Inspiring Young Minds, striving for a Greener Hong Kong 新能源STEM世代 New Energy STEM Generation
可”可載人太陽能車”工作坊(一) 初談高效節能設計
13Apr2019 Contents • Introduction to Solar Vehicle • World Solar Challenge • NESG 2019 Rule and regulation • Main components in Solar Vehicle • Power consumption calculation
2 “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. 3 EVs in Hong Kong
• city scale • well-established power network • well-established road • severe roadside emissions • increasing concern on environment • affordability
4 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
5 Electric Vehicle (EV)
6 Content of Smart Grid Integrate more distributed energy resources such as rooftop solar and electric vehicles
7 Solar EVs On-board charging by using solar energy
Battery
Solar DC-DC Main Bus Panel converter
Motor Motor Controller
8 Solar Car Racing
World Solar Challenge "New Energy STEM Generation" Solar Car Competition Shell Eco Marathon(Asia, Americas, Europe) South African Solar Challenge North American Solar Challenge World Green Challenge(WGC Solarcar Rally)
9 World Solar Challenge
Challenger Class Cruiser Class Adventure Class
SOPHIE VI (Hong Kong)- Cruiser class
10 World Solar Challenge 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
11 Limitations Overall Dimensions 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. 12 Inspiring Young Minds, striving for a Greener Hong Kong
新能源STEM世代 New Energy STEM Generation 2019 “Ridable Solar Car” semi-final track
Semi-final track
IVE (Tsing Yi) 20 Tsing Yi Road
From IVE (TY) swimming pool to VTC Halls of Residence(TY) Total ≈1.2km
14 “Ridable Solar Car” semi-final
10 team of entrants will advance Each team can race 2 times to the final within the specific time;
2 laps per times;
Each time must stop 1 time at designated place (10 seconds stopping time). 15 “Ridable Solar Car” final track (TBC)
Final track (TBC)
Zero Carbon Building – ZCB
Each lap ≈ 0.3km
16 “Ridable Solar Car” final
Each team can race 2 times within the specific time; 2 laps per times; 季軍) Each time must stop 1 time at designated place (10 seconds stopping time).
17 Rule and regulation • Vehicle Dimension: Max. Length :3.5m Max. Width: 1.3 m Max. Height: 1.3m Max. Weight: 225 kg (Without driver)
• No of seats: Single seat only
• No of wheels: 3-4 wheels
• Speed limit: 30 km/hr
18 Rule and regulation • If a Lithium-Ion battery is used, either as a propulsion or accessory battery, provide printed/written documentation on the BMS operation. • 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 19 Etc. Project Process
Concept Preliminary Detailed Race Analysis Design Design Design
Finish Testing Manufacturing
20 Main Components Item Essential Component 1 Bodyshell 2 Chassis and Rollbar • Mechanical System 3 Wheels and tires 4 Braking system 5 Safety belts • Electrical System 6 Motor 7 Solar Panel 8 Battery pack • Instrumentations 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 22 Electrical System
In-wheel motor Battery Pack
Accelerator Motor Controller
23 23 Design flow Before building up Item Essential Component 1 Bodyshell the solar car, 2 Chassis and Rollbar What have to do 3 Wheels and tires first? 4 Braking system 5 Safety belts 6 Motor -Body shell? -Electrical system? 7 Solar Panel -Mechanical system? 8 Battery pack 9 Lighting 10 Horn 11 Radio 12 Fire Extinguisher 24 Inspiring Young Minds, striving for a Greener Hong Kong
新能源STEM世代 New Energy STEM Generation 2019 Tea Break Design flow Before building up Item Essential Component 1 Bodyshell the solar car, 2 Chassis and Rollbar What have to do 3 Wheels and tires first? 4 Braking system 5 Safety belts 6 Motor -Body shell? -Electrical system? 7 Solar Panel -Mechanical system? 8 Battery pack 9 Lighting 10 Horn 11 Radio 12 Fire Extinguisher 26 Overview
Input Solar cells →Battery Power pack →motor
Output Rolling resistance Power Wind resistance Acceleration
27 Car Power Fundamentals
Car
Wind resistance
Rolling Acceleration resistance
28 1) Force a) Rolling Resistance b) Wind Resistance c) Acceleration d) Climbing(Gradient)
29 1) Force
a) Rolling Resistance
• The resistance of automotive tires to rolling can consume 20% to 50% of the energy
• So if engineers could cut the rolling resistance in passenger-car tires by 10% gas travel range would improve by 3%.
30 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.
31 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 32 1) Force
Rolling Resistance Coefficient a) Rolling Resistance c c (mm) l 0.001 - 0.002 0.5 railroad steel wheels on steel rails
0.001 bicycle tire on wooden track
휇(푟표푙푙푖푛푔) = 0.002 - 0.005 low resistance tubeless tires Rolling coefficient of friction 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
33 1) Force
a) Rolling Resistance
How to reduce rolling resistance • Inflation pressure • Load • Tread depth • …etc
34 1) Force
b) Wind Resistance
total power usage Percentaerodynamic drag to ~50% energy consumption
due to aerodynamic drag 0.5 when speed up to 75km/h
75
35 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 Frontal Projected Area
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) 2 A = characteristic frontal area of the body (m ) 36 1) Force b) Wind Resistance How to reduce the drag?
Fd ∝ cd & A
∴↓ cd & ↓ A ↓Fd
37 1) Force b) Wind Resistance Aerodynamic development
38 1) Force b) Wind Resistance
Wind Tunnel Test Computational Fluid dynamics
39 1) Force b) Wind Resistance Some free apps/softwares 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
40 1) Force c) Acceleration
퐹표푟푐푒 푎푐푐푒푙 = 푚 푥 푎
41 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
42 1) Force c) Acceleration 퐹표푟푐푒 푎푐푐푒푙 = 푚 푥 푎
equation for average acceleration
풅풊풔풕풂풏풄풆 Velocity =Car speed = 풕풊풎풆 Unit normal in km/h
43 1) Force c) Acceleration 퐹표푟푐푒 푎푐푐푒푙 = 푚 푥 푎
Example:
44 2) Power required
푃표푤푒푟 = 퐹표푟푐푒 푟표푙푙𝑖푛푔 + 퐹표푟푐푒 푎푐푒푙 푥 푉푒푙표푐𝑖푡푦
45 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
46 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)!
47 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)
48 4)Counter-check of Torque
푃 = 퐹표푟푐푒 푟표푙푙𝑖푛푔 + 퐹표푟푐푒 푎푐푒푙 푥 푉푒푙표푐𝑖푡푦 푷 = 푻 풙 흎 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
49 5)Power source requirements
Determine the motor requirement:
• Power • Torque • Speed
50 Essential Question
1) What are the key factors of a rideable solar car ? 2) Are you designing for speed or endurance?
51 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
52 Solar EVs On-board charging by using solar energy
Battery
Solar DC-DC Main Bus Panel converter
Motor Motor Controller
53 Solar cell to PV System
54 Solar Cell Efficiency
55 Converter
56 Energy Conversion System
57 Time to design the electrical system for your car
58 Inspiring Young Minds, striving for a Greener Hong Kong
新能源STEM世代 New Energy STEM Generation 2019 Q&A