Transcript Portable Solar Power Supply
Portable Solar Power Supply
Group V: David Carvajal Amos Nortilien Peter Obeng September 11, 2012
Project Definition
Mobile harnessing of solar energy Store this energy into a battery Supply the stored energy when desired
Project Overview
Solar Panel Solar Tracking Maximum Power Point Tracking (MPPT) Charge Controller DC/DC Converter DC/AC Inverter
Goals and Objectives
Harvest solar energy Convenient mobile power Lightweight Provide Power for broad range AC and DC devices
Portable Solar Power Supply
Block Diagram
Power from Solar Panel Solar Panel Mount Microcontroller (MPPT) Charge Regulator 12 V Lead Acid Battery Microcontroller and Motor (Solar Tracking) LCD Display Provision of AC and DC Power
Specifications and Requirements
Convert 12 V DC to 120 V AC at 60Hz Capable of supplying 5 V DC at 500mA for USB outputs The efficiency (Input power from solar panel to output power from outlet devices) should be at least 90 percent An MPPT algorithm that works very well to keep the solar panel operating at its maximum power point (MPP) Horizontal rotation for solar panel mount (solar tracking)
Solar Panel Types
Crystalline PV Panels
Higher Efficiency High power per area Ease of fabrication High stability Higher liability
Thin Film PV Panels
Low Priced Suited for large areas Better tolerance in the shade Less susceptible to damage Flexible and easier to handle
24 in.
Monocrystalline Solar Panel
21in.
Specifications
Efficiency Weight Dimensions Price Voltage 50 Watt Solar Panel Monocrystalline Photovoltaic Solar Panel Up to 50 Watts (power) Up to 2.92 Amps (current)
Monocrystalline
17% 8.8lbs
24.6x1.2x21 in.
$169.99
12V nominal output
Polycrystalline
12% 12.6lbs
30.6x1.9x27.2 in.
$149.99
12V nominal out put
Solar Angle of Incidence
Depends on the geographic location and time of year. The fixed angles are dependent of the seasons.
Multiple solar angle calculators can be found online.
Photoresistor
A sensor whose resistance varies with light intensity Decreases in resistance as the light intensity increases The resistance must be converted to a voltage
Solar Tracker
2 photocells
IC comparator
Resistors and Diodes
2 limit switches
2 relays
Terminal connectors
Powered by 12VDC
Single axis tracker
12VDC motor
Solar panel mount
2.5 in.
2 in.
2.75 in.
DC to DC Converter
LM3481 Input Voltage from 3.0 V to 48V Outputs 5V, 1 A Current divider to have output of 500 mA 84% efficiency Switching frequency: between 100kHz and 1 MHz
DC/DC Converter
Schematic Diagram
DC to DC converter
LT3502 Input Voltage from 3.0 V to 40V Outputs 5V, 500 mA 87% efficiency Switching frequency: 2.2MHz
Battery
Specification
Manufacture: Battery Mart Type: Sealed Lead Acid Battery Voltage Output: 12 Volt Capacity: 35 Ah Size: 7.65 L x 5.25 w x 7.18 h in. Cost : Donated Weight: 29.00 Pounds Battery Life: 100,000 hours
Convenience
Deep Cycle Sealed Long Service Life Long Shelf Life Wide Operating Temperature Ranges (-40°C to +60°C ) No Memory Effect Recyclable
Maximum Power Point Tracking (MPPT)
The current and voltage at which a solar module generates the maximum power Location of maximum power point is not known in advance Modifies the electrical operating point of a solar energy system to ensure it generates the maximum amount of power.
Finding the current or voltage of the solar panel at which maximum power can be generated Improves electrical efficiency of a solar energy system
Maximum Power Point Tracking (MPPT)
Algorithms
Perturb and Observe: Most commonly used because of its ease of implementation Modifies the operating voltage or current of the photovoltaic panel until maximum power can be obtained Incremental Conductance: Take advantage of the fact that the slope of the power-voltage curve is zero at the maximum power point - The slope of the power voltage curve is positive at the left of the MPP and negative at the right of the MPP MPP is found by comparing the instantaneous conductance (I/V) to the incremental conductance ( Δ I/ Δ V) When MPP is obtained, the solar module maintains this power unless a change in Δ I occurs.
Maximum Power Point Tracking (MPPT)
Algorithms
Hill Climbing Algorithm (Implemented in this project): Uses an iterative approach to find the constantly changing MPP The power-voltage graph in the figure to the right resembles a hill with the MPP at the summit Microcontroller measures the watts generated by the solar panel Controls the conversion ratio of DC/DC converter to implement the algorithm
Charge Regulator
DC/DC Converter (Buck) Built on Arduino Protoshield.
Changes the solar panel’s higher voltage and lower current to the lower voltage and higher current needed to charge the battery.
Controlled by PWM signal that switches the MOSFETS at 50kHz Prevents battery from discharging at night Measures battery and solar panel’s voltage
Charge Controller
Schematic Diagram
Charge Controller
Current Sense Resistor and High Side Current Sense Amplifier
Charge Controller
Switching MOSFETS and Blocking MOSFET, and MOSFET Driver
Protoshield
Schematic
Microcontroller
Arduino Duemilanove
Specification:
Processor: ATmega168 Operating Voltage: 5 V Digital I/O Pins: 14 (6 provides PWM output) Analog Input Pins: 6 DC Current per I/O Pin 40mA Flash Memory: 16KB (2KB is used by bootloader) SRAM: 1 KB EEPROM: 512 bytes Clock Speed: 16MHz
Function:
Controls Charge Controller to Optimize battery charging Displays status of the portable solar power supply on LCD display
Microcontroller
Arduino Duemilanove Schematic
LCD Display
Pin connections 10 11 12 13 14 5 6 7 Pin 1 2 3 4 8 9 15 16 Symbol
VSS VDD V0 RS R/W E DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 LEDA LEDB
Level
--- --- --- H/L H/L H/L H/L H/L H/L H/L H/L H/L H/L H/L --- ----
Functions
GND (0V) Supply Voltage for Logic (+5V) Power supply for LCD H: Data; L: instruction Code H: Read; L: Write Enable Signal Data Bus Line Backlight Power (+5V) Backlight Power (0V)
Pure sine wave Inverter
Specifications
95% of Efficiency Output voltage of 120V AC at 60 Hz Power rating of 500 W
Inverter
Inversion Process
Stepping up the low DC voltage to a much higher voltage using boost converter Transforming the high DC voltage into AC signal using Pulse Width Modulation u E + = i S u S L + u M
Block Diagram
Voltage Regulator MCU Signal Generation MOSFETs Drivers H bridge AC Output Signal DC Input High DC Voltage
High Voltage DC/DC Converter
Specification
Feed the high side of the H-bridge Efficiency of 90% Isolated voltage feedback Cooling passively
High Voltage DC/DC Converter
Schematic Diagram
Pulse Width Modulation
Method of generating AC Power in Electronic Power Conversion through: 1.
Simple Analog Components 2.
3.
Digital Microcontroller Specific PWM Integrated Circuits
Pulse Width Modulation
2 Level PWM Signal
H-Bridge Circuit
Circuit that enables a voltage to be across a load Consists of 4 switches, MOSFETS
H-Bridge Circuit
Control of the Switches
High side left High side right Low side left Low side right Voltage load On Off
Off On Off On On Off Positive Negative
On Off
On Off Off On Off On Zero Zero
Table 4.4.4-1: Switches Position and Load Sign
H-Bridge Circuit
Control and Operation
MOSFET Driver
To switch a low voltage on the device Bootstrap Capacitor 𝐶 ≥ 2[2𝑄 𝑔 + 𝐼𝑞𝑏𝑠 𝑓 + 𝑄 𝐼𝑠 + 𝐼𝐶𝑏𝑠 𝑓 ] 𝑉 𝐶𝐶 − 𝑉 𝑓 − 𝑉 𝐿𝑆 − 𝑉 𝑀𝑖𝑛
Microcontroller
MSP430F449
Specification
Frequency: 8 MHz Flash: 60 KB SRAM: 2048 KB Comparator: Yes
Functionality
Generate signals for the MOSFET drivers Control the PWM Provides easier feedback to control power
Inverter Circuit Diagram
V5 R1 V1 R2 V2 R3 V3 R4 V4 R5 Q1 R6 Q2 R7 Q3 R8 Q4 U1 U2 V6 R9 C1 D1 Q5 R10 C4 R11 C2 D2 Q6 Q7 R12 C3 Q8 L1 C5 R13
Progress
Progress
AC/DC Inverter Arduino Charge Controller MSP430 LCD Screen Solar Tracker DC/DC Solar Mount 0,00% 20,00% 40,00% 60,00% 80,00% 100,00% Progress
Problems
Microcontroller MSP430 How efficient it will handle and control the pulse width modulation Mechanical portion of the project Solar Panel Mount
Budget
$200,00 $180,00 $160,00 $140,00 $120,00 $100,00 $80,00 $60,00 $40,00 $20,00 $ Budget Actual $ Spent