風力發電機製作及相關物理計算 MAKING OF WIND TURBINE AND RELATED CALCULATION

風力發電機製作 及相關物理計算 MAKING OF WIND TURBINE AND RELATED CALCULATION 香港理工大學應用物理學系學生翟振亨 HKPU Applied Physics Student Chka Chun Hang

目錄 • 引言 • 理論 • 發電機的設計 • 製作過程 • 相關計算 • 演示

Where do winds come from?風從哪裡來? • Because of the temperature differences(溫差) around the world Surface Wind Convection updraft of rising warm Air

What is wind turbine(風力發電機)? Wind’s kinetic energy(動能) -> electrical energy(電能)

Theory理論 • By Lenz’s Law (冷次定律) Induced current(感生電流) opposes(對抗)the change of the magnetic force Heinrich Lenz 海因里希·冷次

Theory理論

Induced emf-感生電壓 Where , • N is the number of turn of coil, • B is the magnetic field strength (磁場強度) • A is the area(面積) of the coil

Design-設計

Design-設計 (3D View)

Design-設計 (3D View) Brace 支架

Design-設計 (3D View) Axle 軸

Design-設計 (3D View) Turbine 渦輪

Design-設計 (3D View) Rotor 轉片

Design-設計 (3D View) Coil 電線圈

Design-設計 (3D View) Supporting Base 支撐底部

Design-設計 (3D View) Magnet 磁鐵

Material-物料 • Screw(螺絲) x 8 Bearing(滾珠軸承)x 2 • Wooden borad(5”x10”) Wooden board(2”x10”) • Copper wire(漆皮銅線) Chopstick(筷子) x 3 • Water bottle(水樽) Magnet (磁石)x 4 • LED 燈x 1 CD case x 1 • )

Making Process-製作過程 • 1. Preparing the material

Making Process-製作過程 • 2.making the frame(骨架) and base 1 2 3

Making Process-製作過程 Finished product

Making Process-製作過程 • 3. Assembly(集合) the CD case and the base 1 3 4 2

Making Process-製作過程 • 4. making the coil by the copper wire

Making Process-製作過程 • 5. assembly to the CD case

Making Process-製作過程 • 6. making the rotor(轉片)

Making Process-製作過程 • 6. making the rotor (轉片) 2 3 1

Making Process-製作過程 • 7. making the turbine(渦輪) 1 3 2 4

Making Process-製作過程 • 7. making the turbine (渦輪) 5 7 6

Making Process-製作過程 • 8. assembly all the component(部件)

Final Product-製成品 Finish!!

Calculation 相關計算

Power(功率) of Wind turbine • kinetic energy of a mass in motions is: • The power in the wind is given by the rate ofchange of energy: • As mass flow rate is given by:

Power (功率) of Wind turbine • Also, the rate of change of distance is given by: • we get: • Hence, the power can be defined as:

Power (功率) of Wind turbine Power coefficient(功率系數), Cpmax= 0.59 Therefore, the extractable power: No wind turbine can convert(轉換)more than 16/27 (59.3%) of the kinetic energy of the wind into mechanical energy turning a rotor. German physicist Albert Betz Picture captured from http://www.eoearth.org/article/Betz,_Albert

Power (功率) of Wind turbine • For this turbine, 假設 , • Power Coefficient(功率系數), Cp = 0.5 • Air density(密度), ρ = 1.23 kg/m3 • Area of blades(扇葉), A= 0.04*0.2 = 0.008 m2 Wind speed(風速), v = 20km/h = 5.56 m/sec 所以, • P = ½*0.5*1.23*0.008*5.563 = 0.423 W

Induced voltage-感生電壓 • Since, Thus,

Induced voltage-感生電壓 • Normally, an AAbattery(電池) is having 1.5V

Applications(應用)

Factor (影響因素) Factor(影響因素) of output voltage: • Wind speed(風速) • Strength of magnet(磁石強度) • *The number ofturns of coil, N(線圈圈數) • *Internal resistance of wire, r(電線內阻) • Since因為 N ->r ,Iout

延伸探究 • 內阻同圈數對於輸出電流的連帶關係 • 計算輸出功率 • 計算效率

Demonstration-演示

風力發電機製作及相關物理計算 MAKING OF WIND TURBINE AND RELATED CALCULATION