Full Report Changed

Design of Converting Solar Energy into Electrical Energy for Domestic

Utilization Incorporating MPPT

Session 2003

Project Advisor Dr. Suhail Aftab Qureshi

Author

Arsalan A Rahim 2003-E-121

Department of Electrical Engineering University of Engineering & Technology

Lahore, Pakistan 2007

In the name of Allah, the most gracious, the most merciful & he taught Adam the names of all things

and he taught man that which he know not

Al-Quran

Acknowledgements First and foremost, all praise to Almighty Allah who gave me the courage and patience to carry out this work successfully. Who created the heaven and the earth, night and day and sun for solar energy which named the title of my project. I express my sincere appreciation for the encouragement, excellent advice and valuable help which I got from my project adviser Dr. Suhail Aftab Qureshi, without whose sympathetic supervision this work would have not been possible. He provided me an innovative and professional hand to streamline all my activities and maximize my potential. My special thanks goes to my friend Mr Zafar for solving my problems, providing technical skills and invaluable help during the project. Finally, my deepest and most sincere thanks to my family for their endless love, encouragement and understanding they have shown during the whole time and helping me in completing the most expensive Solar energy project without any financial assistance from any other source.

Contents: Page # Chapter 1 Introduction 1 1.1 Alternate Energy Development Board 3 Chapter 2 Project Abstracts 7 2.1 Solar Cells 7 2.1.1 History 8 2.1.2 Structure 8 2.1.3 Size & Wattage 10 2.1.4 Modules 11 2.1.5 Array 11 2.1.6 General Diagram of a Module 12 2.2 Solar Insolation 13 2.2.1 Solar Insolation Map of World 14 2.3 What is MPPT? 15 2.4 Phases of the Project 18 2.5 Block Diagram of the Project 20 Chapter 3 Scope, Socio-Economic Benefits & Utilization 21 3.1 Present Status Around the Globe 22 3.2 Cost per Watt 24 3.3 StandAlone Home PV Systems Around the Globe 26 3.3.1 Grid Interactive Systems 28 3.4 Power Plants Around the Globe 29 3.5 Recent Developments In the World 31 3.6 Scope in Pakistan 32 Chapter 4 Purchased Hardware Items 33 4.1 Solar Panel 33 4.1.1 Sharp Solar Panel NT-175U1 37 4.2 Batteries 38 Chapter 5 Problem Statement 39 5.1 Techniques for MPPT 39 5.2 Algorithm for Maximum Power Point 41 5.2.1 Selection 42

5.3 Solar Tracker Implementation 43 5.3.1 Sun Intensity 44 5.3.2 Movable Stand Implementation 45 5.3.3 Software Technique 49 5.4 Battery Charging Phases 50 5.4.1 State of Charge 51 5.5 Charge Controllers 51 Chapter 6 Software Development 52 6.1 Time Dependant Solar Tracker Software 52 6.1.1 Display Procedure 53 6.1.2 Checking the Min and Hour Limits 54 6.1.3 Incrementing the Min & Hour Code After Checking 54 6.1.4 Season Check Code 55 6.1.5 October Season Setting Pre-programmed in Mirco-controller 56 6.2 MPPT Algorithm 57 6.2.1 16 bit by 16 bit Multiply Algorithm 58 6.2.2 24 bit by 8 bit Division Algorithm 59 6.2.3 32 bit by 8 bit Division Algorithm 61 6.2.4 Battery Voltage Testing 63 6.2.5 MPPT Algorithm 65 6.2.6 Block Always Running 66 6.2.7 Button Selection for Value to be Displayed 67 6.2.8 Serially Receiving Data from Tracker & Input Controller Code 68 Chapter 7 Simulation 72 7.1 Solar Tracker Simulations 72 7.1.1 Simulation Results 76 7.2 MPPT Controller Simulations 77 7.2.1 ADC Simulation 77 7.2.2 DAC Simulation 78 7.2.3 Tracker & Input Controller Keypad Simulations 78 7.2.4 MPPT Controller 79 7.2.5 MOSFET Driver & MOSFET 80 7.2.6 MOSFET Driver Simulation Results 81

Chapter 8 Hardware 83 8.1 DC Supply 83 8.2 Time Dependant Solar Tracker 84 8.2.1 Hardware Abstracts 85 8.3 MPPT Controller 86 8.4 MOSFET Driver & MOSFET 87 Chapter 9 Results 91 Chapter 10 Alternate Energy Resources 92 10.1 Solar Thermal Energy 92 10.1.1 Parabolic Trough 94 10.1.2 Central Reciever 95 10.1.3 Dish Reciever 96 10.2 Wind Energy 96 10.3 Tidal Energy 98 10.3.1 Advantages 99 10.3.2 Disadvantages 99 Chapter 11 Appendix 101

Dedicated to my loving parents

Chapter 1 INTRODUCTION

1

1. INTRODUCTION Energy is need of the modern world and for a developing nation like Pakistan the need of the hour is to explore new means of energy which are cheap and environment friendly. Keeping in the view the bullish energy demand which is increasing more than 10% per year for which these sources are unable to meet the demand:

• Thermal • Hydro • Nuclear • Gas

Due to the following economical, political and geological problems present in Pakistan:

• No national consensus on the construction of new Dams due to provincial problems

• Limited sites for construction of Dams • Increasing oil prices for Thermal Power Plants around the

globe resulting in high cost per unit which greatly effects the industrial sector

• Non-availability of civilian nuclear technology with refusal of

developed nations for co-operation in this sector • Large Transmission Line Losses due to distances between

generations and load centers

• Non-usage of biggest coal reserviours in Sindh for power generation at-least for few years to come as efforts have been started to use those reserviors.


2

In the light of the above mentioned points, it is desirable that a quick bulk power be provided to the National Grid through other energy resources so that black-outs in our industrial city like Karachi could be avoided which can greatly contribute to the industrial sector which demands consistency and realiability of power which will sustain our growth in the coming years until new dams and nuclear installations are ready for power generation. All over the world new means of energy are being discovered like Wind and Solar which will be the source of energy for the new generation. Keeping in view the mushroom growth in the industrial sector in Pakistan the energy requirement is increasing day by day and is expected to be double in 10 years. With the shortage of new water reserviors and soaring Oil rates which are the major raw material for energy generation in Pakistan we should try to find Alternate Energy Resources like Solar Energy which is cheap and affordable with a little investment for a longer period. Significance of the proposed research and application duly supported with recent developments in the outer world support that there are many energy sources yet to be explored like Solar in Pakistan. Solar Energy the gift of God free to everyone can be utitlized with a little investment for a longer period which provides clean, safe and environment friendly Energy for any Application from House Hold to Industrial use. The Electricity in Pakistan is an expensive source of energy & with everyday increasing prices the common man plus the industrial sector is getting underneath this burden. Much of the Industrial Sector has shifted to produce its own energy by gas, fuel or any other fossil fuel but the increase in Oil Prices in the world market has held back this source too. Pakistan being a developing Nation has a Max energy requirement. This requirement is expected to double up to year 2015 and to meet this challenge we don’t have water reserviors for hydro energy which is the cheap source of energy in Pakistan. With no new dam being completed in Pakistan the Prime Minister and the President has ordered to utilize other sources of energy. In this context a board with the name of Alternate Energy Resource Development (AEDB) been formed to promote, explore and make use of other sources of energy.


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1.1 Alternate Energy Development Board (AEDB) Alternate Energy Development Board re-organized by the present Government in Febraury 2005 to promote alternate energy resources in Pakistan through public and private sector. Some of the main features and targets assigned to the board as as follows:

• The main area that has been approved is that 10% of all electrical energy produced in the country will be shifted to Alternative/Renewable energy resources by the year 2015. This gives a target of around 1700 MW of production through Alternative technologies on the lower side and 2700 MW on the higher side.

• More than 800 million dollars investment has been offered to

the Alternative Energy Development Board. The interested groups belong to Canada, China, Denmark, Germany, India, Iran, Russia, Spain, Sweden, USA, and UAE etc.

• 2% of investment made in power sector should be dedicated to

development of Alternative/ Renewable Energy Technologies Base in Pakistan.

• All localities not planned/anticipated to be connected with

national grid in next 20 years are to be earmarked for Alternative/ Renewable Energy resources.

• All industrial production related to Alternative/ Renewable

Energy will be given special tax holidays for next ten years, development in Pakistan.

The Board has also tabulated some graphs

Proposed Growth of Alternate Renewable Energy in Pakistan Depletion of Oil and Gas reserves in Pakistan

Which are presented for an insight in the whole matter.


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So as the development of Alternate Energy Resources in Pakistan is heading its course I have presented in my project the basic building blocks of a Solar Photovoltaic Power System for Domestic use which can be installed at the load center.

Chapter 2 PROJECT ABSTRACTS

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2 PROJECT ABSTRACTS The sun has produced energy for billions of years. Solar energy is the solar radiation that reaches the earth. Enough sunlight falls on the Earth's surface each minute to meet world energy demands for an entire year. The sun is a fusion reactor delivering 1.52 x 1018 KWh/year to earth. All of mankind's energy needs total less than 0.1% of this amount. The United States receives more energy in the form of sunlight in less than 40 minutes than from all the fossil fuels they burn every year. Solar energy can be converted directly or indirectly into other forms of energy, such as heat and electricity. The major drawbacks (problems, or issues to overcome) of solar energy are:

1. The intermittent and variable manner in which it arrives at the earth's surface

2. The large area required to collect it at a useful rate 2.1 Solar Cells Solar cells as the name implies are designed to convert at-least a portion of available light into electrical energy. They do this with the use of chemical reactions. The photovoltaic effect is the electrical potential developed between two dissimilar materials when their common junction is illuminated with radiation of photons. So the electrical energy generated through solar cells is categorized as Photovoltaic energy or simply PV energy.


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2.1.1 History The development of the solar cell stems from the work of the French physicist Antoine-Cesar Becquerel in 1839. Becquerel discovered the photovoltaic effect while experimenting with a solid electrode in an electrolyte solution; he observed that voltage developed when light fell upon the electrode. About 50 years later, Charles Fritts constructed the first true solar cells using junctions formed by coating the semiconductor selenium with an ultra thin nearly transparent layer of gold. Fritts's devices were very inefficient, transforming less than 1 percent of the absorbed light into electrical energy. These early solar cells however, still had energy-conversion efficiencies of less than 1 percent. This impasse was finally overcome with the development of the silicon solar cell by Russell Ohl in 1941. In 1954, three other American researchers, G.L. Pearson, Daryl Chapin, and Calvin Fuller, demonstrated a silicon solar cell capable of a 6-percent energy-conversion efficiency when used in direct sunlight. By the late 1980s silicon cells, as well as those made of gallium arsenide, with efficiencies of more than 20 percent had been fabricated. In 1989 a concentrator solar cell, a type of device in which sunlight is concentrated onto the cell surface by means of lenses, achieved an efficiency of 37 percent due to the increased intensity of the collected energy. In general, solar cells of widely varying efficiencies and cost are now available. 2.1.2 Structure Modern solar cells are based on semiconductor physics .They are basically P-N junction photodiodes with a very large light-sensitive area. The photovoltaic effect, which causes the cell to convert light directly into electrical energy, occurs in the three energy-conversion layers.


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The first of these three layers necessary for energy conversion in a solar cell is the top junction layer (made of N-type semiconductor).

The next layer in the structure is the core of the device, this is the absorber layer (the P-N junction).

The last of the energy-conversion layers is the back junction layer (made of P-type semiconductor).

Fig 2.1.2


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Sunlight is composed of photons or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed. Only the absorbed photons provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material's atoms. Special treatment of the material surface during manufacturing makes the front surface of the cell more receptive to free electrons, so the electrons naturally migrate to the surface.

When the electrons leave their position, holes are formed. When many electrons, each carrying a negative charge, travel toward the front surface of the cell, the resulting imbalance of charge between the cell's front and back surfaces creates a voltage potential like the negative and positive terminals of a battery. When the two surfaces are connected through an external load, electricity flows. 2.1.3 Size & Wattage The photovoltaic cell is the basic building block of a PV system. Individual cells can vary in size from about 1 cm (1/2 inch) to about 10 cm (4 inches) across. One cell only produces 1 or 2 watts.


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2.1.4 Modules As one cell only produces 1 or 2 watts which isn't enough power for most applications. To increase power output, cells are electrically connected into a packaged weather-tight module. 2.1.5 Array The solar array is defined as a group of several modules electrically connected in series-parallel combinations to generate the required current and voltage.

Fig 2.1 Fig 2.1.4 Fig 2.1.5


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2.1.6 General Diagram of a Module Construction of PV module: 1) Frame 2) Weather-proof junction box 3) Rating plate 4) Weatherprotection for 30-year life 5) PV cell 6) Tempered high transmissivity coverglass, 7) Outside electrical bus, 8) Frame clearance Source: Solarex Corporation, Frederick, Maryland,

Fig 2.1.6


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2.2 Solar Insolation The amount of electromagnetic energy (solar radiation) incident on the surface of the earth is called Solar Insolation. Basically that means how much sunlight is shining down on us. By knowing the insolation levels of a particular region we can determine the size of solar collector that is required. An area with poor insolation levels will need a larger collector than an area with high insolation levels. Once you know your region's insolation level you can more accurately calculate collector size and energy output. The values are generally expressed in kWh/m2/day. This is the amount of solar energy that strikes a square metre of the earth's surface in a single day. Of course this value is averaged to account for differences in the days' length. There are several units that are used throughout the world. The conversions based on surface area as follows:

1 KWh/m2/day = 317.1 btu/ft2/day = 3.6MJ/m2/day

The raw energy conversions are:

1kWh = 3412 Btu = 3.6MJ = 859.8kcal

It is presumed that at "peak sun", 1000 W/m² of power reaches the surface of the earth. One hour of full sun provides 1000 Wh per m² = 1 kWh/m² - representing the solar energy received in one hour on a cloudless summer day on a one-square meter surface directed towards the sun.


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Some Facts about Solar PV power available to us

1. The United States receives more energy in the form of sunlight in less than 40 minutes than from all the fossil fuels they burn every year

2. Roughly 100 square miles of solar panels placed in the

southwestern U.S. could power the whole USA. 3. The sun is a fusion reactor delivering 1.52 x 10 18 kWh/year to

earth. All of mankind's energy needs total less than 0.1% of this amount

2.2.1 Solar Insolation Map of World

Fig 2.2.1


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2.3 What is MPPT ?

Solar cells are characterized by a maximum Open Circuit Voltage (Voc) at zero output current and a Short Circuit Current (Isc) at zero output voltage. Since power can be computed via this equation:

P = I * V

Then with one term at zero these conditions

(V = Voc / I = 0, V = 0 / I = Isc )

also represent zero power. As you might then expect, a combination of less than maximum current and voltage can be found that maximizes the power produced (called, not surprisingly, the "maximum power point").

The function of a MPPT is analogous to the transmission in a car. When the transmission is in the wrong gear, the wheels do not receive maximum power. That's because the engine is running either slower or faster than its ideal speed range. The purpose of the transmission is to couple the engine to the wheels, in a way that lets the engine run in a favorable speed range in spite of varying accelleration and terrain. In a PV panel, voltage is analogous to engine speed. Its ideal voltage is that at which it can put out maximum power. This is called its maximum power point. (It's also called peak power voltage, abbreviated Vpp). Vpp varies with sunlight intensity and with solar cell temperature. In order to charge a battery (increase its voltage), the PV module must apply a voltage that is higher than that of the battery. If the PV module's Vpp is just slightly below the battery voltage, then the current drops nearly to zero. When the panel is directly connected to the battery bank, the module voltage is dragged down to a lower-than-ideal voltage. Thus the panel starts working at the battery voltage giving a less current then it can supply at its Maximum Power Point Voltage.


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The Current and Voltage Characteristics of a typical panel are presented here:

The above plot is at 1 Sun i.e. the total energy available from the sun is purely converted into electrical energy having 100% efficiency but this is rarely achieved as sunlight is not present all round the day at equal strength with also clouds present at some days.

Fig 2.3.1


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Another plot for different variations of Sun energy available is given below The maximum power point of a solar module is the point along the I-V curve that corresponds to the maximum output power possible for the module. This value can be determined by finding the maximum area under the current versus voltage curve.

I-V Curve

Fig 2.3.2

Fig 2.3.3


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2.4 Phases Of The Project 1. Availability and Purchase of Solar Panel with Its Shipping

Plus Testing:

• Testing includes the formation of table giving us the total voltage, total current, wattage at different times of a day.

• Calculating the average solar energy produced per day • Total AH battery rating needed when the sun is not available. • Calculate the sun rotation path and find it from PAKMET office

2. In order to save time, using a domestically made Inverter which converts the stored energy in battery to AC Power for domestic use 3. Testing the Process Uptil This Point by Connecting the Main Components by Manual Switches:

• Testing the three equipments Solar Panel, SCC, DC to AC Inverter and load connected and this is done using Manual Switches (Direct contact of Panel to Batteries without any Charge Controller)

4. Solar Panel Movement Using Motor/Hydraulics and Rotating with Computer Control Using Mirco-Controller

• Solar Panel Rack/Mount design. • Deciding which solution to use to rotate it either motor or

hydraulics • Software Development of Solar Tracker with its Simulation • Then the biggest challenge is to rotate with computer control

integrated with a Micro-Controller • Also tryin to make it automatic control according to sun

movement.


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5. Designing MPPT (Maximum Power Point Tracker) Charge Controller and its Implementation on a PCB (if possible) plus Testing:

• Software Development of MPPT Controller with its Simulation • Availability of components of the Solar Charge Controller • Testing it by implementing it on the BreadBoard • Designing it on the Protel Software and implementing it on PCB • Testing the PCB

6 Project Summary (Report):

• Project Report 7. Simulation :

• Simulation in FLASH MX of the total Project plus Power Point Presentation


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Chapter 3 SCOPE, SOCIO-ECONOMIC BENEFITS & UTILIZATION

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3. SCOPE, SOCIO-ECONOMIC BENEFITS & UTILIZATION Photovoltaic energy is useful for several reasons.

Conversion from sunlight to electricity is direct, so that bulky mechanical generator systems are unnecessary.

The environmental impact of a photovoltaic system is minimal, requiring no water for system cooling and generating no by-products.

Short lead time to design, install, and start up a new plant

The plant economy is not a strong function of size.

Power output matches very well with peak load demands.

Static structure, no moving parts, hence, no noise.

High power capability per unit of weight.

Longer life with little maintenance because of no moving parts.

Highly mobile and portable because of light weight.


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3.1 Present Status Around the Globe At present, PV power is extensively used in stand-alone power systems in remote villages all around the globe especially in these countries.

1. U.S.A. 2. Australia 3. Austria 4. Mexico 5. Japan

A graph showing the cummulative growth of PV installations in U.S.A is shown below for a span of 16 years

Fig 3.1.1


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For around the globe, the trend is easily depicted from the below graph

Fig 3.1.2


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3.2 Cost Per Watt The cost $ per watt for PV power plants or standalone system is quite high due the energy consumption in Silicon Layers preparation and forming it in crystalline form for Junction formation, but it is decreasing with new technologies introduced such as concentrator technology & Thin Film PV Juntion Technology. A graph showing the decrease in energy consumption per cm2 of PV cell manufactured is shown:

Fig 3.2.1


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With decreasing energy consumption for PV cell manufacture the cost $ per KWhr has decreased considerably. International Standard nowadays for PV installation cost are generally $4.5 to $5 per watt.

Fig 3.2.2


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3.3 StandAlone Home PV Systems Around the Globe Many StandAlone PV Systems are installed at homes which vary from 2 KW to 9 KW. Initial cost for these installations is high but with the facility of Tax Rebates, Constitution Laws & Monetary assistances in developed countries facilitates the development of such systems Some of the systems are presented here

Germany, 3 kW System

Fig 3.3.1


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Kyoto, Japan 5KW System

Claifornia, USA 6.1KW System

Source: Mitsubishi Electric

Fig 3.3.3

Fig 3.3.2


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3.3.1 Grid Interactive Systems A recent development in renewable energy technology is grid-interactivity. In a grid-interactive system, electricity is still generated by solar panels. The DC electricity from the panels passes through a grid-interactive inverter, which converts the DC electricity into AC.

This AC electricity is then used by any loads operating in the house, and if there is surplus electricity being generated by the panels, the inverter will feed the electricity into the main electricity grid. Conversely, when the panels aren't generating enough electricity to power the house, the grid will supply power to the house via the inverter.

In Australia, a growing number of electricity utilities are supportive of grid-interactive systems, and will pay you for your electricity if the amount you generate exceeds the amount you use during the billing period.

The roof of the Aquatic Center in Atlanta (Figure 3-8), venue of the 1996 Olympic swimming competition, is one of the largest grid-connected powerplants.

Roof (pv) of Atlanta’s Aquatic Center with 345 kW grid-connected power system.

Source: Georgia Institute of Technology

Fig 3.3.4


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3.4 Power Plants Around the Globe Many Power Plants are present around the globe supplying power to the Grids. Many are present in U.S.A. but now with recent surge in oil prices many countries are planning and infact many have started to develop Power Plants ranging upto 300MW. Some of the PV Power Plants are

Power Generation Plant Okinawa, Japan 750 kW System

Fig 3.4.1


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Small Power Plant Austria 400KW System

Platform Gunma, Japan 200 kW System

Source: Mitsubishi Electric

Fig 3.4.2

Fig 3.4.3


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3.5 Recent Developments In the World A race between the developed countries in this century has started for the World Largest Solar PV Power Plant Some of the recent deveopments are as follows:

China Plans World's Largest Solar Power Plant with an amount of $766 million

A 154 MW power plant (concentrated solar power, photovoltaic) in Australia has been funded and will begin operations in 2008, reaching full capacity in 2013. The projects are the first to be funded under a $379 million package That sounds like it's farther along than China's project.

A proposed 300 MW power plant in New Mexico recently completed the first study phase, and is now looking for contracts to purchase the power.

Two solar stirling farms ,one 300 MW, the other 500 MW that already have 20-year purchasing contracts in hand. The first 1 MW is scheduled for completion in spring 2007. The full 300 MW farm is scheduled for 2010 completion. The 500 MW farm should be done by 2012.

Some key features which has lead to rapid development in this sector are the laws and the incentives given by the governments of the countries

California Public Schools all power by PV power enforced by a law there

Japan has a residential market of 350 MW per year

Public utilities in New Mexico must acquire or generate at least ten percent (10%) of their electricity from a renewable resource, one that is self-regenerating, such as solar, wind, and/or hydro electric.


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3.6 Scope in Pakistan Present Government has taken considerable efforts for development of Renewable Energy Resources in Pakistan. An Alternate Energy Development Board has been established which has been given consitutional protection and it has formulated its policy for next 10 years whose key features have been discussed before but are again given here.

The main area that has been approved is that 10% of all electrical energy produced in the country will be shifted to Alternative/Renewable energy resources by the year 2015.

2% of investment made in power sector should be dedicated to development of Alternative/ Renewable Energy Technologies Base in Pakistan.

All industrial production related to Alternative / Renewable Energy will be given special tax holidays for next ten years, development in Pakistan.

With these appealing incentives, it is supposed that the day is not far when Pakistan will also be joining the race for the World Largest Solar PV Plants. Many locations in Balochistan and North-West of Punjab have been identified for PV installations which are very far from grid and are best suited for PV installations by climate conditions also.

Chapter 4 PURCHASED HARDWARE ITEMS

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4. PURCHASED HARDWARE ITEMS 4.1 Solar Panel Since I needed Solar cells for my project, I opted to import a big Solar panel as nothing like this is available in Pakistan as no industry or infrastrusture is present. It was a tedious job to first select the best ones from the so big market outside with so many manufacturers with so much fluctuations in the prices with each vendor. Some of the companies which are famous for making Solar panel are as follows:

1. Solarex 2. Siemens 3. Sharp 4. Mitsibushi 5. BP 6. Evergreen 7. Kynocera

Of them Solarex produces the bulk solar panels with Siemens and Sharp having also a large share in PV Panel production around the globe.


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The vendors I contacted through internet are as follows

1. Affordable Solar Online 2. DiscountPtv.com 3. WE Online 4. Other Powers.com 5. PartsOnSale.com 6. Alter Systems Online 7. Dependable Solar Products.com 8. SolarPanelStore.com

I personally phone called them and contacted them for best prices and selected Sharp as the Manufacturer company from the vendor Alter Systems Online. The panel which I selected was NT-175U1 of 175W Peak Power. The module specifications are as under

Electrical Characteristics Cell Single crystal silicon No.of Cells and Connections 72 in series Open Circuit Voltage (Voc) 44.4V Maximum Power Voltage (Vpm) 35.4V Short Circuit Current (Isc) 5.55A Maximum Power Current (Ipm) 4.95A Maximum Power (Pm)* 175W Minimum Power (Pm)* 157.5W Encapsulated Solar Cell Efficiency (ηc) 16.20% Module Efficiency (ηm) 13.45% PTC Rating (W)** 153.80 Maximum System Voltage 600VDC Series Fuse Rating 10A

Type of Output Terminal Lead Wire with MC Connector

* (STC) Standard Test Conditions:25°C,1 kW/m2,AM 1.5 ** (PTC) Pacific Test Conditions:20°C,1 kW/m2,AM 1.5,1 m/s wind speed


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Mechanical Characteristics

Dimensions (A x B x C below) 62.01 x 32.52 x 1.81" / 1575 x 826 x 46mm

Weight 37.485lbs / 17.0kg Packing Configuration 2 pcs per carton

Size of Carton 66.93 x 38.19 x 5.12" / 1700 x 970 x 130mm

Loading Capacity (20 ft container) 168 pcs (84 cartons) Loading Capacity (40 ft container) 392 pcs (196 cartons)

Absolute Maximum Ratings Operating Temperature -40 to 194°F / -40 to +90°C Storage Temperature -40 to 194°F / -40 to +90°C Dielectric Isolation Voltage 2200 VDC max.

Fig 4.1.1


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The I-V curves and P-V curves of the Panel are shown below

Fig 4.1.2


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4.1.1 Sharp Solar Panel NT-175U1 Some Key features which make it one of the best in market are

• Module features 16.2% encapsulated cell efficiency and 13.45% module efficiency.

• Using breakthrough technology • Modules use a textured cell surface to reduce reflection of

sunlight and BSF (Black SurfaceField) structure to improve conversion efficiency.

• An anti-reflective coating provides a uniform blue color and increases the absorption of light in allweather conditions.

• Ideal for grid-connected systems and designed to withstand rigorous operating conditions

Fig 4.1.3


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4.2 Batteries The size of the battery bank required will depend on the storage capacity required, the maximum discharge rate, the maximum charge rate, and the minimum temperature at which the batteries will be used. Battery voltage is difficult to change after your system is built, so carefully selection is necessary I selected a battery bank voltage of 24V as the panel is desgined for this purpose and it is normally used voltage around the world for simple small systems. Many types of Batteries can be used 1. Lead Acid Batteries 2. Wet Gell Batteries I selected Lead Acid Batteries due to their deep cycle charging and discharging capability and it is easily available here. Since maximum 12V battery is available I had to put two batteries in series to make a 24V battery bank. Each battery is 42Ah. Thus the total energy that could be stored is V x I = 24 x 42Ah = 960Wh Selection of 24V Battery bank is also on the fact that the panel Open circuit voltage does not drop below 24V from the dawn to the dusk so it can effectively provide produced amperes to the battery thus charging it

Chapter 5 PROBLEM STATEMENT

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5. PROBLEM STATEMENT On the hardware point of view the following were the problems being faced:

• Technique Used for Isolation between the Battery and Panel • Algorithm used to calculate the Maximum Power Point on the

V-I curve • Hardware Deisgn of the Movable stand to track the Sun • Technique used for the Solar Tracker • Battery Charging States to be implemented by the MPPT

controller 5.1 Techniques for MPPT To understand what is MPPT (Maximum Power Point Tracker) the examination of the electrical principle of the peak power operatio is done. If the array is operating at voltage V and current I on the i-v curve, thepower generation is P = V · I watts. If the operation moves away from the above point, such that the current is now I + ∆ I, and the voltage is V + ∆ V,the new power is as follows:

P + ∆P = (V + ∆V) . (I + ∆I) Which, after ignoring a small term, simplifies to the following:

∆P = ∆V.I + ∆I.V

The ∆P should be zero at peak power point, which necessarily lies on a locally flat neighborhood.


40

Therefore, at peak power point, the above expression in the limit becomes as follows:

dV / dI = - V / I

We take note here that dV/dI is the dynamic impedance of the source, and V / I is the static impedance.

Fig 5.1.1


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5.2 Algorithm for Maximum Power Point There are three electrical methods of extracting the peak power from the module, as described below: 1. Impedance Method In the first method, a small signal current is periodically injected into the array bus and the dynamic bus impedance Zd = dV/dI and the static bus impedance Zs = V/I are measured. The operating voltage is then increased or decreased until

Z d = – Zs

At this point, the maximum power is extracted from the source.

2. Slope Method In another electrical method, the operating voltage is increased as longas dP/dV is positive. That is, the voltage is increased as long as we get more power. If dP/dV is sensed negative, the operating voltage is decreased. The voltage is kept put if the dP/dV is near zero within a preset dead band.


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3. Factor Method The third method makes use of the fact that for most pv cells, the ratio of the voltage at the maximum power point to the open circuit voltage (i.e.,Vmp / Voc ) is approximately constant, say K. For example, for high-quality crystalline silicon cells K = 0.72. An unloaded cell is installed on the array and kept in the same environment as the power-producing module, and its open circuit voltage is continuously measured. The operating voltage of the power-producing array is then set at K·Voc , which will produce the maximumpower. 5.2.1 Selection

• I selected Slope Method because it is easy to implement it at the point where the slope is 1 on the I-V curve using Micro-Controllers.

• A buck-converter with the MOSFET operated by the Micro-

controllers with DAC as interface between the gate and the micro-controllers is used. The buck converter provides islolation between the Solar panel and the batteries and because of the duty cycle the effective voltage at which the Solar Panel operates is given by

Vo = Vin * D

where D is the duty cycle. For example in case of maximum power being produced, the open circuit voltage is 44.4V and maximum power point voltage is 35.4V. thus the Duty cycle needed at the MOSFET is

D = 35.4 / 44.4 = 0.7973 or 79.73% of the total cycle time.


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5.3 Solar Tracker Implementation

Solar tracking is the process of varying the angle of solar panels and collectors to take advantage of the full amount of the sun’s energy. This is done by rotating panels to be perpendicular to the sun’s angle of incidence. Initial tests in industry suggest that this process can increase the efficiency of a solar power system by up to 50%.

Given those gains, it is an attractive way to enhance an

existing solar power system. The goal is to build a rig that will accomplish the solar tracking and realize the maximum increase in efficiency. The ultimate goal is that the project will be cost effective – that is, the gains received by increased efficiency will more than offset the one time cost of developing the rig over time. In addition to the functional goals, it must be aesthetically pleasing, and it must be weatherproof. The major factors influencing the electrical design of the solar array are as follows:

• Sun intensity • Sun angle • Load matching for maximum power • Operating temperature.

The first two points can be handled by a Solar Tracker which keeps the solar panel directing the sun at a desired angle.


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5.3.1 Sun Intensity The magnitude of the photo current is maximum under full bright sun (1.0 sun). On a partially sunny day, the photocurrent diminishes in direct proportion to the sun intensity. The i-v characteristic shifts downward at a lower sun intensity as shown in Figure. On a cloudy day, therefore, the short circuit current decreases significantly. The reduction in the open-circuit voltage however is small. The photoconversion efficiency of the cell is insensitive to the solar radiation in the practical working range.

Fig 5.3.2

Fig 5.3.1


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For example, upper Figure shows that the efficiency is practically the same at 500 watts/m2 and 1,000 watts/m2 .This means that the conversion efficiency is the same on a bright sunny day and a cloudy day. Lower power output on a cloudy day is only because of the lower solar energy impinging the cell. The sun really only rises exactly in the east and sets exactly in the west on two days of the year - the first day of spring and the first day of fall. The sun rises in a direction north of east and sets in a direction north of west during the spring and summer months (northerly latitudes). The sun rises in a direction south of east and sets in a direction south of west during the fall and winter months (northerly latitudes). The sun reaches its peak (zenith) at a point due south of the observer (northerly latitudes). The time this occurs is defined as solar noon. The sun's zenith is closer to the horizon during fall and winter months, and is higher in the sky during spring and summer months. The sun rises earlier and sets later during the spring and summer months, with the opposite being true during the fall & winter months. Since the Sun rises from the east and sets in the west. It is preferable to move the panel from the east to the west as the day progresses. Around the year the sun trajectory also changes For Solar Tracker, there were two objectives (i) Firstly to develop the movable stand which can be moved within 120o atleast (ii) Software technique used to move it 5.3.2 Movable Stand Implementation A movable stand was designed in AutoCad by a Mechanical Engineer. The diagram of it are shown here.


46

Fig

5.3.

3


47

Fig

5.3.

4


48

Fig

5.3.

5


49

5.3.3 Software Technique Two options were present to be used. They were as follows (i) Using a photo-sensor to calculate the sun position and directing the motor to that specific position (ii) Using just time dependant Solar Tracker which after a specific time rotates the panel in the fixed direction and returns it back to the east position after sunset. I selected the second technique because my intentions were to concentrate on the MPPT not the tracking of Solar panel, because there is only a slight increase in current if the panel is kept at perpendiculat to the sun position. Also the two axis tracking was rejected by me because of its cost. As it is only a single solar panel two much investment on the tracking mechanism will increase the cost per watt of the system. So to keep it simple one axis rotation with time as the parameter was chosen as the ultimate solution.


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5.4 Battery Charging Phases Lead acid batteries used in the project can be charged in three phases: 1. Bulk Charge The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take. 2. Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts. 3. Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging. PWM, or "pulse width modulation" accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called "pulse width" because the width of the pulses may vary from a few microseconds to several seconds. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.


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5.4.1 State of Charge The state of charge for a 12V Lead acid battery is given below with volts per cell indicated. A 12V battery has 6 cells

State of Charge

12 Volt battery

Volts per Cell

100% 12.7 2.12 90% 12.5 2.08 80% 12.42 2.07 70% 12.32 2.05 60% 12.20 2.03 50% 12.06 2.01 40% 11.9 1.98 30% 11.75 1.96 20% 11.58 1.93 10% 11.31 1.89

0 10.5 1.75 5.5 Charge Controllers A charge controller is a regulator that goes between the solar panels and the batteries. Regulators for solar systems are designed to keep the batteries charged at peak without overcharging. Since my project also uses MPPT Algorithm, I opted for the bulk charging and the float charge phases of charging the battery. Bulk charging occurs when the battery voltage is less than the required voltage and the MPPT algorithm works. When the required voltage is reached, float charge phase takes place just tapering off the current until a significant constant value + the required voltage is reached. At this point the battery charging is totally stopped. All this is done with the automatic programmed micro-controllers.

Fig 5.4.1

Chapter 6 SOFTWARE DEVELOPMENT

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6 SOFTWARE DEVELOPMENT Software development for the two circuits is to be done 1. Time Dependant Solar Tracker 2. MPPT Algorithm

6.1 Time Dependant Solar Tracker Software The technique to be used here is that a digital clock giving real time is developed, A calendar year divided in 4 parts 1. January – March 2. April – June 3. July – September 4. October – December This was done because the axis of solar rotation from the east to the west remains almost constant during one of the divided parts. Thus the Sun takes almost a constant time to move from east to the west during the whole day. The rising of the sun at the dusk and the sunset times were recorded. It was decided that the panel will be moved after every 1 hr to make it perpendicular to the sun position. A linear actuator speed motor was used to move the panel from the east to the west. The motor moves panel a definite length if the motor supply is kept on for a definite time. I used Assembly Language for code writing as I decided to use AT89C51 micro-controller.


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Some parts of the software developed are shown here for knowledge of the reader about the work done: 6.1.1 Display Procedure DISPLAY: CALL JOIN DIGIT_1: MOV A, #11110000b ANL A,R5 RR A RR A RR A RR A MOV B,#0 CJNE A,B, DIGIT_1_PRINT JMP DIGIT_2 DIGIT_1_PRINT: MOV P2, A SETB P1.0 ;MAKING PORT 1.0 TO PRINT THIS CALL D_DELAY MOV P1,#0 DIGIT_2: MOV A, #00001111b ANL A,R5 MOV P2, A SETB P1.1 ;MAKING PORT 1.1 TO PRINT THIS CALL D_DELAY MOV P1,#0 DIGIT_3: MOV A, #11110000b ANL A,R6 RR A RR A RR A RR A MOV P2, A SETB P1.2 ;MAKING PORT 1.4 TO PRINT THIS CALL D_DELAY MOV P1,#0 DIGIT_4: MOV A, #00001111b ANL A,R6 MOV P2, A SETB P1.3 ;MAKING PORT 1.3 TO PRINT THIS CALL D_DELAY


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MOV P1,#0 RET 6.1.2 Checking the Minute and Hour Limits ;--------------------CHECKING IF MIN HAND HAS REACHED 59------------------- CHECK_MIN: MOV A, R6 MOV B, #59h CJNE A,B, CHECK_MIN_RET MOV 62H,#0 MOV 63H,#0 CALL CHECK_HR RET CHECK_MIN_RET: CALL INC_MIN RET ;---------------------------CHECKING IF HR HAS REACHED 23:00--------------- CHECK_HR: MOV A,R5 MOV B,#23h CJNE A,B, CHECK_HR_RET MOV A,R6 MOV B,#59h CJNE A,B,CHECK_HR_RET MOV 60H, #0 MOV 61H, #0 RET CHECK_HR_RET: CALL INC_HR RET 6.1.3 Incrementing Minute & Hour Code after Checking ;---------------------------------INC MIN HAND------------------------ INC_MIN: MOV A, 63H MOV B, #9 CJNE A,B,INC_MIN_2 JMP INC_MIN_1 INC_MIN_2: INC A MOV 63H, A RET INC_MIN_1: MOV 63H, #0 MOV A, 62H INC A MOV 62H, A RET ;----------------------------INCREMENTING HR HAND-----------------------


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INC_HR: MOV A, 61H MOV B, #9 CJNE A,B,INC_HR_2 JMP INC_HR_1 INC_HR_2: INC A MOV 61H, A RET INC_HR_1: MOV A, #0 MOV 61H, A MOV A, 60H INC A MOV 60H, A RET 6.1.4 Season Check Code ;-------------------------------SEASON CHECK--------------------- SEASON_CHECK: JB P1.4, JAN_MARCH JB P1.5, APR_JUNE JB P1.6, JULY_SEP JB P1.7, OCT_DEC RET JAN_MARCH: CLR P0.2 SETB P0.3 SETB P0.4 SETB P0.5 CALL JAN_SETTING RET APR_JUNE: SETB P0.2 CLR P0.3 SETB P0.4 SETB P0.5 CALL APR_SETTING RET JULY_SEP: SETB P0.2 SETB P0.3 CLR P0.4 SETB P0.5 CALL JULY_SETTING RET OCT_DEC: SETB P0.2 SETB P0.3 SETB P0.4


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CLR P0.5 CALL OCT_SETTING RET 6.1.5 October Season Settings Pre-programmed in Micro- Controller OCT_SETTING: MOV 50H, #0 ;6 am in Morning MOV 51H, #3 ;7 am in Morning MOV 52H, #4 ;8 am in Morning MOV 53H, #5 ;9 am in Morning MOV 54H, #5 ;10 am in Morning MOV 55H, #4 ;11 am in Morning MOV 56H, #3 ;12 pm in Noon MOV 57H, #3 ;1 pm in Noon MOV 58H, #4 ;2 pm in Noon MOV 59H, #4 ;3 pm in Noon MOV 5AH, #4 ;4 pm in Evening MOV 5BH, #0 ;5 pm in Evening MOV 5CH, #39 ;6 pm in Evening MOV 5DH, #0 ;7 pm in Evening RET


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6.2 MPPT Algorithm As the slope algorithm is selected, the technique to be used is given in detail below: The following steps are followed in loop again and again 1. For a given duty Cycle D, the current, voltage are taken from the ADC’s thus calculating the power P 2. Secondly the duty cycle is decreased a little from D to D1 by a constant value and similary at this point Power P1 is calculated. 3. Then the duty cycle is increased from D to D2 by a specified constant and the power P2 is calculated again. 4. If P2 – P1 > 0 then D is given the value D2 and P = P2 else If P2 – P1 < 0 then D is given the value D1 and P = P1 else If P2 – P1 = 0 ≈ Tolerance then D is not changed 5. Again repeating from step 1. The above stated algorithm operates the MOSFET at the duty cycle D which is at slope 1 or the point where the Maximum Power is achieved or the point where there is maximum area under the I-V curve. Tolerance value in the step 4 is used because it is very rarely possible that the power calculated in two step is exactly equal so matching upto some significant digit is used. It was decided that the hardware to be distributed because of the numerous calculation to be done in micro-controllers. So there are 3 micro-controllers to be used, so three different programs doing different steps of the algorithm using three mico-controllers.


58

Distributed Elements 1. Data Logger 2. Tracker or Input Controller 3. Display Controller 1. Data Logger It interfaces the ADC to the micro-controller AT89S51 for the measurement of Voltage, Current, Power, Battery voltage Since the programs will be written in Assembly so tedious calculations algorithms have to be implemented such as

• 24 bit by 8 bit division Algorithm • 16 bit by 16 bit multiplication Algorithm • 32 bit by 8 bit Division Algorithm with Rounding off facility

Since it calculates the data parameters, it is named the data logger as it logs the data for the Tracker or Input controller. Different code segment of the Data logger are shown below 6.2.1 16 bit by 16 bit Multiply Algorithm ;---------------------------MULTIPLICATION ALGORITHM (16 BIT BY 16 BIT)------ MULTIPLY: ;Multiply R5 by R7 MOV A,R5 ;Move the R5 into the Accumulator MOV B,R7 ;Move R7 into B MUL AB ;Multiply the two values MOV R2,B ;Move B (the high-byte) into R2 MOV R3,A ;Move A (the low-byte) into R3 ;Multiply R5 by R6 MOV A,R5 ;Move R5 back into the Accumulator MOV B,R6 ;Move R6 into B MUL AB ;Multiply the two values ADD A,R2 ;Add the low-byte into the value already in R2 MOV R2,A ;Move the resulting value back into R2 MOV A,B ;Move the high-byte into the accumulator ADDC A,#00h ;Add zero (plus the carry, if any) MOV R1,A ;Move the resulting answer into R1 MOV A,#00h ;Load the accumulator with zero ADDC A,#00h ;Add zero (plus the carry, if any) MOV R0,A ;Move the resulting answer to R0. ;Multiply R4 by R7 MOV A,R4 ;Move R4 into the Accumulator


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MOV B,R7 ;Move R7 into B MUL AB ;Multiply the two values ADD A,R2 ;Add the low-byte into the value already in R2 MOV R2,A ;Move the resulting value back into R2 MOV A,B ;Move the high-byte into the accumulator ADDC A,R1 ;Add the current value of R1 (plus any carry) MOV R1,A ;Move the resulting answer into R1. MOV A,#00h ;Load the accumulator with zero ADDC A,R0 ;Add the current value of R0 (plus any carry) MOV R0,A ;Move the resulting answer to R1. ;Multiply R4 by R6 MOV A,R4 ;Move R4 back into the Accumulator MOV B,R6 ;Move R6 into B MUL AB ;Multiply the two values ADD A,R1 ;Add the low-byte into the value already in R1 MOV R1,A ;Move the resulting value back into R1 MOV A,B ;Move the high-byte into the accumulator ADDC A,R0 ;Add it to the value already in R0 (plus any carry) MOV R0,A ;Move the resulting answer back to R0 ;Return - answer is now in R0, R1, R2, and R3 RET 6.2.2 24 bit by 8 bit Division Algorithm ;---------------------------DIVISION ALGORITHM (24 BIT BY 8 BIT)----------- DIV24: MOV R4, #0H MOV R5, #0H MOV R6, #0H MOV 30H, #0H MOV 31H, #0H MOV 32H, #0H MOV 33H, #0H MOV 34H, #0H CLR C ;Clear carry initially MOV B,#00h ;Clear B since B will count the number of left-shifted bits div1: INC B ;Increment counter for each left shift MOV A,R3 Move the current divisor low byte into the accumulator RLC A ;Shift low-byte left, rotate through carry to apply highest bit to high-byte MOV R3,A ;Save the updated divisor low-byte MOV A,33h RLC A MOV 33h,A MOV A,34h RLC A MOV 34h,A JNC div1 ;Repeat until carry flag is set from high-byte


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div2: Shift right the divisor MOV A,34H ;Move high-byte of divisor into accumulator RRC A ;Rotate high-byte of divisor right and into carry MOV 34H,A ;Save updated value of high-byte of divisor MOV A,33H ;Move high-byte of divisor into accumulator RRC A ;Rotate high-byte of divisor right and into carry MOV 33H,A ;Save updated value of high-byte of divisor MOV A,R3 ;Move low-byte of divisor into accumulator RRC A ;Rotate low-byte of divisor right, with carry from high-byte MOV R3,A ;Save updated value of low-byte of divisor CLR C ;Clear carry, we don't need it anymore MOV 32h,R2 ;Make a safe copy of the dividend high-byte MOV 31h,R1 ;Make a safe copy of the dividend middle-byte MOV 30h,R0 ;Make a safe copy of the dividend low-byte MOV A,R0 ;Move low-byte of dividend into accumulator SUBB A,R3 ;Dividend - shifted divisor = result bit (no factor, only 0 or 1) MOV R0,A ;Save updated dividend MOV A,R1 MOV R7,33H SUBB A,R7 MOV R1,A MOV A,R2 MOV R7,34H SUBB A,R7 MOV R2,A JNC div3 ;If carry flag is NOT set, result is 1 MOV R2,32h MOV R1,31h ;Otherwise result is 0, save copy of divisor to undo subtraction MOV R0,30h div3: CPL C ;Invert carry, so it can be directly copied into result MOV A,R4 RLC A ;Shift carry flag into temporary result MOV R4,A MOV A,R5 RLC A MOV R5,A MOV A, R6 RLC A MOV R6, A DJNZ B,div2 ;Now count backwards and repeat until "B" is zero RET


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6.2.3 32 bit by 8 bit Division Algorithm DIVISION: CALL DIV24 MOV A, R4 CALL BANK_1 MOV R0, A CALL BANK_3 MOV A, R0 MOV B, #0 CJNE A,B, DIV_AGAIN_1 CALL BANK_1 MOV A, R0 RL A RL A RL A RL A MOV R0, A CALL BANK_3 JMP DIV_STOP DIV_AGAIN_1: MOV A, R0 MOV B, #10 MUL AB MOV R0, A MOV R1, B CALL DIV24 CALL BANK_1 MOV A, R0 RL A RL A RL A RL A MOV R0, A CALL BANK_3 ORL A, R4 CALL BANK_1 MOV R0, A CALL BANK_3


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MOV A, R0 MOV B, #0 CJNE A,B, DIV_AGAIN_2 JMP DIV_STOP DIV_AGAIN_2: MOV A, R0 MOV B, #10 MUL AB MOV R0, A MOV R1, B CALL DIV24 MOV A, R4 CALL BANK_1 MOV R1, A CALL BANK_3 MOV A, R0 MOV B, #0 CJNE A,B, DIV_AGAIN_3 JMP DIV_STOP DIV_AGAIN_3: MOV A, R0 MOV B, #10 MUL AB MOV R0, A MOV R1, B CALL DIV24 CALL BANK_1 MOV A, R1 RL A RL A RL A RL A MOV R1, A CALL BANK_3 ORL A, R4 CALL BANK_1 MOV R1, A CALL BANK_3 DIV_STOP: RET


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2. Tracker & Input Controller This part of the distributed system implements the MPPT algorithm using the Voltage, Current, Battery Voltage which are serially transferred from the Data Logger. In addition to this it also sets the required voltage of battery for the Control Check Algorithm for Battery Voltage by an input keypad. Also the whole circuitary can be made to operate at a desired Duty Cycle which is inputted by the same keypad. Some part of codes of the MPPT Algorithm and the Input Algorithms are presented: 6.2.4 Battery Voltage Testing ;-------------------------------------------BATTERY VOLTAGE TEST------------------------------------- BATTERY_TEST: CALL RBV_TEST ;Checking if the BSV is not Zero else it should be Default Value BV: ;------CONVERTING BATTERY VOLTAGE INTEGRAL PART IN DECIMAL VALUE------------------- MOV A, 42H ANL A, #11110000B SWAP A MOV B, #10 MUL AB MOV B, A MOV A, 42H ANL A, #00001111B ADD A, B MOV 57H, A ;-------CONVERTING BATTERY VOLTAGE FRACTIONAL PART IN DECIMAL VALUE---------- MOV A, 43H ANL A, #11110000B SWAP A MOV B, #10 MUL AB MOV B, A MOV A, 43H ANL A, #00001111B ADD A, B MOV 58H, A ;------CONVERTING REQUIRED VOLTAGE INTEGRAL PART IN DECIMAL VALUE---------- MOV A, 4CH ANL A, #11110000B SWAP A MOV B, #10


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MUL AB MOV B, A MOV A, 4CH ANL A, #00001111B ADD A, B MOV 59H, A ;-----ONVERTING REQUIRED VOLTAGE FRACTIONAL PART IN DECIMAL VALUE---------- MOV A, 4DH ANL A, #11110000B SWAP A MOV B, #10 MUL AB MOV B, A MOV A, 4DH ANL A, #00001111B ADD A, B MOV 5AH, A ;------CONVERTING PANEL VOLTAGE INTEGRAL PART IN DECIMAL VALUE---------- MOV A, 40H ANL A, #11110000B SWAP A MOV B, #10 MUL AB MOV B, A MOV A, 40H ANL A, #00001111B ADD A, B MOV 5BH, A ;------CONVERTING PANEL VOLTAGE FRACTIONAL PART IN DECIMAL VALUE---------- MOV A, 41H ANL A, #11110000B SWAP A MOV B, #10 MUL AB MOV B, A MOV A, 41H ANL A, #00001111B ADD A, B MOV 5CH, A ;-------PANEL CONDITION TESTING----------------------------------- PC: CLR C MOV A, 57H SUBB A, 5BH ;SUBTRACTING INTEGRAL PART OF BV AND PV VALUES JC BC ;JUMPING TO CHARGE IF PV IS LARGER THAN BC MOV B, #0 CJNE A, B, NO_CHARGE ;CHECKING IF THE INTEGRAL VALUE ;CALCULATED ARE EXACTLY EQUAL OR NOT P_B_EQUAL: MOV A, 58H SUBB A, 5CH ;SUBTRACTING THE FRACTIONAL PART OF A AND B VALUES JC BC ;JUMPING TO CHARGE IF FRACTIONAL RV PART ;IF LARGE THAN BC MOV B, #0


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CJNE A, B, NO_CHARGE ;CHECKING IF THE FRACTIONAL VALUE ;CALCULATED ARE EXACTLY EQUAL OR NOT MOV R7, #0 ;INDICATION R7 TO KNOW THAT THEY ARE ;EXACTLY EQUAL JMP BATTERY_CONCLUSION 6.2.5 MPPT Algorithm (Calculating P1 after decrementing Duty Cycle) ;-------------------------------------------MPPT-ALGORITHM------------------------- MPPT: CALL BANK_0 MOV R2, 66H ;------------------------------------A CALCULATION---------------------------- A_CALCULATION: MOV A, R2 MOV R3, A MOV A, R3 MOV B, #0H CJNE A, B, A_1 JMP A_2 A_1: DEC R3 DEC R3 A_2: MOV P2, R3 ;CHANGING THE DUTY CYCLE ON PORT 2 MOV 66H, R3 CALL D_DELAY ;CALL D_DELAY MOV A, 46H MOV 54H, A MOV A, 47H MOV 55H, A CALL VALUE_DECIMAL MOV A, 54H MOV 50H, A MOV A, 55H MOV 51H, A


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6.2.6 BLOCK ALWAYS RUNNING (Moving in jump statements) ;-----------------------------------------ALWAYS BLOCK---------------------------------- BACK: CALL DC_CALC ;Calculting DC for Display at 4Ah, 4Bh CALL CHECK_INPUT_BUTTON ;Checking Input for RBVI or DCI ;Starting MPPT After Battery and PC Check if ViceVersa SJMP BACK


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3. Display Controller This part of the Controller displays the following items

1. Panel Voltage 2. Battery Voltage 3. Panel Current 4. Panel Power 5. Required Battery Voltage 6. Duty Cycle

on the LED display. It gets all these values serially from the Tracker or Input Controller. Some codes of this software section belonging to Display Controller are shown below: 6.2.7 Button Selection for Value to be Displayed ;----------------------------------BUTTON---------------------------- BUTTON: JB P3.2, B13 JB P3.3, B12 JB P3.5, B2 JMP B1 B1: JB P3.6, B4 JMP B3 B2: JB P3.6, B6 JMP B5 B3: JB P3.7, B8 JMP B7 B4: JB P3.7, B10 JMP B9 B5: JB P3.7, B12 JMP B11 B6: JB P3.7, B14 JMP B13 B7: MOV R3, #1 MOV R0, #2 RET B8: MOV R3, #2 MOV R0, #2 RET B9:


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MOV R3, #3 MOV R0, #2 RET B10: MOV R3, #4 MOV R0, #3 RET B11: MOV R3, #5 MOV R0, #2 RET B12: MOV R3, #6 MOV R0, #3 RET B13: MOV R3, #7 MOV R0, #2 RET B14: RET 6.2.8 Serially Receiving Data from Tracker & Input Controller Code SERIAL: JB TI, TRANS MOV 60H, A MOV 61H, B MOV 62H, PSW MOV 64H, SBUF ;copy received data CALL VALUE_R CALL CHECK_R MOV A, 60H MOV B, 61H MOV PSW, 62H CLR RI ;clear RI RETI TRANS: CLR TI ;do nothing RETI ;ISR does not handle TXend ;---------CHECKING R4 FOR NO OF VALUE ENTERED OR TO BE ENTERED (RECIEVE)-------- CHECK_R: MOV A, 63H MOV B, #15 CJNE A,B, INC_R MOV 63H, #0 RET INC_R: MOV A, 63H INC A MOV 63H, A


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RET ;------------VALUE RECIEVING WITH RESPECT TO ITS ORIGINAL CODE (RECIEVE)----------- VALUE_R: V1: MOV A, 63H MOV B, #0 CJNE A, B, V2 MOV A, 64H MOV 40H, A RET V2: MOV A, 63H MOV B, #1 CJNE A, B, V3 MOV A, 64H MOV 41H, A RET V3: MOV A, 63H MOV B, #2 CJNE A, B, V4 MOV A, 64H MOV 42H, A RET V4: MOV A, 63H MOV B, #3 CJNE A, B, V5 MOV A, 64H MOV 43H, A RET V5: MOV A, 63H MOV B, #4 CJNE A, B, V6 MOV A, 64H MOV 44H, A RET V6: MOV A, 63H MOV B, #5 CJNE A, B, V7 MOV A, 64H MOV 45H, A RET V7: MOV A, 63H MOV B, #6 CJNE A, B, V8 MOV A, 64H MOV 46H, A RET V8:


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MOV A, 63H MOV B, #7 CJNE A, B, V9 MOV A, 64H MOV 47H, A RET V9: MOV A, 63H MOV B, #8 CJNE A, B, V10 MOV A, 64H MOV 48H, A RET V10: MOV A, 63H MOV B, #9 CJNE A, B, V11 MOV A, 64H MOV 49H, A RET V11: MOV A, 63H MOV B, #10 CJNE A, B, V12 MOV A, 64H MOV 4AH, A RET V12: MOV A, 63H MOV B, #11 CJNE A, B, V13 MOV A, 64H MOV 4BH, A RET V13: MOV A, 63H MOV B, #12 CJNE A, B, V14 MOV A, 64H MOV 4CH, A RET V14: MOV A, 63H MOV B, #13 CJNE A, B, V15 MOV A, 64H MOV 4DH, A RET V15: MOV A, 63H MOV B, #14 CJNE A, B, V16 MOV A, 64H MOV 4EH, A RET


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V16: MOV A, 63H MOV B, #15 CJNE A, B, VALUE_RET MOV A, 64H MOV 4FH, A RET VALUE_RET: RET

Chapter 7 SIMULATIONS

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7 SIMULATIONS Simulations of the circuits developed were done in the following softwares for the validations of the results: 1 Protues v6.3 2. Orcad v10.0 3. Pspice 7.1 Solar Tracker Simulations Since all the implementation of ideas was purely my effort, step by step conversion of programs was done to reach the final software embedded in the micro-controller. Firstly a digital clock was made which did not used Interrupt. It had problem of accuracy. Its circuit implemented in the simluation software Proteus are presented for review on the next page Due to the lack of accuracy I shifted the digital clock to interrupt based and now adding the relay mechanism to reverse the polarity of the 36V DC supply applied to the Linear Actuator speed motor. Simulated circuit is presented in the subsequent pages to follow. Also the 36V DC Supply Simulations in Orcad are shown


73

Sim

ulat

ed S

olar

Tra

cker

Circ

uit

Fig

7.1.

1


74

Prac

tical

Sol

ar T

rack

er C

ircui

t

Fig

7.1.

2


75

36V

Reg

ulat

ed D

C S

uppl

y

Fig

7.1.

3


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7.1.1 Simulation Results

Fig 7.1.4


77

7.2 MPPT Controller Simulations Since the micro-controller used is the AT89S51, Proteus provides a good simulations for these micro-controller so I used it for the MPPT Controller too. Before using any component or interfacing it with the micro-controller, I tried to use it independantly so to work out all the control specifications needed. Those circuits are also included in the diagrams presented below 7.2.1 ADC Simulation Testing the ADC using the below circuit

Fig 7.2.1


78

7.2.2 DAC Simulation DAC Simulations using the Op-amp to get the final voltage level 7.2.3 Tracker & Input Controller Keypad Simulations

Fig 7.2.2

Fig 7.2.3


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7.2.4 MPPT Controller (not showing the MOSFET Driver & MOSFET)

MPP

T C

ontr

olle

r Circ

uit

Fig

7.2.

4


80

7.2.5 MOSFET Driver & MOSFET

MO

SFET

Driv

er &

MO

SFET

Fig

7.2.

5


81

7.2.6 Mosfet Driver Simulation Results (Graphs)

Fig

7.2.

6


82

Fig

7.2.

7

Chapter 8 HARDWARE

83

8 HARDWARE

Being a big project, hardware for different items were to be developed. Hardware were done in the following order 1. 36V DC Supply 2. Time Dependant Solar Tracker 3. MPPT Controller 4. MOSFET Driver & MOSFET 8.1 DC Supply The hardware used in this is as follows S.No Item Quantity

1 220V AC to 40V AC Transformer 1 2 Diode 2A Rating 4 3 2200uF Capacitor 1 4 2SD1051 (2A npn Transistor) 1 5 2SC1384 (Driver Transistor) 1 6 Zener 3.3V 1 7 Resistance 220Ω, 1KΩ, 3.77KΩ 1 each

All this hardware was implemented on a varo-board and installed in a box which supplies the 36 V supply to the Time Dependant Solar Tracker.

Chapter 8 HARDWARE

84

8.2 Time Dependant Solar Tracker The hardware used in this is as follows S.No Item Quantity

1 AT89S51 1 2 74LS47 1 3 2N3904 as Driver Transistor 5 4 2N3906 as Relay Driver 2 5 7 Segment Display 1 6 Relay (5V) 2 7 Resistance 10KΩ, 4.7KΩ 5 each 8 Resistance 35Ω 2 9 78L05 Regulator 1

10 LED 4 All these items on two varo-boards.

Chapter 8 HARDWARE

85

8.2.1 Hardware Abstracts:

• Ports & Pins Classification:

Pin # Work Color of Wire P0.0 Relay 1 Turn-On Bit Yellow P0.1 Relay 2 Turn-On Bit Green P0.2 Blue LED (Jan-March) Black P0.3 Green LED (April-June) Light Purple P0.4 Red LED (July-Sept) Red P0.5 Yellow LED (Oct-Dec) Green P0.6 P0.7 P1.0 Digit # 1 Select on Display P1.1 Digit # 2 Select on Display P1.2 Digit # 3 Select on Display P1.3 Digit # 4 Select on Display P1.4 Blue LED Button (Jan-March) Dark Purple P1.5 Green LED Button (April-June) Brown P1.6 Red LED Button (July-Sept) Orange P1.7 Yellow LED Button (Oct-Dec) Grey P2.0 Bit 0 for 74LS47 Chip (Display) P2.1 Bit 1 for 74LS47 Chip (Display) P2.2 Bit 2 for 74LS47 Chip (Display) P2.3 Bit 3 for 74LS47 Chip (Display) P2.4 P2.5 P2.6 P2.7 P3.0 P3.1 P3.2 Button for Fast Minute Movement Yellow P3.3 Button for Fast Hour Movement Blue P3.4 Button for Force Movement (Clockwise) White

P3.5 Button for Force Movement (Anti-Clockwise)

Bluish Black

P3.6 Blinking Dots in Display Input P3.7 Blinking Dots in Display Output

Chapter 8 HARDWARE

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8.3 MPPT Controller The hardware used in this is as follows S.No Item Quantity

1 AT89S51 3 2 74LS47 1 3 74LS148 1 4 ADC0808 1 5 DAC0808 1 6 TL494 1 7 LM358 1 8 LM1458L 1 9 74LS373 2

10 NE555 1 11 LED 4 12 12MHz Oscillator 3 13 Capacitor 10uF 5 14 Capacitor 0.1uF 2 15 Capacitor 22uF 1 16 Resistance 4.7K Ω 4 17 Resistance 35Ω, 10K Ω 5 each 18 4 x 3 Keypad 1 19 78L05 Regulator 1 20 7 Segment Display 1 21 Capacitor 500pF 2

Chapter 8 HARDWARE

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8.4 MOSFET Driver & MOSFET The hardware used in this is as follows S.No Item Quantity

1 IRF540 1 2 Diode 6A 1 3 Capacitor 2200uF 1 4 Resistance 1.5Ω (5W) 2 5 Resistance 1KΩ (2W) 1 6 Resistance 47KΩ (2W) 1 7 BD139 1 8 BD140 1 9 Zener 3.3V 2

10 Capacitor 47uF 2 11 Capacitor 0.1uF 2

It is a high power circuit so it is preferable to keep it away from the sensitive electronic circuit comprising of the Micro-controllers.

Chapter 8 HARDWARE

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Sola

r Mod

ule

Stan

d So

lar T

rack

er

Chapter 8 HARDWARE

89

Solar Tracker with Power Supply

Batteries with Inverter

Chapter 8 HARDWARE

90

MPP

T C

ontr

olle

r with

Sol

ar T

rack

er a

nd P

ower

Sup

ply

Chapter 9 RESULTS

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9 RESULTS The results achieved were encouraging in the sense that it resembled a great resemblance in the simulated results and the practical results. Although the inductor value in between the MOSFET and the Battery could not be decided because there was a large difference in the simulated and the practical value but the MOSFET Switching at 10Khz produced an isolation between the Solar Panel and the Battery and due to the duty cycle variation the panel worked at the maximum Power Point Voltage of the available conditions. The Solar Tracker successfully tracked the sun for 3 months for which it was intended. For the next months the settings were to be re-programmed taking in consideration the positions of sun round the day. The Digital Clock included in this design was a great success which almost performed with accuracy with an error of 2 min/20days.

Chapter 10 RENEWABLE ENERGY RESOURCES

92

10 RENEWABLE ENERGY RESOURCES Apart from the Solar Photovoltaic energy discussed in the above chapters, there are various other forms of energy as well which are categorized as Alternate or Renewable Energy Resources. These are the following

1. Solar Thermal Energy

2. Wind Energy 3. Tidal Energy

A brief knowledge of these is given in this text. 10.1 Solar Thermal Energy Solar thermal power plants use the sun's rays to heat a fluid, from which heat transfer systems may be used to produce steam. The steam, in turn, is converted into mechanical energy in a turbine and into electricity from a conventional generator coupled to the turbine. Solar thermal power generation is essentially the same as conventional technologies except that in conventional technologies the energy source is from the stored energy in fossil fuels released by combustion. Solar thermal technologies use concentrator systems due to the high temperatures needed for the working fluid. The three types of solar-thermal power systems in use or under development are:

1. Parabolic Trough 2. Central Reciever 3. Dish Reciever


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In the figure, a schematic of a large-scale solar thermal power station developed, designed, built, tested, and operated with the U.S. Department of Energy funding. In this plant, the solar energy is collected by thousands ofsun-tracking mirrors, called heliostats, that reflect the sun’s energy to a single receiver atop a centrally located tower. The enormous amount of energy focused on the receiver is used to generate high temperature to melt a salt.The hot molten salt is stored in a storage tank, and is used, when needed,to generate steam and drive the turbine generator. After generating the steam, the used molten salt at low temperature is returned to the cold salt storage tank. From here it is pumped to the receiver tower to get heated again for the next thermal cycle. The usable energy extracted during such athermal cycle depends on the working temperatures.

Fig 10.1.1


94

A major benefit of this scheme is that it incorporates the thermal energy storage for duration in hours with no degradation in performance, or longer with some degradation. This feature makes the technology capable of producing high value electricity for meeting peak demands. Moreover, compared to the solar photovoltaic, the solar thermal system is economical, as it eliminates the costly semiconductor cells. 10.1.1 Parabolic Trough The parabolic trough system is by far the most commercially matured of thethree technologies. It focuses the sunlight on a glass-encapsulated tube run-ning along the focal line of the collector. The tube carries heat absorbing liquid, usually oil, which in turn, heats water to generate steam. More than 350 MW of parabolic trough capacity is operating in the California Mojave Desert and is connected to the Southern California Edison’s utility grid. This is more than 90 percent of the world’s solar thermal capacity at present.

Fig 10.1.2


95

10.1.2 Central Reciever In the central receiver system, an array of field mirrors focus the sunlight on the central receiver mounted on a tower. To focus the sun on the central receiver at all times, each heliostat is mounted on the dual-axis suntracker to seek position in the sky that is midway between the receiver and the sun.Compared to the parabolic trough, this technology produces higher concentration, and hence, higher temperature working medium, usually a salt.Consequently, it yields higher Carnot efficiency, and is well suited for utilityscale power plants in tens or hundreds of megawatt capacity.

World’s Largest Solar Thermal Power Plant in

California Mojave Desert

Fig 10.1.3


96

10.1.3 Dish Reciever The parabolic dish tracks the sun to focus heat, which drives a sterling heat engine-generator unit. This technology has applications in relatively small capacity (tens of kW) due the size of available engines and wind loads on the dish collectors. Because of their small size, it is more modular than other solar thermal power systems, and can be assembled in a few hundred kW to few MW capacities. This technology is particularly attractive for small stand-alone remote applications. 10.2 Wind Energy The wind energy stands out to be one of the most promising new sources of electrical power in the near future. Many countries promote the wind-power technology by national programs and market incentives.

Fig 10.1.4


97

The average turbine size of the wind installations has been 300 kW until the recent past. The newer machines of 500 to 1,000 kW capacity have beendeveloped and are being installed. Prototypes of a few MW wind turbinesare under test operations in several countries, including the U.S.A. Improved turbine designs and plant utilization have contributed to adecline in large-scale wind energy generation costs from 35 cents per kWhin 1980 to less than 5 cents per kWh in 1997 in favorable locations At this price, wind energy has become one of the least-costpower sources. Major factors that have accelerated the wind-power technol-ogy development are as follows:

1. High-strength fiber composites for constructing large low-cost blades

2. Falling prices of the power electronics 3. Variable-speed operation of electrical generators to capture

maxi-mum energy 4. Improved plant operation, pushing the availability up to 95

percent 5. Economy of scale, as the turbines and plants are getting larger

in size 6. Accumulated field experience (the learning curve effect)

improving the capacity factor. In Pakistan wind corridor has been discovered where average summer wind direction from Gharo to Hyderabad flows where a considerable amount of power could be generated. For this AEDB is doing wonderful work for inviting investors to Pakistan. Due to the efforts about 700MW capacity would be installed till early 2007 in Private sector. Fig 10.2.1


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10.3 Tidal Energy Tidal energy is the utilization of the sun and moon's gravitational forces - as the tide is the result of their influences. Like other alternative energies, tidal energy is not really anything new. Tidal-power is the power achieved by capturing the energy contained in moving water mass due to tides. Two types of tidal energy can be extracted: kinetic energy of currents between ebbing and surging tides and potential energy from the difference in height (or head) between high and low tides. The former method - generating energy from tidal currents - is considered much more feasible today than building ocean-based dams or barrages, and many coastal sites worldwide are being examined for their suitability to produce tidal (current) energy. The tide moves a huge amount of water twice each day, and harnessing it could provide a great deal of energy

These work rather like a hydro-electric scheme, except that the dam is much bigger. A huge dam (called a "barrage") is built across a river estuary. When the tide goes in and out, the water flows through tunnels in the dam.

The ebb and flow of the tides can be used to turn a turbine, or it can be used to push air through a pipe, which then turns a turbine. Large lock gates, like the ones used on canals, allow ships to pass.

The largest tidal power station in the world (and the only one in Europe) is in the Rance estuary in northern France. It was built in 1966.

Fig 10.3.1


99

10.3.1 Advantages

The major advantage of tidal energy is its economical benefits. For example, tidal energy does not require any fuel. Tides rise and fall every day in a very consistent pattern. Another benefit is the economic life of a tidal power plant. A plant is expected to be in production for 75 to 100 years, in comparison with the 35 years of a conventional fossil fuel plant. Besides the economical factors, tidal energy is clean and renewable, unlike fossil fuels.

10.3.2 Disadvantages The altering of the ecosystem at the bay is the biggest drawback of tidal power. Damages like reduced flushing, winter icing and erosion can change the vegetation of the area and disrupt the balance. Similar to other ocean energies, tidal energy has several prerequisites that make it only available in a small number of regions. Another option is to use offshore turbines, rather like an underwater wind farm. This has the advantage of being much cheaper to build, and does not have the environmental problems that a tidal barrage would bring.

Fig 10.3.2


100

A tidal power scheme is a long-term source of electricity. More importantly, as the fossil fuel resource is likely to be eliminated by the end of the twenty-first century, tidal power is one of the alternative source of energy that will need to be developed to satisfy the human demand for Energy.

Fig 10.3.3

Chapter 11 APPENDIX

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11 APPENDIX

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