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Modern World = Electrical World
• Can you list TEN items in your home that are operated by electricity?
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Learning Objectives
1. History of Fuel Cells
2. Operation of Fuel Cells
3. Comparison between Fuel cells and
Batteries
4. Applications of Fuel Cells
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Two types of Energy Supplies
1. Fossil Fuel ( 化石燃料 )/
Non-renewable energy( 非再生能源 ).
2. Renewable Energy Source ( 可再生能源 )
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1. Fossil Fuel ( 化石燃料 )
• Coal ( 煤 )
• Natural gas ( 天然氣 )
• Oil ( 石油 )
• Tar sands ( 焦油沙 )
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2. Renewable Energy Source ( 可再生能源 )
• Hydroelectric power (水力發電)• solar power (太陽能)• wind power (風力發電)• wave and tidal power (潮汐發電)• geothermal power (地熱能源)
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Electrical Cells
Electrical cell – device for generating
electricity
1. Solar cell
2. Chemical cell
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1. Solar Cell
- A device for converting the sun’s energy to electricity
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2. Chemical Cell
- A device for converting chemical energy into electrical energy
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Classification of Chemical Cells
a. Simple chemical cells
b. Dry cells/batteries
c. Wet cells
d. Fuel cells
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Simple chemical cells
e.g. Mg/Cu cell
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Dry Cells
- A portable source of electricity
2 classes of dry cells
1. Primary cells - non-rechargeable batteries
2. Secondary cells - rechargeable batteries
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Dry Cells
Common Primary Dry Cells原電池1. Zinc-carbon cells 鋅碳電池2. Alkaline manganese cells 鹼性錳電池3. Silver oxide cells 氧化銀電池4. Mercury cells 水銀電池5. Lithium cells 鋰電池
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Secondary Cell (蓄電池 )
e.g. Nickel-cadmium cells 鎳鎘蓄電池
e.g. Lead acid battery (car battery)
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Worksheet 2
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Expected Answers for Worksheet 2
• Hearing aids are small and they need very small batteries. Silver oxide batteries shaped like a button and satisfied this purpose.
• Silver and its compounds (e.g. silver oxide) are expensive.
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Dry Cells Disposal Problems
• Environmental pollution 環境污染• Toxic 有毒
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Worksheet 3
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Specific Energy of Batteries and FuelCells
30 100 150 100 100300
100250
450600 600
3000
0
500
1000
1500
2000
2500
3000
3500
NiMH Alkaline Zn/Air Li-Ion Li Polymer MethanolFC
Cell Type
Spec
ific
Ener
gy (W
att-h
r/kg)
Nominal
High
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Fuel Cells
e.g. Alkaline fuel cell was used in spacecraft
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Fuel Cell (燃料電池)
An Alternative Energy Source for the Future
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Fuel Cell
The ultimate clean machine for generating electricity
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Brief History of Fuel Cells
1839 Demonstrated operating principle
1950 Demonstrated the operation of a fuel cell stack
Late 1950 NASA choose AFC to provide power for spaceship
1960 – 70 Alkaline fuel cell (AFC) went to the moon
1970s Fuel cell extended – Phosphoric Acid, Solid Oxide, Molten Carbonate, Proton Exchange Membrane
Late 1970s Fuel cell as s stationary power generation source
The Hydrogen economy concept proposed
Late 1980s Fuel cell car appeared
Late 1990s Small fuel cell replaced battery, Iceland plan to use
geothermal energy and hydroelectric power for hydrogen economy
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What is a Fuel Cell ?
• A device that generates electricity without combustion
• Chemical energy is converted directly into electrical energy
• Similar to a battery but much better
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How Fuel Cell Works
• There are two electrodes
• Electrolyte must be placed between the electrodes
• Fuel is supplied to anode
• Oxidant is supplied to cathode
• The reaction between fuel and oxidant in the fuel cell generates electrical current
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An Alkaline Fuel Cell
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Hydrogen Economy
• An economic model where hydrogen is used as the main fuel.– The economic development requires an unlimited
supply of energy.
– Fossil fuel are polluting the environment.
• First proposed in the late 1970s• Iceland may be the first country to fully
implement the hydrogen economy concept.
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Demonstration on Reversible Operation of Fuel Cell – Electrolysis
Beaker 燒 杯 6 volt Battery 電 池
Anode陽 極
Cathode陰 極
H2
氫氣H2
氫氣O2
氧氣O2
氧氣
Water水
Water水
Cardboard硬咭紙
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Applications for Fuel Cells
• Space program (太空計劃)• Power Generation (發電)• Transportation (運輸)• Landfill/Wastewater Treatment( 廢物堆填
及廢水處理)• Portable power (可攜式電源)
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Comparison between Fuel Cell and Battery
Fuel Cell Battery
Energy from chemical energy Energy from chemical energy
Electrodes separated by electrolyte Electrodes separated by electrolyte
No electrode consumed during reaction
At least one electrode consumed during reaction
Outside sources supply reactants continuously
Reactants stores inside battery
Reaction product remove from the cell continuously
Reaction product stored inside the battery
Precious metal as catalyst, least pollution problem
Contain heavy metal, cause pollution
High power density Low power density
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Worksheet 4
33FUEL CELL OPERATION DIAGRAM燃 料 電 池 示 意 圖
FUEL CELL OPERATION DIAGRAM燃 料 電 池 示 意 圖
Electrical LoadElectrical Load電 流 強 度電 流 強 度
氫氣 H2氫氣 H2 O2 氧氣O2 氧氣
ELECTROLYTEELECTROLYTE電 解 質電 解 質
FUELFUEL OXIDANTOXIDANT
H2O水
H2O水
H2O水
H2O水
POROUS NICKEL ELECTRODEPOROUS NICKEL ELECTRODE多 孔 性 鎳 電 極多 孔 性 鎳 電 極
Anode ElectrodeAnode Electrode陽 極陽 極
Cathode ElectrodeCathode Electrode陰 極陰 極
-- ++
Electric Motor馬 達
Electric Motor馬 達
11 22
66
55
77
4433
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Advantages of Fuel Cells
• Less Pollution (減輕污染)• High Efficiency (高效能)• High Power Quality and Reliability (電
源品質好和可靠性高)• Distributed Power Supply (分散供電)• High Power Density (能源密度高)
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Problems with Fuel Cell Technologies
1. Fuel cells require catalyst (催化劑) : - expensive catalyst - problem of catalyst poisoning2. Specialty materials to withstand corrosive
(侵蝕) environment of alkaline solution at high temperature
3. Hydrogen : flammable (易燃) and explosive (爆炸)
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Fuel Cell Terminology
• Anode( 陽極 ) – the negative electrode• Cathode( 陰極 ) – the positive electrode• Electrochemical( 電子學的 ) – convert chemical energ
y to electrical energy• Electricity( 電、電流 ) – flow of electrons in a circuit• Electrolysis( 電解 ) – a process of chemical changes b
y passing an electric current through a solution resulting in a transfer of electrons to the electrode
• Electrolyte( 電解質 ) – a chemical means in the transfer of ions from one medium to another
• Fuel cell( 燃料電池 ) – an electrochemical/self generating power source
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Fuel Cell Terminology
• Hydrogen( 氫 ) – chemical fuel of a fuel cell flowing through the anode
• Membrane( 薄膜 ) – substance allowing hydrogen and oxygen to pass through
• Oxygen( 氧 ) – chemical fuel flowing through the cathode
• PEM( 質子交換膜 ) – proton exchange membrane• Stacking( 堆疊 ) – method of adding fuel cells to incre
ase voltage output• Voltage( 伏特 ) – a measure of electrical potential of a
n electrical circuit or device• ZEV( 零排放車輛 ) – zero emission vehicle
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Demonstration on Operation of Fuel Cell
Chemical energy of a bio-fuel-methanol converts to Electrical energy
1. Mix 1.5 mL of methanol (fuel) into 25 mL 1M KOH solution(electrolyte) in a beaker.
2. Stir for a few minutes with a glass rod.
3. Pour the mixed fuel and electrolyte into the Fuel Cell and wait for 5 minutes.
4. Put the top cover onto the cell body.
5. The fan will turn! Electricity produced by the fuel cell turns the fan.
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Reversible Operation of Fuel Cell - Electrolyis
1. Fill the beaker with about 400 mL of tap water.
2. Add a few drops of dilute sulphuric acid.
3. Cut 2 small slits into the card board paper to serve as a holder and insulator for the lead strip electrodes.
4. Place the lead strips into the water
5. Connect the leads to the battery terminals as illustrated in the diagram.
6. Bubbles of hydrogen and oxygen gas will be observed after a few minutes indicating that the electrolysis is on progress.
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