POWER GENERATION THROUGH SOALR AND WIND ENERGY BY USING AUTOTRACKING

SYSTEM

ABSTRACT:

The basic idea of the project is to obtain electricity by using sunlight as

fuel. These can be thought of as “packets of sunlight” that carry a phenomenal amount of

energy to earth at a prodigious rate. These photons are captured by the solar panel. Solar

panel consists of photovoltaic cells. Photovoltaic means sunlight converted into flow of

electrons. Photovoltaic devices, or solar cells, are like generators that work in sunlight.

They make electricity without waste, noise or pollution.

This can be used as an alternative to a battery. Using battery for small

applications is affordable but for applications such as satellites and other large projects, it

is not possible to use batteries because it costs too much they are to be replaced as the

time passes. Mainly the hardware of the project includes solar panel and a stepper motor

to rotate it. The solar panel is made to rotate in all directions facing the sunlight and

tracks to obtain the position where there is maximum intensity of sunlight and rests in

that position. It waits for some time in that position and begins to track again to obtain the

maximum intensity position at that time. This is because the sun is not stationary.

1

CONTENTS Page no

1. INTRODUCTION 3

2. BLOCK DIAGRAM 4

3. HARDWARE COMPONENTS 5

3.1 Microcontroller description 6

3.1.1 Introduction 7

3.1.2 Pin description 8

3.1.3 Memory organization 10

3.2 Analog to digital converter 16

3.3 LCD unit 19

3.4 Driver circuit 30

3.5 LDR 44

3.6 Power supply 48

3.7 Battery 50

4. SOLAR PANELS 61

5. WIND POWER 75

6. APPLICATIONS AND LIMITATIONS 90

7. CONCLUSION 91

8. BIBLIOGRAPHY 92

2

1. INTRODUCTION

The basic idea of the project is to obtain electricity by using sunlight as

fuel. These can be thought of as “packets of sunlight” that carry a phenomenal amount of

energy to earth at a prodigious rate. These photons are captured by the solar panel. Solar

panel consists of photovoltaic cells. Photovoltaic means sunlight converted into flow of

electrons. Photovoltaic devices, or solar cells, are like generators that work in sunlight.

They make electricity without waste, noise or pollution.

This can be used as an alternative to a battery. Using battery for small

applications is affordable but for applications such as satellites and other large projects, it

is not possible to use batteries because it costs too much they are to be replaced as the

time passes. Mainly the hardware of the project includes solar panel and a stepper motor

to rotate it. The solar panel is made to rotate in all directions facing the sunlight and

tracks to obtain the position where there is maximum intensity of sunlight and rests in

that position. It waits for some time in that position and begins to track again to obtain the

maximum intensity position at that time. This is because the sun is not stationary.

3

2. BLOCK DIAGRAM:

LDR1 LDR2

4

8051MICRO

CONTROLLER

16X2LCD

MOTORS

BATTERY

ADC0808

DRIVER CIRCUIT

POWER SUPPLY

HOME APPLIANCES

SOLAR PANEL

3. HARDWARE COMPONENTS

AT89C51 Microcontroller

L293D Driver IC

Motors

SOLAR PANEL

WIND BLADES

16X2 LCD

ADC 0808

TRACKING SYSTEM USING LDR

Battery

SOFTWARE TOOLS

Embedded c

Keil-2

ASSEMBLY

3.1 AT89C52 MICROCONTROLLER:

5

6

3.1.1 INTRODUCTION:

8051 MICROCONTROLLER

8051 Family

Intel fabricated the original 8051 which is known as MCS-51. The other two members of

the 8051 family are:

I. 8052

II. 8031

About the 8051

The Intel 8051 is an 8-bit microcontroller which means that most available operations are

limited to 8 bits. There are 3 basic "sizes" of the 8051: Short, Standard, and Extended.

The Short and Standard chips are often available in DIP (dual in-line package) form, but

the Extended 8051 models often have a different form factor, and are not "drop-in

compatible". All these things are called 8051 because they can all be programmed using

8051 assembly language, and they all share certain features (although the different

models all have their own special features).

Typical applications

8051 chips are used in a wide variety of control systems, telecom applications, and

robotics as well as in the automotive industry. By some estimation, 8051 family chips

make up over 50% of the embedded chip market.

3.1.2 PIN DESCRIPTION:

Pin diagram of the 8051 DIP

BASIC PINS

PIN 9: PIN 9 is the reset pin which is used to reset the microcontroller’s internal registers

and ports upon starting up. (Pin should be held high for 2 machine cycles.)

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PINS 18 & 19: The 8051 has a built-in oscillator amplifier hence we need to only

connect a crystal at these pins to provide clock pulses to the circuit.

PIN 40 and 20: Pins 40 and 20 are VCC and ground respectively. The 8051 chip needs

+5V 500mA to function properly, although there are lower powered versions like the

Atmel 2051 which is a scaled down version of the 8051 which runs on +3V.

PINS 29, 30 & 31: As described in the features of the 8051, this chip contains a built-in

flash memory. In order to program this we need to supply a voltage of +12V at pin 31. If

external memory is connected then PIN 31, also called EA/VPP, should be connected to

ground to indicate the presence of external memory. PIN 30 is called ALE (address latch

enable), which is used when multiple memory chips are connected to the controller and

only one of them needs to be selected. We will deal with this in depth in the later

chapters. PIN 29 is called PSEN. This is "program store enable". In order to use the

external memory it is required to provide the low voltage (0) on both PSEN and EA pins.

PORTS

There are 4 8-bit ports: P0, P1, P2 and P3.

PORT P1 (Pins 1 to 8): The port P1 is a general purpose input/output port which can be

used for a variety of interfacing tasks. The other ports P0, P2 and P3 have dual roles or

additional functions associated with them based upon the context of their usage. The port

1 output buffers can sink/source four TTL inputs. When 1s are written to portn1 pins are

pulled high by the internal pull-ups and can be used as inputs.

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PORT P3 (Pins 10 to 17): PORT P3 acts as a normal IO port, but Port P3 has additional

functions such as, serial transmit and receive pins, 2 external interrupt pins, 2 external

counter inputs, read and write pins for memory access.

PORT P2 (pins 21 to 28): PORT P2 can also be used as a general purpose 8 bit port

when no external memory is present, but if external memory access is required then

PORT P2 will act as an address bus in conjunction with PORT P0 to access external

memory. PORT P2 acts as A8-A15, as can be seen from fig 1.1

PORT P0 (pins 32 to 39): PORT P0 can be used as a general purpose 8 bit port when no

external memory is present, but if external memory access is required then PORT P0 acts

as a multiplexed address and data bus that can be used to access external memory in

conjunction with PORT P2. P0 acts as AD0-AD7.

OSCILLATOR CIRCUITS

The 8051 requires an external oscillator circuit. The oscillator circuit usually runs around

12MHz, although the 8051 (depending on which specific model) is capable of running at

a maximum of 40MHz. Each machine cycle in the 8051 is 12 clock cycles, giving an

effective cycle rate at 1MHz (for a 12MHz clock) to 3.33MHz (for the maximum 40MHz

clock). The oscillator circuit generates the clock pulses So that all internal operations are

synchronized.

INTERNAL ARCHITECTURE

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3.1.3 MEMORY ORGANISATION

DATA AND PROGRAM MEMORY

The 8051 Microcontroller can be programmed in PL/M, 8051 Assembly, C and a number

of other high-level languages. Many compilers even have support for compiling C++ for

an 8051.

Program memory in the 8051 is read-only, while the data memory is considered to be

read/write accessible. When stored on EEPROM or Flash, the program memory can be

rewritten when the microcontroller is in the special programmer circuit.

PROGRAM START ADDRESS

The 8051 starts executing program instructions from address 0000 in the program

memory. The A register is located in the SFR memory location 0xE0. The A register

works in a similar fashion to the AX register of x86 processors. The A register is called

the accumulator, and by default it receives the result of all arithmetic operations.

SPECIAL FUNCTION REGISTER

The Special Function Register (SFR) is the upper area of addressable memory, from

address 0x80 to 0xFF. A, B, PSW, DPTR are called SFR.This area of memory cannot be

used for data or program storage, but is instead a series of memory-mapped ports and

registers. All port input and output can therefore be performed by memory move

operations on specified addresses in the SFR. Also, different status registers are mapped

into the SFR, for use in checking the status of the 8051, and changing some operational

parameters of the 8051.

GENERAL PURPOSE REGISTERS

The 8051 has 4 selectable banks of 8 addressable 8-bit registers, R0 to R7. This means

that there are essentially 32 available general purpose registers, although only 8 (one

bank) can be directly accessed at a time. To access the other banks, we need to change

the current bank number in the flag register.

A AND B REGISTERS

The A register is located in the SFR memory location 0xE0. The A register works in a

similar fashion to the AX register of x86 processors. The A register is called the

accumulator, and by default it receives the result of all arithmetic operations. The B

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register is used in a similar manner, except that it can receive the extended answers from

the multiply and divide operations. When not being used for multiplication and Division,

the B register is available as an extra general-purpose register.

THE DATA POINTER (DPTR)The Data Pointer (DPTR) is the 8051’s only user- accessible 16-bit (2-byte) register. The

Accumulator, "R" registers, and "B" register are all 1-byte values. DPTR, as the name

suggests, is used to point to data. It is used by a number of commands which allow the

8051 to access external memory. When the 8051 accesses external memory it will access

external memory at the address indicated by DPTR.While DPTR is most often used to

point to data in external memory, many programmers often take advantage of the fact that

it’s the only true 16- bit register available. It is often used to store 2- byte values which

have nothing to do with memory locations.

THE PROGRAM COUNTER (PC):

The Program Counter (PC) is a 2-byte address which tells the 8051 where the next

instruction to execute is found in memory. When the 8051 is initialized PC always starts

at 0000h and is incremented each time an instruction is executed. It is important to note

that PC isn’t always incremented by one. Since some instructions require 2 or 3 bytes the

PC will be incremented by 2 or 3 in these cases. The Program Counter is special in that

there is no way to directly modify its value. That is to say, you can’t do something like

PC=2430h. On the other hand, if you execute LJMP 2340h you’ve effectively

accomplished the same thing.

THE STACK POINTER (SP) The Stack Pointer, like all registers except DPTR and PC, may hold an 8-bit (1-

byte) value. The Stack Pointer is used to indicate where the next value to be removed

from the stack should be taken from. When you push a value onto the stack, the 8051 first

increments the value of SP and then stores the value at the resulting memory location.

When you pop a value off the stack, the 8051 returns the value from the memory location

indicated by SP and then decrements the value of SP.

IDLE MODE:

In idle mode, the CPU puts itself to sleep while all the on-chip peripherals remain

active. The mode is invoked by software. The content of the on-chip RAM and all the

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special function registers remain unchanged during this mode. The idle mode can be

terminated by any enabled interrupt or by a hardware reset.

When idle mode is terminated by a hardware reset, the device normally resumes

program execution from where it left off, up to two machine cycles before the internal

reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this

event, but access to the port pins is not inhibited.

To eliminate the possibility of an unexpected write to a port pin when idle mode

is terminated by a reset, the instruction following the one that invokes idle mode should

not write to a port pin or to external memory.

POWER-DOWN MODE:

In the Power-down mode, the oscillator is stopped, and the instruction that

invokes Power-down is the last instruction executed. The on-chip RAM and Special

Function Registers retain their values until the Power-down mode is terminated. Exit

from Power-down mode can be initiated either by a hardware reset or by activation of an

enabled external interrupt (INT0 or INT1). Reset redefines the SFRs but does not change

the on-chip RAM. The reset should not be activated before VCC is restored to its normal

operating level and must be held active long enough to allow the oscillator to restart and

stabilize.

TIMER 0 AND TIMER 1 OPERATION:

The 8051 comes equipped with two timers, both of which may be controlled, set,

read, and configured individually.

The 8051 timers have three general functions:

1) Keeping time and/or calculating the amount of time between events,

2) Counting the events themselves, or

3) Generating baud rates for the serial port.

SERIAL COMMUNICATION

In order to connect micro controller or a PC to GSM modem a serial port is used.

Serial, is a very common protocol for device communication that is standard on almost

every PC. Most computers include RS-232 based serial ports. Serial is also a common

communication protocol that is used by many devices for instrumentation.

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In serial communication, the data is sent one bit at a time in contrast parallel

communication, in which the data is sent a byte or more at time. Serial communication

uses a single data line where as the parallel communication uses 8 bit data line , this

makes serial communication not only inexpensive but also makes it possible for two

computers located in two different cities to communicate over the telephone.

Serial data communication uses two methods, asynchronous and synchronous.

The synchronous method transfers a block of data at a time while the asynchronous

transfers a single byte at a time. The 8051 has a in built UART (Universal Asynchronous

Receiver-Transmitter).

Typically, serial is used to transmit ASCII data. Communication is completed

using 3 transmission lines: (1) Transmitter, (2) Receiver and (3) Ground. Since serial is

asynchronous, the port is able to transmit data on one line while receiving data on

another. Other lines are available for handshaking, but are not required. The important

characteristics are Data Transfer Rate, Start and Stop bits, Data bits and Parity bits. For

two ports to communicate, these parameters must match.

DATA TRANSFER RATE:

The rate of data transfer in serial data communication is stated in bps (bits per

second).Another widely used terminology for bps is baud rate. However the baud rate

and bps are not necessarily equal .Baud rate is defined as the number of signal changes

per second. In modems, there are occasions when a single change of signal transfers

several bits of data .As far as conductor wire is considered bps and baud rate is the same.

DATA FRAMING:

Asynchronous serial data communication is used for character oriented

transmissions, each character is placed in between start and stop bits. This is called

framing .In data framing for asynchronous communications , the data ,such as ASCII

characters ,are packed in between a start bit and a stop bit .The start bit is always one bit

but the stop bit can be one or more bits .The start bit is always 0(low) whereas stop bit is

1(high).

Since the data is clocked across the lines and each device has its own clock, it is

possible for the two devices to come out slightly out of synchronous .Therefore, the stop

bits not only indicate the end of transmission but also give the computers some room for

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error in clock speeds .The more the stop bits the greater the lenience in synchronizing the

different clocks, but slower the data transmission rate.

PARITY BITS:

In order to maintain data integrity, parity bit of the character byte is included in

the data frame .The parity bit is odd or even .In the case of an odd parity bit the number

of data bits, including the parity bits has an odd number of 1’s.Similarly, in an even

parity bit system the total number of bits, including the parity bits has an even number of

1’s.UART chips allow programming of the parity bit for odd-even- and no- parity

options.

3.2 ANALOG TO DIGITAL CONVERTER:

An analog-to-digital converter, or ADC as it is more commonly called, is a

device that converts analog signals into digital signals. Analog information is transmitted

by modulating a continuous transmission signal by amplifying a signal's strength or

varying its frequency to add or take away data. Digital information describes any system

based on discontinuous data or events. Computers, which handle data in digital form,

require analog-to-digital converters to turn signals from analog to digital before it can be

read. One example is a modem which turns signals from digital to analog before

transmitting those signals over communication lines such as telephone lines that carry

only analog signals. The signals are turned back into digital form (demodulated) at the

receiving end so that the computer can process the data in its digital format.

This is a very simple analog to digital converter circuit based on 8-bit analog-to-digital

converter ADC0808. Typically analogue-to-digital converter (A/D Converter / ADC)

requires interfacing through a microprocessor to convert analogue information into digital

format. This needs extra hardware and appropriate software, resulting in more complexity

and hence the total amount of cost.

The circuit of Analogue to Digital converter shown here is configured around ADC0808,

getting rid of the utilization of a microprocessor. The ADC0808 is definitely an 8-bit A/D

converter that has data output lines D0-D7. It operates on the principle of successive

approximation. It features a total of eight analogue input channels, out of which any one

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can be chosen working with address lines A, B and C. Right here, in this case, input

channel IN0 is chosen by grounding A, B and C address lines.

Typically the control signals ALE (address latch enable), EOC (end of conversion), OE

(output enable) and SC (start conversion) are interfaced by means of a microprocessor.

Even so, the circuit shown right here is constructed to operate in its continuous mode

without working with any microprocessor. Therefore the input control signals ALE and

OE, getting active-high, are tied to Vcc (+5 volts). The input control signal SC, getting

active-low, initiates start of conversion at falling edge of the pulse, whereas the output

signal EOC becomes high after completion of conversion (digitization). This EOC output

15

is coupled to SC input, where falling edge of EOC output acts as SC input to direct the

ADC to begin the subsequent conversion.

Since the conversion starts, EOC signal goes high. At next clock pulse EOC output again

goes low, and hence SC is enabled to get started on the next conversion. Thus, it delivers

continuous 8-bit digital output corresponding to instantaneous value of analogue input.

The optimum level of analogue input voltage ought to be properly scaled down below

positive reference (+5V) level.

The ADC0808 IC needs clock signal of normally 550 kHz, which can be simply

produced from an a stable multi vibrator constructed applying 7404 inverter gates. In

order to visualize the digital output, the row of eight LEDs (LED1 through LED8) have

been utilized, wherein every single LED is connected to respective data output lines D0

through D7. Considering that A/D Converter runs in the continuous mode, it shows

digital output as soon as analogue input is applied.

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3.3 LIQUID CRYSTAL DISPLAY (LCD):

A liquid crystal display (LCD) is a flat panel display, electronic visual display,

or video display that uses the light modulating properties of liquid crystals. Liquid

crystals do not emit light directly.

LCDs are available to display arbitrary images (as in a general-purpose computer display)

or fixed images which can be displayed or hidden, such as preset words, digits, and 7-

segment displays as in a digital clock. They use the same basic technology, except that

arbitrary images are made up of a large number of small pixels, while other displays have

larger elements.

LCDs are used in a wide range of applications including computer monitors, televisions,

instrument panels, aircraft cockpit displays, and signage. They are common in consumer

devices such as video players, gaming devices, clocks, watches, calculators, and

telephones, and have replaced cathode ray tube (CRT) displays in most applications.

They are available in a wider range of screen sizes than CRT and plasma displays, and

since they do not use phosphors, they do not suffer image burn-in. LCDs are, however,

susceptible to image persistence.

Both the liquid crystal material and the alignment layer material contain ionic

compounds. If an electric field of one particular polarity is applied for a long period of

time, this ionic material is attracted to the surfaces and degrades the device performance.

This is avoided either by applying an alternating current or by reversing the polarity of

the electric field as the device is addressed (the response of the liquid crystal layer is

identical, regardless of the polarity of the applied field).

Displays for a small number of individual digits and/or fixed symbols (as in digital

watches and pocket calculators) can be implemented with independent electrodes for

each segment. In contrast full alphanumeric and/or variable graphics displays are usually

implemented with pixels arranged as a matrix consisting of electrically connected rows

on one side of the LC layer and columns on the other side, which makes it possible to

address each pixel at the intersections. The general method of matrix addressing consists

17

of sequentially addressing one side of the matrix, for example by selecting the rows one-

by-one and applying the picture information on the other side at the columns row-by-row.

For details on the various matrix addressing schemes see Passive-matrix and active-

matrix addressed LCDs.

LCD panels produce no light of their own; they require external light to produce a visible

image. While passive-matrix displays are usually not backlit (e.g. calculators,

wristwatches); active-matrix displays almost always are (with a few exceptions, such as

the display in the original Game Boy Advance).

Specifications

Important factors to consider when evaluating an LCD:

Resolution versus range: Fundamentally resolution is the granularity (or number

of levels) with which a performance feature of the display is divided. Resolution

is often confused with range or the total end-to-end output of the display. Each of

the major features of a display has both a resolution and a range that are tied to

each other but very different. Frequently the range is an inherent limitation of the

display while the resolution is a function of the electronics that make the display

work.

Spatial performance: LCDs come in only one size for a variety of applications

and a variety of resolutions within each of those applications. LCD spatial

performance is also sometimes described in terms of a "dot pitch". The size (or

spatial range) of an LCD is always described in terms of the diagonal distance

from one corner to its opposite. This is an historical remnant from the early days

of CRT television when CRT screens were manufactured on the bottoms of glass

bottles, a direct extension of cathode ray tubes used in oscilloscopes. The

diameter of the bottle determined the size of the screen. Later, when televisions

went to a more square format, the square screens were measured diagonally to

compare with the older round screens.[42]

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The spatial resolution of an LCD is expressed by the number of columns and rows of

pixels (e.g., 1024×768). Each pixel is usually composed 3 sub-pixels, a red, a green, and

a blue one. This had been one of the few features of LCD performance that was easily

understood and not subject to interpretation. However there are newer schemes that share

sub-pixels among pixels and to add additional colors of sub-pixels. So going forward,

spatial resolution may now be more subject to interpretation.

Temporal/timing performance: Contrary to spatial performance, temporal

performance is a feature where smaller is better. Specifically, the range is the

pixel response time of an LCD, or how quickly a sub-pixel's brightness changes

from one level to another. For LCD monitors, this is measured in btb (black to

black) or gtg (gray to gray). These different types of measurements make

comparison difficult.[43] Further, this number is almost never published in sales

advertising.

Refresh rate or the temporal resolution of an LCD is the number of times per second in

which the display draws the data it is being given. Since activated LCD pixels do not

flash on/off between frames, LCD monitors exhibit no refresh-induced flicker, no matter

how low the refresh rate.[44] High-end LCD televisions now feature up to 240 Hz refresh

rate, which requires advanced digital processing to insert additional interpolated frames

between the real images to smooth the image motion. However, such high refresh rates

may not be actually supported by pixel response times and the result can be visual

artifacts that distort the image in unpleasant ways.

Temporal performance can be further taxed if it is a 3D display. 3D displays work by

showing a different series of images to each eye, alternating from eye to eye. Thus a 3D

display must display twice as many images in the same period of time as a conventional

display, and consequently the response time of the LCD is more important. 3D LCDs

with marginal response times will exhibit image smearing.

These artifacts are most noticeable in a person's black and white vision (rod cells) than in

color vision (cone cells). Thus they will be more likely to see flicker or any sort of

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temporal distortion in a display image by not looking directly at the display, because their

eyes' rod cells are mostly grouped at the periphery of their vision.

Color performance: There are many terms to describe color performance of an

LCD. They include color gamut which is the range of colors that can be displayed

and color depth which is the color resolution or the resolution or fineness with

which the color range is divided. Although color gamut can be expressed as three

pairs of numbers, the XY coordinates within color space of the reddest red,

greenest green, and bluest blue, it is usually expressed as a ratio of the total area

within color space that a display can show relative to some standard such as

saying that a display was "120% of NTSC". NTSC is the National Television

Standards Committee, the old standard definition TV specification. Color gamut

is a relatively straight forward feature. However with clever optical techniques

that are based on the way humans see color, termed color stretch,[45] colors can be

shown that are outside of the nominal range of the display. In any case, color

range is rarely discussed as a feature of the display as LCDs are designed to

match the color ranges of the content that they are intended to show. Having a

color range that exceeds the content is a useless feature.

Color depth or color support is sometimes expressed in bits, either as the

number of bits per sub-pixel or the number of bits per pixel. This can be

ambiguous as an 8-bit color LCD can be 8 total bits spread between red, green,

and blue or 8 bits each for each color in a different display. Further, LCDs

sometimes use a technique called dithering which is time averaging colors to get

intermediate colors such as alternating between two different colors to get a color

in between. This doubles the number of colors that can be displayed; however this

is done at the expense of the temporal performance of the display. Dithering is

commonly used on computer displays where the images are mostly static and the

temporal performance is unimportant.

Brightness and contrast ratio: Contrast ratio is the ratio of the brightness of a

full-on pixel to a full-off pixel and, as such, would be directly tied to brightness if

not for the invention of the blinking backlight (or burst dimming). The LCD itself

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is only a light valve, it does not generate light; the light comes from a backlight

that is either a fluorescent tube or a set of LEDs. The blinking backlight was

developed to improve the motion performance of LCDs by turning the backlight

off while the liquid crystals were in transition from one image to another.

However, a side benefit of the blinking backlight was infinite contrast. The

contrast reported on most LCDs is what the LCD is qualified at, not its actual

performance. In any case, there are two large caveats to contrast ratio as a

measure of LCD performance.

Advantages

Very compact and light.

Low power consumption. On average, 50-70% less energy is consumed than CRT

monitors.

No geometric distortion.

The possible ability to have little or no flicker depending on backlight technology.

Usually no refresh-rate flicker, as the LCD panel itself is usually refreshed at

200 Hz or more, regardless of the source refresh rate.

Is very thin compared to a CRT monitor, which allows the monitor to be placed

farther back from the user, reducing close-focusing related eye-strain.

Razor sharp image with no bleeding/smearing when used at native resolution.

Emits less electromagnetic radiation than a CRT monitor.

Not affected by screen burn-in, though an identical but less severe phenomenon

known as image persistence is possible.

Can be made in almost any size or shape.

No theoretical resolution limit.

Can be made to large sizes (more than 24 inches) lightly and relatively

inexpensively.

Masking effect: the LCD grid can mask the effects of spatial and grayscale

quantization, creating the illusion of higher image quality.

As an inherently digital device, the LCD can natively display digital data from a

DVI or HDMI connection without requiring conversion to analog, like a CRT

would need.

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Many LCD monitors run on an external 12v power supply, which means that

(with a proper cable) they can also be run directly on one of the computer's 12v

power supply outputs, removing the overhead and quiescent power consumption

of the monitor's own power supply. If the computer has a PFC power supply, this

will increase the power efficiency as well, as the cheap switching power supplies

included with LCD monitors rarely implement PFC. This is also convenient

because the monitor will power on when the computer is switched on, and will

power off when the computer sleeps or is shutdown.

Disadvantages

Limited viewing angle, causing color, saturation, contrast and brightness to vary,

even within the intended viewing angle, by variations in posture.

Uneven backlighting in some (mostly older) monitors, causing brightness

distortion, especially toward the edges. Black levels may appear unacceptably

bright due to the fact that individual liquid crystals cannot completely block all

light from passing through.

Display motion blur on moving objects caused by slow response times (>8 ms)

and eye-tracking on a sample-and-hold display.

As of 2012, most implementations of LCD backlighting use PWM to dim the

display, which makes the screen flicker more acutely (this does not mean visibly)

than a CRT monitor at 85 Hz refresh rate would (this is because the entire screen

is strobing on and off rather than a CRT's phosphor sustained dot which

continually scans across the display, leaving some part of the display always lit),

causing severe eye-strain for some people. Unfortunately, many of these people

don't know that their eye-strain is being caused by the invisible strobe effect of

PWM. This problem is worse on many of the new LED backlit monitors, because

the LEDs have a faster turn-on/turn-off time than a CCFL bulb.

Only one native resolution. Displaying any other resolution either requires a video

scaler, causing blurriness and jagged edges; or running the display at native

resolution using 1:1 pixel mapping, causing the image either not to fill the screen

(letterboxed display), or to run off the lower right edge of the screen.

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Fixed bit depth, many cheaper LCDs are only able to display 262,000 colors. 8-bit

S-IPS panels can display 16 million colors and have significantly better black

level, but are expensive and have slower response time.

Input lag, because the LCD's A/D converter waits for each frame to be completely

outputted before drawing it to the LCD panel.

Dead or stuck pixels may occur during manufacturing or through use.

In a constant-on situation, thermalization may occur, in which part of the screen

has overheated and looks discolored compared to the rest of the screen.

Unacceptably slow response times in low temperature environments.

Loss of contrast in high temperature environments.

Not usually designed to allow easy replacement of the backlight.

Poor display in direct sunlight. Transflective LCDs provide a large improvement

by reflecting natural light, but have not yet been widely adopted.

Cannot be used with light guns/pens.

Does not support interlaced video.

LCD (Liquid Crystal Display) screen is an electronic display module and find a

wide range of applications. A 16x2 LCD display is very basic module and is very

commonly used in various devices and circuits. These modules are preferred over

seven segments and other multi segment LEDs. The reasons being: LCDs are

23

economical; easily programmable; have no limitation of displaying special &

even custom characters (unlike in seven segments), animations and so on.

A 16x2 LCD means it can display 16 characters per line and there are 2 such

lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD has

two registers, namely, Command and Data.

The command register stores the command instructions given to the LCD. A

command is an instruction given to LCD to do a predefined task like initializing

it, clearing its screen, setting the cursor position, controlling display etc. The data

register stores the data to be displayed on the LCD. The data is the ASCII value of

the character to be displayed on the LCD. Click to learn more about internal

structure of a LCD. 

PIN:

Pin Description:  Pin No

 Function  Name

1 Ground (0V) Ground2 Supply voltage; 5V (4.7V – 5.3V)  Vcc

24

3 Contrast adjustment; through a variable resistor  VEE

4 Selects command register when low; and data register when high

Register Select

5 Low to write to the register; High to read from the register

Read/write

6 Sends data to data pins when a high to low pulse is given

Enable

7

8-bit data pins

DB08 DB19 DB210 DB311 DB412 DB513 DB614 DB715 Backlight VCC (5V) Led+16 Backlight Ground (0V) Led-

3.4 L293D DIVER CIRCUIT:

L293D is a dual H-bridge motor driver integrated circuit (IC). Motor drivers act as

current amplifiers since they take a low-current control signal and provide a higher-

current signal. This higher current signal is used to drive the motors.L293D contains two

inbuilt H-bridge driver circuits. In its common mode of operation, two DC motors can be

driven simultaneously, both in forward and reverse direction. The motor operations of

two motors can be controlled by input logic at pins 2 & 7 and 10 & 15. Input logic 00 or

11 will stop the corresponding motor. Logic 01 and 10 will rotate it in clockwise and

anticlockwise directions, respectively.

Enable pins 1 and 9 (corresponding to the two motors) must be high for motors to

start operating. When an enable input is high, the associated driver gets enabled.

As a result, the outputs become active and work in phase with their inputs.

Similarly, when the enable input is low, that driver is disabled, and their outputs

are off and in the high-impedance state. 

25

PIN DESCRIPTION: 

 Pin

No

 Function  Name

1 Enable pin for Motor 1; active high Enable 1,2

2 Input 1 for Motor 1 Input 1

3 Output 1 for Motor 1 Output 1

4 Ground (0V) Ground

5 Ground (0V) Ground

6 Output 2 for Motor 1 Output 2

7 Input 2 for Motor 1 Input 2

8 Supply voltage for Motors; 9-12V (up to 36V)  Vcc 2

9 Enable pin for Motor 2; active high Enable 3,4

10 Input 1 for Motor 1 Input 3

11 Output 1 for Motor 1 Output 3

12 Ground (0V) Ground

13 Ground (0V) Ground

14 Output 2 for Motor 1 Output 4

15 Input2 for Motor 1 Input 4

16 Supply voltage; 5V (up to 36V) Vcc 1

26

LM7812 AND LM7805:

• Output Current of 1.5A

• Output Voltage Tolerance of 5%

• Internal thermal overload protection

• Internal Short-Circuit Limited

• No External Component

• Output Voltage 5.0V, 6V, 8V, 9V, 10V,

12V, 15V, 18V, 24V

• Offer in plastic TO-252, TO-220 & TO-263

• Direct Replacement for LM78XX

Description:

The Bay Linear LM78XX is integrated linear positive regulator with three

terminals. The LM78XX offer several fixed output voltages making them useful in wide

range of applications. When used as a zener diode/resistor combination

Replacement, the LM78XX usually results in an effective output impedance

improvement of two orders of magnitude, lower quiescent current.

The LM78XX is available in the TO-252, TO-220 & TO-263 Packages

Applications:

• Post regulator for switching DC/DC converter

• Bias supply for analog circuits

27

28

DC MOTORS:

A DC motor is a mechanically commutated electric motor powered from direct current

(DC). The stator is stationary in space by definition and therefore so is its current. The

current in the rotor is switched by the commutator to also be stationary in space. This is

how the relative angle between the stator and rotor magnetic flux is maintained near 90

degrees, which generates the maximum torque.

DC motors have a rotating armature winding (winding in which a voltage is induced) but

non-rotating armature magnetic field and a static field winding (winding that produce the

main magnetic flux) or permanent magnet. Different connections of the field and

armature winding provide different inherent speed/torque regulation characteristics. The

speed of a DC motor can be controlled by changing the voltage applied to the armature or

by changing the field current. The introduction of variable resistance in the armature

circuit or field circuit allowed speed control. Modern DC motors are often controlled by

power electronics systems called DC drives.

The introduction of DC motors to run machinery eliminated the need for local steam or

internal combustion engines, and line shaft drive systems. DC motors can operate directly

from rechargeable batteries, providing the motive power for the first electric vehicles.

Today DC motors are still found in applications as small as toys and disk drives, or in

large sizes to operate steel rolling mills and paper machines.

Brush:

A brushed DC electric motor generating torque from DC power supply by using internal

mechanical commutation, space stationary permanent magnets form the stator field.

Torque is produced by the principle of Lorentz force, which states that any current-

carrying conductor placed within an external magnetic field experiences a force known as

Lorentz force. The actual (Lorentz) force (and also torque since torque is F x l where l is

rotor radius) is a function for rotor angle and so the green arrow/vector actually changes

length/magnitude with angle known as torque ripple) Since this is a single phase two pole

29

motor the commutator consists of a split ring, so that the current reverses each half turn

(180 degrees).

The brushed electric motor generates torque directly from DC power supplied to the

motor by using internal commutation, stationary magnets and rotating electrical magnets.

Like all electric motors or generators, torque is produced by the principle of Lorentz

force, which states that any current-carrying conductor placed within an external

magnetic field experiences a torque or force known as Lorentz force. Advantages of a

brushed DC motor include low initial cost, high reliability, and simple control of motor

speed. Disadvantages are high maintenance and low life-span for high intensity uses.

Maintenance involves regularly replacing the brushes and springs which carry the electric

current, as well as cleaning or replacing the commutator. These components are

necessary for transferring electrical power from outside the motor to the spinning wire

windings of the rotor inside the motor. Brushes are made of conductors.

Brushless:

Typical brushless DC motors use a rotating permanent magnet in the rotor, and stationary

electrical current/coil magnets on the motor housing for the rotor, but the symmetrical

opposite is also possible. A motor controller converts DC to AC .This design is simpler

than that of brushed motors because it eliminates the complication of transferring power

from outside the motor to the spinning rotor. Advantages of brushless motors include

long life span, little or no maintenance, and high efficiency. Disadvantages include high

initial cost, and more complicated motor speed controllers. Some such brushless motors

are sometimes referred to as "synchronous motors" although they have no external power

supply to be synchronized with, as would be the case with normal AC synchronous

motors.

Uncommutated:

Other types of DC motors require no commutation.

30

HOMOPOLAR MOTOR– A homopolar motor has a magnetic field along the axis

of rotation and an electric current that at some point is not parallel to the magnetic

field. The name homopolar refers to the absence of polarity change.

Homopolar motors necessarily have a single-turn coil, which limits them to very low

voltages. This has restricted the practical application of this type of motor.

BALL BEARING MOTOR– A ball bearing motor is an unusual electric motor

that consists of two ball bearing-type bearings, with the inner races mounted on a

common conductive shaft, and the outer races connected to a high current, low

voltage power supply. An alternative construction fits the outer races inside a

metal tube, while the inner races are mounted on a shaft with a non-conductive

section (e.g. two sleeves on an insulating rod). This method has the advantage that

the tube will act as a flywheel. The direction of rotation is determined by the

initial spin which is usually required to get it going.

DC motors are configured in many types and sizes, including brush less, servo,

and gear motor types. A motor consists of a rotor and a permanent magnetic field

stator. The magnetic field is maintained using either permanent magnets or

electromagnetic windings. DC motors are most commonly used in

Variable speed and torque.

Motion and controls cover a wide range of components that in some way are used

to generate and/or control motion. Areas within this category include bearings and

bushings, clutches and brakes, controls and drives, drive components, encoders

and resolves, Integrated motion control, limit switches, linear actuators, linear and

rotary motion components, linear position sensing, motors (both AC and DC

motors), orientation position sensing, pneumatics and pneumatic components,

positioning stages, slides and guides, power transmission (mechanical),seals, slip

rings, solenoids, springs.

Motors are the devices that provide the actual speed and torque in a drive

system.  This family includes AC motor types (single and multiphase motors,

universal, servo motors, induction, synchronous, and gear motor) and DC motors

31

(brush less, servo motor, and gear motor) as well as linear, stepper and air motors,

and motor contactors and starters.

In any electric motor, operation is based on simple electromagnetism. A

current-carrying conductor generates a magnetic field; when this is then placed in

an external magnetic field, it will experience a force proportional to the current in

the conductor, and to the strength of the external magnetic field. As you are well

aware of from playing with magnets as a kid, opposite (North and South)

polarities attract, while like polarities (North and North, South and South) repel.

The internal configuration of a DC motor is designed to harness the magnetic

interaction between a current-carrying conductor and an external magnetic field to

generate rotational motion.

Let's start by looking at a simple 2-pole DC electric motor (here red represents a

magnet or winding with a "North" polarization, while green represents a magnet

or winding with a "South" polarization).

Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator,

commutator, field magnet(s), and brushes. In most common DC motors (and all

that Beamers will see), the external magnetic field is produced by high-strength

permanent magnets1. The stator is the stationary part of the motor -- this includes

the motor casing, as well as two or more permanent magnet pole pieces. The rotor

(together with the axle and attached commutator) rotates with respect to the stator.

The rotor consists of windings (generally on a core), the windings being

electrically connected to the commutator. The above diagram shows a common

motor layout -- with the rotor inside the stator (field) magnets.

32

The geometry of the brushes, commutator contacts, and rotor windings

are such that when power is applied, the polarities of the energized winding and

the stator magnet(s) are misaligned, and the rotor will rotate until it is almost

aligned with the stator's field magnets. As the rotor reaches alignment, the brushes

move to the next commutator contacts, and energize the next winding. Given our

example two-pole motor, the rotation reverses the direction of current through the

rotor winding, leading to a "flip" of the rotor's magnetic field, and driving it to

continue rotating.

In real life, though, DC motors will always have more than two poles (three is a

very common number). In particular, this avoids "dead spots" in the commutator.

You can imagine how with our example two-pole motor, if the rotor is exactly at

the middle of its rotation (perfectly aligned with the field magnets), it will get

"stuck" there. Meanwhile, with a two-pole motor, there is a moment where the

commutator shorts out the power supply (i.e., both brushes touch both

commutator contacts simultaneously). This would be bad for the power supply,

waste energy, and damage motor components as well.

Yet another disadvantage of such a simple motor is that it would exhibit a high

amount of torque” ripple" (the amount of torque it could produce is cyclic with

the position of the rotor).

So since most small DC motors are of a three-pole design, let's tinker with the

workings of one via an interactive animation (JavaScript required):

33

You'll notice a few things from this -- namely, one pole is fully energized at a

time (but two others are "partially" energized). As each brush transitions from one

commutator contact to the next, one coil's field will rapidly collapse, as the next

coil's field will rapidly charge up (this occurs within a few microsecond). We'll

see more about the effects of this later, but in the meantime you can see that this is

a direct result of the coil windings' series wiring:

There's probably no better way to see how an average dc motor is put together,

than by just opening one up. Unfortunately this is tedious work, as well as

requiring the destruction of a perfectly good motor.

This is a basic 3-pole dcmotor, with 2 brushes and three commutator contacts.

PWM technique:

34

A pulse width modulator (PWM) is a device that may be used as an

efficient light dimmer or DC motor speed controller. A PWM works by making a

square wave with a variable on-to-off ratio; the average on time may be varied

from 0 to 100 percent. In this manner, a variable amount of power is transferred to

the load. The main advantage of a PWM circuit over a resistive power controller

is the efficiency, at a 50% level, the PWM will use about 50% of full power,

almost all of which is transferred to the load, a resistive controller at 50% load

power would consume about 71% of full power, 50% of the power goes to the

load and the other 21% is wasted heating the series resistor. Load efficiency is

almost always a critical factor in solar powered and other alternative energy

systems. One additional advantage of pulse width modulation is that the pulses

reach the full supply voltage and will produce more torque in a motor by being

able to overcome the internal motor resistances more easily. Finally, in a PWM

circuits, common small potentiometers may be used to control a wide variety of

loads whereas large and expensive high power variable resistors are needed for

resistive controllers.

Pulse width modulation consists of three signals, which are modulated by a

square wave. The duty cycle or high time is proportional to the amplitude of the

square wave. The effective average voltage over one cycle is the duty cycle times

the peak-to-peak voltage. Thus, the average voltage follows a square wave. In

fact, this method depends on the motor inductance to integrate out the PWM

frequency.

A very simply off line motor drive can be built using a TRIAC and a control IC.

This circuit can control the speed of a universal motor. A universal motor is a

series wound DC motor. The circuit uses phase angle control to vary the effective

motor voltage.

35

A micro controller can also be used to control a triac. A PNP of transistor may be

used to drive the triac. As shown, the MCU ground is connected to the AC line.

The gate trigger current is lower if instead the MCU 5V supply is connected to the

AC line. The MCU must have some means of detecting zero crossing and a timer,

which can control the triac firing. A general-purpose timer with one input capture

and one output compare makes an ideal phase angle control.

3.5 LDR:

LDRs or Light Dependent Resistors are very useful especially in light/dark sensor

circuits. Normally the resistance of an LDR is very high, sometimes as high as 1000 000

ohms, but when they are illuminated with light resistance drops dramatically

.

36

INTRODUCTION

A photo resistor or light dependent resistor is a component that is sensitive to light.

When light falls upon it then the resistance changes. Values of the resistance of the LDR

may change over many orders of magnitude the value of the resistance falling as the level

of light increases. It is not uncommon for the values of resistance of an LDR or photo

resistor to be several me ohms in darkness and then to fall to a few hundred ohms in

bright light. With such a wide variation in resistance, LDRs are easy to use and there are

many LDR circuits available.

 LDRs are made from semiconductor materials to enable them to have their light sensitive

properties. Many materials can be used, but one popular material for these photo resistors

is cadmium sulphide (CdS). Light dependent resistors or LDRs are often used in circuits

where it is necessary to detect the presence or the level of light. They can be described by

a variety of names from light dependent resistor, LDR, photo resistor, or even photo cell

(photocell) or photoconductor.

37

The symbol for a photo resistor

The internal components of a photoelectric control for a typical American streetlight. The

photo resistor is facing rightwards, and controls whether current flows through the heater

which opens the main power contacts. At night, the heater cools, closing the power

contacts, energizing the street light. The heater/bimetal mechanism provides a built-in

light level transient filter.

A photo resistor or light dependent resistor (LDR) is a resistor whose resistance

decreases with increasing incident light intensity; in other words, it exhibits

photoconductivity.

A photo resistor is made of a high resistance semiconductor. If light falling on the device

is of high enough frequency, photons absorbed by the semiconductor give bound

electrons enough energy to jump into the conduction band. The resulting free electron

(and its hole partner) conduct electricity, thereby lowering resistance.

A photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor has

its own charge carriers and is not an efficient semiconductor, for example, silicon. In

intrinsic devices the only available electrons are in the valence band, and hence the

photon must have enough energy to excite the electron across the entire band gap.

Extrinsic devices have impurities, also called dopants, added whose ground state energy

is closer to the conduction band; since the electrons do not have as far to jump, lower

energy photons (that is, longer wavelengths and lower frequencies) are sufficient to

trigger the device. If a sample of silicon has some of its atoms replaced by phosphorus

38

atoms (impurities), there will be extra electrons available for conduction. This is an

example of an extrinsic semiconductor. Photo resistors are basically photocells.

Specification and model

There are many types of photo resistors, with different specifications and models. Photo

resistors can be coated with or packaged in different materials that vary the resistance,

depending on the use for each LDR.

Applications

Photo resistors come in many types. Inexpensive cadmium sulphide cells can be found in

many consumer items such as camera light meters, street lights, clock radios, alarm

devices, outdoor clocks, solar street lamps and solar road studs, etc.

They are also used in some dynamic compressors together with a small incandescent

lamp or light emitting diode to control gain reduction and are also used in bed lamps,

etc.Lead sulphide (PbS) and indium antimonide (InSb) LDRs (light dependent resistor)

are used for the mid infrared spectral region. Ge:Cu photoconductors are among the best

far-infrared detectors available, and are used for infrared astronomy and infrared

spectroscopy

3.6 POWER SUPPLY

Description:

The Power Supply is a Primary requirement for the project work. The

required DC power supply for the base unit as well as for the recharging unit is derived

from the mains line. For this purpose center tapped secondary of 12V-012V transformer

is used. From this transformer we getting 5V power supply. In this +5V output is a

regulated output and it is designed using 7805 positive voltage regulator. This is a 3 Pin

voltage regulator, can deliver current up to 800 milli amps. Rectification is a process of

rendering an alternating current or voltage into a unidirectional one. The component used

for rectification is called ‘Rectifier’. A rectifier permits current to flow only during

39

positive half cycles of the applied AC voltage. Thus, pulsating DC is obtained to obtain

smooth DC power additional filter circuits required.

Circuit diagram:

Fig 3.1: Block diagram of power supply

A diode can be used as rectifier. There are various types of diodes. However,

semiconductor diodes are very popularly used as rectifiers. A semiconductor diode is a

solid-state device consisting of two elements is being an electron emitter or cathode, the

other an electron collector or anode. Since electrons in a semiconductor diode can flow in

one direction only-form emitter to collector-the diode provides the unilateral conduction

necessary for rectification. The rectified Output is filtered for smoothening the DC, for

this purpose capacitor is used in the filter circuit. The filter capacitors are usually

connected in parallel with the rectifier output and the load. The AC can pass through a

capacitor but DC cannot, the ripples are thus limited and the output becomes smoothed.

When the voltage across the capacitor plates tends to rise, it stores up energy back into

voltage and current. Thus, the fluctuation in the output voltage is reduced considerable.

VOLTAGE REGULATOR:

The LM 78XXX series of the three terminal regulations is available with several fixed

output voltages making them useful in a wide range of applications. One of these is local

on card regulation. The voltages available allow these regulators to be used in logic

40

+12v

2200µF/25v

100µF/25v

1N4007 X 2

230v / 12v- 0 -12v500mA Transformer

systems, instrumentation and other solid state electronic equipment. Although designed

primarily as fixed voltage regulators, these devices can be used with external components

to obtain adjustable voltages and currents. The LM78XX series is available in aluminum

to 3 packages which will allow over 1.5A load current if adequate heat sinking is

provided. Current limiting is included to limit the peak output current to a safe value.

The LM 78XX is available in the metal 3 leads to 5 and the plastic to 92. For this type,

with adequate heat sinking, the regulator can deliver 100mA output current.

The advantage of this type of regulator is, it is easy to use and minimize the number of

external components.

3.7 BATTERY

In our prototype, we use 12v battery and they have variety of uses in our

daily life. From consumer electronics to robotics, from health care products to industries,

almost every second device we use has one battery or the other. Batteries have become an

indispensible part of our lives. We cannot comprehend living without cell phones,

torches, laptop computers, music players like the iPod, but how do we power them up?

Answer lies in the batteries. Similarly cars are one of the main modern day necessities

which use batteries to power the head lamps and backlights. In electricity, a battery is a

device consisting of one or more electromechanical cells that convert stored chemical

energy into electrical energy. Since the invention of the first battery (or "voltaic pile") in

1800 by Alessandro Volta and especially since the technically improved Daniell cell in

1836, batteries have become a common power source for many household and industrial

applications. According to a 2005 estimate, the worldwide battery industry generates

US$48 billion in sales each year with 6% annual growth.

There are two types of batteries: primary batteries (disposable batteries), which

are designed to be used once and discarded, and secondary batteries (rechargeable

batteries), which are designed to be recharged and used multiple times. Batteries come in

many sizes; from miniature cells used to power hearing aids and wristwatches to battery

banks the size of rooms that provide standby power for telephone exchanges and

computer data centers.

41

A battery is a device that converts chemical energy directly to electrical energy It consists

of a number of voltaic cells; each voltaic cell consists of two half-cells connected in

series by a conductive electrolyte containing anions and cations. One half-cell includes

electrolyte and the electrode to which anions (negatively charged ions) migrate, i.e., the

anode or negative electrode; the other half-cell includes electrolyte and the electrode to

which cations (positively charged ions) migrate, i.e., the cathode or positive electrode. In

the redox reaction that powers the battery, cations are reduced (electrons are added) at the

cathode, while anions are oxidized (electrons are removed) at the anode. The electrodes

do not touch each other but are electrically connected by the electrolyte. Some cells use

two half-cells with different electrolytes. A separator between half-cells allows ions to

flow, but prevents mixing of the electrolytes.

Each half-cell has an electromotive force (or emf), determined by its ability to drive

electric current from the interior to the exterior of the cell. The net emf of the cell is the

difference between the emfs of its half-cells, as first recognized by Volta. Therefore, if

the electrodes have emfs and , then the net emf is ; in other words, the net

emf is the difference between the reduction potentials of the half-reactions.

The electrical driving force or across the terminals of a cell is known as the

terminal voltage (difference) and is measured in volts. The terminal voltage of a cell that

is neither charging nor discharging is called the open-circuit voltage and equals the emf

of the cell. Because of internal resistance, the terminal voltage of a cell that is discharging

is smaller in magnitude than the open-circuit voltage and the terminal voltage of a cell

that is charging exceeds the open-circuit voltage. An ideal cell has negligible internal

resistance, so it would maintain a constant terminal voltage of until exhausted, then

dropping to zero. If such a cell maintained 1.5 volts and stored a charge of one coulomb

then on complete discharge it would perform 1.5 joule of work. In actual cells, the

internal resistance increases under discharge, and the open circuit voltage also decreases

42

under discharge. If the voltage and resistance are plotted against time, the resulting

graphs typically are a curve; the shape of the curve varies according to the chemistry and

internal arrangement employed.

12 volt lead acid batteries:

One of the most common types of 12V battery is the 12v lead acid battery. It is a dc

battery with lead terminals and an acid, usually hydrochloric acid is used as an electrolyte

in lead acid battery. It is the battery of choice for cars, trucks, tanks, uninterrupted power

supplies and other vehicles. 12V lead acid battery is used in cars as there is no risk of

handling in cars. 12volt lead acid battery is also used in battery banks and backup

systems at power sensitive systems, such as telecom switches, like any other 12v dc

battery because it’s a source of dc 12volt power.

Lead acid 12V battery is rarely used in home appliances and uses. For example, computer

UPS' rarely use lead acid battery as it is not very easy to handle and can cause potential

hazards, such as a fire etc.Home users generally prefer a solid state battery such as the

one used in dry cells over 12v lead acid batteries or rechargeable battery which provides

12volt power . Those are found in torch lights, calculators, watches, clocks and toys.

12v Battery Construction:

In a 12 volt lead acid battery, usually hydrochloric acid is used as an electrolyte in

lead acid battery. The casing is usually made up of plastic, rubber or any other hard

material in order to avoid the acid housed inside. Inside, it is made of up many small

cells. Metals are used for cathodes and anodes (negative and positive terminals

respectively for the 12Volt Battery.

12 volt lead acid battery is the 12 volt dc battery for cars, trucks, tanks, uninterrupted

power supplies and other vehicles. This type of battery is also used in battery banks and

backup systems at power sensitive systems, such as telecom switches.

It is 12v dc battery but is not a portable 12v battery or 12v rechargeable battery and 12v

battery pack due to its size and handling issues. For example, computer UPS' rarely use

43

lead acid battery as it is not very easy to handle and can cause potential hazards, such as a

fire etc.

Lead acid batteries used in the RV and Marine Industries usually consist of two 6-volt

batteries in series, or a single 12-volt battery. These batteries are constructed of several

single cells connected in series each cell produces approximately 2.1 volts. A six-volt

battery has three single cells, which when fully charged produce an output voltage of 6.3

volts. A twelve-volt battery has six single cells in series producing a fully charged output

voltage of 12.6 volts.

A battery cell consists of two lead plates a positive plate covered with a paste of lead

dioxide and a negative made of sponge lead, with an insulating material (separator) in

between. The plates are enclosed in a plastic battery case and then submersed in an

electrolyte consisting of water and sulfuric acid. Each cell is capable of storing 2.1 volts.

In order for lead acid cell to produce a voltage, it must first receive a (forming) charge

voltage of at least 2.1-volts/cell from a charger. Lead acid batteries do not generate

voltage on their own; they only store a charge from another source. This is the reason

lead acid batteries are called storage batteries, because they only store a charge. The size

of the battery plates and amount of electrolyte determines the amount of charge lead acid

batteries can store. The size of this storage capacity is described as the amp hour (AH)

rating of a battery. A typical 12-volt battery used in a RV or marine craft has a rating 125

AH, which means it can supply 10 amps of current for 12.5 hours or 20-amps of current

for a period of 6.25 hours. Lead acid batteries can be connected in parallel to increase the

total AH capacity.

44

In figure # 2 below, six single 2.1-volt cells have been connected in series to make the

typical 12-volt battery, which when fully charged will produce a total voltage of 12.6-

volts.

Lead Acid Batter Discharge Cycle

In figure # 3, above a fully charged battery is connected to a load (light bulb) and the

chemical reaction between sulfuric acid and the lead plates produces the electricity to

light the bulb. This chemical reaction also begins to coat both positive and negative plates

with a substance called lead sulfate also known as sulfation (shown as a yellow build-up

on plates). This build-up of lead sulfate is normal during a discharge cycle. As the battery

continues to discharge, lead sulfate coats more and more of the plates and battery voltage

begins to decrease from fully charged state of 12.6-volts (figure # 4).

45

In figure # 5 the battery is now fully discharged, the plates are almost completely covered

with lead sulfate (sulfation) and voltage has dropped to 10.5-volts.

NOTE: Discharging a lead acid battery below 10.5 volts will severely damage it!

Lead sulfate (sulfation) now coats most of the battery plates. Lead sulfate is a soft

material, which can is reconverted back into lead and sulfuric acid, provided the

discharged battery is immediately connected to a battery charger. If a lead acid battery is

not immediately recharged, the lead sulfate will begin to form hard crystals, which cannot

be reconverted by a standard fixed voltage (13.6 volts) battery converter/charger.

NOTE: Always recharge your RV or Marine battery as soon as possible to prevent loss of

battery capacity due to the build-up of hard lead sulfate crystals!

BATTERY LIFETIME

Primary batteries

Disposable (or "primary") batteries typically lose 8 to 20 percent of their original charge

every year at room temperature (20°–30°C This is known as the "self discharge" rate, and

is due to non-current-producing "side" chemical reactions which occur within the cell

even if no load is applied. The rate of the side reactions is reduced if the batteries are

stored at lower temperature, although some batteries can be damaged by freezing. High

or low working temperatures may reduce battery performance. This will affect the initial

voltage of the battery. For an AA alkaline battery, this initial voltage is approximately

46

normally distributed around 1.6 volts.Discharging performance of all batteries drops at

low temperature.

Secondary batteries

Storage life of secondary batteries is limited by chemical reactions that occur between the

battery parts and the electrolyte; these are called "side reactions". Internal parts may

corrode and fail, or the active materials may be slowly converted to inactive forms. Since

the active material on the battery plates changes chemical composition on each charge

and discharge cycle, active material may be lost due to physical changes of volume; this

may limit the cycle life of the battery.

RECHARGEABLE BATTERIES:

Old chemistry rechargeable batteries self-discharge more rapidly than disposable alkaline

batteries, especially nickel-based batteries; a freshly charged nickel cadmium (NiCd)

battery loses 10% of its charge in the first 24 hours, and thereafter discharges at a rate of

about 10% a month. However, newer low self-discharge nickel metal hydride (NiMH)

batteries and modern lithium designs have reduced the self-discharge rate to a relatively

low level (but still poorer than for primary batteries). Most nickel-based batteries are

partially discharged when purchased, and must be charged before first use Newer NiMH

batteries are ready to be used when purchased, and have only 15% discharge in a year.

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Extending battery life

Battery life can be extended by storing the batteries at a low temperature, as in a

refrigerator or freezer, which slows the chemical reactions in the battery. Such storage

can extend the life of alkaline batteries by about 5%; rechargeable batteries can hold their

charge much longer, depending upon type. To reach their maximum voltage, batteries

must be returned to room temperature; discharging an alkaline battery at 250 mA at 0°C

is only half as efficient as it is at 20°C Alkaline battery manufacturers such as Duracell

do not recommend refrigerating batteries. Imagine a world where everything that used

electricity had to be plugged in. Flashlights, hearing aids, cell phones and other portable

devices would be tethered to electrical outlets, rendering them awkward and

cumbersome. Cars couldn't be started with the simple turn of a key; a strenuous cranking

would be required to get the pistons moving. Wires would be strung everywhere, creating

a safety hazard and an unsightly mess. Thankfully, batteries provide us with a mobile

source of power that makes many modern conveniences possible.

While there are many different types of batteries, the basic concept by which they

function remains the same. When a device is connected to a battery, a reaction occurs that

produces electrical energy. This is known as an electrochemical reaction. Italian

physicist Count Alessandro Volta first discovered this process in 1799 when he created a

simple battery from metal plates and brine-soaked cardboard or paper. Since then,

scientists have greatly improved upon Volta's original design to create batteries made

from a variety of materials that come in a multitude of sizes.

Today, batteries are all around us. They power our wristwatches for months at a time.

They keep our alarm clocks and telephones working, even if the electricity goes out.

They run our smoke detectors, electric razors, power drills, mp3 players, thermostats --

and the list goes on. If you're reading this article on your laptop or smart phone, you may

even be using batteries right now! However, because these portable power packs are so

prevalent, it's very easy to take them for granted. This article will give you a greater

appreciation for batteries by exploring their history, as well as the basic parts, reactions

and processes that make them work. So cut that cord and click through our informative

guide to charge up your knowledge of batteries.

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Disadvantages of battery:

The main disadvantage 12volt lead acid is that it has one of the lowest energy to weight

ratio. This means that this type of 12v battery also has a low energy to volume ratio,

which in turn means that the size of the battery has to be big in order to provide

significant amount of power. Secondly it’s not portable.

Another major concern about lead acid 12v battery, which is a 12volt power source, is

that about environment. Almost all the batteries used in vehicles are lead acid and this

means that the disposal of these batteries can beome a big hurdle. Since there are a lot of

cars, this mean a lot of old batteries need to be dumped somewhere and improper disposal

means damaged environment. The automotive industry is now looking for alternatives to

replace lead acid battery in automotive applications towards a environmentally safe

option

Note : Please do note that the current rating is VERY important. DONOT plug in a

battery which has higher amperage than your modem or router can handle. Most modems

and routers are usually rated at around 1 ampere. So a 12V Battery of that rating should

be used.

4. SOLAR PANEL

Solar energy is energy that comes from the sun. Every day the sun radiates an

enormous amount of energy. The sun radiates more energy in one second than people

have used since the beginning of time. All this energy comes from within the sun itself.

Like other stars, the sun is a big gas ball made up mostly of hydrogen and helium. The

sun generates energy in its core in a process called nuclear fusion.

During nuclear fusion, the sun’s extremely high pressure and hot temperature cause

hydrogen atoms to come apart and their nuclei to fuse or combine. Some matter is lost

during nuclear fusion. The lost matter is emitted into space as radiant energy.

It takes millions of years for the energy in the sun’s core to make its way to the solar

surface, and then approximately eight minutes to travel the 93 million miles to earth. The

solar energy travels to the earth at a speed of 186,000 miles per second, the speed of light.

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Only a small portion of the energy radiated by the sun into space strikes the earth, one

part in two billion. Yet this amount of energy is enormous. Every day enough energy

strikes the United States to supply the nation’s energy needs for one and a half years!

About 15 percent of the sun’s energy that hits the earth is reflected back into space.

Another 30 percent is used to evaporate water, which, lifted into the atmosphere,

produces rainfall. Plants, the land, and the oceans also absorb solar energy. The rest

could be used to supply our needs.

A solar cell (also called a photovoltaic cell) is

an electrical device that converts the energy of light

directly into electricity by the photovoltaic effect. It is a

form of photoelectric cell (in that it’s electrical

characteristics—e.g. current, voltage, or resistance—

vary when light is incident upon it) which, when

exposed to light, can generate and support an electric

current without being attached to any external voltage

source.

The term "photovoltaic" comes from the Greek φῶς (phōs) meaning "light", and from

"Volt", the unit of electro-motive force, the volt, which in turn comes from the last name

of the Italian physicist Alessandro Volta, inventor of the battery (electrochemical cell).

The term "photo-voltaic" has been in use in English since 1849.

Photovoltaic’s is the field of technology and research related to the practical application

of photovoltaic cells in producing electricity from light, though it is often used

specifically to refer to the generation of electricity from sunlight. Cells can be described

as photovoltaic even when the light source is not necessarily sunlight (lamplight, artificial

light, etc.). In such cases the cell is sometimes used as a photo detector (for example

infrared detectors), detecting light or other electromagnetic radiation near the visible

range, or measuring light intensity.

The operation of a photovoltaic (PV) cell requires 3 basic attributes:

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1. The absorption of light, generating either electron-hole pairs or excitons.

2. The separation of charge carriers of opposite types.

3. The separate extraction of those carriers to an external circuit.

In contrast, a solar thermal collector collects heat by absorbing sunlight, for the purpose

of either direct heating or indirect electrical power generation. "Photo electrolytic cell"

(photo electrochemical), on the other hand, refers either a type of photovoltaic cell (like

that developed by A.E. Becquerel and modern dye-sensitized solar cells) or a device that

splits water directly into hydrogen and oxygen using only solar illumination.

Building block of a solar panel

Assemblies of photovoltaic cells are used to make solar modules which generate

electrical power from sunlight. Multiple cells in an integrated group, all oriented in one

plane, constitute a solar photovoltaic panel or "solar photovoltaic module," as

distinguished from a "solar thermal module" or "solar hot water panel." The electrical

energy generated from solar modules, referred to as solar power, is an example of solar

energy. A group of connected solar modules (such as prior to installation on a pole-

mounted tracker system) is called an "array."

History of solar cells

The photovoltaic effect was first experimentally demonstrated by French physicist

A. E. Becquerel. In 1839, at age 19, experimenting in his father's laboratory, he built the

world's first photovoltaic cell. Willoughby Smith first described the "Effect of Light on

Selenium during the passage of an Electric Current" in an article that was published in the

20 February 1873 issue of Nature. However, it was not until 1883 that the first solid state

photovoltaic cell was built, by Charles Fritts, who coated the semiconductor selenium

with an extremely thin layer of gold to form the junctions. The device was only around

1% efficient. In 1888 Russian physicist Aleksandr Stoletov built the first photoelectric

cell based on the outer photoelectric effect discovered by Heinrich Hertz earlier in 1887.

Albert Einstein explained the underlying mechanism of light instigated carrier excitation

—the photoelectric effect—in 1905, for which he received the Nobel prize in Physics in

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1921. Russell Ohl patented the modern junction semiconductor solar cell in 1946,which

was discovered while working on the series of advances that would lead to the transistor.

The first practical photovoltaic cell was developed in 1954 at Bell Laboratories by Daryl

Chapin, Calvin Souther Fuller and Gerald Pearson. They used a diffused silicon p-n

junction that reached 6% efficiency, compared to the selenium cells that found it difficult

to reach 0.5%.Les Hoffman CEO of Hoffman Electronics Corporation had his

Semiconductor Division pioneered the fabrication and mass production of solar cells.

From 1954-1960 Hoffman improved the efficiency of Solar Cells from 2% to 14%. At

first, cells were developed for toys and other minor uses, as the cost of the electricity they

produced was very high; in relative terms, a cell that produced 1 watt of electrical power

in bright sunlight cost about $250, comparing to $2 to $3 per watt for a coal plant.

Solar cells were brought from obscurity by the suggestion to add them, probably due to

the successes made by Hoffman Electronics to the Vanguard I satellite, launched in 1958.

In the original plans, the satellite would be powered only by battery, and last a short time

while this ran down. By adding cells to the outside of the body, the mission time could be

extended with no major changes to the spacecraft or its power systems. In 1959 the

United States launched Explorer 6. It featured large solar arrays resembling wings, which

became a common feature in future satellites. These arrays consisted of 9600 Hoffman

solar cells. There was some skepticism at first, but in practice the cells proved to be a

huge success, and solar cells were quickly designed into many new satellites, notably

Bell's own Telstar.

Improvements were slow over the next two decades, and the only widespread use was in

space applications where their power-to-weight ratio was higher than any competing

technology. However, this success was also the reason for slow progress; space users

were willing to pay anything for the best possible cells, there was no reason to invest in

lower-cost solutions if this would reduce efficiency. Instead, the price of cells was

determined largely by the semiconductor industry; their move to integrated circuits in the

1960s led to the availability of larger boules at lower relative prices. As their price fell,

the price of the resulting cells did as well. However these effects were limited, and by

1971 cell costs were estimated to be $100 per watt.

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Further improvements

In the time since Berman's work, improvements have brought production costs down

under $1 a watt, with wholesale costs well under $2. "Balance of system" costs are now

more than the panels themselves. Large commercial arrays can be built at below $3.40 a

watt, fully commissioned.

As the semiconductor industry moved to ever-larger boules, older equipment became

available at fire-sale prices. Cells have grown in size as older equipment became

available on the surplus market; ARCO Solar's original panels used cells with 2 to 4 inch

(51 to 100 mm) diameter. Panels in the 1990s and early 2000s generally used 5 inch

(125 mm) wafers, and since 2008 almost all new panels use 6 inch (150 mm) cells. This

material has less efficiency, but is less expensive to produce in bulk. The widespread

introduction of flat screen televisions in the late 1990s and early 2000s led to the wide

availability of large sheets of high-quality glass, used on the front of the panels.

In terms of the cells themselves, there has been only one major change. During the 1990s,

polysilicon cells became increasingly popular. These cells offer less efficiency than their

monosilicon counterparts, but they are grown in large vats that greatly reduce the cost of

production. By the mid-2000s, poly was dominant in the low-cost panel market, but more

recently a variety of factors has pushed the higher performance mono back into

widespread use.

Current events

Other technologies have tried to enter the market. First Solar was briefly the largest panel

manufacturer in 2009, in terms of yearly power produced, using a thin-film cell

sandwiched between two layers of glass. Since then silicon panels reasserted their

dominant position both in terms of lower prices and the rapid rise of Chinese

manufacturing, resulting in the top producers being Chinese. By late 2011, efficient

production in China, coupled with a drop in European demand due to budgetary turmoil

had dropped prices for crystalline solar-based modules further, to about $1.09 [13] per watt

in October 2011, down sharply from the price per watt in 2010.

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A more modern process, mono-like-multi, aims to offer the performance of mono at the

cost of poly, and is in the process of being introduced in 2012.

Applications

Polycrystalline photovoltaic cells laminated to backing material in a module

Polycrystalline photovoltaic cells

Solar cells are often electrically connected and encapsulated as a module. Photovoltaic

modules often have a sheet of glass on the front (sun up) side, allowing light to pass

while protecting the semiconductor wafers from abrasion and impact due to wind-driven

debris, rain, hail, etc. Solar cells are also usually connected in series in modules, creating

an additive voltage. Connecting cells in parallel will yield a higher current; however, very

significant problems exist with parallel connections. For example, shadow effects can

shut down the weaker (less illuminated) parallel string (a number of series connected

cells) causing substantial power loss and even damaging the weaker string because of the

excessive reverse bias applied to the shadowed cells by their illuminated partners. Strings

of series cells are usually handled independently and not connected in parallel, special

54

paralleling circuits are the exceptions. Although modules can be interconnected to create

an array with the desired peak DC voltage and loading current capacity, using

independent MPPTs (maximum power point trackers) provides a better solution. In the

absence of paralleling circuits, shunt diodes can be used to reduce the power loss due to

shadowing in arrays with series/parallel connected cells.

To make practical use of the solar-generated energy, the electricity is most often fed into

the electricity grid using inverters (grid-connected photovoltaic systems); in stand-alone

systems, batteries are used to store the energy that is not needed immediately. Solar

panels can be used to power or recharge portable devices.

Theory

The solar cell works in three steps:

1. Photons in sunlight hit the solar panel and are absorbed by semiconducting

materials, such as silicon.

2. Electrons (negatively charged) are knocked loose from their atoms, causing an

electric potential difference. Current starts flowing through the material to cancel

the potential and this electricity is captured. Due to the special composition of

solar cells, the electrons are only allowed to move in a single direction.

3. An array of solar cells converts solar energy into a usable amount of direct current

(DC) electricity.

Efficiency

55

Solar panels on the International Space Station absorb light from both sides. These

Bifacial cells are more efficient and operate at lower temperature than single sided

equivalents.

The efficiency of a solar cell may be broken down into reflectance efficiency,

thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency.

The overall efficiency is the product of each of these individual efficiencies.

A solar cell usually has a voltage dependent efficiency curve, temperature coefficients,

and shadow angles.

Due to the difficulty in measuring these parameters directly, other parameters are

measured instead: thermodynamic efficiency, quantum efficiency, integrated quantum

efficiency, VOC ratio, and fill factor. Reflectance losses are a portion of the quantum

efficiency under "external quantum efficiency". Recombination losses make up a portion

of the quantum efficiency, VOC ratio, and fill factor. Resistive losses are predominantly

categorized under fill factor, but also make up minor portions of the quantum efficiency,

VOC ratio.

The fill factor is defined as the ratio of the actual maximum obtainable power to the

product of the open circuit voltage and short circuit current. This is a key parameter in

evaluating the performance of solar cells. Typical commercial solar cells have a fill factor

> 0.70. Grade B cells have a fill factor usually between 0.4 to 0.7. Cells with a high fill

factor have a low equivalent series resistance and a high equivalent shunt resistance, so

less of the current produced by the cell is dissipated in internal losses.

Single p-n junction crystalline silicon devices are now approaching the theoretical

limiting power efficiency of 33.7%, noted as the Shockley–Queisser limit in 1961. In the

extreme, with an infinite number of layers, the corresponding limit is 86% using

concentrated sunlight.

Many currently available solar cells are made from bulk materials that are cut into wafers

between 180 to 240 micrometers thick that are then processed like other semiconductors.

56

Other materials are made as thin-films layers, organic dyes, and organic polymers that are

deposited on supporting substrates. A third group are made from nanocrystals and used as

quantum dots (electron-confined nanoparticles). Silicon remains the only material that is

well-researched in both bulk and thin-film forms.

Crystalline silicon

Basic structure of a silicon based solar cell and its working mechanism.

By far, the most prevalent bulk material for solar cells is crystalline silicon (abbreviated

as a group as c-Si), also known as "solar grade silicon". Bulk silicon is separated into

multiple categories according to crystallinity and crystal size in the resulting ingot,

ribbon, or wafer.

Analysts have predicted that prices of polycrystalline silicon will drop as companies build

additional polysilicon capacity quicker than the industry's projected demand. On the other

hand, the cost of producing upgraded metallurgical-grade silicon, also known as UMG Si,

can potentially be one-sixth that of making polysilicon.

Manufacturers of wafer-based cells have responded to high silicon prices in 2004–2008

prices with rapid reductions in silicon consumption. According to Jef Poortmans, director

of IMEC's organic and solar department, current cells use between eight and nine grams

57

of silicon per watt of power generation, with wafer thicknesses in the neighborhood of

0.200 mm. At 2008 spring's IEEE Photovoltaic Specialists' Conference (PVS'08), John

Wohlgemuth, staff scientist at BP Solar, reported that his company has qualified modules

based on 0.180 mm thick wafers and is testing processes for 0.16 mm wafers cut with

0.1 mm wire. IMEC's road map, presented at the organization's recent annual research

review meeting, envisions use of 0.08 mm wafers by 2015.

Thin films

Market share of the different PV technologies In 2010 the market share of thin film

declined by 30% as thin film technology was displaced by more efficient crystalline

silicon solar panels (the light and dark blue bars).

Silicon thin films

Silicon thin-film cells are mainly deposited by chemical vapor deposition (typically

plasma-enhanced, PE-CVD) from silane gas and hydrogen gas. Depending on the

deposition parameters, this can yield

1. Amorphous silicon (a-Si or a-Si:H)

2. Protocrystalline silicon or

3. Nan crystalline silicon (nc-Si or nc-Si:H), also called microcrystalline silicon.

It has been found that protocrystalline silicon with a low volume fraction of

nanocrystalline silicon is optimal for high open circuit voltage. These types of silicon

present dangling and twisted bonds, which results in deep defects (energy levels in the

band gap) as well as deformation of the valence and conduction bands (band tails). The

solar cells made from these materials tend to have lower energy conversion efficiency

58

than bulk silicon, but are also less expensive to produce. The quantum efficiency of thin

film solar cells is also lower due to reduced number of collected charge carriers per

incident photon.

An amorphous silicon (a-Si) solar cell is made of amorphous or microcrystalline silicon

and its basic electronic structure is the p-i-n junction. a-Si is attractive as a solar cell

material because it is abundant and non-toxic (unlike its CdTe counterpart) and requires a

low processing temperature, enabling production of devices to occur on flexible and low-

cost substrates. As the amorphous structure has a higher absorption rate of light than

crystalline cells, the complete light spectrum can be absorbed with a very thin layer of

photo-electrically active material. A film only 1 micron thick can absorb 90% of the

usable solar energy. This reduced material requirement along with current technologies

being capable of large-area deposition of a-Si, the scalability of this type of cell is high.

However, because it is amorphous, it has high inherent disorder and dangling bonds,

making it a bad conductor for charge carriers. These dangling bonds act as recombination

centers that severely reduce the carrier lifetime and pin the Fermi energy level so that

doping the material to n- or p- type is not possible. Amorphous Silicon also suffers from

the Staebler-Wronski effect, which results in the efficiency of devices utilizing

amorphous silicon dropping as the cell is exposed to light. The production of a-Si thin

film solar cells uses glass as a substrate and deposits a very thin layer of silicon by

plasma-enhanced chemical vapor deposition (PECVD). A-Si manufacturers are working

towards lower costs per watt and higher conversion efficiency with continuous research

and development on Multijunction solar cells for solar panels. Anwell Technologies

Limited recently announced its target for multi-substrate-multi-chamber PECVD, to

lower the cost to US$0.5 per watt.[

5. WIND POWER

Wind is a force of nature familiar to every polar researcher. Although often

perceived as something with which to contend, it also offers tremendous opportunities in

the support of scientific research. Many polar locales such as ice caps, coastal regions,

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and areas experiencing katabatic winds are ideally suited for the use of wind turbines. In

areas such as these, wind turbines can often provide the primary or even sole source of

electrical power generation. Even locations typically regarded as having relatively poor

wind resources, such as interior Alaska, often experience adequate wind speeds to

provide at least a supplemental charging source for a battery-based system. However, in

almost all locations, the wind is an extremely variable source of power. A turbine must be

able to take advantage of fairly low wind speeds to maximize energy production yet must

also be able to survive the hurricane-force winds that sweep through the Polar Regions

with varying frequency. Researchers have tried for many years to take advantage of this

renewable energy power source—sometimes with disappointing results. Many

researchers have returned to remote instrument sites in Antarctica and the Arctic to find

their turbines non-functional due to broken blades, burned-up electronics, or, in some

instances, an empty tower with no turbine remaining at all. Advancements in wind

turbine technology and manufacture in the last 10 years have resulted in units much more

capable of harnessing this force and surviving the rigors of the polar environment.

Numerous mechanical furling systems designed to angle the blades out of the direct force

of the wind, sophisticated electronic controls, and new and more robust blade and bearing

materials have all contributed to the generally higher quality wind turbines found on the

market today. For many research projects, wind turbines represent a viable and cost-

effective solution for providing all or part of an experiment’s electrical power

requirements.

Turbines are available in a wide range of outputs, from 50 watts up to several

megawatts. Indeed, several mid-sized units (50-500 kilowatts) offer tremendous potential

for powering larger polar research facilities. The Australian Mawson Station in

Antarctica now has two Enercon 300-kilowatt turbines This installation, completed in

2004, has reduced diesel fuel consumption at this facility by approximately 50%.

Although the challenges are many, several other polar research facilities are highly

suitable for employing this technology. With the high cost of transporting, handling, and

storing fuel, wind turbines represent an economically viable alternative. The

environmental benefits are also quite significant and are typically more in keeping with

the requirements of the research community. Because the majority of researchers have

60

relatively low power requirements for seasonal or year-round instrument platforms,

small- to mid-sized wind turbines will be the principle focus of this paper.

The primary determining factor influencing the electrical power production from any

given wind turbine is wind speed. “Wind energy potential increases very rapidly with

increasing wind speed. In fact, if wind speed doubles, the energy content goes up by a

factor of eight”. Additionally, air temperature and density play a role in how much power

one can hope to obtain from the resource.

Wind speed can be expressed as meters per second (m/sec), miles per hour (mph), or

knots (kts). Here is the relationship between them:

1 mph = 0.447 m/sec = 0.868 kts

1 kt = 0.514 m/sec = 1.152 mph

1m/sec = 2,237 mph = 1.943 kts

In general, Polar Regions are pretty windy places. Antarctica boasts the highest average

wind speed of any continent. At Black Island, a communications hub near McMurdo

Station, wind speeds in excess of 140 mph have been recorded. There is a wind

installation at this site, and it has provided a lot of valuable lessons on how to deal with

polar extremes. The Arctic, as a region, experiences a somewhat similar wind regime to

that of Antarctica. In both Polar Regions, the highest average wind speeds occur along

the coasts and in mountainous areas, whereas the interiors can often experience fairly low

average wind speeds. Moreover, the windiest times of the year tend to be when solar

insolation is lowest—that is, during the boreal or austral winter. It is for this reason that

photovoltaic (PV) panels and wind turbines are such complementary technologies. Both

power sources can be utilized to feed a common battery bank and balance-of-system

components in a hybrid system. For year-round system deployments, this is a sound

strategy to pursue. Properly sized and designed, this also confers a measure of

redundancy to a power system that directly relates to overall reliability.

WIND SYSTEM CONSIDERATIONS

There are four elements that will determine whether the wind can be successfully

harnessed in support of a scientific research project:

1. Is it a good wind site?

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• For remote applications, a good site will have average wind speeds of greater than 4

m/sec (9mph), although sites with significantly lower average wind speeds are acceptable

if power requirements are modest or wind is not the exclusive energy source. A good

wind site will not have major surface obstructions to cause turbulence or lees.

2. Are the project’s power requirements suitable for utilizing wind energy?

•High, continuous power demand may necessitate the utilization of an on-demand power

supply as part of a hybrid system. Low or intermittent power demands combined with a

good site and balanced system design may allow for the use of wind as the sole energy

source.

3. Do you have the appropriate wind turbine for the job?

•Wind turbines vary widely in size, quality, and the type of site for which they are

designed. Some turbines are designed to take advantage of low wind speeds but may not

hold up well to sustained high wind speeds or turbulence. Others are designed to survive

high-speed, turbulent winds but will fail to produce much usable power at lower wind

speeds.

•Some turbines produce a higher voltage alternating current (AC) thereby allowing the

tower to be located some distance from the controller and battery bank. Others rectify the

power to direct current (DC) right at the point of generation and must therefore be located

close to the point of use (or at least close to the point of energy storage).Some turbines

are designed to hold up well to icing conditions, whereas the design of other turbines may

not account for this potential environmental issue.

4. Have you taken a comprehensive, “system design” approach?

• A power system is really a chain of elements or components integrated into a whole.

The chain is only as strong as its weakest link. Errors at any stage of the design or

implementation can lead to failure of the system. An excellent turbine mounted on an

insufficiently tall tower will likely yield poor performance. If the tower collapses because

an anchor pulls out, the performance will be dismal indeed.

SYSTEM COMPONENTS

There are two basic wind turbine configurations: the horizontal axis and the

Vertical axis.

VERTICAL-AXIS

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Vertical-axis wind turbines can be further subdivided into two basic designs

The Savonius design was invented in 1924 by Finnish inventor Sigurd Savonius. Only a

few years later, the Darrieus wind turbine was patented in France. Vertical Axis There are

advantages and disadvantages to vertical-axis wind turbines. The most desirable

attributes include nearly silent operation and an avian-friendly design. However, most

vertical-axis wind turbines are difficult to mount high on a tower to capture the higher

speed and less turbulent winds found at greater elevations above grade. As such, they

must utilize the generally lower speed winds found near ground level with a consequent

reduction in power output. The silver lining is that having the generator mounted at or

near ground level makes maintenance significantly less challenging. Also, vertical-axis

wind turbines are omni-directional and accept wind from any direction. This somewhat

reduces the penalty of utilizing more turbulent air. Vertical-axis wind turbines tend to be

significantly more expensive to produce, and this above all else is likely responsible for

the small number of models available for purchase. In terms of polar applications, there

are really only two vertical-axis wind turbine manufacturers to consider: the Finish Wind

sides and the Italian Ropatec design. They are extremely robust, heavy machines capable

of withstanding the most extreme environmental conditions. They are also quite

expensive with a very poor power-to-weight ratio.

HORIZONTAL AXIS

Given the reasons listed above, with cost perhaps representing the most

significant

factor, the horizontal-axis wind turbine has come to dominate the industry. Whereas the

researcher has few choices when it comes to vertical-axis wind turbine manufacturers,

there are many horizontal- axis wind turbines suitable for use in polar environments. The

basic elements of a horizontal-axis wind turbine are described below. The rotor

constitutes the spinning part of the wind turbine—basically, the blades and hub. The

swept area, or amount of area captured by the rotor, is a definitive measure of a wind

turbine, as much as the rated power output. The longer the blade is, the greater the

amount of torque that can be exerted on the generator. Doubling the length of each blade,

thereby doubling the rotor diameter, increases the swept area of a wind turbine by 4

times. Most modern blades are composed of layered fiberglass, carbon fiber, special

plastics, or combinations thereof. Most are designed to flex with the forces of wind and

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centrifugal motion, and this flexion helps to control rotational speed. An added benefit of

utilizing flexible materials is that ice buildup tends to be minimized and is typically

quickly shed as rotational speeds increase. Some manufacturers offer optional blades for

their machines (e.g., carbon fiber vs. fiberglass) to cope with more extreme

environmental conditions. Many manufacturers utilize mechanical systems to control

blade speed in high wind conditions. Furling changes the angle of the rotor in relation to

the wind direction thus reducing the frontal area intercepting the wind. Some upwind

models furl on a horizontal axis and others on a vertical axis. Either of these strategies

helps to protect the turbine from damage but can sometimes result in dramatically

reduced output in high winds. Downwind Proven turbines allow the blades to furl back,

hinging on the hub. This reduces the swept area and changes the blade pitch to control the

blade speed but allows for continued full-power output in very high winds. Large wind

turbines typically change the pitch of the blade to control rotational speed, often in

conjunction with

other controls. One small wind turbine manufacturer (Kestrel) has adopted this approach.

The mechanical governor actuated pitch control, in combination with a many-poled

alternator, allows for high power output at comparatively low rotational speeds. This

should equate to low noise levels and a long service life, however, at the time of this

writing, the machines have not been tested in polar environments. Other manufacturers

utilize electronic controls to essentially load the generator internally thereby reducing

blade speed. In this strategy, a lot of internal heat can build up, which if not dissipated

can lead to failure. Many early-models Southwest Wind power “Air 403s” met untimely

ends in Antarctic applications due to this design. Even with very low ambient

temperatures, they simply could not dissipate enough heat. Subsequent redesigns have

resulted in more robust and reliable products. Some smaller wind turbines utilize the

blade design exclusively as the rotor speed control. Between blade flexion and the

cavitations created by the blades themselves, severe over speeding is avoided.

Interestingly, several British manufacturers of small wind turbines have utilized rotors

with many blades. LVM, Ampair, and Marlec all offer models with six-blade rotors. Like

the old American farm windmill, this design offers a high starting torque and good low

wind-speed performance. Of course, with low wind speeds, one can never expect too

much power production. However, the above-mentioned turbines do better than most in

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low wind applications, and because of inherent design qualities and rugged construction,

they (usually) do not blow apart in high winds. Large wind turbines employ many diverse

strategies to control rotor speed. Some early models exclusively used mechanical brake

systems to control rotor speed in high winds. However, the duration of the wind events

often exceeded the durability of the braking system, sometimes producing disastrous

results. The history of wind power is a history of lessons learned. Now, most large wind

turbines also incorporate some form of aerodynamic over speed control as a type of fail

safe. Many large wind turbines utilize some type of actuator motor to turn the blades out

of the wind. In large-scale utility applications, the power grid itself can play a role in

regulating rotational speeds. These more sophisticated control schemes are not typically

applicable to polar installations. Some manufactures of small wind turbines offer

mechanical brake systems, but these are typically used for locking the rotor for

maintenance rather than as a means to control rotor speed. There will be more on this

subject later. The nacelle is the body of the wind turbine. It houses the drive train,

generator, and balance-of-system components that allow the unit to follow the wind

direction and transfer electricity. Remember that what the generator is really doing is

converting one form of power (the wind) into another form (electricity). This is why,

regardless of the size of the generator, the swept area of the rotor is the best indicator of

potential power production. Most small wind turbines are direct drive—that is they do not

utilize a gearbox to change the rotational speed of the generator rotor. The rotor attached

to the blades is directly connected to the electrical rotor within the generator. Most small

wind turbines utilize 3-phase alternators with permanent magnets. Permanent magnet

alternators eliminate the need for field windings. Because the majority of wind turbine

manufacturers choose to rectify the 3-phase AC to DC for battery charging via a charge

controller placed near the battery bank, the comparatively poor voltage regulation

inherent with permanent magnet designs is not an issue. In fact, most run a completely

wild AC signal (both voltage and frequency are relatively uncontrolled) to the controller.

There are three main advantages to using this strategy:

- The wind turbine can be made lighter since most of the electronics are located remotely.

- The wiring from the nacelle to the controller and battery bank can be much smaller

given that the higher voltage AC has lower line loss.

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- Many controllers allow for diversion loads. Any power in excess of what is required for

battery charging can be diverted to a resistive heat load. More on this later the primary

function of the tower is to raise the machine above grade where it can better utilize the

wind resource available. Simple in concept but varied in form, the importance of the

tower is often underestimated in designing a wind power system.

Wind speed and therefore power production correlate directly with the height of the rotor

above the ground. The uneven surface of the ground produces friction and turbulence that

reduce wind speed and disrupt the even flow of the air mass. Not only does this reduce

power output, it can dramatically increase the stress on the blades and other components.

Even in most polar areas that lack significant foliage, low-level turbulence exists.

Increasing the tower height by 5 times can double he power production of the wind

turbine. Generally speaking, it is prudent to design for the maximum tower height that

remains practicable to install and maintain, as wind speeds will be stronger, more

constant, and less turbulent at greater heights. Additionally, the greater the distance from

grade, the less blowing snow to which a turbine will be subjected. Most blowing snow

events involve only the first 20 to 30 feet above the surface level. Although taller tower

heights provide definite benefits in power output, they can dramatically increase the

difficulty of installation and service. For most small systems in remote Polar Regions,

erecting towers greater than 50 feet (15 meters) will be problematic. Most installations

are done by hand without the advantage of cranes or any heavy equipment. Sometimes

even providing an adequate anchor for erecting a tall tower can be difficult. Generally

speaking, 30-foot (10-meter) towers will provide good results for wind turbines of 2

kilowatts or less. Smaller wind turbines (< 500 watts) have been erected on towers as low

as 15 feet (4.5 meters), and although the results may be less than optimal, system

performance is still typically adequate to contribute significantly to the overall power

budget.

Due to poor substrates (snow, bog, tundra, permafrost, etc.), tower types employed in the

installation of small wind systems in the Polar Regions are generally limited to guyed

designs. These can be mono-pole, tilt-up towers or sectional lattice towers, such as the

Rohn. For wind turbines of 1 kilowatt or less, the tilt-up tower design is almost always

preferable. Being able to install and maintain the turbine while standing on the ground

has tremendous advantages over clinging to a steel tower 30 or more feet above the

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surface in the bitter cold. However, for turbines larger than 1-kilowatt output, the greater

strength of the guyed lattice tower may be required. More on tower set-up and installation

follows later in this document.

Scale on left edge of graphic is m/s. Note the higher wind speeds with increasing height

above the surface. Note also the stronger winds in the winter months.

SELECTING A WIND TURBINE

If you have determined that a wind turbine will meet (in part or in whole) the power

requirements of your research project, the next step is selecting the appropriate size and

type that suits your environmental conditions. Wind turbines intended for powering

remote scientific research projects must be designed for unattended operation in very

harsh environmental conditions. Features to look for include simplicity, ruggedness, and

low maintenance. Power Output As with many products targeted for emerging markets,

there is tremendous variation in how closely wind turbines produce the claimed rated

output. Some wind turbines will never equal the performance advertised, regardless of

wind conditions. In other cases, wind turbines have been known to significantly exceed

the maximum output stated. Either condition can be bad, as it makes the balance-of-

system design rather difficult to account for. One fairly telling method for determining if

a manufacturer’s claims are based on science or fantasy is to compare the rated outputs

between various models with the same swept area size of the rotor. It will become

apparent that in some instances, performance claims simply cannot be true.

“The rated power for a wind turbine is not a good basis for comparing one product to the

next. This is because manufacturers are free to pick the wind speed at which they rate

their turbine. If the rated wind speeds are not the same then comparing the two products

is very misleading. Fortunately the American Wind Energy Association (AWEA) has

adopted a standard method for rating energy production performance. Manufacturers who

follow the AWEA standard will give information on the Annual Energy Output (AEO) at

various annual average wind speeds”.

Redundancy can sometimes equate to greater reliability. In very critical

applications, a better strategy may be to employ multiple smaller wind turbines than one

large turbine. In the event of a single turbine failure, there will still be power input,

although reduced, to the battery bank. Smaller wind turbines can also be easier to set up.

However, much of the cost and installation time involved with wind power systems is

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really associated with the tower. It will invariably be more expensive and time consuming

to erect multiple smaller turbines. Also, wind turbine placement must be considered so as

to avoid one turbine resting in the turbulence wake of another. In some cases, the wind

direction is predictable enough to plan for this, as the elegant lines of offshore wind farms

in Europe illustrate. Finally, very small wind turbines (< 500 watts) are often simply not

as robust as their larger brethren. This is because weight is often a key design criterion

for these applications. Although it is not true that there are no quality lightweight

turbines, there is a lot to be said for the “heavy metal” school of design. Consider all the

options carefully, for in some instances, a design employing one ruggedly constructed

wind turbine may actually be superior to a system using multiple turbines of lower

quality. Although wind turbines typically bear a superficial resemblance, numerous

design features vary from one model to another.

Here are some features to look for:

- Rugged design

. Does the turbine look like it can handle the rigors of the environment in which it will be

placed? What materials have been used in the construction?

- Minimum wind speed

. This is the speed at which the turbine must spin before it can generate power. If you are

putting the machine in an area with an average wind speed of 3 m/sec and it does not start

producing significant power until 5 m/sec, it is not well suited to the application.

- Rated wind speed.

Again, this value should match up fairly closely with the average wind speeds of the

location in which the turbine will be placed.

- Survival wind speed.

Most manufacturers selling a quality product will post this number. Remember that cold

air is dense, and cold air filled with blowing snow is denser still. Also, extreme cold

usually has a deleterious effect on the strength of materials. For polar applications, de-

rate the claimed survival speed by 25%.

- Power curve

. Does the machine continue to consistently put out power even when it goes into over

speed control?

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This can make a big difference in the total amount of power produced by a turbine. The

production of some units drops off dramatically when wind or rotor speeds cross a certain

threshold.

- Noise level

. In most cases, this may not be an issue. However, if the turbine is to be placed in a

manned site or if wildlife observation is an element of the research project, then the

acceptable level of noise could come into play. Wind turbines can be very loud in some

instances. For example, Southwest Wind power’s “Air Industrial” model, although a fine

turbine in many respects, is exceedingly loud in high wind conditions. Not all

manufacturers post sound-level information, but those companies that have put some

effort into reducing noise levels generally do.

- Marine rated

. If you are placing the machine in a maritime environment, it is essential to make sure

that it is marine rated. Salt is exceedingly hard on electronics, and corrosion can

sometimes occur in as little as a few months. Sealed or encapsulated electronics, stainless

steel fasteners, and specially coated metal are typical attributes of a marine-rated unit.

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BALANCE-OF-SYSTEM COMPONENTS:

Although we have described the basic elements of the wind turbine, there are numerous

other components that must be considered in the overall power system.

The wind does not blow with equal intensity in all places at all times. Gale-force winds

on one day may be followed by a week of calm weather. This is the primary reason why

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wind remains a tricky resource to harness. The load requirements of a power system, on

the other hand, seldom correspond with times of peak power production. For the purposes

of polar scientific research, an energy storage system must be employed. This will most

typically comprise a set of batteries, which allows for the storage of power to help

regulate the variability of the wind.

6. APPLICATIONS AND LIMITATIONS:

APPLICATIONS:

Solar tracking system is used in satellites as a source of fuel.

It is used in solar thermal collector to collect heat.

It is used in water heaters.

It is used in heat exchangers.

It is used in solar power plants.

It is used for desalination of sea water.

It is used in inverters.

It is used in solar water pumps.

LIMITATIONS:

The commercially available tracking systems make use of servo motors

with feedback controllers and add substantially to the overall cost of a solar energy

system. They also require a power supply and a sophisticated level of maintenance.

Since the solar energy devices are important for applications in decentralized systems,

which are usually located in remote and rural areas these two requirements are often

not met.

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7. CONCLUSION:

In order to collect the greatest amount of energy from the sun, solar

panels must be aligned orthogonally to the sun. For this purpose a new solar tracking

technique based on micro-controller was implemented and tested in this study. The

tracking system presented has the following advantages: The tracking system is not

constrained by the geographical location of installation of the solar panel since it is

designed for searching the maximum solar irradiance in the whole azimuth and tilt

angle during day times; namely, the angle of elevation does not need to be adjusted

periodically. The operator interference is minimal because of not needing to be

adjusted. The tracker provides also PC based system monitoring facility. Since the

tracking system is controlled completely bye Microcontroller used for monitoring the

panel. A drawback of the tracker is being affected by temporal variations in the

atmospheric refractions caused by rain, cloud, fog etc. thus the system may give an

erroneous detection in the direction of the sun and lead to wrong positioning of the

solar panel. There are several new solar cell concepts that aim at making better use of

the solar spectrum and doing so achieve much higher energy conversion efficiencies

than the present conventional solar cells.

“As search never stops “still better” never dies”

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8. BIBILOGRAPHY:

IJAEEE, Volume1, Number 1 Noor Fatimaet al.ISSN:2319-1112 /V1N1:9-14 ©IJAEEE

[1] Mukherjee, D., Chakrabarti, S., Fundamentals of renewable energy systems, New Age

international limited publishers, New Delhi, 2005.

[2] Sharma, P.C., Non-conventional power plants, Public printing service, New Delhi,

2003. [3] Mukherje, D., Chakrabarti, S., Non-conventional power plants, New Delhi,

2005. [4] Nota, R., Barelds, R., Engineering method for road traffic and railway noise

after validation and fine-tuning, Harmonoise WP 21-35, 2005.

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