CHAPTER 1

INTRODUCTION

1.1 General

The increasing demand for energy, the continuous reduction in existing sources of fossil fuels and the growing concern regarding environment pollution, have pushed mankind to explore new technologies for the production of electrical energy using clean, renewable sources, such as solar energy, wind energy, etc. Among the non-conventional, renewable energy sources, solar energy affords great potential for conversion into electric power, able to ensure an important part of the electrical energy needs of the planet. The conversion of solar light into electrical energy represents one of the most promising and challenging energetic technologies, in continuous development, being clean, silent and reliable, with very low maintenance costs and minimal ecological impact. Solar energy is free, practically inexhaustible, and involves no polluting residues or greenhouse gases emissions. The conversion principle of solar light into electricity, called Photo-Voltaic or PV conversion, is not very new, but the efficiency improvement of the PV conversion.

Recently, the market for solar-energy is expanding due to introduction of the RPS (Renewable Portfolio Standard). Thus, vigorous research is held on alternatives against the lack of sites to install overland PV systems. The floating PV system demonstrated in this paper is a new method of solar-energy generation utilizing water surface available on dams, reservoirs, and other bodies of water. This method has an advantage that allows efficient use of the nation’s soil without bringing damages to the environment, which the pre-existing PV systems cause when it is installed in farmlands or forests.

1.2 What is a Solar PV

The most abundant and convenient source of renewable energy is solar energy, which can be harnessed by photovoltaic cells. Photovoltaic cells are the basic of the solar system. The word photovoltaic comes from “photo” means light and “voltaic” means producing electricity. Therefore, the photovoltaic process is “producing electricity directly from sunlight”. The output power of a photovoltaic cell depends on the amount of light projected on the cell. Time of the day, season, panel position and orientation are also thefactors behind the output power. The current-voltage and power-voltage characteristics of a photovoltaic cell are shown.A photovoltaic array (also called a solar array) consists of multiple photovoltaic modules, casually referred to as solar panels, to convert solar radiation (sunlight) into usable direct current (DC) electricity. A photovoltaic system for residential, commercial, or industrial energy supply normally contains an array of photovoltaic (PV) modules, one or more DC to alternating current (AC) power converters (also known as inverters), a racking system that supports the solar modules, electrical wiring and interconnections, and mounting for

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other components. Optionally, a photovoltaic system may include any or all of the following: renewable energy credit revenue-grade meter, maximum power point tracker (MPPT), battery system and charger, GPS solar tracker , energy management software, solar concentrators, solar irradiance sensors, anemometer, or task-specific accessories designed to meet specialized requirements for a system owner. The number of modules in the system determines the total DC watts capable of being generated by the solar array; however, the inverter ultimately governs the amount of AC watts that can be distributed for consumption.

Figure 1.1 V-I Curve

1.3 Solar Thermal Energy

Solar thermal technology is not the same as solar panel technology or photovoltaic technology. Solar thermal energy uses solar energy or concentrates the light from the sun to create heat and that heat is used to run a heat engine, which turns a generator to produce electricity. The working fluid that is heated by the concentrated sunlight can be a liquid or a gas. Different working fluids include oil, water, salt, air, nitrogen, helium, etc. All of these engines should be very efficient having effeciency of around 30% to 40% and are capable of generating 10’s to 100’s of megawatts of power.

1.4 History

The first conventional photovoltaic cells were produced in the late 1950s, and throughout the 1960s were principally used to provide electrical power for earth-orbiting satellites. In the 1970s, improvements in manufacturing, performance and quality of PV modules helped to reduce costs and opened up a number of opportunities for powering remote terrestrial applications, including battery charging for navigational aids, signals, telecommunications. In the 1980s, photovoltaic became a popular power source for consumer electronic devices, including calculators, watches, radios, lanterns and other small battery-charging applications. Following the energy crises of the 1970s, significant efforts also began to develop PV power systems for residential and commercial uses, both for stand-alone,

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remote power as well as for utility-connected applications. During the same period, international applications for PV systems to power rural health clinics, refrigeration, water pumping, telecommunications, and off-grid households increased dramatically, and remain a major portion of the present world market for PV products. Today, the industry’s production of PV modules is growing at approximately 25 percent annually, and major programs in the U.S., Japan and Europe are rapidly accelerating the implementation of PV systems on buildings and interconnection to utility networks.

1.5 Development

Increasing the cell efficiency, maximizing the power output and employing a tracking system with solar panel are three ways to increase the overall efficiency of the solar panel Improvement of solar cell efficiency is an on-goingresearch work and people throughout the world are activelydoing research on this. Maximizing the output power fromsolar panel and integrating solar tracking system are the twoways where electronic design methodology can bring success.Maximum power point tracking (MPPT) is the process tomaximize the output power from solar panel by keeping the solar panel’s operation on the knee point of P-V characteristics (Fig. 1). A number of MPPT algorithms havebeen developed and employed around the world . MPPT technology only offers the maximum power that can be received from a stationary array of solar panels at a particular time; it cannot, however, increase the power generation whenthe sun is not aligned with the system.

1.6 Current Situation

A small PV system is capable of providing enough AC electricity to power a single home, or even an isolated device in the form of AC or DC electric. For example, military and civilian Earth observation satellites, street lights, construction and traffic signs, electric cars, solar-powered tents, and electric aircraft may contain integrated photovoltaic systems to provide a primary or auxiliary power source in the form of AC or DC power, depending on the design and power demands.

Large grid-connected photovoltaic power systems are capable of providing an energy supply for multiple consumers. The electricity generated can be stored, used directly (island/standalone plant), fed into a large electricity grid powered by central generation plants (grid-connected or grid-tied plant), or combined with one, or many, domestic electricity generators to feed into a small electrical grid (hybrid plant). PV systems are generally designed in order to ensure the highest energy yield for a given investment.

In the United States, the Authority Having Jurisdiction (AHJ) will review designs and issue permits, before construction can lawfully begin. Electrical installation practices must comply with standards set forth within the National Electrical Code (NEC) and be inspected by the AHJ to ensure compliance with building code, electrical code, and fire safety code. Jurisdictions may require that equipment has been tested, certified, listed, and labelled by at least one of the Nationally Recognized Testing Laboratories (NRTL).

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Despite the complicated installation process, a recent list of solar contractors shows a majority of installation companies were founded since 2000.

1.7 Development of Raft

In this project we are using four PVC pipes having a diameter of 2.5 inches approximately. These pipes are used to make the floating surface of the floating photovoltaic system or the raft in which we are using nine solar panel of ratings 9 volt each along with their reflector. We are using two aluminium sheets for one panel having dimension approximately equal to the dimension of solar panels. The function of reflector is to reflect or to converge the intensity of light towards the panel in order to get maximum output. The raft is made in such a manner that it can easily withstand the complete weight of the system with getting any kind damage.

1.8 Improvement in Efficiency

The overall efficiency of this system is approximately 13% more than the normal conventional sun tracking solar panels due to lower operating temperature and proximity to the water level. This system is having overall greater efficiency because it is placed parallel to the surface of water in a lake or a pond, which considerably increases the brightness and light reflection.

1.9 Literature survey

A photovoltaic system converts sunlight into electricity. The basic device of a photovoltaic system is the photovoltaic cell. Cells may be grouped to form panels or modules. Panels can be grouped to form large photovoltaic arrays. The term array is usually employed to describe a photovoltaic panel (with several cells connected in series and/or parallel) or a group of panels. Most of time one are interested in modeling photovoltaic panels, which are the commercial photovoltaic devices. This paper focuses on modeling photovoltaic modules or panels composed of several basic cells. The term array used henceforth means any photovoltaic device composed of several basic cells. In the Appendix at the end of this paper there are some explanations about how to model and simulate large photovoltaic arrays composed of several panels connected in series or in parallel. The electricity available at the terminals of a photovoltaic array may directly feed small loads such as lighting systems and DC motors. Some applications require electronic converters to process the electricity from the photovoltaic device. These converters may be used to regulate the voltage and current at the load, to control the power flow in grid-connected systems and mainly to track the maximum power point (MPP) of the device. Photovoltaic arrays present a nonlinear I-V characteristic with several parameters that need to be adjusted from experimental data of practical devices. The mathematical model of the photovoltaic array may be useful in the study of the

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dynamic analysis of converters, in the study of maximum power point tracking (MPPT) algorithms and mainly to simulate the photovoltaic system and its components using simulators.

This text presents in details the equations that form the I-V model and the method used to obtain the parameters of the equation. The aim of this paper is to provide the reader with all necessary information to develop photovoltaic array models and circuits that can be used in the simulation of power converters for photovoltaic applications.

Fig. 1 shows the equivalent circuit of the ideal photovoltaic cell. The basic equation from the theory of semiconductors that mathematically describes the I-V characteristic of the ideal photovoltaic cell is:

where Ipv, cell is the current generated by the incident light (it is directly proportional to the Sun irradiation), Id is the Shockley diode equation, I0,cell is the reverse saturation or leakage current of the diode [A], q is the electron charge [1.60217646 ・10−19C], k is the Boltzmann constant [1.3806503 ・ 10−23J/K], T [K] is the temperature of the p-n junction, and a is the diode ideality constant. Fig. 1.9.1 shows the I-V curve originated from (1).

The basic equation (1) of the elementary photovoltaic cell does not represent the I-V characteristic of a practical photovoltaic array. Practical arrays are composed of several connected photovoltaic cells and the observation of the characteristics at the terminals of the photovoltaic array requires the inclusion of additional parameters to the basic equation

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Fig.1.9.1. Characteristic I-V curve of the photovoltaic cell. The net cell current I is composed of the light-generated current Ipv and the diode current Id.

whereIpv and I0 are the photovoltaic and saturation currents of the array and Vt = NskT/q is the thermal voltage of the array with Ns cells connected in series. Cells connected in parallel increase the current and cells connected in series provide greater output voltages. If the array is composed of Np parallel connections of cells the photovoltaic and saturation currents may be expressed as: Ipv=Ipv,cellNp, I0=I0,cellNp. In (2) Rs is the equivalent series resistance of the array and Rp is the equivalent parallel resistance. This equation origin at the I-V curve seen in Fig. 3, where three remarkable points are highlighted: short circuit (0, Isc), maximum power point (Vmp, Imp) and open-circuit (Voc, 0). Eq. (2) describes the single-diode model presented in Fig.1. Some authors have proposed more sophisticated models that present better accuracy and serve for different purposes. For example, in an extra diode is used to represent the effect of the recombination of carriers. In a three-diode model is proposed to include the influence of effects which are not considered by the previous models. For simplicity the single-diode model of Fig. 1 is studied in this paper. This model offers a good compromise between simplicity and accuracy and has been used by several authors in previous works, sometimes with simplifications but always with the basic structure composed of a current source and a parallel diode. The simplicity of the single-diode model with the method for adjusting the parameters and the improvements proposed in this paper make this model perfect for power electronics designers who are looking for an easy and effective model for the simulation of photovoltaic devices with power converters. Manufacturers of photovoltaic arrays, instead of the I-V equation, provide only a few experimental data about electrical and thermal characteristics. Unfortunately some of the parameters required for adjusting photovoltaic array models cannot be found in the manufacturer’s data sheets, such as the light-generated or photovoltaic current, the series and shunt

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resistances, the diode ideality constant, the diode reverse saturation current, and the band gap energy of the semiconductor. All photovoltaic array datasheets bring basically the following information: the nominal open-circuit voltage Voc ,n, the nominal short-circuit current Is ,n, the voltage at the maximum power point Vmp, the current at the maximum power point Imp, the open-circuit voltage/temperature coefficient KV , the short-circuit current/temperature coefficient KI , and the maximum experimental peak output power Pmax ,e. This information is always provided with reference to the nominal or standard test conditions (STC) of temperature and solar irradiation. Some manufacturers provide I-V curves for several irradiation and temperature conditions. These curves make easier the adjustment and the validation of the desired mathematical I-V equation. Basically this is all the information one can get from datasheets of photovoltaic arrays. Electric generators are generally classified as current or voltage sources. The practical photovoltaic device presents an hybrid behavior, which may be of current or voltage source depending on the operating point, as shown in Fig. 3. The practical photovoltaic device has a series resistance Rs whose influence is stronger when the device operates in the voltage source region, and a parallel resistance Rp with stronger influence in the current source region of operation. The Rs resistance is the sum of several structural resistances of the device. The Rp resistance exists mainly due to the leakage current of the p-n junction and depends on the fabrication method of the photovoltaic cell. The value of Rp is generally high and some authors neglect this resistance to simplify the model. The value of Rs is very low and sometimes this parameter is neglected too .The I-V characteristic of the photovoltaic device shown in Fig. 3 depends on the internal characteristics of the device (Rs, Rp) and on external influences such as irradiation level and temperature. The amount of incident light directly affects the generation of charge carriers and consequently the current generated by the device. The light-generated current (Ipv) of the elementary cells, without the influence of the series and parallel resistances, is difficult to determine. Datasheets only inform the nominal short-circuit current (Isc,n), which is the maximum current available at the terminals of the practical device. The assumption Isc≈ Ipv is generally used in photovoltaic models because in practical devices the series resistance is low and the parallel resistance is high. The light generated current of the photovoltaic cell depends linearly on the solar irradiation and is also influenced by the temperature according to the following equation

whereIpv,n [A] is the light-generated current at the nominal condition (usually 25 ◦C and 1000W/m2), _T = T – Tn (being T and Tn the actual and nominal temperatures [K]), G [W/m2] is the irradiation on the device surface, and Gn is the nominal irradiation. The diode saturation current I0 and its dependence on thetemperature may be expressed by (4)

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whereEg is the bandgap energy of the semiconductor (Eg≈ 1.12 eV for the polycrystalline Si at 25 ◦C) and I0,n is the nominal saturation current:

withVt,n being the thermal voltage of Ns series-connected cells at the nominal temperature Tn. The saturation current I0 of the photovoltaic cells that compose the device depend on the saturation current density of the semiconductor (J0, generally given in [A/cm2]) and on the effective area of the cells. The current density J0 depends on the intrinsic characteristics of the photovoltaic cell, which depend on several physical parameters such as the coefficient of diffusion of electrons in the semiconductor, the lifetime of minority carriers, the intrinsic carrier density, and others . This kind of information is not usually available for commercial photovoltaic arrays. In this paper the nominal saturation current I0,n is indirectly obtained from the experimental data through (5), which is obtained by evaluating (2) at the nominal open-circuit condition, with V = Voc,n, I = 0, and Ipv≈ Isc,n. The value of the diode constant a may be arbitrarily chosen. Many authors discuss ways to estimate the correct value of this constant [8, 11]. Usually 1 ≤ a ≤ 1.5 and the choice depends on other parameters of the I-V model. Some values for a are found in [32] based on empirical analysis. As [8] says, there are different opinions about the best way to choose a. Because a expresses the degree of ideality of the diode and it is totally empirical, any initial value of a can be chosen in order to adjust the model. The value of a can be later modified in order to improve the model fitting if necessary. This constant affects the curvature of the I-V characteristic and varying a can slightly improve the model accuracy.

The photovoltaic model described in the previous section can be improved if equation (4) is replaced by:

This modification aims to match the open-circuit voltages of the model with the experimental data for a very large range of temperatures. Eq. (6) is obtained from (5) by including in the equation the current and voltage coefficients KV and KI. The saturation current I0 is strongly dependent on the temperature and (6) proposes a different approach to express the dependence of I0 on the temperature so that the net effect of the

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temperature is the linear variation of the open-circuit voltage according the the practical voltage/temperature coefficient. This equation simplifies the model and cancels the model error at the vicinities of the open-circuit voltages and consequently at other regions of the I-V curve. The validity of the model with this new equation has been tested through computer simulation and through comparison with experimental data. One interesting fact about the correction introduced with (6) is that the coefficient KV from the manufacturer’s datasheet appears in the equation. The voltage/ temperature coefficient KV brings important information necessary to achieve the best possible I-V curve fitting for temperatures different of the nominal value. If one wish to keep the traditional equation (4), instead of using (6), it is possible to obtain the best value of Eg for the model so that the open-circuit voltages of the model are matched with the open-circuit voltages of the real array in the range Tn< T <Tmax. By equaling (4) and (6) and solving for Eg at T = Tmax one gets:

Two parameters remain unknown in (2), which are Rs and Rp. A few authors have proposed ways to mathematically determine these resistances. Although it may be useful to have a mathematical formula to determine these unknown parameters, any expression for Rs and Rp will always rely on experimental data. Some authors propose varying Rs in an iterative process, incrementing Rs until the I-V curve visually fits the experimental data and then vary Rp in the same fashion. This is a quite poor and inaccurate fitting method, mainly becauseRsandRp may not be adjusted separately if a good I-V model is desired. This paper proposes a method for adjusting Rs and Rp based on the fact that there is an only pair {Rs,Rp} that warranties that Pmax,m = Pmax,e = VmpImp at the (Vmp, Imp)point of the I-V curve, i.e. the maximum power calculated by the I-V model of (2), Pmax,m, is equal to the maximum experimental power from the datasheet, Pmax,e , at themaximum power point (MPP). Conventional modeling methods found in the literature take care of the I-V curve but forget that the P-V (power vs. voltage) curve must match the experimental data too. Works like [26, 39] gave attention to the necessity of matching the power curve but with different or simplified models. In [26], for example, the series resistance of the array

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model is neglected. The relation between Rs and Rp, the only unknowns of (2), may be found by making Pmax,m = Pmax,e and solving the resulting equation for Rs, as (8) and (9) show.

Fig.1.9.2. P-V curves plotted for different values of Ra and Rp

Eq. (9) means that for any value of Rs there will be a value of Rp that makes the mathematical I-V curve cross the experimental (Vmp, Imp) point.

The goal is to find the value of Rs (and hence Rp) that makes the peak of the mathematical P-V curve coincide with the experimental peak power at the (Vmp, Imp) point. This requires several iterations until Pmax,m = Pmax,e. In the iterative processRs must be slowly incremented starting from Rs = 0. Adjusting the P-V curve to match the experimental data requires finding the curve for several values of Rs and Rp. Actually plotting the curve is not necessary, as only the peak power value is required. Figs. 4 and 6 illustrate how this iterative process works. In Fig. 4 as Rs increases the P-V curve moves to the left and the peak power (Pmax,m) goes towards the experimental MPP. Fig. 5 shows the contour drawn by the peaks of the power curves for several values of Rs (this example uses the parameters of the Kyocera KC200GT solar array [40]). For every P-V

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curve of Fig. 4 there is a corresponding I-V curve in Fig. 6. As expected from (9), all I-V curves cross the desired experimental MPP point at (Vmp, Imp). Plotting the P-V and I-V curves requires solving (2) for I ∈[0, Isc,n] and V ∈[0, Voc,n]. Eq. (2) does not have a direct solution because I = f(V, I) and V = f(I, V ). This transcendental equationmust be solved by a numericalmethod and this imposes no difficulty. The I-V points are easily obtained by numerically solving g(V, I) = I −f(V, I) = 0 for a set of V values and obtaining the corresponding set of I points.Obtaining the P-V points is straightforward.

Fig.1.9.3. Pmax ,m vs. V for several values of Rs> 0.

Fig.1.9.4. I-V curves plotted for different values of Rs and Rp.

The iterative method gives the solution Rs = 0.221 for the KC200GT array. Fig. 5 shows a plot of Pmax,m as a function of V for several values of Rs. There is an only point, corresponding to a single value of Rs, that satisfies the imposed condition Pmax,m = Vmp Imp at the (Vmp, Imp) point. Fig. 7 shows a plot of Pmax,m as a function of Rs for I = Imp and V = Vmp. This plot shows that Rs = 0.221 is the desired solution, in accordance with the result of the iterative method. This plot may be an alternative way for graphically finding the solution for Rs.

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Fig.1.9.5. Pmax = f(Rs) with I = Imp and V = Vmp.

Fig.1.9.6. P-V curve adjusted to three remarkable points.

Figs. 8 and 9 show the I-V and P-V curves of the KC200GT photovoltaic array adjusted with the proposed method. The model curves exactly match with the experimental data at the three remarkable points provided by the datasheet: short circuit, maximum power, and open circuit. Table I shows the experimental parameters of the array obtained from the data sheet and Table II shows the adjusted parameters and model constants.

The model developed in the preceding sections may be further improved by taking advantage of the iterative solution of Rs and Rp. Each iteration updates Rs and Rp towards the best model solution, so equation (10) may be introduced in the model.

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Eq. (10) uses the resistances Rs and Rp to determine Ipv6= Isc. The values of Rs and Rp are initially unknown but as the solution of the algorithm is refined along successive iterationsthe values of Rs and Rp tend to the best solution and (10) becomes valid and effectively determines the light-generated current Ipv taking in account the influence of the series andparallel resistances of the array. Initial guesses for Rs and Rp are necessary before the iterative process starts. The initial value of Rs may be zero. The initial value of Rp may be given by:

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Eq. (11) determines the minimum value of Rp, which is the slope of the line segment between the short-circuit and the maximum-power remarkable points. Although Rp is still unknown,it surely is greater than Rp,min and this is a good initial guess. The simplified flowchart of the iterative modeling algorithm is illustrated in Fig. 10.

As Tables I and II and Figs. 8 and 9 have shown, the developed model and the experimental data are exactly matched at the nominal remarkable points of the I-V curve and the experimental and mathematical maximum peak powers coincide. The objective of adjusting the mathematical I-V curve at the three remarkable points was successfully achieved. In order to test the validity of the model a comparison with other experimental data (different of the nominal remarkablepoints) is very useful. Fig. 11 shows the mathematical I-V curves of the KC200GT solar panel plotted with the experimental data at three different temperature conditions. Fig. 12 shows the I-V curves at different irradiations. The circular markers in the graphs represent experimental (V, I) points

Fig.1.9.7. Algorithm of the method used to adjust the I-V model.

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Fig.1.9.8. I-V model curves and experimental data of the KC200GT

solar array at different temperatures, 1000W/m2. extracted from the datasheet. Some points are not exactly matched because the model is not perfect, although it is exact at the remarkable points and sufficiently accurate for other points. The model accuracy may be slightly improved by running more iterations with other values of the constant a, without modifications in the algorithm. Fig. 13 shows the mathematical I-V curves of the Solar MSX60 solar panel plotted with the experimental data at two different temperature conditions. Fig. 14 shows the P-V curves obtained at the two temperatures. The circular markers in the graphs represent experimental (V, I) and (V, P) points extracted from the datasheet. Fig. 14 proves that the model accurately matches with the experimental data both in the current and power curves, as expected.

SIMULATION OF THE PHOTOVOLTAIC ARRAY

The photovoltaic array can be simulated with an equivalent circuit model based on the photovoltaic model of Fig. 1. Two simulation strategies are possible. Fig. 15 shows a circuit model using one current source

Fig.1.9.9. I-V model curves and experimental data of the KC200GT solar array at different irradiations, 25 ◦C.

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Fig.1.9.10. I-V model curves and experimental data of the MSX60 solar array at different temperatures, 1000W/m2.

Fig.1.9.11. P-V model curves and experimental data of the MSX60 solar array at different temperatures, 1000W/m2.

Fig.1.9.12. Photovoltaic array model circuit with a controlled current source

This computational block may be implemented with any circuit simulator able to evaluate math functions. Fig. 16 shows another circuit model composed of only one current source. The value of the current is obtained by numerically solving the I-V equation. For every value of V a corresponding I that satisfies the I-V equation (2) is

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obtained. The solution of (2) can be implemented with a numerical method in any circuit simulator that accepts embedded programming. This is the simulation strategy proposed in other authors have proposed circuits for simulating photovoltaic arrays that are based on simplified equations and/or require lots of computational effort. In a circuit-based photovoltaic model is composed of a current source driven by an intricate and inaccurate equation where the parallel resistance is neglected. In an intricate P Spice based simulation was presented, where the I-V equation is numerically solved within the P Spice software. Although interesting, the approach found in is excessively elaborated and concerns the simplified photovoltaic model without the series resistance. In a simple circuit-based photovoltaic model is proposed where the parallel resistance is neglected.

In a circuit-based model was proposed based on the piecewise approximation of the I-V curve. Although interesting and relatively simple, this method does not provide a solution to find the parameters of the I-V equation and the circuit model requires many components. Figs. 17 and 18 show the photovoltaic model circuits implemented with MATLAB/SIMULINK (using the Sym Power Systems block set) and PSIM using the simulation strategy of Fig. 15. Both circuit models work perfectly and may be used in the simulation of power electronics converters for photovoltaic systems. Figs. 19 and 20 show the I-V curves of the Solarex MSX60 solar panel simulated with the MATLAB/ SIMULINK and PSIM circuits.

Figure 1.9.13. I VS V Curve

(V, I) remarkable points without the need to guess or to estimate any other parameters except the diode constant a. This paper has proposed a closed solution for the problem of findingthe parameters of the single-diode model equation of a practical photovoltaic array. Other authors have tried to propose single-diode models and methods for estimating the model parameters, but these methods always require visually fitting the mathematical curve to the I-V points and/or graphically extracting the slope of the I-V curve at a given point and/or successively solving and adjusting the model in a trial and error process. Some authors have proposed indirect methods to adjust the I-V curve through artificial intelligence and interpolation techniques . Although interesting, such methods are not very practical and are unnecessarily complicated and require more computational effort than it would be expected for this problem. Moreover, frequently in these models Rs and Rp are neglected or treated as independent parameters, which is not true if one wish to correctly adjust the model so that the maximum power of the model is equal to the

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maximum power of the practical array. An equation to express the dependence of the diode saturation current I0 on the temperature was proposed and used in the model. The results obtained in the modeling of two practical photovoltaic arrays have demonstrated that the equation is effective and permits to exactly adjust the I-V curve at the open-circuit voltages at temperatures different of the nominal. Moreover, the assumption Ipv≈ Isc used in most of previous works on photovoltaic modeling was replaced in this method by a relation between Ipv and Isc based on the series and parallel resistances. The proposed iterative method for solving the unknown parameters of the I-V equation allows to determine the value of Ipv, which is different of Isc. This paper has presented in details the equations that constitute the single-diode photovoltaic I-V model and the algorithm necessary to obtain the parameters of the equation. In order to show the practical use of the proposed modeling method this paper has presented two circuit models that can be used to simulate photovoltaic arrays with circuit simulators. This paper provides the reader with all necessary information to easily develop a single-diode photovoltaic array model for analyzing and simulating a photovoltaic array.

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CHAPTER 2

MODELING OF SOLAR PV SYSTEM IN MATLAB

2.1 Mathematical model of solar pv

Figure 2.1 - Mathematical model of solar PV

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2.2 Characteristics of panel output ( v-I , p-v)

Figure 2.2 - P-V, I-V characteristic of 9 panels

Figure 2.3 - P-V , I-V characteristic of one panel

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2.3 MPPT

Maximum power point tracking (MPPT) is a technique that grid connected inverters, solar battery chargers and similar devices use to get the maximum possible power from one or more photovoltaic devices, typically solar panels, though optical power transmission systems can benefit from similar technology. Solar cells have a complex relationship between solar irradiation, temperature and total resistance that produces a non-linear output efficiency which can be analyzed based on the I-V curve. 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. MPPT devices are typically integrated into an electric power converter system that provides voltage or current conversion, filtering, and regulation for driving various loads, including power grids, batteries, or motors.

Solar cell I-V curves where a line intersects the knee of the curves where the maximum power point is located. Photovoltaic cells have a complex relationship between their operating environment and the maximum power they can produce. The fill factor, abbreviated FF, is a parameter which characterizes the non-linear electrical behaviour of the solar cell. 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. In tabulated data it is often used to estimate the maximum power that a cell can provide with an optimal load under given conditions, P=FF*Voc*Isc. For most purposes, FF, Voc, and Isc are enough information to give a useful approximate model of the electrical behaviour of a photovoltaic cell under typical conditions.

For any given set of operational conditions, cells have a single operating point where the values of the current (I) and Voltage (V) of the cell result in a maximum power output. These values correspond to a particular load resistance, which is equal to V / I as specified by Ohm's Law. The power P is given by P=V*I. A photovoltaic cell, for the majority of its useful curve, acts as a constant current source. However, at a photovoltaic cell's MPP region, its curve has an approximately inverse exponential relationship between current and voltage. From basic circuit theory, the power delivered from or to a device is optimized where the derivative (graphically, the slope) dI/dV of the I-V curve is equal and opposite the I/V ratio (where dP/dV=0). This is known as the maximum power point (MPP) and corresponds to the "knee" of the curve.

A load with resistance R=V/I equal to the reciprocal of this value draws the maximum power from the device. This is sometimes called the characteristic resistance of the cell. This is a dynamic quantity which changes depending on the level of illumination, as well as other factors such as temperature and the age of the cell. If the resistance is lower or higher than this value, the power drawn will be less than the maximum available, and thus the cell will not be used as efficiently as it could be. Maximum power point trackers utilize different types of control circuit or logic to search for this point and thus to allow the converter circuit to extract the maximum power available from a cell.

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2.4 Classification

Controllers usually follow one of three types of strategies to optimize the power output of an array. Maximum power point trackers may implement different algorithms and switch between them based on the operating conditions of the array.

2.5 Perturb and observe

In this method the controller adjusts the voltage by a small amount from the array and measures power; if the power increases, further adjustments in that direction are tried until power no longer increases. This is called the perturb and observe method and is most common, although this method can result in oscillations of power output. It is referred to as a hill climbing method, because it depends on the rise of the curve of power against voltage below the maximum power point, and the fall above that point. Perturb and observe is the most commonly used MPPT method due to its ease of implementation. Perturb and observe method may result in top-level efficiency, provided that a proper predictive and adaptive hill climbing strategy is adopted.

2.6 Incremental conductance

In the incremental conductance method, the controller measures incremental changes in array current and voltage to predict the effect of a voltage change. This method requires more computation in the controller, but can track changing conditions more rapidly than the perturb and observe method (P&O). Like the P&O algorithm, it can produce oscillations in power output. This method utilizes the incremental conductance (dI/dV) of the photovoltaic array to compute the sign of the change in power with respect to voltage (dP/dV).

The incremental conductance method computes the maximum power point by comparison of the incremental conductance (IΔ / VΔ) to the array conductance (I / V). When these two are the same (I / V = IΔ / VΔ), the output voltage is the MPP voltage. The controller maintains this voltage until the irradiation changes and the process is repeated.

2.7 Current Sweep Method

The current sweep method uses a sweep waveform for the PV array current such that the I-V characteristic of the PV array is obtained and updated at fixed time intervals. The maximum power point voltage can then be computed from the characteristic curve at the same intervals.

2.8 Constant voltage

The term "constant voltage" in MPP tracking is used to describe different techniques by different authors, one in which the output voltage is regulated to a constant value under all conditions and one in which the output voltage is regulated based on a constant ratio to

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the measured open circuit voltage (VOC). The latter technique is referred to in contrast as the "open voltage" method by some authors. If the output voltage is held constant, there is no attempt to track the maximum power point, so it is not a maximum power point tracking technique in a strict sense, though it does have some advantages in cases when the MPP tracking tends to fail, and thus it is sometimes used to supplement an MPPT method in those cases.

In the "constant voltage" MPPT method (also known as the "open voltage method"), the power delivered to the load is momentarily interrupted and the open-circuit voltage with zero current is measured. The controller then resumes operation with the voltage controlled at a fixed ratio, such as 0.76, of the open-circuit voltage VOC. This is usually a value which has been determined to be the maximum power point, either empirically or based on modelling, for expected operating conditions.

2.9 Comparison of methods

Both perturb and observe, and incremental conductance, are examples of "hill climbing" methods that can find the local maximum of the power curve for the operating condition of the array, and so provide a true maximum power point.

The perturb and observe method can produce oscillations of power output around the maximum power point even under steady state illumination.

The incremental conductance method has the advantage over the perturb and observe method that it can determine the maximum power point without oscillating around this value. It can perform maximum power point tracking under rapidly varying irradiation conditions with higher accuracy than the perturb and observe method. However, the incremental conductance method can produce oscillations and can perform erratically under rapidly changing atmospheric conditions. The computational time is increased due to slowing down of the sampling frequency resulting from the higher complexity of the algorithm compared to the P&O method.

In the constant voltage ratio (or "open voltage") method, the current from the photovoltaic array must be set to zero momentarily to measure the open circuit voltage and then afterwards set to a predetermined percentage of the measured voltage, usually around 76%. Energy may be wasted during the time the current is set to zero. The approximation of 76% as the MPP/VOC ratio is not necessarily accurate though. Although simple and low-cost to implement, the interruptions reduce array efficiency and do not ensure finding the actual maximum power point. However, efficiencies of some systems may reach above 95%.

2.10 MPPT placement

Traditional solar inverters perform MPPT for an entire array as a whole. In such systems the same current, dictated by the inverter, flows through all panels in the string. Because

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different panels have different IV curves and different MPPs (due to manufacturing tolerance, partial shading, etc.) this architecture means some panels will be performing below their MPP, resulting in the loss of energy.

Some companies (see power optimizer) are now placing peak power point converters into individual panels, allowing each to operate at peak efficiency despite uneven shading, soiling or electrical mismatch.

Data suggests having one inverter with one MPPT for a project that has east and west-facing modules presents no disadvantages when compared to having two inverters or one inverter with more than one MPPT."Efficient East-West Oriented PV Systems with One MPP Tracker," DietmarStaudacher, 2011

2.11Operation with batteries

At night, an off-grid PV power system may use batteries to supply loads. Although the fully charged battery pack voltage may be close to the PV panel's maximum power point voltage, this is unlikely to be true at sunrise when the battery has been partially discharged. Charging may begin at a voltage considerably below the PV panel maximum power point voltage, and an MPPT can resolve this mismatch.

When the batteries in an off-grid system are fully charged and PV production exceeds local loads, an MPPT can no longer operate the panel at its maximum power point as the excess power has no load to absorb it. The MPPT must then shift the PV panel operating point away from the peak power point until production exactly matches demand. (An alternative approach commonly used in spacecraft is to divert surplus PV power into a resistive load, allowing the panel to operate continuously at its peak power point.)

In a grid connected photovoltaic system, all delivered power from solar modules will be sent to the grid. Therefore, the MPPT in a grid connected PV system will always attempt to operate the PV panel at its maximum power point.

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CHAPTER 3

DEVELOPMENT OF FLOATING SYSTEM

3.1 General

A developed PV floating power generation results from the combination of PV plant technology and floating technology. This fusion is a new concept for technology development. As a new generation technology, it can replace the existing PV plants that are installed on top of woodland, farmland and buildings. The PV floating plant consists of a floating system, mooring system, PV system and underwater cables.

a. Floating System: A floating body (Structure + Floater) that allows the installation of the PV module.b. Mooring System: Can adjust to water level fluctuations while maintaining its position in a southward direction.c. PV System: PV generation equipment, similar to electrical junction boxes, that are installed on top of the floating system.d. Underwater Cable: Transfers the generated power from land to the PV system.

Figure 3.1 Diagram for Floating System

3.2 Floating structure :.

The system consists of a platform with photovoltaic panels supported by a structure in pvc tubes. The power of a module ranges from 20 to 500 kW, depending on the dimension of the platform. Cooling of the panel is ensured by a veil of water generated by a set of irrigators located in the upper part of PV panel. Basically in our project we have used four PVC pipes for the floating structure and nine solar panels are (connected in series) supported by the floating pipe structure.

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Photovoltaic panels are emerging as a robust, efficient, distributed energy source. The costs are decreasing and this justifies the effort to improve their use and to study the possibility of building large plants.There are still three limitations: the thermal drift which lowers the efficiency of the system of 10-15%, the availability of spaces for photovoltaic fields, the high cost of tracking systems.Floating Tracking Cooling Concentrator (FTCC) System allows to exploit small basins and natural and artificial lakes to install PV plants.The FTCC system consists of a series of floating platforms with photovoltaic panels supported by a structure in polyethylene tubes. The power of a single module ranges from 20 to 200 kW, depending on the type of panel used. Cooling of the panel is ensured by a veil of water that is generated by a set of irrigators.

Figure 3.2Arrangement of P-V Panels

The FTCC system overcomes the limitations discussed above. In particular:1. Water veil keeps the PV panel at low temperatures with an average yearly

energy gain of more than 10%. 2. The floating platform allows a very efficient one axis tracking, so that

reflectors can be easily oriented to increase radiation collected on the panels.

3. The system exploits the unused areas of artificial reservoirs and has a very limited environmental impact.

Finally the cost of the system is limited. In practice the cost of tracking, cooling and reflectors (platform included) is less than € 800 for kWp. This further investment is limited compared to the one needed for PV part and it is offset by the increase of the yearly energy yield.

3.3DC to DC buck converter:

A buck converter is a voltage step down and current step up converter. The simplest way to reduce the voltage of a DC supply is to use a linear regulator (such as a 7805), but

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linear regulators waste energy as they operate by dissipating excess power as heat. Buck converters, on the other hand, can be remarkably efficient (95% or higher for integrated circuits), making them useful for tasks such as converting the main voltage in a computer (12 V in a desktop, 12-24 V in a laptop) down to the 0.8-1.8 volts needed by the processor. The basic operation of the buck converter has the current in an inductor controlled by two switches (usually a transistor and a diode). In the idealised converter, all the components are considered to be perfect. Specifically, the switch and the diode have zero voltage drop when on and zero current flow when off and the inductor has zero series resistance. Further, it is assumed that the input and output voltages do not change over the course of a cycle (this would imply the output capacitance as being infinite).

Figure 3.3 Buck converter circuit diagram

Figure 3.4The two circuit configurations of a buck converter

The conceptual model of the buck converter is best understood in terms of the relation between current and voltage of the inductor. Beginning with the switch open (in the "off" position), the current in the circuit is 0. When the switch is first closed, the current will begin to increase, and the inductor will produce an opposing voltage across its terminals in response to the changing current. This voltage drop counteracts the voltage of the source and therefore reduces the net voltage across the load. Over time, the rate of change of current decreases, and the voltage across the inductor also then decreases, increasing the voltage at the load. During this time, the inductor is storing energy in the form of a magnetic field. If the switch is opened while the current is still changing, then there will always be a voltage drop across the inductor, so the net voltage at the load will always be less than the input voltage source.

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Figure 3.5 Connection Diagram

When the switch is opened again, the voltage source will be removed from the circuit, and the current will decrease. The changing current will produce a change in voltage across the inductor, now aiding the source voltage. The stored energy in the inductor's magnetic field supports current flow through the load. During this time, the inductor is discharging its stored energy into the rest of the circuit. If the switch is closed again before the inductor fully discharges, the voltage at the load will always be greater than zero.

3.4 Solar Concentrator As the input to the solar panels are temperature and the solar irradiance and our purpose is to get high radiance throughout the day to obtain the maximum efficiency. Therefor to fulfil this purpose we have used a set of reflectors (i.e a pair of reflector for each panel in our project) to concentrate the incoming radiation.Panels are equipped with reflectors; two solutions have been studied. Experimental tests are ongoing for both solutions.

3.4.a. First solution

Figure 3.6 Solar Concentrator first solution

The first solution. The issue of shadows and reflectors is evident.The panels are inclined by an optimal angle (for example 40°) and the platform is oriented in such a way as to optimize the solar radiation on the panels. Shadows are unavoidable when the sun is low

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on the horizon but can be partially compensated by reflectors which increase the radiation when the sun is high on the horizon.The main problem in this case seems to be the lack of homogeneity in solar radiation on the photovoltaic cells.The unevenness of radiation can significantly reduce the efficiency of the panel and for this reason is required some distance between the rows of reflectors and those of the panels.

3.4.b. Second solutionThe second solution.Reflectors forming an angle of 60°.In order to overcome the mismatched radiation problem, a second solution was proposed: the panel is positioned between two reflectors tilted. In this case the solar panels are tilted by a very small angle and are oriented in such a way as to be always in line with the solar radiation. Reflectors are positioned on both side of the panels and form a suitable angle with the horizon.

Figure 3.7 Solar Concentrator second solution

The limit of this approach lies in the efficiency of the reflectors and in their inability to focus diffuse radiation. The gain due to the concentration, adequately supported by panels cooling, is however remarkable and can reach values between 60 and 70% depending on the latitude.Second solution: a 60° angle. FTCC system in Colignola –Pisa.The second solution

(angle 60°) has been adopted in the pilot plant in Pisa which will be finished by the end of September 2011. This pilot plant will be used to measure the system performance and to test the tracking system efficiency.The FTCC system proposes an innovative solution to exploit surfaces already equipped and available for industrial uses while at the same time improving the efficiency and annual yield of PV plants. Costs of the supporting platform and of cooling, tracking, reflector system are rather limited and compensated by the increase in the annual energy yield.

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Figure 3.8 P-V Panels with Reflectors3.5Reflectors efficiency

The plot below shows data taken in May for a panel with reflectors compared to a panel without reflectors (without and with water). Best values are reached in clear sky days; however interesting gains of 20-30% are obtained even in thepresence of diffuse radiation.It is worth noticing that the water veil is particularly efficient in the presence of reflectors. This is due in part to the increase in the panel temperature for the presenceof reflected radiation, but mainly to the better radiation capture thanks to the graded refraction index. Increase due to reflectors for panel with 2°. Abscissa numerates the different data acquisitions.

3.6 Solar tracker The platform can be of arbitrary form (circular or rectangular) and is built with modular elements (rafts) each supporting 2 or 3 PV panels. The platform is fixed trough a mooring system and rotates thanks to two motors which generate a torque around the central axis. Detail of the platform. The tracking cannot be based uniquely on a geometrical algorithm (astronomical tracking). Actually the platform position is not well defined so that it is necessary to implement a solar sensor. The full system is then composed by the following parts:

1 – An electronic guidance system (EGS) able to recognize the sun position with respect to the platform: this is based on a camera and on a SW able to identify the maximum radiation zone with a precision of a few tenths of one degree.2 – Two electric outboard motors (bow thrusters) positioned at the end of the cross3 – A heavy stone (mooring post) with a chain that allows the platform to turn4 – A second mooring post limiting the rotation of the platform to a certain angle in order to avoid cable twisting when the system is stopped.

The EGS, turning on and off the two motors, sets the platform in the correct direction toward the sun. If the system is to be stopped for whatever reason (night, strong winds etc) the outer mooring post blocks the rotation of the platform over a certain angle to avoid cable twisting. Measurement of the tracking precision

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has been successful and confirms the possibility to orientate the platform with a precision of 1°. Simulations and measurement of wind load and of structure strength have been made and we have verified that the strengths involved are very low because of the system configuration.And task-specific accessories designed to meet specialized requirements for a system owner. The number of modules in the system determines the total DC watts capable of being generated by the solar array; however, the inverter ultimately governs the amount of AC watts that can be distributed for consumption.

3.7Solar Irradiance Sensors :Voltage Sensor

Figure3.9Solar Irradiance Sensors :Voltage Sensor

In order for the MPPT controller to measure the voltage provided by the solar panel, two resistors, R1 and R2, are employed in parallel with the solar panel to act as a voltage divider. The voltage across R2 in the voltage divider is fed into an analog-to-digital converter (ADC) driver circuit (op-amp in a voltage follower configuration that feeds into a low-pass filter) before being delivered to the ADCINA0 channel of the MPPT controller. By choosing the values of R1 and R2 as 1.07 MΩ and 165 kΩ, respectively, the maximum amount of current diverted from the load, I2, is small enough, even in a worst-case scenario, to be considered negligible. The allowable voltage range for each ADC channel of the MPPT controller is 0-3 Vdc. Therefore, the voltage across R2 (which serves as a scaled-down representation of the solar panel's voltage) should not exceed 3 Vdc. Based on the chosen value of R2 as 165 kΩ, the maximum voltage, V(R2,max), sent to the ADC driver circuit (and thus ADC channel ADCINA0) is ~2.81 Vdc.

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3.8 Current Sensor

Figure 3.10Current Sensor

In order for the MPPT controller to measure the current provided by the solar panel, a single resistor (Rsense) is placed in series between the solar panel and the DC-DC converter. The voltage across Rsense is fed into an AD8215 current sensor manufactured by Analog Devices whose output voltage is then fed into an ADC driver circuit (op-amp in a voltage follower configuration that feeds into a low-pass filter) before being delivered to the ADCINA1 channel of the MPPT controller. By choosing the value of Rsense as 51 mΩ, the maximum voltage drop across Rsense, VRsense, is small enough, even in a worst-case scenario, to be considered negligible. As stated previously, the allowable voltage range for each ADC channel of the MPPT controller is 0-3 Vdc. Therefore, the output voltage of the AD8215 current sensor (which serves as an equivalent voltage representation of the solar panel's current) should not exceed 3 Vdc. Based on the chosen value of Rsense as 51 mΩ, the maximum voltage, Vout, sent to the ADC driver circuit (and thus ADC channel ADCINA1) is ~2.73 Vdc.

3.9 Cooling System

According to the requirement of the solar energy production system in FTCC we need suitable solar irradiance and a limited temperature and according to the complex relationship between the solar irradiance ,temperature and load it provide the fixed output in terms of voltage or current for the battery charging or for the supply for the ac purpose through invertor. By installing solar panels over a pond, the panels are naturally cooled, resulting in improved power production performance. The systems can also improve water quality. As water bodies are exposed to the sun, photosynthesis promotes growth of organic matter, including algae. By shading the water, algae growth is reduced, minimizing the associated treatment and labour costs The cooler environment also reduces stress on the system, extending the system’s lifespan. Although to limit the temperature of the panels we require to provide a cooling system for the pv modules. There are basically various methods available for the cooling purpose but for our project of low rating we have

1. Water sprinkling method

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2. Presence of water veilThese two methods are very useful in controlling the temperature of pv module. The cooling system using the water of the basin increases the efficiency by about 15%, bringing the annual yield to 2060 kWh per kWp.

3.10 Tank

The complete system needs water surface to float in order to make it float we designed a tank in our college. It has a length of 6 feet and 4 feet breadth and has approximately 3 feet depth. The tank is made up of bricks and cement and has a volume of 72 cubic feet approximately.

3.11 Budget

The constructional costs and budget can be established in the following macro block:

1. Execution planning (architectional, electric, structural) - 7%.

2.Floating system and structures – 35%

3. Photovoltaic panels – 35%

4. Inverters – 8%

5. Installation and cable harness – 7%

The total budget of this project is around Rs. 12000.

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CHAPTER 4

RESULT AND DISCUSSION

4.1 Results

After successful installation of sun tracking solar plant it was found that the floating photovoltaic system produces 11% more power than the ground based system. In addition to this, it was found that sun tracking solar system is eco-friendly that means it does not effect to environment.

4.2 Discussion

A new eco-friendly solution concerning the production of electric power is the innovative idea of a floating photovoltaic system. In order to work as best the solar energy, we developed and designed an innovative concept that focuses on the production of electric power, while respecting the environment. This solution is adaptable and suitable for any type of water surfaces(as small lakes, ponds, water, mountain, and plain lakes, lagoons etc.). In addition, photovoltaic panels, placed close to water, increase their efficiency due to the better reflection of the light on the water and to the lowest operating temperature, comparing to the ground facilities.The sun energy is available in the form of radiation over visible light and infrared region albeit at a very low intensity. Most commonly used ways of harvesting the radiant solar energy is using photovoltaic panels which basically are interconnected assemblies of photovoltaic cells. The photovoltaic systems receive solar energy mainly in the visible light and near infrared regions of the spectrum. The light power is converted directly into dc electric current. Photovoltaic energy conversion efficiency in most systems, however, is only in teens.

Due to the location, the floating photovoltaic system produces 11% more than the ground based system. This result is achieved thanks to the lower operating temperature of the panels even in the summer, due to their proximity to the water level. In addition, the solar panels have the greater efficiency, because they are placed almost parallel over the pond, which considerably increases the brightness and the light reflection, thanks to the waterglare.The Floating structure doesn't need any maintenance. An annual inspection is usually enough to verify the static stability and the right operation of the photovoltaic plant can be monitor by the remote control. The maintenance of the basin is not different from one done without the floating energy production system. The displacement of the plant is very easy, that allows to clean the blanks, the shores and the bottom of the basin without problems. The cleaning of the panels is left to the rainwater, which does not stagnate on the panel due to a small technical trick.

The simulation is realized on Mat lab/Simulink platform. The simulation consists of four modules: tracking cells, signal conditioning circuit, controller, and motor. The PV tracking cells detect light intensity and convert it into current. The PV tracking cells work as angle detectors. They are mounted on two 45 degree wedges to detect the exact angle

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in which the main solar panel must face to gain maximum power output. The current is amplified using the signal conditioning circuit, and sent to the microcontroller. The microcontroller uses different control algorithms to generate a signal to control the motor to rotate the main solar panel perpendicular to the sun. An embedded Mat labfunction simulate the control algorithm and mathematically generate PWM signal to drive the motor. Finally, the motor module consists of a stepper motor and motor drive. The motor module generates mechanical movement of rotation in terms of angle. The simulation provides an excellent platform for undergraduate engineering technology students to study a sun tracking solar power system.

The sun tracking mechanisms there is a requirement for a certain amount of electrical energy input for the controlling units(PLC, micro-controller, electronic circuit), for the actuators (electrical motor),and, for the sensors (Photo Detector, Light Dependent Resistors). Since electrical energy is needed as an external source to energize the motor, the employability of such mechanisms is restricted only to areas where electrical energy is easily and continuously available or when the unit itself is an electricity generator.

4.3 Application

There are various application of sun tracking solar system in day to day life. As solar system is most economical and eco-friendly system, it can be employed any where we want like small lakes, ponds, water, mountain, and plain lakes, lagoons etc. The application for sun tracking solar system are described under:-

a). When the sun tracking solar system is small in size then it produce small amount of power which can be used for household purposes like driving small mills, supply power to fan, tube light, washing machine, cooler, air conditioner, geyser. If anybody established sun tracking solar system on his ponds or somewhere water is stored then he can easily get sufficient amount of power so that all desire can be fulfilled.

b.) When the sun tracking solar system is larger in size then it will produce large amount of power. Hence the best way to utilize the generated power is to send power to the grid, from where it can be transmitted to the substation from where it is distributed to the large industry, small industry, also used for household purposes etc.

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CHAPTER 5

CONCLUSION

5.1 Conclusion

Insolation is around 650 (as the insolation during month of may in dehradun is 650) during testing of ftcc.Power without structure = 14.01Power with structurre = 17.00Power structure and tank= 17.85Improvement due to structure(%) = 3.01Improvement due to structure and tank (%) = 3.01Improvement due to cooling (%)= .85

Reflectors work well but with an efficiency which is slightly less than expected (50-60% in clear sky days versus the theoretical value of 70-80%). This can be due to lack of perfect homogeneity in reflected radiation. Tracking system gives a gain in efficiency as foreseen of about 25%. (Data are not reported in this short review but are in agreement with standard vertical axis tracking system). In conclusion, the FTCC system is minimally invasive, inexpensive in terms of energy and easy to dismantle.

5.2 Future Prospects

1.With electricity costs increasing nearly 22% in the past five years and even higher and more volatile prices projected, water agencies face a daunting challenge in keeping costs down for ratepayers, while at the same time finding the resources to invest in critical infrastructure project.

2.Water facilities in several states are taking control of their energy costs by turning to solar photovoltaic (PV) power. According to Michael Liebreich chairman of Bloomberg New Energy Finance, the cost of large solar system projects will fall by 50% by 2020. Consumers, businesses and municipalities are putting their assets to work in generating electricity with rooftop, carport and land-based solar installations.

3.Massachusetts has been aggressively rolling out solar projects and energy efficiency measures at 14 water and wastewater facilities across the state in an effort to reduce greenhouse gas emissions and 20% of the energy used by water treatment facilities. Through this program, $3.7 million of annual energy savings is anticipated through energy efficiencies and on-site energy power generation.

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E. Radziemska, “The effect of temperature on the power drop in crystalline silicon solar cells”, Renewable Energy, vol. 28, no. 1, (2003).

C. Hark sun, “A Study on Development of Syntactic Foam(I)”, The Korean Society of Ocean Engineers, (1992).

H. Haeberlin and J. D. Graf, “Gradual Reduction of PV Generator Yield due to Pollution”, 2nd World conference on Photovoltaic Solar Energy Conversion, (1998).

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