Solar Powered water irrigation system

CHAPTER 1INTRODUCTION 1.1 OVERVIEW OF THE PROJECT Solar based agricultural water pumping is an efficient method that drastically reduces the power supply cost of normal method. In this proposed method, the total cost of the apparatus is reduced as only renewable source is used as the source of energy. 1.2 WORK SUMMARY A photovoltaic energy conversion system for converting solar power into useable DC at 5V to 15V has been proposed and implemented which can be used for charging batteries of low power devices like mobile phones. The energy obtained from the photovoltaic module is unregulated. But for charging Lithium ion batteries, we require approximately 11.5V steady DC supply. Therefore the 18V unregulated DC obtained from the PV module is stepped down up to 12V by DC-DC boost converter. For efficient usage of photovoltaic energy conversion system, it is essential to design a maximum power point tracking (MPPT) system. The concept of MPPT is to automatically vary a PV array's operating point so as to get maximum power. This is necessary because the PV cell has a very low conversion efficiency and it is necessary to reduce the cost of the overall system. The power delivered by array increases to maximum as the current drawn rises and after a particular value, the voltage falls suddenly making the power drop to zero. This frequent rise and drop reduces the efficiency drastically, to avoid this the algorithm keeps tracking the maximum power point in the photo voltaic arrays 1 there by keeping the output almost at a constant value given that the illumination of the sun stays within a particular range. The efficiency is also is maintained at its perfect level. 2 CHAPTER 2 LITERATURE SURVEY 2.1 EXISTING METHOD There is a different commercial pump setup that is in existence powered up by solar radiation. It has a disadvantage that it does not use the maximum power point tracking algorithm. It also uses more number of power semiconductor control circuits. It probably leads to the decrease in the efficiency of the pump. The existing setup uses an alternating current motor which needs an additional power semiconductor control setup, an inverter, in addition to the existing power semiconductor control setup, a converter. This is because the energy obtained from photovoltaic cells is direct current energy. 2.2 RENEWABLE ENERGY In recent years, there is a substantial increase of energy consumption in India. This fast rate of energy consumption is influenced by the population growth and economic development in India. In the last four decades the commercial energy consumption in India has grown by about 7 times. This has led to the per capita consumption in India to be in region of 400 KWH per annum. Driven by the rise in population, ever expanding economy and an ultimate quest for improved quality of life, energy usage in India is expected to grow in an exponential rate. Compared to the other developing countries the per capita energy consumption in India is still very low even though there is an overall increase in energy demand every year. Today, India is one of the potential competitors for the effective usage of renewable energy. India is the world‟s largest producer of wind power after Denmark, Germany, Spain and the USA. India has a significant 3 India was probably the first country in the world to set up a separate ministry of nonconventional energy resources in early 1980s.1 billion people. excluding large hydro projects already accounts for 9% of the total installed energy capacity.610 MW. bio-mass and solar energy. equivalent to 12.potential for generation of power from renewable energy sources . and established many agencies that will help it achieve its goal. According to reports Renewable Energy. and there are no signs of a change in this trend. Thus.3 RENEWABLE ENERGY SCENARIO IN INDIA Renewable Energy in India is a sector that is still undeveloped. which apart from being a non-renewable. wind energy. it is imperative that India obtains energy security without affecting the booming economy. In combination with 4 . which would mean that alternative energy sources must be developed. However the results have been very mixed and in recent years it has lagged far behind other developed nations in using renewable energy (RE). India is one of the largest and fastest growing economies in the world with an expansive populace of above 1. The Government of India has already made several provisions.Small hydro power. which is currently satisfied mainly by coal. RE contribution to energy sector is less than 1% of India's total energy needs. foreign oil and petroleum. This would mean that the country must switch from the non-renewable energy (crude oil and coal) to renewable energy. and therefore non-permanent solution to the energy crisis. The price of crude oil has risen sharply over the last few years. 2. There is a very high demand for energy. it is also detrimental to the environment. in a total installed capacity of 1.large hydro. About 7. Combining the two points together. With recent developments.1 lakhs solar home lighting 5 . it is subject to a large amount of solar irradiation throughout the year. it is not difficult to gauge that solar energy in India is a vast and plentiful resource. to begin replacing India's four to five million diesel powered water pumps. Some large projects have been proposed.980 MW.4 SOLAR ENERGY IN INDIA Solar power. Much of the country does not have access to electrical grid. a clean renewable resource with zero emission. one of the first applications of solar power has been for water pumping. India is also.643MW. according to area.100 Giga Watts.5 kilowatts.000 km² area of the Thar Desert has been set aside for solar power projects. Solar energy could be made financially viable with government tax incentives and rebates. sufficient to generate 700 to 2. each consuming about 3. solar energy systems are easily available for industrial and domestic use with the added advantage of minimum maintenance. 5. has got tremendous potential of energy which can be harnessed using a variety of devices. 48. with present pricing and taxes (2010).e. The current architectural designs make provision for photovoltaic cells and necessary circuitry while making building plans. i.7 lakhs solar lanterns.5 lakhs. Most of the developed countries are switching over to solar energy as one of the prime renewable energy source. 2. India is a country near the equator – which means that given its geographical location. and off-grid lighting.44. An exclusive solar generation system of capacity of 250KWh per month would cost around Rs. the seventh largest country in the world. the capacity is more than 34%. and a 35. 82.45 and Rs. under the solar energy programs. 18. about 3. 6 . 7.systems. The present cost of electricity generation from solar thermal and solar photovoltaic energy systems is Rs. 13. stand-alone and grid connected solar photovoltaic (SPV) power plants of about 10 MW peak aggregate capacity.500 solar street lighting systems. respectively as fixed by Central Electricity Regulatory Commission.2009.12 million square meter solar water heater collector area and 6.44 per unit.247 solar water pumping systems. as on 30.11.57 lakhs solar cookers have been distributed/installed in the country. The functions of the components are explained from the functional block diagram of the project shown in figure 3. The functional setup consists of the following.1. 1. PIC microcontroller 6. Boost converter 3.1 INTRODUCTION In this chapter we get to know the specifications of the components used for the demonstration of the solar powered irrigation. Motor pump 5. MPPT 7 . Battery 4. Solar Panel 2.CHAPTER 3 DEVELOPMENT OF SPIP 3. It also gives the functional abilities of the components. energy conservation and demandside management. Owing to their high initial cost.1: Block Diagram 3.2 OBJECTIVE OF THE PROJECT The use of new efficient photovoltaic solar cells (PVSCs) has emerged as an alternative measure of renewable green power. However. This method aims to pump water using solar panel (Renewable energy source) only. 8 . they can be used extensively for water pumping and air conditioning in remote and isolated areas.Solar ray Solar panel Boost Converter Battery Motor PIC Controller Pump Display Output Fig: 3. where utility power is not available or is too expensive to transport. so that the power supply cost is reduced and reliability is increased. PVSCs have not yet been fully an attractive alternative for electricity users who are able to buy cheaper electrical power from the utility grid. 3 Pump Pressure: Flow: 3.2Ah 3.3.3.3. Pump. Boost conversion are given below.4 Battery Rated Voltage: 12V Rated Amp-Hour: 7. 3.5 Controller Frequency: 1A 12 W 9 .1 Solar Panel Rated Voltage: Rated current: Rated power: 3. Battery.2 Motor Rated Voltage: 12 V Rated current: Rated Power: 3.3.3.3. Motor.3 SPECIFICATIONS Specifications of Solar panel. This solar energy is used as the source of energy in the whole apparatus.4.6 Power semiconductor setup 3.1 SOLAR PANEL: It converts the solar energy from the sun into 12V/20W electrical output which can be fed as the input to the battery for the purpose of re-charging.3.3. In between the solar panel and battery a charge controller device is used for producing pulsating DC that can be fed as the input to battery.4 FUNCTIONS OF THE HARDWARE COMPONENTS 3. 10 . could reduce the costs of solar energy production enough for it to compare with oil as an energy source. the lifetime and reliability of the battery will be reduced. If variable DC input is given to the battery. or PETE. The process.2: Solar energy conversion This 12V/20W DC output is variable and that cannot be fed as the input to the lead acid battery. In concentrating collectors. sometimes hundreds of time greater. the area intercepting the solar radiation is greater. 11 .SOLAR PANEL (12V. than the absorber area. 20W) Fig 3. A new process that simultaneously combines the light and heat of solar radiation to generate electricity could offer more than double the efficiency of existing solar cell technology. called “Photon enhanced thermionic emission”. It uses a combination of lead plates or grids and an electrolyte consisting of a diluted sulphuric acid to convert electrical energy into potential chemical energy and back again. one DC input from the lead-acid battery consists of a negative electrode made of spongy or porous lead. BLDC Motor shaft is connected to the pump. power available to the load goes down significantly as voltage decreases. used as the voltage increase mechanism in the circuit. Pulsating DC input is fed as the input to the battery. and is a characteristic of the ubiquitous alkaline battery. 3. The pump has two inputs. Since ( ) as well.3. Both electrodes are immersed in a electrolytic solution of sulfuric acid and water. and is aimed at the ability of a boost converter to 'steal' the remaining energy in a battery. and R tends to be stable. The lead is porous to facilitate the information and dissolution of lead. In case the electrodes come 12 . This energy would otherwise be wasted since the low voltage of a nearly depleted battery makes it unusable for a normal load. A lead-acid battery is an electrical storage device that uses a reversible chemical reaction to store energy. This circuit topology is used with low power battery applications.4. The positive electrode consists of lead oxide. Here MOSFET IRF540 is used in the boost converter circuit for amplifying the energy. is known as the 'Joule thief'.2 BOOST CONVERTER A boost converter.3 BATTERY Battery is charged from the solar panel through the charge controller. The energy would remain untapped because many applications do not allow enough current to flow through a load when voltage decreases.4. This voltage decrease occurs as batteries become depleted. flowing radially outward into a diffuser or volute chamber (casing). The transfer of energy from the mechanical rotation of the impeller to the motion and pressure of the fluid is usually described in terms of centrifugal force. The pump helps to pump out the water for irrigation. 3. This membrane also prevents electrical shorting through the electrolyte. from where it exits. an electrically insulating.4 MOTOR PUMP The brushless DC motor is connected to the battery. but chemically permeable membrane separates the two electrodes. Fig 3. Output from the battery is given as input to the Brushless DC motor.3: Pump The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller.into contact with each other through physical movement of the battery or through changes in thickness of the electrodes. 13 .4. The motor is connected to a centrifugal pump. The algorithm program is embedded on it from an external source. 14 . for boosting the energy as per the necessities.4. The next section deals abt architrcture and func . This work is overlooked and controlled by the PIC microcontroller. It calculates the pulse signal based on the current and voltage sensed on the output end. The battery runs the motor pump. The pulse signal is the duty cycle signal to the MOSFET present in the boost converter. The solar panel absorbs the radiation and gives it to the boost converter which boosts up the energy and provides it to the battery.5 PIC MICROCONTROLLER The PIC microcontroller is the controlling device for this project setup. The PIC microcontroller also carries out the maximum power point tracking on the solar panel based on the embedded algorithm in it. The reason for choosing PIC16F877A is because of its special features which we got to know in the previous chapter. It gives the current boosting limit to the boost converter. The below given figure gives the complete architectural and functional design of PIC microcontroller.3. 4: PIC 16F877A architecture 15 .1 Architecture Fig 3.4.3.5. radiation and load variations. Voc. due to the temperature. In order to ensure that the photovoltaic modules always act supplying the maximum power as possible and dictated by ambient operating conditions. In fact.6. the MPPT is a DC-DC converter controlled through a strategy that allows imposing the photovoltaic module operation point on the Maximum Power Point (MPP) or close to it. and Isc are enough information to give a useful approximate model of the electrical behavior of a photovoltaic cell under typical conditions. For most purposes. abbreviated FF. this efficiency can be highly reduced. Besides. P=FF*Voc*Isc.4. the efficiency of any semiconductor device drops steeply with the temperature. In tabulated data it is often used to estimate the maximum power that a cell can provide with an optimal load under given conditions. a specific circuit known as Maximum Power Point Tracker (MPPT) is employed.3. FF.4. 3.1 I-V curve Photovoltaic cells have a complex relationship between their operating environment and the maximum power they can produce. The fill factor. Fill factor is defined as the ratio of the maximum power from the solar cell to the product of Open Circuit Voltage Voc and Short-Circuit Current Isc. 16 . is a parameter which characterizes the non-linear electrical behavior of the solar cell.6 Maximum power point tracking(MPPT) Operating point of PVA Photovoltaic modules have a very low conversion efficiency of around 15% for the manufactured ones. In most common applications. because it 17 . This is called the perturb and observe method and is most common.4. the controller adjusts the voltage by a small amount from the array and measures power. It is referred to as a hill climbing method. although this method can result in oscillations of power output.2 Perturb and observe In one method. further adjustments in that direction are tried until power no longer increases. if the power increases.6.5: I-V characteristics of MPPT 3.Fig 3. Perturb and observe is the most commonly used MPPT method due to its ease of implementation. 18 . Perturb and observe method may result in top-level efficiency.depends on the rise of the curve of power against voltage below the maximum power point. This combining will eliminate the small flaws in PO method there by giving the best result in maximum power point tracking. provided that a proper predictive and adaptive hill climbing strategy is adopted. and the fall above that point. This PO strategy MPPT is mixed along with the Fuzzy Logic Control (FLC) and used here in this project setup. 3.5 CIRCUIT DIAGRAM The overall circuit diagram of the solar powered irrigation pump setup is given.6 PCB DESIGN The Printed Circuit Board designed specifically for the controller and the converter setup of the SPIP setup is below. 19 . Fig 3.6: Circuit diagram 3. 7: PCB front side design 3.1 Front side Fig 3.3.8: PCB back side design 20 .6.6.2 Back side Fig 3. The efficiency of a panel determines the area of a panel given the same rated output – an 8% efficient 230 watt panel will have twice the area of a 16% efficient 230 watt panel.1 INTRODUCTION In this chapter. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. Each panel is rated by its DC output power under standard test conditions and typically ranges from 100 to 320 watts. most installations contain multiple panels.2.CHAPTER 4 HARDWARE DESCRIPTION 4. 4. description and specifications of the hardware components used in this proposed method of solar based water irrigation are discussed. Because a single solar panel can produce only a limited amount of power.2 PHOTOVOLTAIC CELL PANEL A Solar photovoltaic panel is a packaged and connected assembly of photovoltaic cells.1 Four types of PV cells • Selective – Emitter Cell (SEC) • Emitter wrap. 4.through cells (EWC) • Thin Film Photovoltaic • Single Crystal Silicon Cells 21 . It gives the specifications of the components used for the demonstration setup created and also gives the overview of the functional abilities of the components. • The wafers then have either Phosphorous or Boron added to make each wafer either a negative type layer or a positive type layer respectively. • Silica (SiO2) is the compound used to make the cells.  Cells only have an average efficiency of 30% 22 .4. the size of each array is dependent upon the amount of sunlight in a given area.  Connected by an external circuit electrons flow from the n-side to create electricity and end up in the p-side. 4.2. then melted down and re-solidified so that it can be arranged in perfect wafers for electric conduction.3 The Photoelectric Effect  The photoelectric effect relies on the principle that whenever light strikes the surface of certain metals electrons are released. Used together these two types treated of crystalline silicon form the p-n junction which is the heart of the solar– electrical reaction.  The output current of this reaction is DC (direct) and the amount of energy produced is directly proportional to the amount of sunlight put in.2 Single-Crystal Silicon Cell Construction • The majority of PV cells in use are the single-crystal silicon type. • Many of these types of cells are joined together to make arrays.2. It is first refined and purified. These wafers are very thin.  In the p-n junction the n-type wafer treated with phosphorus has extra electrons which flow into the holes in the p-type layer that has been treated with boron.  Sunlight is the catalyst of the reaction. reducing reliance on energy imports. solar energy contributes positively to the nation‟s energy security because it is produced domestically. • Sunlight is a free abundant source • PV can be designed for a variety of applications • No noise or air pollution 23 . • The PV Manufacturing Research and Development Project focuses on increasing manufacturing capacity so that the cost of manufacturing will decrease.1 photovoltaic array characteristics 4. • Does not require the transportation of hazardous materials across country. • The government has many incentives program which vary from state to state. They aim to achieve break even costs. • However.2. • The industry is still relatively new and extremely hi tech allowing for the creation of more jobs in the American market.4 Pros and Cons of Solar Electricity • Expensive to produce because of the high cost of semi.conducting materials.Fig 4. which could be avoided by reducing manufacturing costs. but they exist to encourage investment in forms of alternative energy. Fig 4.2 solar panel • Require minimal maintenance and have long service life times. • Power can be either centralized in individual homes or distributed by electrical companies. Solar panels use light energy (photons) from the sun to generate electricity through the photovoltaic effect. The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon. The structural member of a module can either be the top layer or the black layer. Cells must also be protected from mechanical damage and moisture. Most solar panels are rigid, but semi-flexible ones are available, based on thin-film cells. Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired current capability. The conducting wires that take the current off the panels may contain silver, copper or other nonmagnetic conductive transition metals. The cells must be connected electrically to one another and to rest of the system. Externally popular agricultural usage 24 photovoltaic panels use connectors to facilitate easy weatherproof connections to the rest of the system. 4.3BRUSHLESS DC MOTOR The motor used in the project is Brushless DC motor. Brushless DC Electric motor (BLDC motors, BL motors) also known as electrically commutated motors (ECMs, EC motors) are synchronous motors which are powered by a DC electric source via an integrated inverter/switching power supply, which produces an AC electric signal to drive the motor (Alternating current, does not imply a sinusoidal waveform but rather a bi-directional current with no restriction on waveform). Additional sensors and electronics control the inverter output amplitude and waveform (and therefore percent of DC bus usage/efficiency) and frequency. Fig 4.3 motor The motor part of a brushless motor is often a Brushless DC motor, but can also be a switched reluctance motor, or induction motor. Brushless motors may be described as stepper motors. 25 4.3.1 Principle of brushless dc motor The brushless DC motor is the combination of a permanent excited synchronous motor and a frequency inverter. The inverter has to replace the commutator of a conventional DC motor. A brushless DC motor can be derived from a mechanically commutated DC motor with three armature slots. Its armature winding corresponds to a three phase winding in delta connection. The commutator acts like a three phase frequency converter. The commutation of a brushless DC motor depends on the position of the rotor. The angle between the magneto-motive forces of stator and rotor is fixed to 90 degree, so the motor produces maximum torque and needs low reactive current that is useful to advance commutation by few degrees to compensate the effects of the stray inductance and minimize reactive current. Brushless motors may be described as stepper motors. However, the term steppers motor tends to be used for motors that are designed specifically to be operated in a mode where they frequently stopped with the rotor in a defined angular position. Brushless DC motor may be described as stepper motors. They develop a maximum torque when stationary, linearly decreasing as velocity increases. Some limitations of brushed motors can be overcome by brushless motors as they include higher efficiency and a lower susceptibility of the commutator assembly to mechanical wear. These benefits come at the cost of potentially less rugged, more complex, and more expensive control electronics. A typical brushless motor has permanent magnets which rotate and a fixed armature, eliminating problems associated with connecting current to the moving 26 Environments and requirements in which manufacturers use brushless-type DC motors include maintenance-free operation. An electronic controller replaces the brush and commutator assembly of the brushed DC motor turning. reduced noise.2 Advantages Brushless motors offer several advantages over brushed DC motors. they are not subjected to centrifugal forces. FPGA). The maximum power that can be applied to a brushless motor is limited almost exclusively by heat. This in turn means that the motor internals can be entirely enclosed and protected from dirt or other foreign matter. Under high mechanical loads. including more torque per weight.armature. high speeds. too much of which weakens the magnets. The controller performs similar timed power distribution by using a solid-state circuit rather than the brush system. 27 .e. and operation where sparking is either hazardous (i. and because the windings are supported by the motor for cooling. elimination of ionizing sparks from the commutator and overall reduction of electromagnetic interference (EMI).3. explosive environment) or affects the digital electronic firmware (ex. and may damage the winding‟s insulation. 4.. more torque per watt ( increased efficiency ). The enhanced efficiency is greatest in the no-load and low-load region of the motor‟s performance curve. brushless motors and high-quality brushed motors are comparable in efficiency. With no windings on the rotor. longer lifetime ( no brush and commutator erosion ). increased reliability. pumps are used. This means that the pump transfers energy to the fluid that it receives from the driving motor.Fig 4.). be it hot or cold.  When we speak of a motor pump then this mechanical energy is provided by a heat engine (combustion engine. At this point we can already make an important distinction based on the driving motor:  When we speak of an electric pump then the mechanical energy necessary for the pump to turn is provided by an electric motor. In other words. diesel engine. 28 . the pump is a machine which has the function of increasing the total (mechanical) energy of a liquid.1 Introduction A fluid. etc. in a more technically appropriate manner.4 Performance curve 4.4CENTRIFUGAL PUMP 4. has to be “moved” in a system.4. or in l/min.4. 29 .] = H[m C. indicated as Hman and measured in m C. means that pump can lift a quantity of water amounting to 3 m3/h up to a maximum height of 12 m. C. this is generally indicated with the letter H and is measured in J/kg or in metres of carried liquid (m.] * ?[kg/dm3].W. It is much more convenient to speak not of the head else of the manometric head.L.2 Flow rate The flow rate of the pump is defined as the useful volume of liquid distributed by the pump in the time unit.3 Head The (total) head of the pump represents the increase in energy acquired by 1 kg of liquid between the input and the output section of the pump itself.  Flow rate  Head  Power  Efficiency  Speed  Net Positive Suction Head (NPHS) 4.Considering the definition.L. They are. where ? = volume of the liquid transported.A. It is generally indicated with the letter Q and is measured in m3/s. 4.). The applicable equation is: H man [m C. (metres of column of water): saying that a certain pump gives a flow rate of 3 m3/h with a manometric head of 12 m C. we may proceed with our description of the pump.W. or in m3/h.4. starting with the fundamental factors that describe its operation. depending on how the pump has been designed and on the system in which the pump is to be fitted. the so-called characteristic curve Q-Hman of the pump is obtained. but vary inversely to one another: when one increases. the other decreases and vice versa. on which the X-axis represents the flow rate and the Y-axis the manometric head. So pumps of the first type will be preferable when a more or less constant head is desired with a flow rate varying within ample margins (this is the case. pumps of the second type will be preferable when a more or less constant flow rate is 30 . the flow rate.All pumps are provided with a data plate which clearly indicates.5 Characteristic curve of centrifugal pump The characteristic curve may be "flat" or "steep". the pumps that have a flat characteristic curve give rise to slight variations in head for strong variations of flow rate. As may be seen in figure 4. among the other data. of pumps for fire-fighting installations). while pumps with a steep characteristic curve give rise to slight variations in flow rate for high variations in head. Fig 4. for example. manometric head and their interconnection. vice versa.5. However these two parameters are not fixed. If the various points of operation of a pump are plotted on a graph. that is. generally equal to 9. where g[m/s2] is the acceleration of gravity.4 Power There is the power supplied by the pump to the liquid.81 m/s2.4. 31 . Fig 4. in the case of electric pumps. expressed as: Pu[W] = g[m/s2] * [kg/m3] * Q[m3/s] * H[m C. Then there is the electric power Pabs absorbed by the electric drive motor from the power mains. Then there is the power Pnom absorbed by the pump.desired with a head varying within a relatively wide field (for example in the case of pumping from wells. where constant flow rates are generally desired even in the presence of high variations in the geodetic difference in level).].6 Characteristic curve 4. the power transferred by the electric motor to the pump axle.L. 6 Speed 32 .4. In the case of electric pumps we frequently speak of the efficiency of the unit.7 Pump power transfer 4. It must be stressed that the efficiency „gr‟ of the unit is a very important parameter for an electric pumps: the higher its value the less the cost. Then there is the efficiency „mot' of the electric motor.5 Efficiency There is the efficiency„p‟ of the pump. in terms of electric energy and in money in the long run. defined as the ratio between the power Pu supplied to the fluid and the power Pnom absorbed by the pump (that is the mechanical power transferred by the electric motor) p = Pu / Pnom. defined as the ratio between the power supplied to the fluid and the power absorbed by the motor: gr = Pu / Pass = p* mot. defined as the ratio between the power absorbed by the pump and that absorbed by the motor: mot = Pnom / Pass.Fig 4. 4. that must be borne to have the electric pump perform a certain job.4. small vapour bubbles are formed. considering the average running of the motors and the fact that the electric energy distributed in the mains generally has a frequency of 50 or 60 Hz.3550 rpm. these bubbles implode shortly after being formed. the NPSH indicates the absolute pressure that must exist at the pump intake to prevent the occurrence of cavitation phenomena.NPSH . 4. When a pump tries to suck up a certain amount of liquid from a depth greater than that allowed by its characteristics.2950 rpm and n(60 Hz) = 3300 . From the physical point of view.4. The maximum suction depth Hmax and NPSH are linked by the relationship: Hmax = A .Hr (m) 33 .Hasp . that is the inability of all centrifugal pumps to suck at a height equal to or higher than 10. the maximum suction depth. this is generally indicated with the letter n and measured in rpm. this gives roughly n(50 Hz) = 2750 . among the characteristics of his machines.7 NPSH (Net Positive Suction Head) This parameter indicates the pump's inability to create an absolute vacuum. or to supply the curve of the NPSH as a function of flow rate. All PENTAX electric pumps are fitted with a 2-pole induction motor. That is why it is important for every pump manufacturer to indicate clearly. cavitation occurs: the impeller interrupts the flow of liquid and. making a loud noise similar to a metallic hammer and causing severe damage to the hydraulic parts of the pump.The rotation speed is the number of revolutions performed by the pump in the time unit.33 m (which generally corresponds to the value of atmospheric pressure at sealevel). as a result. Hr = vapour tension of the liquid transported in m. life and reliability.5. thus reducing the flow rate of the pump. in order to return the pump to regular operation it is often sufficient to choke the delivery gate valve suitably.1 Introduction Lead Acid batteries have changed little since the 1880's although improvements in materials and manufacturing methods continue to bring improvements in energy density. A is equal to the atmospheric pressure. Regular water addition is required for most types of lead acid batteries although low-maintenance types come with excess electrolyte calculated to compensate for water loss during a normal lifetime. 4. to increase the maximum suction depth of a certain pump the load losses Hsuc of the suction pipe may be decreased: that is why it is always convenient to fit a pipe with the largest possible internal diameter at suction. 34 .where: A = absolute pressure in m on the free surface of the fluid in the suction tank.5 BATTERY 4. All lead acid batteries consist of flat lead plates immersed in a pool of electrolyte. The NPSH is influenced by the flow rate value: it grows as the latter increases. if fluid is being sucked from an "open" tank. Hasp = load loss in the suction pipe in m. that is in contact with the atmosphere. as a result. As may be seen from the equation above. Fig 4. A six-volt battery has three single cells.8 parts of the battery 4.1 volts.6 volts. 35 .2 Battery Construction Lead acid batteries used in the RV and Marine Industries usually consist of two 6-volt batteries in series.5. These batteries are constructed of several single cells connected in series each cell produces approximately 2.3 volts. which when fully charged produce an output voltage of 6. A twelve-volt battery has six single cells in series producing a fully charged output voltage of 12. or a single 12-volt battery. Lead acid batteries can be connected in parallel to increase the total AH capacity.5 hours or 20-amps of current for a period of 6. 4.A battery cell consists of two lead plates a positive plate covered with a paste of lead dioxide and a negative made of sponge lead. The plates are enclosed in a plastic battery case and then submersed in an electrolyte consisting of water and sulfuric acid. Progressive Dynamics has developed intelligent charging systems that solve battery problems and reduce battery maintenance. with an insulating material (separator) in between. The size of this storage capacity is described as the amp hour (AH) rating of a battery. Each cell is capable of storing 2. which means it can supply 10 amps of current for 12.5. The size of the battery plates and amount of electrolyte determines the amount of charge lead acid batteries can store.3 Battery Recharge Cycle The most important thing to understand about recharging lead acid batteries is that a converter/charger with a single fixed output voltage will not properly recharge or maintain your battery. 36 .25 hours.1 volts. Proper recharging and maintenance requires an intelligent charging system that can vary the charging voltage based on the state of charge and use of your RV or Marine battery. A typical 12-volt battery used in a RV or marine craft has a rating 125 AH. 37 . These gasses are very flammable and the reason your RV or Marine batteries must be vented outside. • Only 35 single word instructions to learn. resulting in some water loss.→ PbSO3 + H+ + 2e(s) (aq) dis (s) (aq) PbO2 + 3H+ + HSO3. (H2O) is converted into its original elements. If the battery is overcharged pressure from these gasses will cause relief caps to open and vent. hydrogen and oxygen. Sealed lead acid batteries contain most of these gasses allowing them to recombine into the electrolyte.6.During the recharging process as electricity flows through the water portion of the electrolyte and water.6 PIC MICROCONTROLLER 4. Gassing causes water loss and therefore lead acid batteries need to have water added periodically.+ 2e.→PbSO3 + 2H2O Pb + PbO2 + 2H2SO3 → 2PbSO3 + 2H2O 4. H2SO3 → H+ + HSO3 ¯ Pb + HSO3.1 Microcontroller Core Features: • High-performance RISC CPU. The general discharge and recharge cycle‟s chemical reaction can be given as. Most sealed batteries have extra electrolyte added during the manufacturing process to compensate for some water loss. • Selectable oscillator options. indirect and relative addressing modes.• All single cycle instructions except for program branches which are two cycle.200 ns instruction cycle.20 MHz clock input DC . • Power-up Timer (PWRT) and Oscillator Start-up Timer (OST). • Single 5V In-Circuit Serial Programming capability. • Power saving SLEEP mode. • Operating speed: DC . • Up to 8K x 14 words of FLASH Program Memory. • Programmable code-protection. • In-Circuit Serial Programming (ICSP). • Pin out compatible to the PIC16C73B/74B/76/77 • Interrupt capability (up to 14 sources) • Eight level deep hardware stack • Direct. • Power-on Reset (POR). Up to 368 x 8 bytes of Data Memory (RAM) Up to 256 x 8 bytes of EEPROM data memory. • Fully static design. • Low-power. • Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation. 38 . • In-Circuit Debugging via two pins. high-speed CMOS FLASH/EEPROM technology. • High Sink/Source Current: 25 mA.• Processor read/write access to program memory. 39 .5V. • Commercial and Industrial temperature ranges. • Wide operating voltage range: 2.0V to 5. 9 Pin diagram if PIC 40 .6.4.2 Pin diagram of PIC 16F874A/877A Fig 4. 41 .4.0V to 5.5V). • Fully static design.6. • Wide operating voltage range (2. • Low-power consumption.4 CMOS technology • Low-power. high-speed Flash/EEPROM technology. • Commercial and Industrial temperature ranges. current will be reduced as the impedance is higher. They both form the important aspects of the project. In a boost converter.2. Polarity of the left side of the inductor is positive. The magnetic field previously created will be destroyed to maintain the current flow towards the load. 5. Thus the polarity will be reversed (means left side of inductor will be negative now).1 INTRODUCTION The operation of boost converter and the MPPT in the „solar powered irrigation pump‟ setup is given in this chapter. (b) When the switch is opened.2 BOOST CONVERTER 5.1 Operating principle The key principle that drives the boost converter is the tendency of an inductor to resist changes in current by creating and destroying a magnetic field. 42 . The use of boost converter combined with maximum power point tracking is the advancement introduced in this project. (a) When the switch is closed. A schematic of a boost power stage is shown in Figure 1.CHAPTER 5 OPERATION OF BOOST CONVERTER AND MPPT 5. the output voltage is always higher than the input voltage. current flows through the inductor in clockwise direction and the inductor stores some energy by generating a magnetic field. As a result two sources will be in series causing a higher voltage to charge the capacitor through the diode D. 5. the switch S (see figure 5.1: Boost converter schematic The basic principle of a Boost converter consists of 2 distinct states in the On-state.in the Off-state. the inductor will not discharge fully in between charging stages. the switch is open and the only path offered to inductor current is through the fly-back diode D. the capacitor is therefore able to provide the voltage and energy to the load. The switch must of course be opened again fast enough to prevent the capacitor from discharging too much.1) is closed. the capacitor C and the load R. During this time. the capacitor in parallel with the load is charged to this combined voltage. Fig. This results in transferring the energy accumulated during the On-state into the 43 .If the switch is cycled fast enough. resulting in an increase in the inductor current. the blocking diode prevents the capacitor from discharging through the switch. and the load will always see a voltage greater than that of the input source alone when the switch is opened. Also while the switch is opened. When the switch is then closed and the right hand side is shorted out from the left hand side. So it is not discontinuous as in the buck converter and the requirements on the input filter are relaxed compared to a buck converter. which makes the input voltage ( ) appear across the inductor.2. current and voltage When a boost converter operates in continuous mode. in the case of an ideal converter (i. the current through the inductor ( ) never falls to zero. which causes a change in current ( the inductor during a time period (t) by the formula: 44 ) flowing through . the switch S is closed.2: Continuous mode. Figure 5.capacitor.2 shows the typical waveforms of currents and voltages in a converter operating in this mode. 5. 5. using components with an ideal behavior) operating in steady conditions: During the On-state.The input current is the same as the inductor current.2 Continuous mode Fig.e. The output voltage can be calculated as follows. Therefore D ranges between 0 (S is never on) and 1 (S is always on). During the Off-state. In particular. the increase of IL is therefore: D is the duty cycle. the switch S is open. If we consider zero voltage drop in the diode.At the end of the On-state. the variation of IL during the Off-period is: As we consider that the converter operates in steady-state conditions. so the inductor current flows through the load. It represents the fraction of the commutation period T during which the switch is ON. and a capacitor large enough for its voltage to remain constant. the evolution of IL is: Therefore. 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. the energy stored in the inductor is given by: 45 . the inductor current has to be the same at the start and end of the commutation cycle. This is why this converter is sometimes referred to as a step-up converter. theoretically to infinity as D approaches 1. 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: The above expression shows that the output voltage is always higher than the input voltage (as the duty cycle goes from 0 to 1). 46 . and that it increases with D.So. the difference has a strong effect on the output voltage equation. In this case. 5.2. This commonly occurs under light loads. Although slight. its maximum value (at ) is 47 .3 Discontinuous mode Fig.5. the current through the inductor falls to zero during part of the period (see waveforms in figure 5. It can be calculated as follows: As the inductor current at the beginning of the cycle is zero.3). the inductor may be completely discharged before the end of a whole commutation cycle.3: Discontinuous mode. current and voltage If the ripple amplitude of the current is too high. 48 . the output voltage gain can be written as follows: Compared to the expression of the output voltage for the continuous mode. the output voltage gain not only depends on the duty cycle. in discontinuous operation. Therefore the output current can be written as: Replacing ILmax and δ by their respective expressions yields: Therefore. the diode current is equal to the inductor current during the offstate. but also on the inductor value. this expression is much more complicated. the input voltage. Furthermore. the switching frequency.During the off-period. As can be seen on figure 4. and the output current. δ is: The load current Io is equal to the average diode current (ID). IL falls to zero after : Using the two previous equations. f. It tracks down the point of maximum power on the solar panel and makes the setup to draw power from that point.RX.c3. batteries.set1=0.set=0.d3. 49 .d2.3 MPPT ALGORITHM Maximum power point tracking (MPPT) is a technique that grid connected inverters. MPPT devices are typically integrated into an electric power converter system that provides voltage or current conversion.on=0. Solar cells have a complex relationship between solar irradiation.c2.volt1.h> unsigned int j.1 MPPT program The following program is embedded into the PIC micro controller for MPPT purpose. sec.count12=35. though optical power transmission systems can benefit from similar technology. unsigned int t1. n=0. The program is created on the basis of the PO method with the fuzzy logic control.g. or motors.3.SET11. i. . typically solar panels. including power grids. #include<pic. filtering.c4.c1. It is the purpose of the MPPT system to sample the output of the cells and apply the proper resistance (load) to obtain maximum power for any given environmental conditions.d. k.f1. b[8]={0}. solar battery chargers and similar devices use to get the maximum possible power from one or more photovoltaic devices.d1. temperature and total resistance that produces a non-linear output efficiency which can be analyzed based on the I-V curve.5. xyz=1. msg.f2. 5. and regulation for driving various loads. 50 . PORTA=0X00. CCP1IE=0. TRISB=0X00. PORTD=0X00.void main() { ADCON1=0X06. PORTC=0X00. TRISA=0x00. TRISC=0X00. TRISE=0X00. PORTB=0X00. TRISD=0X00. PORTE=0X00. T1CON=0X01. TMR1IE=1. TMR1L=0XEF.PR2 = 0b01000100 . PR2 = 0b00011000. CCP2CON = 0b00101100 . 51 . TMR1IF=0. TMR1H=0XD8. T2CON = 0b00000111 . //CCPR1L = 0b00000000 . T2CON =0b00000101. while(ADGO). //right 52 . //06 0r 05 TMR0 =69 .0048). //69 //28 TMR0IE=1. //status check volt1=((ADRESH*256+ADRESL)*0. GIE=PEIE=RCIE=1. ADCON0=0X81.OPTION=0X80. //0x81 //delay(). ADGO=1. while (1) { count12++. if(count12>=5) { count12=0. 53 .6*curr1). a=a%100. while(ADGO).0048). } a=(int)volt. //status check curr1=((ADRESH*256+ADRESL)*0. //1000 1001 ADGO=1. //98--200 68--100 curr=(0. a1=a/100.volt=(46*volt1)*2. a3=a. a=a%10. a2=a/10. //230/5*2 ADCON0=0X89. //3/5 curr=(curr*10). CCP1CON = 0b00011100 . g=(int)p. c1=g%10. //123 g=g%100. p=((volt*curr)/10). if(p==7) { PR2 = 0b11111001 .f=(int)curr. T2CON = 0b00000101 .8 b2=f/10. c2=g/10. d=4. c3=g/100. 54 . c4=g/1000. //1234 g=g%1000. //12. T2CON = 0b00000101 . d=5. d=7. CCP1CON = 0b00111100 . T2CON = 0b00000101 .} if(p==8) { PR2 = 0b10100110 . } if(p==10) 55 . CCP1CON = 0b00101100 . } if(p==9) { PR2 = 0b01010010 . //if(f==10) { PR2 = 0b00011000 . d=8. //CCPR1L = 0b00000010 . } f1=f/10. } CCPR1L=d. 56 . //CCPR1L = 0b00000000 . CCP1CON = 0b00011100 .{ PR2 = 0b11111001 . T2CON = 0b00000101 . f2=f%10. CCP1CON = 0b00001100 . T2CON = 0b00000100 . msg. xyz. d3=d%10. CCPR2H=100-d. j TMR1IF=0. } } void interrupt isr() { if(TMR1IF==1) { // t1. CCPR2L=d. d2=(d%100)/10. n.CCPR1H=100-d. } if(TMR0IF) 57 . sec. d1=d/100. b[8]={0}. RX=0. } if(RCIF==1) { RCIF=0. } } 58 . RX=RCREG-0x30.{ TMR0IF=0. t1=0. 1 OUTCOME From the observations made above. But practically. In such cases.2 LIFE SPAN Most commercially available solar panels are capable of producing electricity for at least twenty years. 6.6 CONCLUSION AND FUTURE SCOPE 6. The typical warranty given by panel manufacturers is over 90% of rated output for the first 10 years. The insulation may change in two to three minutes. The ambient temperature of the system is assumed not to change for a reasonably long time (about 5 minutes).CHAPTER . The value obtained can be latched as the reference voltage and MPP can be obtained automatically without any manual intervention. 6. this may not be the case. we conclude that the system developed is capable of extracting maximum power from the photovoltaic module at the same time providing a regulated DC supply. Panels are expected to function for a period of 30 to 35 years. we need to derive the reference voltage from the short circuit current of the PV panel. The results obtained from experiment are in synchronization with the theoretical results. and over 80% for the second 10 years.3 FURTHER IMPROVEMENTS 59 . During the 1990s. As the semiconductor industry moved to ever-larger boules. poly was dominant in the low-cost panel market. These cells offer less efficiency than their mono-silicon counterparts. Without a boost converter. Two battery-powered applications that use boost converters are hybrid electric vehicles (HEV) and lighting systems. 6. there has been only one major change. panel size increased. and since 2008 almost all new panels use 6 inch (150 mm) cells.In the time since Berman's work. However. used on the front of the panels. but they are grown in large vats that greatly reduce the cost of production. By the mid-2000s. poly-silicon cells became increasingly popular. However. but more recently a variety of factors has pushed the higher performance mono back into widespread use.4 APPLICATION Battery power systems often stack cells in series to achieve higher voltage. Boost converters can increase the voltage and reduce the number of cells. a Prius actually uses only 168 cells and boosts the battery voltage from 202 V to 500 V. Boost converters also power devices at smaller scale applications. improvements have brought production costs down. The NHW20 model Toyota Prius HEV uses a 500 V motor. the Prius would need nearly 417 cells to power the motor. In 1980s panels used cells with 2 to 4 inch (51 to 100 mm) diameter. In terms of the cells themselves. The widespread introduction of flat screen televisions in the late 1990s and early 2000s led to the wide availability of large sheets of high-quality glass. sufficient stacking of cells is not possible in many high voltage applications due to lack of space. Panels in the 1990s and early 2000s generally used 5 inch (125 mm) wafers. such as 60 . While the cost of photovoltaic power is decreasing. A white LED typically requires 3.3 V to emit light. Increases in photovoltaic cell efficiency decrease the cost of photovoltaic power.portable lighting systems. Boost converters can also produce higher voltages to operate cold cathode fluorescent tubes (CCFL) in devices such as LCDbacklights and some flashlights. This eventually reduces the scale of the setup size and also provides sufficient power to run the power semiconductor control circuits present in the setup. The cost of photovoltaic modules has fallen 400 percent in the last 30 years and this trend continues. 6. and a boost converter can step up the voltage from a single 1. because fewer modules arerequired to produce the same amount of power. 61 . Usually the power semiconductor circuit setup tops the power loss list. The quantum dot solar cells are half or one-fourth in size when compared to normal photovoltaic cells and provide up to four times the output power provided by the photovoltaic cells. Photovoltaic technology also continues to improve the power conversion efficiency of the photovoltaic cell.6 FUTURE SCOPE The invention of quantum dot solar cells has led to a great scope in solar power utilization. the cost of power derived from fossil fuels is increasing. 6.5 V alkaline cell to power the lamp.5 ECONOMIC ASPECTS IN FUTURE The cost of photovoltaic-powered water pumping systems is decreasing. Combining this with the quantum dot solar cells would give a never before efficiency in solar power utilization. The high output power helps in running one or even more drives in a completely efficient manner. It will be a milestone in solar energy production. This setup can carry out both buck process as well as boost process as per the necessities. the voltage is either bucked or limited to a lower value or boosted up to a higher value. Depending upon the necessity of the drive being run.The electrical drive stands next to it. Another scope is the usage of the CUK converter in the power semiconductor control setup. 62 . The power loss caused can be compensated by the boost process of the quantum dot cell‟s solar power produced. Gazoli and E.May 2009 . [5] SavitaNema.JJ. Issue 3.K.R. Volume 1. [3] Huan-Liang Tsai. IAENG.. R. Villalva. Ci-Siang Tu. •\Model of photovoltaic Module in Matlab. 2008.J. IEEE Trans on Power Electronics. San Francisco.I. 2010. Member. 24. J. ―Matlab / simulink based study of photovoltaic cells / modules / array and their experimental verification‖. .. (II CIBELEC 2005). 2010 pp. International Journal of Energy and Environment. Vol. [4] M. Gonzalez-Longatt. October 22 . n°5. Zamora Belver. ―Comprehensive approach to modeling and simulation of photovoltaic array‖.G. CampayoMartin... Proceedings of the World Congress on Engineering and Computer Science 2008. 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