Solar electricity

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Introduction of solar Electricity & Proposed Block Diagram 1.1 Introduction Energy is the most basic and essential of all resources .All the energy we use on Earth comes from fission or fusion of atomic nuclei or from energy store in the Earth. The problem with both fission and fusion is that, they have dangerous radioactivity and side effect. Therefore, most of the generation of energy in our modern industrialized society is strongly depending on very limited non-renewable resources such as petroleum. As the world’s energy demands rise and resources become scarce, the petroleum is getting more and more expensive. The search for alternative energy resources has become an important issue for our time. The people seek for new green and unlimited energy sources, e.g. wind energy, water energy, solar energy, etc. The most effective, reliable and harmless energy source is probably solar energy. Solar energy can be harvested by the use of photovoltaic (PV) array. But, there are still some drawbacks as follow: the install cost of solar panels is high, and the conversion efficiency is still lower. PV array has an optimum operating point to extract the maximum power called the maximum power point (MPP), which varies depending on cell temperature and insulation level 1.2 Power from the sun The sun has been worshipped as a life-giver to our planet since ancient times. The industrial ages gave us the understanding of sunlight as an energy source. This discovery has never been more important than now as we realize that the exploitation of fossil energy sources is affecting the planet's ambient temperature.

The sun is humanity’s oldest energy source , scientists and engineers have long sought to harness the power of sunlight for a wide range of heating, lighting, and industrial tasks. Every child knows that focused sunlight is hot enough to set things afire; engineers and scientists know that every square meter of the earth receives 1 kilowatt of thermal energy when the sun is over heat. All solar thermal system capture the energy of the sun by absorbing light as heat.

Solar thermal systems focus sunlight ,usually with mirrors, to heat a fluid to high temperatures and drive an engine. Photovoltaic solar power systems, in which light interacts with special materials directly to separate charges and generate electricity.

Types of solar energy conversion:  Photovoltaic solar power system  Solar thermal power system 1.3 Solar heat into electricity Producing electricity from the energy in the sun’s rays is a straightforward process: direct solar radiation can be concentrated and collected by a range of concentrating solar power technologies to provide medium to high temperature heat this heat is then used to operate a conventional power cycle through a steam turbine solar heat collected during the day can also be stored in liquid or solid media .At night, it can be extracted from the storage medium and ,thus, continues turbine operation.

1.4 Solar thermal conversion system The hot thermo fluid is used to generated steam or hot gases, which are then used to operate a heat engine. In these systems, the efficiency of the collector reduces marginally as its operating temperature increases, whereas the efficiency of the heat engine increases with the increase in its operating temperature.

1.5 Solar Power-Advantages and Disadvantages There are two sides to everything, and there is a list of solar power disadvantages to accompany the list of advantages.

Advantage: • • • • • • • •

Solar energy is a completely renewable resourceo.

Solar energy is renewable unlike the conventional resources (coal, oil) which will inevitably run out.

Non-polluting, no carbon dioxide like fossil fuels Free except for capital expenses.

Longevity - solar panels can last over twenty years Low maintenance - solar panels require very little upkeep Independence - an off-grid system allows you to break free from the electrical grid It is free

Disadvantage: • • • •

Takes up a lot of space, Only works when Sun is shining.

It doesn't produce much electricity for one single panel.

It is extremely expensive.

1.6 Proposed Block Diagram Block diagram is a diagram of a system, in which the principal parts or functions are represented by blocks connected by lines, that show the relationships of the blocks. They are heavily used in the engineering world in hardware design, electronic design, software design, and process flow diagrams.

A block diagram is a useful tool both in designing new processes and in improving existing processes. In both cases the block diagram provides a quick, high-level view of the work and may rapidly lead to process points of interest. Because of its high-level perspective, it may not offer the level of detail required for more comprehensive planning or analysis. Team members who construct a block diagram must have a clear understanding of how the process operates.

Fig.1.1: Proposed Block Diagram The system includes a photovoltaic array, a PWM controller DC_DC converter and Sensing circuit. The designed controller regulates the converter output voltage by varying duty cycle of the PWM signal using maximum Power point algorithm and it maximizes the output power extracted from PVarray.

MPPT is assured by varying duty cycle of the PWM signal to control MOSFET switch applied to a boost Converter. The control logic is implemented to a Microcontroller AT Mega 48.

Photovoltaic Solar Electricity 2.1 Introduction We know solar energy means all the energy that reaches the earth from the sun. It provides daylight make the earth hot and is source of energy for plants to grow. the energy supply from the sun is truly enormous on average earth surface receives about 1.2*10^17w of solar power. Most of the other renewable power generation also depends on the sun. Solar energy is also put two types of use to help our lives directly as solar heating and solar electricity.

2.2 Solar electricity Solar electricity generated directly from sunlight using solar or photovoltaic cell. The word photovoltaic refers to an electric voltage caused by light.

Most solar cells are made of silicon, this is hard material that is either dark blue or red in appearance. As sunlight shines on the surface of the silicon, electricity is generated by a process known as photovoltaic effect. Each silicon solar cell produces about 0.4v.So solar cells are connected to together to produce a higher voltage that is more useful.

2.3 Application of solar electricity The main application for solar electricity is on remote but sunny areas that have no main electricity. Solar electricity is already used in many large project.

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Pumping water for drinking and irrigation.

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Lighting and signaling in a small stations alone railway line.

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Powering telecommunication stations.

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Grid connected photovoltaic system with battery storage.

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Grid connected photovoltaic system without battery storage.

• • •

Home: lighting, radio, cassette player, record player, television, cooling fan etc.

School: lighting, science laboratory apparatus, slide projector.

Hospital and office: lighting, refrigerator, laboratory, cooling fan etc.

2.4 Parts of a solar electric system A small solar electric system can be divided into five basic parts.

• Solar modules generate electricity from sunlight.

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Rechargeable batteries.

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Some type of control unit is necessary for all solar electric system.

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Long runs of wiring in a solar system require thick cable to avoid a large drop of voltage.

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A voltage adaptor to reduce the voltage or a power inverter to increase the voltage and change it to ac.

2.5 Solar cells Solar cells are devices which convert solar energy directly into electricity, either directly via the photovoltaic effect, or indirectly by first converting the solar energy to heat or chemical energy. The most common form of solar cells are based on the photovoltaic (PV) effect in which light falling on a two layer semi-conductor device produces a photo voltage or potential difference between the layers. This voltage is capable of driving a current through an external circuit and thereby producing useful work.

2.6 Solar Cell Structure

Fig.2.1: Solar Cell Structure A. Encapsulate - The encapsulate, made of glass or other clear material such clear plastic, seals the cell from the external environment.

B. Contact Grid- The contact grid is made of a good conductor, such as a metal, and it serves as a collector of electrons.

C. The Antireflective Coating (AR Coating)- Through a combination of a favorable refractive index, and thickness, this layer serves to guide light into the solar cell. Without this layer, much of the light would simply bounce off the surface.

D. N-Type Silicon - N-type silicon is created by doping (contaminating) the Si with compounds that contain one more valence electrons* than Si does, such as with either Phosphorus or Arsenic. Since only four electrons are required to bond with the four adjacent silicon atoms, the fifth valence electron is available for conduction.

E. P-Type Silicon- P-type silicon is created by doping with compounds containing one less valence electrons* than Si does, such as with Boron. When silicon (four valence electrons) is doped with atoms that have one less valence electrons (three valence electrons), only three electrons are available for bonding with four adjacent silicon atoms, therefore an incomplete bond (hole) exists which can attract an electron from a nearby atom.

F. Back Contact - The back contact, made out of a metal, covers the entire back surface of the solar cell and acts as a conductor.

2.7 Construction of solar cell The process of fabricating conventional single and polycrystalline silicon PV cells begins very simply by gradually semiconducting polysilicon a material processed from quartz and used extensively throughout the electronics industry. The polysilicon is then heated to melting temperature and trace amounts of boron are added to the melt to create P-type semiconductor material. Next, an ingot, or block silicon is formed, commonly using one of two methods: by growing a pure crystalline silicon ingot from a seed crystal draw from molten polysilicon or by casting the molten polysilicon in a block, creating a polycrystalline silicon material.

Next an anti-reflective coating is applied to the top surface of the cell, and electrical contacts are imprinted on the top surface of cell. An aluminized conductive material is deposited on the back surface of each cell, restoring the P-type properties of the back surface by displacing the diffused phosphorus layer.

Fig.2.2: Construction of solar cell 2.8 How do Solar Cells WorkTo understand the operation of a PV cell, we need to consider both the nature of the material and the nature of sunlight. Solar cells consist of two types of material, often p-type silicon and n-type silicon. Light of certain wavelengths is able to ionize the atoms in the silicon and the internal field produced by the junction separates some of the positive charges ("holes") from the negative charges (electrons) within the photovoltaic device. The holes are swept into the positive or p-layer and the electrons are swept into the negative or n-layer. Although these opposite charges are attracted to each other, most of them can only recombine by passing through an external circuit outside the material because of the internal potential energy barrier. Therefore if a circuit is made (see figure 3) power can be produced from the cells under illumination, since the free electrons have to pass through the load to recombine with the positive holes.

Fig. 2.3: The

Photovoltaic Effect in a Solar Cell The amount of power available from a PV device is determined by; • • •

the type and area of the material; the intensity of the sunlight; and the wavelength of the sunlight.

Fig.2.4: Graph showing current and voltage output of a solar cell at different light intensities.

An important feature of PV cells is that the voltage of the cell does not depend on its size, and remains fairly constant with changing light intensity. However, the current in a device is almost directly proportional to light intensity and size. When people want to compare different sized cells, they record the current density, or amps per square centimeter of cell area.

2.9 Types of silicon solar cell Three types of solar cells available in the market, they are:

Single crystal silicon cells: Made using cells saw cut from a single sylindrical crystal of silicon, this is most efficient for PV technologies. The main advantage of single crystal silicon sells are there high efficiencies, typically around 15%, resulting in slightly higher costs than other technologies.

Multicrystalline silicon cells: Made from cells cut from an ingot of melted recrystallined silicon. Multicrystalline silicon cells are cheaper to produce than Single crystal silicon, due to the simpler manufacturing process.

Amorphous silicon cells: Amorphous silicon cells are composed of silicon atoms in a thin homogeneous layer rather than a crystal structure and it absorb light more effectively than crystallined silicon so cell can be thinner. Amorphous silicon cells are cheaper to produce than Single crystal silicon, due to the simpler manufacturing process.

2.10 PV Panels As single PV cells have a working voltage of about 0.5 V, they are usually connected together in series (positive to negative) to provide larger voltages. Panels are made in a wide range of sizes for different purposes. They generally fall into one of three basic categories: Low voltage/low power panels are made by connecting between 3 and 12 small segments of amorphous silicon PV with a total area of a few square centimeters for voltages between 1.5 and 6 V and outputs of a few mill watts. They are used mainly in watches, clocks and calculators, cameras and devices for sensing light and dark, such as night lights.  Small panels of 1 - 10 watts and 3 - 12 V, with areas from 100cm2 to 1000cm2 are made by either cutting 100cm2 single or polycrystalline cells into pieces and joining them in series . The main uses are for radios, toys, small pumps, electric fences and trickle charging of batteries.  Large panels, ranging from 10 to 60 watts, and generally either 6 or 12 volts, with areas of 1000cm2 to 5000cm2 are usually made by connecting from 10 to 36 fullsized cells in series. They are used either separately for small pumps and caravan power or in arrays to provide power for houses, communications pumping and remote area power supplies (RAPS). 

2.11 Solar power and Bangladesh Bangladesh has an agriculture based low economy and 85% people live in rural area. Many of these rural areas people live too far from the national grid. As a result 57% people are disconnected from grid electricity so people use renewable energy such as kerosene, coal, rechargeable batteries. Yet Bangladesh is suffering from electricity crisis. Expert suggest that renewable energy is the main solution specially solar energy. To make the use of solar energy familiar and effective in Bangladesh many company NGO’s are working to provide solar energy in village.

2.12 Future development

A lot of research is going on develop the performance and reduce the manufacturing cost of solar cells. Apart from silicon, other material that are being investigated are gallium arsenide (GaAs), Cadmium sulfide (CdS), Cadmium tellurium (CdT), and Copper indium. The last material CIS is sensitive to the red and infrared parts of the sunlight spectrum that amorphous silicon does not absorb.

The market for photovoltaic cells is presently growing at about 30% per year, and the cost of panels is declining continuously in real terms (figure 9), due to both new technologies and mass production. There are confident predictions from leading PV manufacturers in USA, Japan and Europe that the price of PV power will be competitive with mains electricity within 10 years PV characteristic of a Solar Module 3.1 Introduction When designing a solar system and choosing a solar module, it is necessary to understand a little about how the electrical output of a module is affected by the different conditions.

Manufacturers usually provide a lot of information about there modules. The use solar modules are quite straightforward. Installation simply involves mounting the module at the correct angle and making connections to two terminal posts on the back. The manufacture of solar modules requires sophisticated equipment and techniques. This chapter explains what the information means and which specification are important for selecting the most suitable module.

3.2 Solar panel Solar panels get energy from the sun to create electricity. Solar panels make renewable energy. A common misconception about solar panels is that they produce energy from the sun's heat. They actually produce energy from the sun's light.

As far as a single solar panel can produce just limited amount of power, many installations contain several panels. This is known as a photovoltaic array. A photovoltaic installation typically includes an array of solar panels, an inverter, and interconnection wiring.

3.3 Modules Each silicon solar cell produces a little over 0.4 V d.c in bright sunshine. Higher voltage is produced when several cells are connected in series as in a module. For charging 12 V batteries, solar modules must produce a minimum of about 13 V at the battery terminals. The cells selected to make up one module are carefully matched by the manufacturers to ensure that they have the same output current. This is important since if just one cell gives a low current, the performance of the whole module is affected.

3.3.1 Module performance and lifetime Module performance is generally rated under standard test conditions (STC): irradiance of 1,000 W/m², solar spectrum of AM 1.5 and module temperature at 25°C.Electrical characteristics include nominal power (PMAX, measured in W), open circuit voltage (VOC), short circuit current (ISC, measured in amperes), maximum power voltage (VMPP), maximum power current (IMPP), peak power, kWp, and module efficiency (%).Nominal voltage refers to the voltage of the battery that the module is best suited to charge; this is a leftover term from the days when solar panels were only used to charge batteries. The actual voltage output of the panel changes as lighting, temperature and load conditions change, so there is never one specific voltage at which the panel operates. Nominal voltage allows users, at a glance, to make sure the panel is compatible with a given system. Open circuit voltage or V OC is the maximum voltage that the panel can produce when not connected to an electrical circuit or system. VOC can be measured with a meter directly on an illuminated panel's terminals or on its disconnected cable.The peak power rating, kWp, is the maximum output according under standard test conditions (not the maximum possible output).Solar panels must withstand heat, cold, rain and hail for many years. Many crystalline silicon module manufacturers offer a warranty that guarantees electrical production for 10 years at 90% of rated power output and 25 years at 80%.

3.3.2 Electrical Characteristics of modules Manufacturers often rate their modules their peak power. However ,peak power is not the best way of comparing different types and makes of modules.

What really matters is how quickly a module can charge up a battery. This is decided by the charging current in units of amperes (A) that the module can generated under different conditions.

The following details are an example of the specifications for a solar module(Under standard test conditions of 1000w/m2 25^0 C cell temperature, and 1.5 air mass) Power: Watts peak(w)

53 V 10w

Open circuit voltage(V):

22.5V

Short circuit current(A):

0.61A

Maximum Power Current(A)

0.56A(

)

Maximum Power Voltage(V)

18 V (

)

Dimension of Panel Weight

320*290*18mm 1.2 kgs

Irradiance TC 3.4 Open circuit voltage and short circuit current When a module faces the sun, a voltage can be measured between the positive and negative terminals on the back using a volt meter ,no current is flowing because no appliance has been connected yet, so this measurements is called the open circuit voltage or Voc. When an appliance or rechargeable battery is connected between the two terminals, a current flows from the module. The module now has a voltage less than Voc. By adding more load with another appliance in parallel, more current flows and the voltage gets lower again. For the highest current, the terminals of a module can be connected directly to each other. The voltage is now zero and the current is maximum. By shorting the terminals through an ammeter, the maximum current is measured and is called the short circuit current or Isc. 3.5 Solar Cell Equivalent Circuit To understand the electronic behavior of a solar cell, it is useful to create a model which is electrically equivalent, and is based on discrete electrical components whose behavior is well known. An ideal solar cell may be modeled by a current source in parallel with a diode in practice no solar cell is ideal, so a shunt resistance and a series resistance component are added to the model. The resulting equivalent circuit of a solar cell is shown on the left. Also shown, on the right, is the schematic representation of a solar cell for use in circuit diagrams.

I PV = N P I LG − N P I OS [e

G(

VPV + I PV RS ) −1 nS

]

I-V Characteristics I V C U R V E S A T2 5D e g r e ec e lc e u sC E L LT E M P E R A T U R E 4

3 .5

C U R R E N T ( A )

3

2 .5

2

1 .5

1

0 .5

2 5D e g r e ec e lc e u s 0 0

5

1 0

1 5 V O L T A G E ( V )

Fig 3.4: I-V Characteristics

2 0

2 5

3.6 Irradiance The amount of sunshine reaching the solar cells at any moment is reffered to by many names as like light intensity, light level, solar illumination, solar intensity, solar flux, solar radiation, insolation,irradiation and irradiance. Irradiance is often measured in units of watts per square meter (W/m2) and milliwates per square centimeter (mW/cm2).

3.6.1 Effect of irradiance The characteristics curve of I-V for one module at irradiances of 100 W/m2,500 W/m2, and 1000 W/m2 shows in Figure. The I-V curve at 1000 W/m2 is for a module that faces the sun directly.

The sun takes up many positions in the sky according to the time of day and the time of year. When the sun is exactly overhead in tropical countries, the module should be horizontal for maximum current

Fig 3.5: Effect of irradiance at various points When the sun is low in the sky at 30^0 above the horizone,the module should be tilted towards the sun at an angle of 60^0 from horizontal for maximum current. However ,modules are usually fixed in one position ,so they face the sun directly at only a few times .When a module is facing away from the sun,the irradiance actually on the module is less.For example, when the sun is 30^0 above the horizon and the module is mounted horizontally, the irradiance on the cells is about half the value of 1000W/m2 when the sun is overhead.

The effect of this on the current is shown by the 500w/m2 I-V curve in figure. Therefore the current from a module fixed in one position varies through the day, even when the weather is clear with no cloudes. The charging current rises during the morning, reaches its high level at midday, and then falls during the afternoon. Most charging of a battery happens over a few hours in the middle of the day. It is possible to increase the irradiance above 1000w/m2 using mirrors or lenses to concentrate sunlight on the cells. However the irradiance may be uneven over the module which will cause over –heating and damage in cells receving less light.Also the whole module becomes hotter and extra cooling is then needed.

3.7: Effect of cell temperature As light shines on the solar cells, they warm up and the electrical output of the module changes. An irradiance of 1000w/m2 means the sun is shining directly on the module and it is found that the cells are warmer than the surrounding air by about 30^0.For the 1000 w/m2 IV curve,

Fig 3.6: Shows the effect of cell temperature

Fig.3.6: Shows the effect of cell temperature As the temperature rises above 0^0C,Voc falls while Isc gets slightly higher.

3.8 Advantages & Disadvantages of Solar Panels Advantages of Solar Panels: •

Installation and Maintenance: Since solar panels do not require fuel to operate, maintenance is kept at a minimum.

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Simple Storage: Solar panels are equipped with battery backup to store energy for times when the sun does not shine or there is a power outage.

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No Pollution: The use of solar panels for energy does not exacerbate the problems of acid rain, climate change, smog and the expensive storage of nuclear waste.

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Money Savings: Electricity bills may be substantially reduced if not eliminated. Moreover, fluctuations in the price of fossil fuel do not impact the cost of energy from solar panels.

Disadvantages of Solar Panels:  cost has historically been prohibitive for most potential consumers.  location will continue to be an issue for solar power use. Cloudy areas may  maintenance can be an issue. When your solar energy goes out, you can’t  just call the power company.  space for both storage batteries and solar panels can be an issue MPP Tracking 4.1 Introduction Energy is the most basic and essential of all resources .The most effective, reliable and harmless energy source is probably solar energy. Solar energy can be harvested by the use of photovoltaic (PV) array. But, there are still some drawbacks as follow: the install cost of solar panels is high, and the conversion efficiency is still lower. PV array has an optimum operating point to extract the maximum power called the maximum power point (MPP), which varies depending on cell temperature and insolation level, as shown in Fig.4 1 and Fig.4 2 respectively.

Fig 4.1: Maximum power varies with different cell temperature at the same insulation

Fig4.2: Maximum power varies with different isolation at the same temperature Variation in lighting intensity causes this trackers to deviate from the maximum power point when lighting conditions change, the tracker needs to response with in a short time to the change to avoid energy loss. Therefore, it is not easy to track the maximum power point of the PV cell quickly and effectively in the real application. To overcome this drawback, many MPPT algorithms were suggested for tracking the MPP of solar module . We have proposed a scheme as shown in Fig.4.3, based on the use of conventional DC-DC converter, where combination of voltage and power feedback control system is implemented with the use of artificial intelligence algorithm which results in a two-dimensional tracking strategy that makes tracking response faster and maximizes the power extracted from the solar module and the power delivered to the load. Maximum power point tracking is assured by varying duty cycle of the PWM signal to control MOSFET switch applied to a boost converter . The control logic is implemented to a microcontroller (ATMega48) with the use of algorithm.

Fig 4.3: MPPT system block diagram The results show how well this controller eliminates the complexity and maximizes the power extracted from the solar module and the power delivered to the load.

When a direct connection is carried out between the source and load, the output of the PV module is seldom maximum and the operating point is not optimal. So, a MPPT controller with a DC-DC converter is connected between the source and the load as shown in Fig.4. 3.

4.2 Maximum power point tracking (MPPT)

Maximum power point tracking frequently referred to as MPPT, is an electronic system that operates the photovoltaic modules in a manner that allows the modules to produce all the power they are capable of.

Fig4.4: Maximum Power Point Tracking

MPP is defined by

(n) 0When

(n) or

(n)then

the then the operation point is on the left (or right) of the MPP, and should be tuned toward opposite direction.

The power flow is controlled by varying the on/off duty cycle of the switching. The converter is operated at the switching frequency of 20 KHz. The average output voltage is determined by the Eq.

Where, OUT V is the output voltage IN V is the input voltage and D is the duty cycle of controllable switch.

4.3 Important of MPPT Most solar charge controllers on the market do not have MPPT function.

Typically, they can only harvest 50% to 70% of the maximum solar energy over 10 hours of daily charging.

In another word, 30% to 50% of the solar panel capacity is wasted. In contrast, a solar charge controller with MPPT function will increase the utilization efficiency of the solar panel; hence improve the net system conversion efficiency.

The end result: 30% to 50% increase in ROI (return on investment) for your solar power system

Fig.4.5: Necessity of a maximum power point tracker 4.4 How Maximum Power Point Tracking worksHere is where the optimization or maximum power point tracking comes in. Assume your battery is low, at 12 volts. A MPPT takes that 17.6 volts at 7.4 amps and converts it down, so that what the battery gets is now 10.8 amps at 12 volts Now you still have almost 130 watts, and everyone is happy. Ideally, for 100% power conversion you would get around 11.3 amps at 11.5 volts, but you have to feed the battery a higher voltage to force the amps in. And this is a simplified explanation - in actual fact the output of the MPPT charge controller might vary continually to adjust for getting the maximum amps into the battery.

If you look at the green line, you will see that it has a sharp peak at the upper right - that represents the maximum power point. What an MPPT controller does is "look" for that exact point, then does the voltage/current conversion to change it to exactly what the battery needs.

In real life, that peak moves around continuously with changes in light conditions and weather. A MPPT tracks the maximum power point, which is going to be different from the STC (Standard Test Conditions) rating under almost all situations. Under very cold conditions a 120 watt panel is actually capable of putting over 130+ watts because the power output goes up as panel temperature goes down - but if you don't have some way of tracking that power point, you are going to lose it. On the other hand under very hot conditions, the power drops - you lose power as the temperature goes up. That is why you get less gain in summer. MPPT's are most effective under these conditions: Winter, and/or cloudy or hazy days - when the extra power is needed the most. Cold weather - solar panels work better at cold temperatures, but without a MPPT you are losing most of that. Cold weathe is most likely in winter - the time when sun hours are low and you need the power to recharge batteries the most.

Fig.4.6: How Maximum Power Point Tracking works Low battery charge - the lower the state of charge in your battery, the more current a MPPT puts into them - another time when the extra power is needed the most. You can have both of these conditions at the same time. Long wire runs - If you are charging a 12 volt battery, and your panels are 100 feet away, the voltage drop and power loss can be considerable unless you use very large wire. That can be very expensive. But if you have four 12 volt panels wired in series for 48 volts, the power loss is much less, and the controller will convert that high voltage to 12 volts at the battery. That also means that if you have a high voltage panel setup feeding the controller, you can use much smaller wire Sensing Circuit 5.1 Introduction of Sensing Circuit The feedback circuit consists of a voltage sensor and a current sensor. The sensors provide analog data as an output. For further processing of these data, A/D conversion is needed.

Since ADC module contained in ATMega48 microcontroller and can work on voltage up to 5V, so it is an added advantage which reduces the cost of two A/D converters IC. The analog output of two sensors is connected to ADCO and ADC1 pin of ATMega48 microcontroller and the A/D conversion is completed by using software program. With a 10-bit ADC over the full range of mains voltage (0~30V) scaled to 0 to 5V. The resolution is 30/1024 or0.03V. This is too high a resolution called for.

5.2 Voltage sensor A Voltage sensor is a one kind of Electromagnetic sensors which can be defined as, An electronic device used to measure a physical quantity such as pressure or loudness and convert it into an electronic signal of some kind (e.g. a voltage).

5.2.1 Definition A voltmeter is a high impedance device that measures the voltage across a circuit. A device, such as a photoelectric cell, that receives and responds to a signal or stimulus.

5.2.2 Operation of Voltage sensor Voltage divider network is used as voltage sensor for the controller.

The voltage can be calculated by the voltage difference of two nodes as can be calculated by as following:

(From microcontroller)

-

.And

So, the voltage difference: So, the total voltage

:

5.2.3 Application • • • • • • • • •

as power demand control power failure detection load sensing safety switching motor overload control building control systems fault detection data acquisition temperature control

5.3 Current Sensor A current sensor is a device that detects electrical current (AC or DC) in a wire, and generates a signal proportional to it.

Technologies: • Current transfect IC current sensor • Resistor, whose voltage is directly proportional to the current through it.

5.3.1 Operation of Current sensor Shunt resistor (0.1Ω) is used as current sensor for the controller. By connecting a current resistor at the inputs of the differential amplifier, the current from the PV array passing through the resistor and gives rise to a voltage drop across it. The current can be measured by the following equation.

Measurement of current : Where,

(From voltage sensor calculation)

So, 5.3.2 Application of Current Sensor • • •

Measuring Contamination with a Current Sensor Sensing Failed HID Lighting To Detect a Failed Lamp

Fig.5.1: Simulation of Current sensor & Voltage sensor with ATMega48 & LCD

Fig.5.2: Hardware implementation of Current sensor & Voltage sensor with ATMega48 & LCD DC-DC Converter for MPPT section 6.1Introduction Power can also come from DC sources such as batteries, solar panels, rectifiers and DC generators. A process that changes one DC voltage to a different DC voltage is called DC to DC conversion. A boost converter is a DC to DC converter with an output voltage greater than the source voltage. A boost converter is sometimes called a step-up converter since it “steps up� the source voltage. Since power P=VI must be conserved, the output current is lower than the source current.

6.2 Definition A boost converter (step-up converter) is a power converter with an output DC voltage greater than its input DC voltage. It is a class of switching-mode power supply (SMPS) containing at least two semiconductor switches (a diode and a transistor) and at least one energy storage element. Filters made of capacitors (sometimes in combination with inductors) are normally added to the output of the converter to reduce output voltage ripple.

6.3 Design of DC-DC Converter

Fig.6.1: Circuit diagram of a boost converter The switch is typically a MOSFET, IGTB, or BJT. The DC/DC converters are widely used in regulated switch mode DC power supplies. The input of these converters is an unregulated DC voltage, which is obtained by PV array and therefore it will be fluctuated due to changes in radiation and temperature. In these converters the average DC output voltage must be controlled to be equated to the desired value although the input voltage is changing. From the energy point of view, output voltage regulation in the DC/DC converter is achieved by constantly adjusting the amount of energy absorbed from the source and that injected into the load, which is in turn controlled by the relative durations of the absorption and injection intervals. These two basic processes of energy absorption and

injection constitute a switching cycle. Intuitively speaking, if the energy storage capacity of the converter is too small or the switching period is relatively too long, then the converter would have transmitted all the stored energy to the load before the next cycle begins. This introduces an idling period immediately following the injection interval, during which the converter is not performing any specific task .The converter can therefore operate in two different modes depending upon its energy storage capacity and the relative length of the switching period. These two modes are known as the discontinues conduction and continuous modes.

6.3.1Inductor At this stage, it can be assumed that, • • •

The converter output voltage is constant at 12 Volts The converter is 100% efficiency Inductor current ripple can be varying between 10% and 20% of its dc value

•

Operating at frequency of 31 kHz (i.e. Ts= 10 µs)

The minimum inductance value:

Hence Inductor of 0.155mH and its rating current of 5.5 Amps with resistance of 63 Ω is chosen for the converter.

6.3.2 Capacitor At this stage, it can be assumed that,  

Output voltage ripple is 1% of its DC value Operating at frequency of 31 kHz =12v,

=20v,

=0.56A,f=31 kHz; K= 1-

The minimum Capacitance value: 0.16 µF is chosen for the design.

6.4 Circuit analysis

=1-

=0.4;

R=

= 40; Hence

The non-isolated boost DC-DC converter is widely used in stand alone PV system because it is simple, low cost and high efficiency. In general, the conversion efficiency is reading 90%.

So, the boost is suitable for simple stand alone system. Here we adopted this converter as our regulator Fig.4.3 depicts the circuits of the boost converter connected from the output of the solar cell. The power flow is controlled by varying the on/off duty cycle of the switching.

The converter is operated at the switching frequency of 20 KHz. The average output voltage is determined by the Eq.

Where, OUT V is the output voltage IN V is the input voltage and D is the duty cycle of controllable switch.

Fig.6.2: Hardware Implementation of a boost converter 6.5 MPPT operating at 20%,30 %,40% duty cycle

Fig.6.3: Hardware implementation (MPPT operating at 20%,30 %,40% duty cycle) 6.6 Operating principle The key principle that drives the boost converter is the tendency of an inductor to resist changes in current. In a boost converter, the output voltage is always higher than the input voltage. A schematic of a boost power stage is shown in Figure 6.4. When the switch is turned-ON, the current flows through the inductor and energy is stored in it. When the switch is turned-OFF, the stored energy in the inductor tends to collapse and its polarity changes such that it adds to the input voltage. Thus, the voltage across the inductor and the input voltage are in series and together charge the output capacitor to a voltage higher than the input voltage.

Fig.6.4: Boost converter schematic Fig.6 5: The two configurations of a boost converter, depending on the state of the switch S. The basic principle of a Boost converter consists of 2 distinct states (see figure6.4): • • •

in the On-state, the switch S (see figure 6.3) is closed, resulting in an increase in the inductor current; In the Off-state, the switch is open and the only path offered to inductor current is through the fly back diode D, the capacitor C and the load R. This results in transferring the energy accumulated during the On-state into the capacitor.

The input current is the same as the inductor current as can be seen in figure 2. So it is not discontinuous as in the buck converter and the requirements on the input filter are relaxed compared to a buck converter.

6.6.1 Continuous mode

Fig.6 6: Waveforms of current and voltage in a boost converter operating in continuous mode.

When a boost converter operates in continuous mode, the current through the inductor ( ) never falls to zero. Figure 3 shows the typical waveforms of currents and voltages in a converter operating in this mode. The output voltage can be calculated as follows, in the case of an ideal converter (i.e. using components with an ideal behaviour) operating in steady conditions: During the On-state, the switch S is closed, which makes the input voltage ( ) appear across the inductor, which causes a change in current ( ) flowing through the inductor during a time period (t) by the formula:

At the end of the On-state, the increase of IL is therefore:

D is the duty cycle. It represents the fraction of the commutation period T during which the switch is On. Therefore D ranges between 0 (S is never on) and 1 (S is always on).

During the Off-state, the switch S is open, so the inductor current flows through the load. If we consider zero voltage drop in the diode, and a capacitor large enough for its voltage to remain constant, the evolution of IL is:

Therefore, the variation of IL during the Off-period is:

As we consider that the converter operates in steady-state conditions, the amount of energy stored in each of its components has to be the same at the beginning and at the end of a commutation cycle. In particular, the energy stored in the inductor is given by:

So, the inductor current has to be the same at the start and end of the commutation cycle. This means the overall change in the current (the sum of the changes) is zero:

Substituting

and

by their expressions yields:

This can be written as:

Which in turn reveals the duty cycle to be:

From the above expression it can be seen that the output voltage is always higher than the input voltage (as the duty cycle goes from 0 to 1), and that it increases with D, theoretically to infinity as D approaches 1. This is why this converter is sometimes referred to as a step-up converter 6.7Applications Boost converters can increase the voltage and reduce the number of cells. Two batterypowered applications that use boost converters are hybrid electric vehicles (HEV) and lighting systems. Boost converters also power devices at smaller scale applications, such as portable lighting systems. Boost converters can also produce higher voltages to operate cold cathode fluorescent tubes (CCFL) in devices such as LCD backlights and some flashlights.

6.8 Duty Cycle of a Boost Converter

Fig.6.7: Duty Cycle of a Boost Converter at 20%, 30%, 40%

Liquid crystal display 7.1 Introduction The most common application of liquid crystal technology is in liquid crystal displays (LCDs). From the ubiquitous wrist watch and pocket calculator to an advanced VGA computer screen, this type of display has evolved into an important and versatile interface. A liquid crystal display consists of an array of tiny segments (called pixels) that can be manipulated to present information. This basic idea is common to all displays, ranging from simple calculators to a full color LCD television. Why are liquid crystal displays important?

The first factor is size. As will be shown in the following sections, an LCD consists primarily of two glass plates with some liquid crystal material between them. There is no bulky picture tube. This makes LCDs practical for applications where sizes (as well as weight) are important .Liquid crystal displays do have drawbacks, and these are the subject of intense research

7.2 Interfacing LCD with Microcontroller Frequently, an AVR program must interact with the outside world using input and output devices that communicate directly with a human being. One of the most common devices attached to an AVR is an LCD display. Some of the most common LCDs connected to the AVR are 16x2 and 20x2 displays. This means 16 characters per line by 2 lines and 20 characters per line by 2 lines, respectively.

Fortunately, a very popular standard exists which allows us to communicate with the vast majority of LCDs regardless of their manufacturer. The standard is referred to as HD44780U, which refers to the controller chip which receives data from an external source (in this case, the AVR) and communicates directly with the LCD. 7.2.1Features • • • • •

5 x 8 dots with cursor Built-in controller (KS 0066 or Equivalent) + 5V power supply (Also available for + 3V)1/16 duty cycle B/L to be driven by pin 1, pin 2 or pin 15, pin 16 or A.K (LED) N.V. optional for + 3V power supply

Fig7.5: Pin configuration of LCD 7.3 Pin Configuration

Most of the LCD Displays available in the market are 16X2 (That means, the LCD displays are capable of displaying 2 lines each having 16 Characters a), 20X4 LCD Displays (4 lines, 20 characters). It has 14 pins. It uses 8lines for parallel data plus 3 control signals, 2 connections to power, one more for contrast adjustment and two connections for LED back light. Let us have a look to typical pin configurations Pin Configuration table for a 16X2 LCD character display: Pin Number 1 2

Symbol

Function

Vss

Ground Terminal Positive Supply

Vcc Vdd RS

3 4 5

R/W E

6 7

DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 LED-(K) LED+(A)

8 9 10 11 12 13 14 15 16

Contrast adjustment Register Select; 0→Instruction Register, 1→Data Register Read/write Signal; 1→Read, 0→ Write Enable; Falling edge

Bi-directional data bus, data transfer is performed once, thru DB0 to DB7, in the case of interface data length is 8-bits; and twice, through DB4 to DB7 in the case of interface data length is 4-bits. Upper four bits first then lower four bits Back light LED cathode terminal Back Light LED anode terminal

Table7.1: Pin Configuration table for a 16X2 LCD character display 7.4 Code Command to LCD Instruction No. 1 2 3 4 5 6 7 8 9 10 11 12 13

Hex 1 2 4 6 5 7 8 A C E F 10 14

Resister Clear screen display Return home Decrement Cursor (Shift cursor to left) Increment Cursor (Shift cursor to right) Shift Display Right Shift Display Left Display off, Cursor off Display off ,Cursor on Display on, Cursor off Display on, Cursor Blinking Display on, Cursor Blinking Shift cursor position to Left Shift cursor position to Right

14 15 16

18 1C 80

Shift the entire display to the left Shift the entire display to the Right Force Cursor to beginning of the line

17

C0

Force Cursor to beginning of the

18

28

2 lines & 5×7 matrix (

19

38

2 lines & 5×7 matrix (

line

Table7.2: Code Command to LCD Instruction 7.5 Block Diagram of LCD Display

7.6. Basic structure of an LCD A liquid crystal cell consists of a thin layer (about 10 u m) of a liquid crystal sandwiched between two glass sheets with transparent electrodes deposited on their inside faces. With both glass sheets transparent, the cell is known as transitive type cell. When one glass is transparent and the other has a reflective coating, the cell is called reflective type. The LCD does not produce any illumination of its own. It, in fact, depends entirely on illumination falling on it from an external source for its visual effect 7.6.1 Making of LCD  Though the making of LCD is rather simple there are certain facts that should be noted while making it.  The basic structure of an LCD should be controllably changed with respect to the applied electric current.  The light that is used on the LCD can be polarized.  Liquid crystals should be able to both transmit and change polarized light.  There are transparent substances that can conduct electricity.

To make an LCD, you need to take two polarized glass pieces. The glass which does not have a polarized film on it must be rubbed with a special polymer which creates microscopic grooves in the surface. It must also be noted that the grooves are on the same direction as the

polarizing film. Then, all you need to do is to add a coating of nematic liquid crystals to one of the filters. The grooves will cause the first layer of molecules to align with the filter’s orientation. At right angle to the first piece, you must then add a second piece of glass along with the polarizing film.

7.7 Working principle of LCD We always use devices made up of Liquid Crystal Displays (LCDs) like computers, digital watches and also DVD and CD players. They have become very common and have taken a giant leap in the screen industry by clearly replacing the use of Cathode Ray Tubes (CRT).

CRT draws more power than LCD and are also bigger and heavier. All of us have seen an LCD, but no one knows the exact working of it. Let us take a look at the working of an LCD. Till the uppermost layer is at a 90-degree angle to the bottom, each successive layer of TN molecules will keep on twisting. The first filter will naturally be polarized as the light strikes it at the beginning. Thus the light passes through each layer and is guided on to the next with the help of molecules. When this happens, the molecules tend to change the plane of vibration of the light to match their own angle. When the light reaches the far side of the liquid crystal substance, it vibrates at the same angle as the final layer of molecules. The light is only allowed an entrance if the second polarized glass filter is same as the final layer. Take a look at the figure below

Fig.7.6: Working principle of LCD The main principle behind liquid crystal molecules is that when an electric current is applied to them, they tend to untwist. This causes a change in the light angle passing through them.

This causes a change in the angle of the top polarizing filter with respect to it. So little light is allowed to pass through that particular area of LCD. Thus that area becomes darker comparing to others.

For making an LCD screen, a reflective mirror has to be setup in the back. An electrode plane made of indium-tin oxide is kept on top and a glass with a polarizing film is also added on the bottom side. The entire area of the LCD has to be covered by a common electrode and above it should be the liquid crystal substance. Next comes another piece of glass with an electrode in the shape of the rectangle on the bottom and, on top, another polarizing film. It must be noted that both of them are kept at right angles. When there is no current, the light passes through the front of the LCD it will be reflected by the mirror and bounced back. As the electrode is connected to a temporary battery the current from it will cause the liquid crystals between the common-plane electrode and the electrode shaped like a rectangle to untwist.

Thus the light is blocked from passing through. Thus that particular rectangular area appears blank.

7.8 LCD connection with AT Mega 48

Fig.7.7: 3D connection of LCD with microcontroller 7.9 Specifications Important factors to consider when evaluating an LCD: • • •

Resolution versus range Spatial performance Temporal/timing performance.

7.10 Application • Computer monitor, television • instrument panels • aircraft cockpit display • video players(gaming devices, clocks ,watches, calculators & telephones) 7.11 Advantages and disadvantages In spite of LCDs being a well proven and still viable technology, as display devices LCDs are not perfect for all applications.

Advantages: • • • • • • • • •

In spite of LCDs being a well proven and still viable technology, as display devices LCDs are not perfect for all applications.

Very compact and light.

Low power consumption.

No geometric distortion.

Little or no flicker depending on backlight technology.

Not affected by screen burn-in.

Can be made in almost any size or shape.

No theoretical resolution limit.

No theoretical resolution limit.

Disadvantages: • Limited viewing angle, causing color, saturation, contrast and brightness to vary, even within the intended viewing angle, by variations in posture.

• Bleeding and uneven backlighting in some monitors, causing brightness distortion, especially toward the edges.

• Not all LCDs are designed to allow easy replacement of the backlight.

• Cannot be used with light guns/pens.

• Loss of contrast in high temperature environments.

Battery Storage of Electricity

8.1 Introduction Batteries are used in solar electricity systems to store electricity generated during daylight hours for later use .Rechargeable batteries are required for this purpose: the main ones used in solar electric systems are lead-acid batteries. These batteries are available in a variety of different types whose suitability for solar systems variety of different types whose suitability for solar systems varies a lot. The choice of which type to use is a matter of balancing a number of factors, because the most suitable types may be unavailable or too expensive.

8.2 Basics of rechargeable batteries Batteries are familiar to everyone as a convenient source of electricity. When a battery is in a circuit flows because of electrochemical changes taking place inside the battery which gradually discharges. Rechargeable batteries are the type that can be charged up from a d.c source and reused many times. The are also known as accumulators or storage batteries. The simplest operating unit of battery is called an electromechanical cell or just a cell. One cell produces a particular voltage depending on the materials it contains. The word ‘battery’ describes a group of cells connected in series. This is done to achieve a higher voltage than can be obtained from one cell, in the same way that solar cells are connected in series to form a solae module.

8.3 Unit of rechargeable battery

Although the coulomb(c) is the basic unit of charge in electricity, a more useful unit of charge for the measurement of battery capacity is the ampere-hour(A h).To measure the capacity of a cell, a fixed current is drawn and the number of hours that the cell can supply this current before complete discharge is counted.

Multiplying the current by the number of hours gives the capacity in Ah. As an example, a cell with a capacity specified as 80 A h can supply 8 A for 10 hour 4 A for 20h 8.4 Over- charging A cell is fully charged when all the discharged form of the active material on of the electrodes is converted to the charged form. If charging is continued, a different chemical reaction takes place at which electrode is fully charged.

One of the new reactions is decomposition of water that forms part of the electrolyte.

This is called gassing because bubbles appear on the surface of the electrodes. Water is made up of oxygen and hydrogen as H2O .During gassing; bubbles of oxygen are formed on the positive electrodes and bubbles of hydrogen on the negative electrodes. Slow gassing does not damage a cell, the gentile stirring action of the bubbles is beneficial because it breaks up any strafication of the electrolyte.

8.5 Self discharge All batteries gradually discharge of their own accord when not in use, this is called self discharge. The rate of self discharge is normally specified by the amount of charge, as a percentage of capacity ,that is lost over one month. It is related to how easily the plates gas when over- charging and increases at high operating temperatures.

8.6 Voltage measurement A cell or battery has a nominal voltage (Vnom).The actual voltage varies during normal operation. The voltage can be measured in three different states:  Open circuit voltage (Voc) when no current is flowing through the battery.  Voltage at load(Val)when a current is being drawn by appliances and the battery is discharging.  Charging voltage(Vch)when the battery is being charged up from a solar module.

8.7 Cycle depth The sequence of discharging and then charging back up to the state of charge at the state is called a cycle. The depth of discharge in one cycle depends on what the cell is being used for and is not always down to 0 percent state of charge. A shallow cycle is when a cell is discharged by only a few percent before being charged back up. In a deep cycle, the depth of discharge is 50 percent or more.

8.8 Cell life The natural of a cell is usually defined as when the fully charged capacity is reduced to 80 percent of its original value when the cell was new .This is a permanent loss of 20 percent of the capacity because of cycling and age.

8.9 Control units The electrical conditions of charging need to be controlled to prevent damage to a battery.

Sometimes the size of a solar module can be matched to a battery so that no damage is caused.A module is called self-regulating when used in this way. In other systems ,it is necessary to use a control unit to regulate churching. Control units may also be needed to prevent batteries being discharged too much. This is particularly necessary for lead-acid batteries.

8.10 Charging efficiency Churching efficiency compares the amount of charge used by the loads to the amount of charge needed to recharge the battery back to the original leave. An efficiency of per cent means that all the charge gonging in be recovered during discharge. When cycling up to 80 per cent state of charge, the charging efficiency is generally high at 90 percent or more for most types of battery. On approaching full charge, the charge, the charging efficiency decreases because of gassing which wastes charge. A low efficiency means that more solar module are needed for a given electrical requirement of the appliances.

8.11 Requirements for a solar system The operation of battery used in a solar system can be summarized by two types of cycling: 1.A shallow cycle each day.

2.Deep cycle over several days or weeks during cloudy weather and winter.

The deep cycles occur when charging during the day is not enough to replace the amount of charge used by the appliances over the whole day. Therefore the state of charge after each daily cycle is reduced slightly and this builds up to a deep cycle over a period of several days.

When the whether improves or the days lengthen, her is extra charging and the state of charge after each daly cycle gets higher. The characteristics required for a battery to parform well in a solar system: • High cycle life for deaf cycle.

•

Low maintenance requirements.

•

High charging efficiency.

•

Ability to survive complete discharge.

•

Low rate of self discharge.

•

Reliability.

•

Minimum charge in performance over temperature range of operation.

The next selections different types of lead-acid and nickel-cadmium batteries. The performance of these batteries is compared to the list of characteristics above to see how suitable they are for use in a solar system. Here is a list of other factors which it may be

necessary to consider when choosing a battery for a solar system. These factors relate to the setting up of a system:  Availability from suppliers.  Distance, duration, and cost of transport to site.  Cost of usable capacity over one cycle.  Cost of total usable capacity over cycle life.  Maintenance requirements during storage.  Weight.  Availability and cost of control units if required.

These factors may vary a lot between each type of battery and depend on the local circumstances at each site.

Program Algorithm & Embedded Software 9.1 Program Algorithm Most MPPT techniques attempt to find (search) the PV voltage that results in the maximum power point VMPP , or to find the PV current IMPP corresponding to the maximum power point. The proposed algorithm tracks neither the VMPP nor th IMPP. However, it tracks directly the maximum possible power PMAX that can be extracted from the PV. The flowchart of the proposed MPPT method is shown in Fig.9.1.

Fig.9.1: MPPT ALGORITHMS 9.2 Embedded Software Each peripheral to be used in the MPPT project was investigated and played with in these first few weeks. Most significantly, unit tests for the PWM and the ADC (using DMA) were developed. Each unit test was built with pre-defined pass/fail criteria. For the PWM unit test, the duty cycle of the PWM would be automatically, continuously varied through the entire operating range of the final MPPT project as defined by the DC-DC converter control pin specs. The test would pass if the PWM duty never exceeded or fell under the defined upper and lower limits and if the PWM duty was continuously increasing or decreasing. This test could run without interfacing with the DC-DC converter; an oscilloscope was hooked into the PWM pins of the controller and the test behavior was observed. For the ADC unit test, the result of an ADC conversion would be stored in a monitored variable. The reference analog signal was varied through a range of values and the variables value was recorded for each analog value. These recorded values were compared to calculated, expected values to verify operation.

9.2.1 Microcontroller program for Current & Voltage sensor $regfile = "m8def.dat" Config Adc = Single , Prescaler = Auto , Reference = Avcc Config Lcdpin = Pin , Db4 = Portd.4 , Db5 = Portd.5 , Db6 = Portd.6 , Db7 = Portd.7 , E = Portd.1 , Rs = Portd.0 Config Lcd = 16 * 2 Start Adc Dim W1 As Word , W2 As Word Dim Y As Single Cls Locate 1 , 1 : Lcd "Current(A)=" Locate 2 , 1 : Lcd "Voltage(V)=" Cursor Off Do W1 = Getadc(0) W2 = Getadc(1) W1 = W1 * 11

W2 = W2 * 11 W1 = W1 - W2 Y = W2 * 5 Y = Y / 1024 Locate 2 , 12 : Lcd " " Locate 2 , 12 : Lcd Y Y = W1 * 50 Y = Y / 1024 Locate 1 , 12 : Lcd " " Locate 1 , 12 : Lcd Y Waitms 500 Loop End

'5*10=50 10 is found from I=V_drop/0.1

'5*10=50 10 is found from I=V_drop/0.1

9.2.2 Microcontroller program for Boost converter $regfile = "m48def.dat" ' specify the used micro $crystal = 1000000 Set Ddrd.6 'Config Portd = Input Config Adc = Single , Prescaler = Auto , Reference = Avcc Config Lcd = 16 * 2 Config Lcdpin = Pin , Db4 = Portb.4 , Db5 = Portb.5 , Db6 = Portb.6 , Db7 = Portb.7 , E = Portb.1 , Rs = Portb.0 Tccr0a = &H83 Tccr0b = &H01 Ocr0a = 80 'dimension a variable that receives the value of the pressed key Dim W As Word Cls Locate 1 , 1 : Lcd "Duty=% " Locate 2 , 1 : Lcd "Adc_Value=" Start Adc Do W = Getadc(0) W=W Locate 2 , 12 : Lcd " " Locate 2 , 12 : Lcd W If W > 60 And W < 150 Then Ocr0a = 50 Locate 1 , 13 : Lcd "20" End If If W > 200 And W < 350 Then Ocr0a = 70 Locate 1 , 13 : Lcd "30" End If If W > 400 And W < 600 Then

Ocr0a = 100 Locate 1 , 13 : Lcd "40" End If If W > 700 And W < 1000 Then Ocr0a = 170 Locate 1 , 13 : Lcd "60" End If Waitms 50 Loop End Data Sheet 10.1 Introduction of AT mega 48 The ATmega48P is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the ATmega48P achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed.

10.1.2 Features  High Performance, Low Power AVR® 8-Bit Microcontroller  Advanced RISC Architecture • 131 Powerful Instructions – Most Single Clock Cycle Execution • 32 x 8 General Purpose Working Registers • Fully Static Operation • Up to 20 MIPS Throughput at 20 MHz • On-chip 2-cycle Multiplier  High Endurance Non-volatile Memory Segments • 4/8/16K Bytes of In-System Self-Programmable Flash progam memory • (ATmega48P/88P/168P) • 256Bytes EEPROM (ATmega48P) • 512Bytes Internal SRAM (ATmega48P) • Write/Erase Cycles: 10,000 Flash/100,000 EEPROM • Data retention: 20 years at 85°C/100 years at 25°C • Optional Boot Code Section with Independent Lock Bits  In-System Programming by On-chip Boot Program  True Read-While-Write Operation • Programming Lock for Software Security  Peripheral Features • Two 8-bit Timer/Counters with Separate Prescaler and Compare Mode • One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture  Mode • Real Time Counter with Separate Oscillator • Six PWM Channels • 8-channel 10-bit ADC in TQFP and QFN/MLF package  Temperature Measurement

• 6-channel 10-bit ADC in PDIP Package  Temperature Measurement • Programmable Serial USART • Master/Slave SPI Serial Interface • Byte-oriented 2-wire Serial Interface (Philips I2C compatible) • Programmable Watchdog Timer with Separate On-chip Oscillator • On-chip Analog Comparator • Interrupt and Wake-up on Pin Change  Special Microcontroller Features • Power-on Reset and Programmable Brown-out Detection • Internal Calibrated Oscillator • External and Internal Interrupt Sources • Six Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, Standby, and Extended Standby  I/O and Packages • 23 Programmable I/O Lines • 28-pin PDIP, 32-lead TQFP, 28-pad QFN/MLF and 32-pad QFN/MLF  Operating Voltage: • 1.8 - 5.5V for ATmega48P • 2.7 - 5.5V for ATmega48P  Temperature Range: • -40°C to 85°C  Speed Grade: • ATmega48P: 0 - 4 MHz @ 1.8 - 5.5V, 0 - 10 MHz @ 2.7 - 5.5V • ATmega48P: 0 - 10 MHz @ 2.7 - 5.5V, 0 - 20 MHz @ 4.5 - 5.5V  Low Power Consumption at 1 MHz, 1.8V, 25°C for ATmega48P • Active Mode: 0.3 mA • Power-down Mode: 0.1 μA • Power-save Mode: 0.8 μA (Including 32 kHz RTC)

Fig.10.1: AT Mega48 Microcontroller 10.1.3 Pin Configurations

Fig.10.2: Pin Configurations of AT mega 48 Pin Descriptions AT mega 48 VCC GND Port B (PB7..PB0) XTAL1/XTAL2/ TOSC1/ TOSC2

Port (PC5..PC0) PC6/RESET Port

Digital supply voltage.

Ground.

Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have high sink and source symmetrical drive characteristics with both capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active even if the clock is not running. Depending on the clock selection fuse settings, PB6 can be used as input to the inverting Oscillator amplifier and input to the internal clock operating circuit. Depending on the clock selection fuse settings, PB7 can be used as output from the inverting Oscillator amplifier. If the Internal Calibrated RC Oscillator is used as chip clock source, PB7..6 is used as TOSC2..1 input for the Asynchronous Timer/Counter2 if the AS2 bit in ASSR is set.

C Port C is an 7-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port C output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors are activated.

If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin. Note that the electrical characteristics of PC6 differ from those of the other pins of Port C. If the RSTDISBL Fuse is unprogrammed, PC6 is used as a Reset input.

D Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected

(PD7..PD0)

for each bit). The Port D output buffers have symmetrical drive characteristics with both high sink and sourc capability.

RESET Reset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock is not running.

AVCC AVCC is the supply voltage pin for the A/D Converter, Port C (3..0), and ADC (7..6). It should be externally connected to VCC, even if the ADC is not used.

AREF AREF is the analog reference pin for the A/D Converter.

ADC7..6 (TQFP In the TQFP and QFN/MLF package, ADC7..6 serve as analog inputs to the A/D and converter. These pins are powered from the analog supply and serve as 10-bit QFN/MLF ADC channels.

Package Only) Table10.1: Pin Descriptions of AT mega 48 Control register Timer 1 Fast PWM Mode TCCR1A – Timer/Counter1 Control Register A TCCR1B – Timer/Counter1 Control Register B TCNT1H and TCNT1L – Timer/Counter1 OCR1AH and OCR1AL – Output Compare Register 1 A OCR1BH and OCR1BL – Output Compare Register 1 B TIMSK1 – Timer/Counter1 Interrupt Mask Register 10.1.4 Block Diagram

Fig.10.3: Block Diagram of AT Mega 48 10.2.1 IR2110 Features             

Floating channel designed for bootstrap operation Fully operational to +500V or +600V Tolerant to negative transient voltage dV/dt immune Gate drive supply range from 10 to 20V Undervoltage lockout for both channels 3.3V logic compatible Separate logic supply range from 3.3V to 20V Logic and power ground ±5V offset CMOS Schmitt-triggered inputs with pull-down Cycle by cycle edge-triggered shutdown logic Matched propagation delay for both channels Outputs in phase with inputs Fig.10.4: IR2110

10.2.2 Description The IR2110/IR2113 are high voltage, high speed power MOSFET and IGBT drivers with independent high and low side referenced output channels. Proprietary HVIC and latch immune CMOS technologies enable ruggedized monolithic construction. Logic inputs are compatible with standard CMOS or LSTTL output, down to 3.3V logic. The output drivers feature a high pulse current buffer stage designed for minimum driver cross-conduction.

Propagation delays are matched to simplify use in high frequency applications. The floating channel can be used to drive an N-channel power MOSFET or IGBT in the high side configuration which operates up to 500 or 600 volts.

10.2.3 Typical operating Circuit

Fig.10.5: Typical operating Circuit of IR 2110 10.2.4 Ordering Information Part

Temp Range

DS1307+

to +

DS1307N+ DS1307Z+

to to +

DS1307ZN+ DS1307Z+T&R DS1307ZN+T&R

to to + to

Voltage(V ) 5.0

Pin- Package

5.0

8 PDIP(300 mils)

5.0

8 SD(150 mils)

5.0

8 SD(150 mils)

5.0

8 SD(150 mils) Tape & Real

5.0

8 SD(150 mils) Tape & Real

8 PDIP(300 mils)

Table10.2: Ordering Information 10.2.5 Functional Block Diagram

Fig.10.6: Functional Block Diagram of IR 2110 10.2.6 Lead Definitions Symbol VDD HIN SD LIN VSS VB HO VS VCC LO

Description Logic supply Logic input for high side gate driver output (HO), in phase Logic input for shutdown Logic input for low side gate driver output (LO), in phase Logic ground High side floating supply High side gate drive output High side floating supply return Low side supply Low side gate drive output

COM

Low side return Table10.3: Lead Definitions

10.2.7 Lead Assignments Fig.11.7: Lead Assignment

10.3.1 IRF 540 N Features • • • • • •

Advanced Process Technology Ultra Low On-Resistance Dynamic dv/dt Rating 175°C Operating Temperature Fast Switching Fully Avalanche Rated

Fig.10.7: IRF 540 N 10.3.2 Absolute Maximum Ratings & Thermal Resistance

Table10.4: Absolute Maximum Ratings & Thermal Resistance

10.3.3 Electrical Characteristics @ TJ = 25째C (unless otherwise specified)

10.3.4 Source-Drain Ratings and Characteristics

10.4.1 Power Supply Unit A power supply is a device that supplies electric power to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy (mechanical, chemical, solar) to electrical energy. A regulated power supply is one that controls the output voltage or current to a specific value; the controlled value is held nearly constant despite variations in either load current or the voltage supplied by the power supply's energy source.

Regulated power supplies are commonly used in engineering projects. Power supply is food of any circuit. We would like to share 5V, 12V regulated power supply circuits which can be used for Embedded or Micro controller projects.

10.4.2 Circuit Diagram of 12v & 5v DC Supply

Fig.10.8: Circuit Diagram of 12v & 5v DC Supply

1. Input

3.Output IC 7805

2. GND Design & Fabrication of PCB 11.1 PCB design of the circuit The required value of the components has been collected from the market & then the performance of the circuit has been tested in the laboratory. After satisfactory performance PCB has been designed By Express PCB software & layout has been shown in the following figure.

Fig.11.1: PCB design of the Complete Circuit

11.2 Complete Circuit Diagram

Fig.11.3: Complete Circuit Diagram

11.3 Complete Hardware Implementation Current Sensor & Voltage sensor Circuit IRF540N

IR2110

DC-DC Boost Converter

Current Sensor Resistor Micro-Controller Fig.11.4: Complete Hardware Implementation 11.4 Complete Hardware Implementation for PCB

Fig.11.5: Complete Hardware Implementation for PCB Result, Discussion & Conclusion 12.1 Result The overall performance of the project is very good & the response of MPPPT is acceptable.

The result depends on the duty cycle of DC-DC Boost Converter. If the duty cycle increase then the output voltage also increase. But duty cycle should not more than 60%.Theoretical is clear that it can be practically implemented & we have faced some problem .In other case it is proved more efficient.

12.2 Discussion At first we need to select a protocol then have to know in details so that we can write a program in the micro controller to decode the encoded signal. Then we have to check properly so we get accurate data. In this purpose we have to use LCD to display the received data & then compare itâ&#x20AC;&#x2122;s with the sending data thus accuracy is obtained & error can minimize by reforming the program if required. Although the above task is so hard because for small error the whole process will be broken down, but the sending data has satisfactorily received by doing hard work & proper design. At first we developed current sensor &Voltage

sensor circuit. Then we developed DC-DC Boost converter. By changing duty cycle the output voltage can be changed. Thus we developed the whole system.

The overall cost is more, which is not available for common people but if the company economically produces it then it can be low cost & available. The appropriate components are not available in the local market & also expensive.

12.3 Conclusions There are many approaches to finding and tracking the maximum power point for PV cells and groups of cells. Additional interesting methods are presented in References 2 and 3.

These are by no means the only practical maximum power point tracking methods. Many systems will combine methods, such as using VOC to find the starting point for the iterative methods like P and O or IC. In some cases, changing from one method to another is based on the level of irradiance. At low levels of irradiance, methods like Open Circuit Voltage and Short Circuit Current may be more appropriate as they can be more noise immune. When the cells are arranged in a series, the iterative methods can be a better solution. When a portion of the string is shade or does not have the same angle of incidence, then searching algorithms are needed.

In general, for whatever method that is chosen, it is better to be accurate than fast. Fast methods tend to bounce around the maximum power point due to noise present in the power conversion system. Of course, an accurate and fast method would be preferred but the cost of implementation needs to be considered. A solar panel MPPT charge controller represents a practical and valuable piece of technology relevant to the needs of the emerging â&#x20AC;&#x153;greenâ&#x20AC;? energy movement. However, these challenges were easily overcome through teamwork and challenges than developing the standalone components. a combined engineering effort. The assorted strengths of the individual team members was key to overcoming every obstacle and achieving a successful final project.

References: [1] Introduction of solar Electricity: (i) http://www.newenglandsolar.comi (ii) http:// www.southampton.ac.uk (iii) http:// www.solar.gwu.

[2] Photovoltaic Solar Electricity (i) http://en.wikipedia.org/wiki/Photovoltaics (ii) http://science.howstuffworks.com (iii) http://www.electrical-equipment.org (iv) http://www.energy.ca.gov (v) http://www.solardirect.com (vi)Solar (vii) Photovoltaic Insider Report - Vol. X No. Vol. XIV No. 4 April 1995, Vol XVII No. 2 February 1998 [3] PV characteristic of a Solar Module (i) http://www.altestore.com (ii) http://www.greenrhinoenergy.com

2

Electricity February 1991

(iii) http://en.wikipedia.org/wiki/Solar_panel (iv) http://answers.yahoo.com (v) http://www.solarenergy-solarpower.com [4] MPP Tracking (i) http://en.wikipedia.org/wiki/Maximum_power_point_tracker (ii) Chihching Hua and ChihmingShen “Study of Maximum Power Tracking Techniques and control of DC/DC Converters for Photovoltaic Power Systems” IEEE 1998 (iii) Balakrishna S, Thansoe, Nabil A, Rajamohan G, Kenneth A.S., Ling C. J.’, “The Study And Evaluation Of Maximum Power Point Tracking Systems”, Proceedings Of International Conference On Energy And Environment 2006 (ICEE 2006), [5] Current Sensor & Voltage sensor (i) http://en.wikipedia.org/wiki/Current_sensor (ii) http://www.dentinstruments.com (iii) http://en.wikipedia.org/wiki/Voltage_sensor [6] DC-DC Converter for MPPT section (i) http://www.powerdesigners.com (ii) http://en.wikipedia.org/wiki/Boost_converter (iii) Muhammad H. Rashid, "Power Electronics: Circuits, Devices and Applications", Prentice-Hall, Inc., Englewood Cliffs, Book, Third Edition.

[7] Liquid crystal display (i) http://en.wikipedia.org/wiki/Liquid_crystal_display (ii) http://www.physlink.com (iii) http://www.circuitstoday.com [8] Basics of rechargeable batteries (i) http://www.all-battery.com/batterybasics.aspx (ii) http://en.wikipedia.org/wiki/Rechargeable_battery (9) ATmega8, IR2110 ,IR540N (i) http://www.atmel.com (ii) http://www.irf.com (iii) http://www.irf.com