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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.