Transcript Power

Power
SOLAR & ELECTRIC POWER
The GO
The Green Tricycle uses electric power. This requires:
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A Charge
Battery
Controller
Motor
Charge
Battery
Controller
Motor
How Much Power Do I Need?
Preq=M*g*V*µ+(q*A*V*Cd)
Preq=Power Required in Watts (W)
M=Mass of Vehicle (kg)
g=Gravitational Acceleration (9.81m/s2)
V=Vehicle Forward Velocity (m/s)
µ=Coefficient of Rolling Resistance (Use rubber-to-concrete in ideal conditions to start)
q=1/2*ρ*V2
◦ (ρ=Density [1.225 kg/m3])
A=Vehivle Frontal Area (m3) (Use A of Similar Sized Vehicle)
Cd=Vehicle Drag Coefficient (Use Cd of Similar Sized Vehicle ~0.55)
What’s My “Range”?
Determine battery’s Watt-Hour capacity (Battery Voltage * Battery Amp Hour Rating)
To get runtime, Divide Watt-Hour capacity (above), by Power Required in watts (see previous
slide)
◦ Remember Power Required is a function of Velocity (Depends on Velocity)
Get RANGE by multiplying forward velocity by runtime at that velocity
◦ See next slide for an example of a graph that can be created with these calculations
Power Considerations in the Design of a Green-Energy Tricycle
Top Speed and Power Calculations
Pedal system connects to rear hub motor powered by battery
Motor
Battery
Golden Motor Magic
Pie V5
48V 20Ah Samsung 18650
What else to consider?
Torque from Start
Top Speed
Battery Capacity/Output
Will the rider pedaling assist the motor, or will motor produce all power?
Worked Example
http://www.diyelectriccar.com/forums/showthread.php?t=15508
Solar Power
Solar Power
A solar panel works by allowing photons (particles of light) to knock electrons free from atoms, generating a flow
of electricity. Solar panels actually comprise many, smaller units called photovoltaic cells. Many cells linked
together make up a solar panel.
3 Major Solar Panel Manufacturers (Forbes):
◦ Trina Solar, Yingli Solar, Canadian solar
Specs and Cost:
◦ CS6K-P-PG
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Dimension: 39.05 in X 64.96in X .39in
Peak Power: 260-265 Watts
Cost: ~$200
Weight: 50.71 lbs
◦ YGE 60 Cell Series
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Dimensions : 64.57in X 38.98in X 1.38in
Peak Power: 240-260 Watts
Cost: ~$200
Weight: 40.8 lbs
Solar Power
Powering the Vehicle?
◦ Using a Solar Panel for power requires
◦ Charge Controller - provides suitable charging capabilities for the battery
◦ Inverter – produces usable power from solar power for devices or motors
◦ They’re not free of cost and weight.
◦ They aren’t “pretty” & don’t come in customizable shapes.
◦ (See top right image)
◦ In many cases, they’re better left behind.
◦ It’s not efficient for small solar panel alone to move a large
vehicle like the Green Tricycle.
Batteries
Batteries - It’s all about storage
Keeping Charged:
◦ Electric vehicles store energy in a battery. When this energy is depleted,
it must be recharged. We do this everyday with our high use electronic
devices (smartphones, laptops…)
◦ Considerations:
◦ Avoid deep cycling - A partial discharge is better than a full discharge.
◦ Avoid abuse - A battery is stressed more if discharged and charged too quickly
Tesla vehicles have large
batteries in chassis
Batteries - It’s all about storage
Cost
◦ Nickel metal hydride batteries are the less-expensive technology.
Weight
◦ NiMH batteries are larger and heavier than Li-ion batteries.
◦ Weight matters in our tricycle for maximum mileage.
Power
◦ Li-ion and NiMH batteries can actually hold a similar amount of power.
◦ Li-ion cells can be charged and discharged more rapidly.
◦ Li-ion doesn't have as much of a "memory effect," which occurs when a battery is recharged before it is
fully empty. This can diminish a battery's capacity.
Durability
◦ NiMH has an advantage.
◦ Some Li-ion batteries don't last as long in extreme temperatures, particularly in very hot climates.
Batteries - It’s all about storage
Other Options?
Deep Cycle Auto/Marine Batteries
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Easily swappable/widely available
Relatively low cost (typically $50-$200 dependent on size)
Not properly suited for multiple charge/recharges
Better suited for cold-cranking – getting an engine started
Best suited for use with an alternator to keep float charge
Getting More from Your Batteries
This is how it works:
◦ Batteries Connected in Series
◦ Doubles Voltage (V), Capacity in Amp Hours (AH) Remains the Same.
◦ Batteries Connected in Parallel
◦ Doubles Capacity in Amp Hours (AH), Voltage (V) Remains the Same.
Controllers
CONTROLLING YOUR MOTOR
How they work…
Simplest case is a switch to connect a motor to a power source
◦ On & Off. Stop & GO.
Accurately control the speed and torque of the connected motor (or motors)
◦ PWM: Pulse Width Modulation
◦ Alternating “On & Off” signals at different frequencies that simulate speed control
◦ Narrow Pulses=Slow. Wide Pulses=Fast
Motor
Focus on DC Motors
Since batteries create “Direct Current (DC)” signals, Use an DC
Motor for Simplicity
AC Motor will require additional component called an inverter
◦ Invertor takes DC signal and turns into AC
A DC motor consist basically of two parts:
◦ Stationary body of the motor called the “Stator”
◦ Rotating inner part which rotates producing the movement called the
“Rotor”
Find a motor that produces enough Power & Torque for your worst
case (from stop, heavy, etc…).
See the wattage ratings and contact manufacturers to make the
final judgment.
All-in-One Units
Some suppliers sell “systems” that sometimes
incorporate batteries, controllers and motors in one easy
to manage package. Some examples used in the Green
Tricycle project include:
Bafang
◦ www.szbaf.com
Magic Pie
◦ www.goldenmotor.com
Our Green Tricycle
Motor: Magic Pie 5 by Golden Motor
Motor operates on a 48V source – Samsung 18650 20Amp Hour lithium-ion battery.
Tricycle can generate over 800 Watts of power to drive
the vehicle.
Motor uses regenerative braking system to store
additional energy that would otherwise be wasted
during braking.
Motor is controlled by a throttle and includes a “cruise
control” option for added operator comfort.
Battery Plug-in to solar float charger or wall outlet to
recharge.
Powertrain Components
Samsung 18650 E-Bike Battery
Magic Pie 5
48 Volts
12 pounds
Regenerative
Braking
960 Watt Hours
1000 Charges
Complete System
Bluetooth
Connection
7.5 pounds
What Are Others Using?
The Elf
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Continuously variable transmission
Pedal-assisted motor mounted in middle of bike frame
750W DC Permanent Neodymium Magnet Motor
Lithium-ion NMC with BMS
48-V 10 Ah battery
Charged by solar panel or outlet
HP Velotechnik S-Pedelec
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Scorpion FS 26
Start assist button
Rear hub motor
Thumb throttle on handlebar
500-watt rear wheel hub motor
36 V Li-Ion rechargeable battery
530 W-h capacity