新能源新世代 New Energy New Generation

Inspiring Young Minds, striving for a Greener Hong Kong 新能源新世代 New Energy New Generation

可”可載人太陽能車”工作坊(一) 初談高效節能設計課前問卷調查

Step 1: Step 2: 學生資料老師資料活動前問卷調查

2 Contents

• Introduction to Solar Vehicle • World Solar Challenge • NENG 2018 Rule and regulation • Main components in Solar Vehicle • Power consumption calculation

3 “Zero” Emissions? • Local Emission  Zero road emission

• Global Carbon Emission  Reduced by about 5% with the use of EVs and energy-efficient power plants.  This improvement may be further increased with the use of higher percentages of clean or renewable power generation, but may even be negative when adopting inefficient coal-fired power plants. 4 EVs in Hong Kong

• city scale • well-established power network • well-established road • severe roadside emissions • increasing concern on environment • affordability

5 Pros and Cons of EVs PROS  Zero local emissions and low global emissions  Energy efficient  Energy diversified  Silent operation CONS  Heavy weight due to heavy battery weight  High initial cost due to expensive batteries  Short driving range and range anxiety problem (40% of ICEV)  Degraded handling  Long charging time  Lack of charging infrastructure

6 Electric Vehicle (EV)

7 Content of Smart Grid

Integrate more distributed energy resources such as rooftop solar and electric vehicles

8 Solar EVs On-board charging by using solar energy

Battery

Solar DC-DC Main Bus Panel converter

Motor Motor Controller

9 Solar Car Racing World Solar Challenge "New Energy New Generation" Solar Car Competition Shell Eco Marathon(Asia, Americas, Europe) South African Solar Challenge North American Solar Challenge World Green Challenge(WGC Solarcar Rally)

10 Challenge Classes

Challenger Class Cruiser Class Adventure Class

SOPHIE VI (Hong Kong)- Cruiser class

11 Challenger Class – finishing time* Cruiser Class – finishing time, external energy use and practicality* Adventure Class – non-competitive*

Challenger Class – Nuna 8(Netherlands) Cruiser Class – Stella (Eindhoven) Adventure Class – Sophie IV (Hong Kong)

*Based on the WSC 2017 Regulation

12 Overall Dimensions Limitations No. of seat 2 seats for cruiser class No. of Wheels 4 wheels for challenger and cruiser class Area of Solar Panel Types of solar panel and class Battery Size Occupant Cell and Space Safety Performance Braking Steering

Etc. 13 Inspiring Young Minds, striving for a Greener Hong Kong

新能源新世代 New Energy New Generation 2018 「可載人太陽能車」比賽賽道

比賽賽道

IVE 青衣細山路由 IVE 青衣泳池至職業訓練局學生舍堂 (青衣)

全長約1.2公里

15 「可載人太陽能車」比賽賽道

16 每組可於指定時間內行走 3 轉;

每轉 2 個圈;

每轉必須於指定地點停車 1 次 (停車時間10秒).     

17 • Vehicle Dimension:  Length :2.2 m – 3.5m  Width: 1.2 m – 1.3 m  Height: 1.0m – 1.3m  Max. Weight: 200 kg (Without driver)

• No of seats:  Single seat only • No of wheels:  3-4 wheels

18 • Battery capacity- 20Wh • Occupant Cell and Space  Safety • Lighting  2 front head lights;  2 front and 2 rear turn indicators;  3 stoplights, • Vehicle equip:  Horn  cockpit  Safety belts  E-stop  Joulemeter  Safety equipment • Performance  Braking  Steering Etc. 19 Project Process

Preliminary Race Analysis Concept Design Detailed Design Design

Finish Testing Manufacturing

20 Item Essential Component 1 Bodyshell Main Components 2 Chassis and Rollbar 3 Wheels and tires • Electrical System 4 Braking system • Mechanical System • Instrumentations 5 Safety belts 6 Motor 7 Solar Panel 8 Battery pack 9 Lighting 10 Horn 11 Radio 12 Fire Extinguisher 21 Mechanical System Recumbent Trike Provide most of necessary mechanical components Without seat belt Seat Steering control rod Braking System

Tires and rims

Remove the pedal and chain 22 Electrical System

In-wheel motor Battery Pack

Accelerator Motor Controller

23 Aerodynamic consideration

~50% energy consumption total power usage due to aerodynamic drag Percentaerodynamic drag to when speed up to 75km/h 0.5

24 How to reduce the drag?

Frontal Projected Area

25 Aerodynamic development

26 Difficulties However, there is no easy way to obtain the accurate Cd value…

Wind Tunnel Test Computational Fluid dynamics

27 Design the profile of your car Some free apps can be used to insight and improve the design 3. Modify a car (Reduce the size of eddies zone)

1. Draw a car (closed loop)

2. Draw a ground 28 Inspiring Young Minds, striving for a Greener Hong Kong

新能源新世代活動小休 Item Essential Component Before building up 1 Bodyshell the solar car, 2 Chassis and Rollbar What have to do 3 Wheels and tires 4 Braking system first? 5 Safety belts 6 Motor -Body shell? 7 Solar Panel -Electrical system? 8 Battery pack -Mechanical system? 9 Lighting 10 Horn 11 Radio 12 Fire Extinguisher 30 Overview Input Solar cells →Battery Power pack →motor

Rolling resistance Output Wind resistance Power Acceleration

31 Car Power Fundamentals Car

Wind resistance

Rolling Acceleration resistance

32 1) Force a) Rolling Resistance b) Wind Resistance c) Acceleration d) Climbing(Gradient)

33 1) Force a) Rolling Resistance

The force that resists the motion of a body rolling on a surface is called the rolling resistance or the rolling friction.

Rolling friction is caused primarily by the interference of small indentations formed as one surface rolls over another.

34 1) Force a) Rolling Resistance 퐹 = 휇푟표푙푙푖푛푔 푥 푚 푥 푔 퐹표푟푐푒 푟표푙푙𝑖푛푔 = 퐹표푟푐푒 푢푠푒푑 푡표 푐표푣푒푟 푡ℎ푒 푟표푙푙𝑖푛푔 푟푒푠𝑖푠푡푎푛푐푒 푤ℎ푒푛 푡ℎ푒 푐푎푟 𝑖푠 푑푟𝑖푣𝑖푛푔 Unit = N 휇(푟표푙푙푖푛푔) = Rolling coefficient of friction

푚= mass of person and solar car Weight of driver and solar car Unit = kg

푔= acceleration of gravity, directed downwards 10N/kg 35 1) Force

a) Rolling Resistance Rolling Resistance Coefficient

c cl (mm) 0.001 - 0.002 0.5 railroad steel wheels on steel rails

휇(푟표푙푙푖푛푔) = 0.001 bicycle tire on wooden track Rolling coefficient of friction 0.002 - 0.005 low resistance tubeless tires 0.002 bicycle tire on concrete

0.004 bicycle tire on asphalt road 0.005 dirty tram rails 0.006 - 0.01 truck tire on asphalt

0.008 bicycle tire on rough paved road

ordinary car tires on concrete, new asphalt, cobbles 0.01 - 0.015 small new

0.02 car tires on tar or asphalt

0.02 car tires on gravel - rolled new

0.03 car tires on cobbles - large worn car tire on solid sand, gravel loose worn, soil medium 0.04 - 0.08 hard 0.2 - 0.4 car tire on loose sand 36 1) Force b) Wind Resistance

Any object moving through a fluid experiences drag - the net force in the direction of flow due to pressure and shear stress forces on the surface of the object 2 Fd = cd 1/2 ρ v A where

Fd = drag force (N) cd = drag coefficient ρ = density of fluid (1.2 kg/m3 for air at NTP) v = flow velocity (m/s) A = characteristic frontal area of the body (m2)

37 1) Force b) Wind Resistance

Any object moving through a fluid experiences drag - the net force in the direction of flow due to pressure and shear stress forces on the surface of the object 2 Frontal Projected Area Fd = cd 1/2 ρ v A where

Fd = drag force (N) cd = drag coefficient ρ = density of fluid (1.2 kg/m3 for air at NTP) v = flow velocity (m/s) A = characteristic frontal area of the body (m2)

38 1) Force c) Acceleration

퐹표푟푐푒 푎푐푐푒푙 = 푚 푥 푎

39 1) Force c) Acceleration 퐹표푟푐푒 푎푐푐푒푙 = 푚 푥 푎

Equation for average acceleration

a = Δv / Δt a is acceleration, Δv is the change in velocity, Δt is the amount of time it took for that change to occur

40 1) Force c) Acceleration 퐹표푟푐푒 푎푐푐푒푙 = 푚 푥 푎

equation for average acceleration

풅풊풔풕풂풏풄풆 Velocity =Car speed = 풕풊풎풆 Unit normal in km/h

41 1) Force c) Acceleration 퐹표푟푐푒 푎푐푐푒푙 = 푚 푥 푎

Example:

42 2) Power required

푃표푤푒푟 = 퐹표푟푐푒 푟표푙푙𝑖푛푔 + 퐹표푟푐푒 푎푐푒푙 푥 푉푒푙표푐𝑖푡푦

43 3)Speed of the wheel Find N(rpm of the wheel):

푉 = 푟 푥 휔

푑푖푠푡푎푛푐푒 푑푆 V= linear velocity = = 푡푖푚푒 푑푡 휔=angular velocity (rate of change of angular displacement)

Since our displacement/distance is the length of the arc which is made by the angle dθ: s=rdθ 푟푑휃 푑휃 푉 = ,휔 = , r is the radius of wheel 푑푡 푑푡

44 3)Speed of the wheel 푉 = 푟 푥 휔

푑휃 푁 휔 = =2휋푓 = 2휋 =0.1047 x N 푑푡 60 , 푤ℎ푒푟푒 푓 = 푓푟푒푞푢푒푛푐푦, 푁 = 푟푝푚 표푓 푤ℎ푒푒푙

푉 = 푟 푥 0.1047 푥푁 We can find the N(rpm of the wheel out)!

45 3)Torque (Nm needed at the wheel)

푃 = 푇 푥 휔 P= Power (W) T= Torque from the wheel 휔=angular velocity (rate of change of angular displacement)

46 4)Counter-check

푃 = 퐹표푟푐푒 푟표푙푙𝑖푛푔 + 퐹표푟푐푒 푎푐푒푙 푥 푉푒푙표푐𝑖푡푦 푃 = 푇 푥 휔 푉 휔 = 푟 푉 Should be the same 푃 = 푇 푥 푟 with 3) result! 푟 푇 = 푃 푥 푉 푟 푇 = 퐹표푟푐푒 푟표푙푙𝑖푛푔 + 퐹표푟푐푒 푎푐푒푙 푥 푉 푥 푉

푇표푟푞푢푒 = 퐹표푟푐푒 푟표푙푙𝑖푛푔 + 퐹표푟푐푒 푎푐푒푙 푥 푟 푟푎푑𝑖푢푠 표푓 푡ℎ푒 푤ℎ푒푒푙 47 5)Power source requirements

Determine the motor requirement:

Power Torque Speed

48 Essential Question

1) What are the key factors of a rideable solar car ? 2) Are you designing for speed or endurance?

49 Next lessons

Vehicle Dynamics Connections between mathematics and engineering design; Driving forces, friction and inertia Alignment tips and measurements The speed of the wheel and speed tips

50 Solar EVs On-board charging by using solar energy

Battery

Solar DC-DC Main Bus Panel converter

Motor Motor Controller

51 Time to design the electrical system for your car

52 Inspiring Young Minds, striving for a Greener Hong Kong

新能源新世代活動

問答環節