen atoms
electrons leaving positively charged protons.
to give up
 Oxygen ions at Cathode side attract the hydrogen protons.
Cont…..
 Protons pass through electrolyte membrane.
 Electrons are redirected to Cathode through external
circuit.
 Thus producing the current - power
Fuel cell working
Types of fuel cells
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Alkaline (AFC)
Phosphoric Acid
(PAFC)
Solid Polymer
(PEMFC)
Moltan Carbonate
(MCFC)
Solid Oxide
(SOFC)
Direct Methanol
(DMFC)
Temp.°C
Application
70-90
150-210
Space
Commercially available
70-90
Automotive application
550-650
Power generation
1000-1100
Power generation
70-90
Under development
Alkaline Fuel Cell
 Used in spacecraft to provide drinking
water and electricity
 Electrolyte: Aqueous solution of
alkaline potassium Hydroxide
 Output of 300w -5KW
 Power generation efficiency of about
70%
 Too expensive for commercial
applications
Phosphoric Acid Fuel cell
 Used in hospitals, nursing homes and
for all commercial purposes
 Electrolyte: Liquid Phosphoric acid
 Catalyst: platinum
 Electrical efficiency of 40%
 Advantages :using impure hydrogen
as fuel and 85% of the steam can be
used for cogeneration
Contd …
 Disadvantages: uses expensive
platinum as catalyst
 Large size and weight
 Low power and current
 Existing PAFC’s have outputs of
200kw and 1Mw are being tested
Proton Exchange Membrane Cells
 Also called as Solid Polymers and used for
quick startup in automobiles, light duty
vehicles and potentially to replace
rechargeable batteries
 Electrolyte :Solid organic polymer polyperflourosulfonic acid.
 Catalyst: Metals (usually platinum) coated
on both sides of membrane act as catalyst
 Advantages: Use of solid electrolyte
reduces corrosion and management
problems
Contd..
 Disadvantages: Sensitive to fuel
impurities
 Cell outputs generally range from 50
to 250 kW.
Molten Carbonate Fuel cell
 Majorly used for electric utility
applications
 Electrolyte: Liquid solution of lithium,
sodium and/or potassium carbonates.
 Catalyst: Inexpensive metals can be
used as catalyst other than Platinum
 Advantages: High operating
temperature allow for inexpensive
catalysts
Contd..
 Higher efficiency and flexibility to use more
type of fuels like carbon monoxide,
propane, marine gas due to high
temperatures
 Disadvantage: Higher temperature
enhances corrosion and breakage of cell
components
 High fuel to electricity generation of about
60% or 85% with cogeneration.
 10 kw’s -1 mw’s MCFCS have been tested
Solid Oxide Fuel Cell
 Highly promising fuel cell
 Used in big, high-power applications
including industrial and large-scale
central electricity generating stations
 Some developers also see SOFC use
in motor vehicles
 Power generating efficiencies could
reach 60% and 85%
Cont..
 Two Variations
 One type of SOFC uses an array of
meter-long tubes, and other variations
include a compressed disc that
resembles the top of a soup can
 Closer to commercialization
 Demonstrations of tubular SOFC
technology have produced as much
as 220 kW
Direct Methanol Fuel Cells
 Similar to the PEM cells in that they both
use a polymer membrane as the electrolyte
 The anode catalyst itself draws the
hydrogen from the liquid methanol,
eliminating the need for a fuel reformer.
 Efficiency of about 40%
 typically operate at a temperature between
120-190 degrees F
Cont..
 Relatively low range
 Attractive for tiny to mid-sized
applications, to power cellular phones
and laptops
 Higher efficiencies are achieved at
higher temperatures
 Major problem: Fuel crossing over
from the anode to the cathode
without producing electricity.