Introduction
 Low electrification rates
worldwide
 Expensive or dangerous
means of energy
 In the US, natural disasters
cause people to lose power
for extended amounts of
time.
Solar Power
 Solar power generation is ideal for these
situations.
 It is virtually harmless to the environment
and inexpensive with greatest cost from
battery replacement.
 PV modules convert solar radiation into DC
electricity.
Overview of System
Engineering Requirements

Performance
The PV array will include a solar tracker which will track the Sun with a maximum error of 15°.
 The PV array will have module efficiency greater than 13%.
 Economic
The cost for the entire system (parts and labor) should not exceed $2,500.
 Energy
The system should be able to supply a load demand of at least 500 Watt-hours per day.
 Maintainability
The system should have a robust design such that failed components can be replaced easily by a
technician.
 Operational
The system should be able to operate in a temperature range of 0 to 75°C.
The PV array will be positioned such that it is not shaded by trees, buildings, or other physical
objects at any time.
 Availability
The PV array will output dc power from sunrise to sunset, 365 days a year, except during unsuitable
conditions (cloud cover, inclement weather, e.g.)
Grape Solar 100W Solar Panel
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$189.99 from Costco
36 cell Monocrystalline
18.5 Vmpp, 5.42 Impp
47.0” tall x 21.1” wide x 1.57” thick
17.6 lbs
Approximately 19% efficiency
Average daily production
 Run a 60W light bulb for 4 hours
 Power a laptop for 5 hours
 Operate a 25” TV for 2 hours through an
inverter
 Fully charge over 30 cell phone batteries.
2-Axis Tracking
 The percentage of incident
solar energy the panel can
convert into electrical
energy depends on the
amount of energy in the
solar radiation but also the
angle between the
radiation and the module.
 2-axis tracking keeps that
angle at 90 degrees,
maximizing conversion
efficiency.
 34% increase in energy
absorption, as opposed to
no tracking.
Solar Tracking
 Began with LED based
tracking using
photodiodes
 Implementation of
Arduino to increase
accuracy
 Replaced photodiodes
with solar cells to
increase output power
PCB Schematics
Voltage Regulator
Solar Tracker
The Solar Tracker
 Analog Design Recap
 Project advancements
- Arduino Usage
- Servos/Recalibration
- Power Consumption
 Programming
- Ideal
- Non-Ideal
Analog Design Recap
Comparator
Compares Solar Cell to
Vref
Vref makes tracking
accurate
Outputs to Logic Circuit
TTL Logic Issue
Analog Design Recap
Uses output from
comparator
Gives proper input to HBridge
H-Bridge Drives the motor
Command
R1
R2
R3
R4
Sensor L
Sensor R
Stop/Coast
0
1
0
1
0
0
Clockwise
0
0
1
1
1
0
C-Clockwise
1
1
0
0
0
1
Brake
1
1
1
1
1
1
Analog Design Recap
Found about 35-40 Degrees
was best
Test done indoors and
outdoors
Tests proved little
recalibration was needed
Fixed Swivel Issue
Analog Design Recap
Added multi-turn pot to increase accuracy
Arduino doesn’t need adjusting
Current approx. Vref
Inside Vref
2.9v
Inside Solar Cell
3.5v
Outside Vref
6.25v
Outside Solar Cell
~6.80v
Project advancements
 Replaced analog circuitry (LC/H-Bridge)
 Allows programming of non-idea conditions
 Can power prototype servos
 Takes input from analog comparators, then controls
servos based on the analog input
Project Advancements
Servo Positioning
 Gearbox coupled to the
shaft
 Used to directly move the
solar panel for Azimuth
and Altitude
 No weight put on the
servo itself
 Loosening the coupler
allows calibration of
servos
Recalibration of Servos
Calibrated servos to
0th degree
Issue with Altitude
coupling
Resolved issue by
recalibrating
Adjusted ~20
Degrees
Integrating the Solar Tracker
Similar to the
prototype but larger
Still using the same
circuitry
Tracker added to side
of system
Adjusted Vref for
sunlight
Servo Power Consumption
Power less than
expected
HS-805BB Servo
consumes .2 - .5A
Servo specification
show .8A or higher
Possible to reach 1A
under certain weather
conditions
Programming: Ideal
Programming: Ideal
Programming: Ideal
Programming: Non-Ideal
Programming: Non-Ideal
System Testing
Charge Controller
• Protect Battery Life
– Preventing Overvoltage
– Preventing Overcurrent
– Displays
• Status
• Voltage
• State of Charge
Charge Controller
Components
• Solid State Relay
– 4 port operation
– Driven with low voltage input
10.67 V
Components
• Voltage Regulator
– With heatsink to withstand 8 A
– 13.75 = 1.25 * (1 + R2/R1)
Components
• Current Sensor
– Hall Effect Sensor
– Current flows through terminals
– Output to Arduino analog pin
– 133 mV/A
Components
• Voltage Divider
Total System Overview
Panel Testing
Elevation Angle (in
degrees up from
horizon)
Voltage (in Volts DC)
0
20.7
90
20.2
45
20.2
58
20.4
Elevation = 0°
Elevation = 90°
Elevation = 45°
Elevation = 58°
The Battery
12 V
85 AH
Dry Cell battery – has
virtually identical
performance
characteristics to SLA’s.
$200
Discover EV Traction Dry Cell: EV24A-A
Inverter
• Cobra CPI880
• 800 W
• Two AC receptacles
and a USB outlet
• Will Power
– Arduino/Charge
Controller
– Motors
– Output power
Inverter shown connected to battery
Battery Capability
• 20 HR rating = 85
Amp Hours
• Can power a
constant 4.25
Amp load for 20
hours
• Wattage levels
much higher when
connected to
panel
Battery Capacity
700
648
600
500
400
264
300
200
100
172.8
94
85
11.28
51
78 93.6
72
66
54
0
100
20
10
5
3
1
Rating Level (Hrs)
AH
Watts
Graph shows battery data for the battery isolated
from the charging system
Construction