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  $ 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 H- Bridge  H-Bridge Drives the motor CommandR1R2R3R4Sensor LSensor R Stop/Coast Clockwise C-Clockwise Brake111111

Analog Design Recap  Found about 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 Vref2.9v Inside Solar Cell3.5v Outside Vref6.25v 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 0 th 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: 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 V

Components Voltage Regulator – With heatsink to withstand 8 A – = 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) Elevation = 0° Elevation = 45° Elevation = 90° Elevation = 58°

The Battery Discover EV Traction Dry Cell: EV24A-A  12 V  85 AH  Dry Cell battery – has virtually identical performance characteristics to SLA’s.  $200

Inverter Cobra CPI 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 Graph shows battery data for the battery isolated from the charging system

Construction