Design And Construction Of A 7.5KVA Solar Inverter

ABSTRACT

This work is on design and construction of a 7.5KVA solar inverter. Solar inverter converts the variable direct current (DC) output of a photovoltaic (PV) solar panel into a utility frequency alternating current (AC) that can be fed into a commercial electrical grid or used by a local, off-grid electrical network. It is a critical component in a photovoltaic system, allowing the use of ordinary AC-powered equipment.

In solar inverter, Solar panels produce direct electricity with the help of electrons that are moving from negative to positive direction. Most of the appliances that we use at home work on alternative current. This AC is created by the constant back and forth of the electrons from negative to positive. In AC electricity the voltage can be adjusted according to the use of the appliance.  As solar panels only produce Direct current the solar inverter is used to convert the DC to AC.

 TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

1.2      PROBLEM STATEMENT

1.3      AIM AND OBJECTIVE OF THE PROJECT

1.4      SCOPE OF THE PROJECT

1.5     SIGNIFICANCE OF THE PROJECT

1.6      INVERTERS

1.6.1 Central Inverters

1.6.2 Micro Inverters

1.7      THE BALANCE OF SYSTEM (BOS)

1.8      SOLAR PANELS

1.8.1 Solar Panel Mono or Poly

CHAPTER TWO

2.0     LITERATURE REVIEW

2.1      INTRODUCTION

2.2         COMPONENTS USED FOR THE DESIGN

2.3          REVIEW OF THE RELATED STUDY

2.4      KNOWLEDGE GAP

CHAPTER THREE

3.0     DESIGN AND IMPLEMENTATION

3.1      INTRODUCTION

3.2      DESIGN SPECIFICATIONS

3.3      THE RELAY UNIT

3.4      BATTERY UNIT

3.5      BATTERY CHARGING UNIT

3.6      SOLAR PANNEL

3.7      OSCILLATOR STAGE

3.8       POWER SWITCHING MOSFET

3.9    CONTROL UNIT

3.10     SOFTWARE PART

3.11     DISPLAY UNIT

3.12     TEMPERATURE SENSOR

3.13     COMPLETE INVERTER CIRCUIT AND MODE OF OPERATION

CHAPTER FOUR

RESULT ANALYSIS

4.0      RESULT AND DISCUSSION

4.1      CONSTRUCTION AND TESTING

4.2      TESTING AND WORK ABILITY OF THE INVERTER

4.3      RESULTS FROM TESTING

4.4      ASSEMBLING AND PACKAGING

4.5       SUMMARY OF RESULTS

CHAPTER FIVE

5.0      CONCLUSION

5.1      RECOMMENDATION

5.2      REFERENCES

CHAPTER ONE

INTRODUCTION

1.1 Background

The solar inverter is a vital component in a solar energy system. It performs the conversion of the variable DC output of the Photovoltaic (PV) module(s) into a clean sinusoidal 50 or 60 Hz AC current that is then applied directly to the commercial electrical grid or to a local, off-grid electrical network. A solar cell (also called photovoltaic cell) is the smallest solid-state device that converts the energy of sunlight directly into electricity through the photovoltaic effect. A Photovoltaic (PV) module is an assembly of cells in series or parallel to increase voltage and/or current. A Panel is an assembly of modules on a structure. An Array is an assembly of panels at a site. Typically, communication support scheme is included so users can monitor the inverter and report on power and operating conditions, provide firmware updates and control the inverter grid connection.

At the heart of the inverter is a real-time micro controller. The controller executes the very precise algorithms required to invert the DC voltage generated by the solar module into AC. This controller is programmed to perform the control loops necessary for all the power management functions necessary including DC/DC and DC/AC. The controller also maximizes the power output from the PV through complex algorithms called maximum power point tracking (MPPT). The PV maximum output power is dependent on the operating conditions and varies from moment to moment due to temperature, shading, cloud cover, and time of day so adjusting for this maximum power point is a continuous process. For systems with battery energy storage, the two controller can control the charging as well as switch over to battery power once the sun sets or cloud cover reduces the PV output power. (Aditee P. Bapatet al 2013)

1.2 Statement of Problem

If there is one factor that has perpetually maintained the status of Nigeria as a less developed country, it is its electricity sector. Till date, many households and industrial businesses cannot be guaranteed of 24 hours supply of electricity from the National grid. At this stage of Nigeria’s social and economic development, the country cannot deliver sufficient energy to the citizens despite huge financial resources that have been expended in the sector.

Rather, Nigerians have continued to rely on electricity generators for their power supply, fuel marketers are taking significant portion of households’ institutions of learning’and businesses’ incomes to supply power, noise pollution from regular humming generators have become integral part of living for many Nigerians with imaginable consequences on their health. The federal university of technology minna is not immune to the aforementioned problems of Nigeria’s power sector, which has led to increase in day to day running cost of the university. Because of these problems, there is a need to design and construct the hybrid solar panel inverter for the department of electrical and electronics, federal university of technology minna to complement or augment the electricity supply from the National grid, reduce cost of energy consumed and eliminate noise/environmental pollution that is associated with running of generator.

1.3 Aim and Objectives

The aim of this project is to design and construct an efficient and economical 7500-Watthybrid solar inverter that will utilize the appropriate use of office electrical appliances.

The objectives are as follows: –

• (i) To provide efficiency, steadiness in the use of power appliances, by ensuring continuous availability of power supply in the cause of main outage during an execution of an important or urgent assignment. Thereby enabling the department meet up with its office duties even when central power is not available.
• (ii) Reduce load on the National grid that turn to be reduce the overall energy consumption dependency on the main energy supply in the country
• (iii) Decrease customer utility bill on energy utilization because of its non-fuel consumption, low price and maintenance cost as compared to the convectional sources of power supplies within International and Local market.
• (iv) Again, reduce carbon discharges and subsequently reduce global warming particularly in a period when poor climatic change has become a threat to human survival and life in general to all living creatures hence an ever increasing concern to control it.

1.4 Scope of Study

Basically, solar power source makes it possible to provide a clean reliable and quality supply of alternative electricity free of surges or sags which could be found in the line voltage frequency (50Hz). This project design aims at creating a 7500watts power source which can be utilized as a regular power source for private individuals in the office or at home. This project involves the design and construction of a 7500Watt hybrid Solar PV (photovoltaic) system which involves a solar panel, car battery and an inverter. Furthermore, as a consumer is generating his or her own electricity they also will benefit from a reduction in their electricity bills.

1.5 Significance of the Project

The solar inverter is the second most significant (and second most expensive) component of a solar PV system. It’s important because it converts the raw Direct Current (DC) solar power that is produced by the solar panels into Alternating Current (AC) power that comes out of the wall sockets outlet. Inverters also have technology that maximizes the power output of that DC energy.

The use of solar power has many advantages. Firstly, the energy from the sun is free and readily accessible in most parts of the world. Moreover, the sun will keep shining until the world’s end. Also, silicon from which most photovoltaic cells are made is an abundant and nontoxic element (the second most abundant material in the earth’s crust).

Secondly, the whole energy conversion process is environmentally friendly. It produces no noise, harmful emissions or polluting gases. The burning of natural resources for energy can create smoke, cause acid rain and pollute water and air. Carbon dioxide, CO2, a leading greenhouse gas, is also produced in the case of burning fuels. Solar power uses only the power of the sun as its fuel. It creates no harmful by-product and contributes actively to the reduction of global warming.

1.6 Inverters

The inverter takes direct current DC power from the charged battery bank and converts it to sinusoidal alternating current AC power for the typical household or office lights and appliances. Once the number of watt-hours required for a day is determined, the peak loads need to be ascertained to properly size the inverter. This is the amount of watts used based on all appliances and loads that will be running at one time. A slit star air conditioner is an example of what may be the peak load requirement for office as case study. A 1/2 HP (horse power) split air conditioner will use about 1490 (adjusted) watts per hour. If this represents the total peak loads for an office as the case study, an inverter that will be able to supply at least 1490 watts of continuous power from the battery bank; let’s assume one in the 1500-watt range will be required. It is a smart idea to begin the system with the size of inverter you plan to develop into, as upgrading to newer, larger models is expensive. (Pure Energies 2014)

There are two basic types of inverters.

1.6.1 Central Inverters

Central inverters are well-tested and reliable systems that have been around for decades. These are the most common types of inverters. With central inverters, every solar panel is wired in a “string” to the inverter box. The conversion from DC to AC occurs at one central location, such as a garage. Because the solar panels are wired in “series,” each panel’s power output depends on all of the panels working. For example, In a string of Christmas tree lights. If one bulb goes out, the whole string of lights goes out until the bad bulb is replaced. So, if shade from a tree covers one panel, it can seriously diminish the power produced by the whole solar system until the shade clears. This is reason accurate shade analysis is so important.

1.6.2 Micro Inverters

Micro inverters are relatively new to solar. Instead of converting the DC to AC power at a central location, micro inverters are installed right under each solar panel. The main advantage to micro inverters is the ability for each solar panel to transmit power into the house independently. In other words, each panel produces its own solar power and keeps producing out solar watts regardless of what happening to the panel beside it. The down side of micro inverters is that they can be more expensive and take more labour cost to replace each inverter. Also, because they are so new, micro inverter reliability is unproven outside of laboratory testing. (Pure Energies 2014)

1.7 The Balance of System (BOS)

There are many other less well known and less expensive parts to a solar system. Installers typically wrap these up into “Balance of System” or “The BOS”

The balance of system includes components such as wiring, emergency DC disconnects, system monitoring hardware, the frames or “racking” that holds your panels to the roof and at the right angle, nuts, bolts, roof “flashing” to prevent leaks, and more. (Pure Energies 2014)

1.8 Solar Panels

Generally, Solar Panels are used for charging batteries. They provide a good solution for those that want to be self-sufficient and go on long camping missions through remote areas. They are available in various voltage and power ratings. More than one solar panel can be used in parallel to combine their power output. Solar panels joined in parallel work most efficiently if they are the same. If they are the same, you can design it so that they both generate power at their optimal

operating points. Mixing different panels together gives a compromised operating point. It will work but the panels will not operate as efficiently.

1.8.1 Solar Panel Mono or Poly

Silicon solar panels have two basic construction methods – polycrystalline or monocrystalline. There are slight differences between poly and mono cells. Mono are slightly more expensive, require more energy to make, and are slightly more efficient. Poly are slightly cheaper, use less energy to make so are better for the environment, are slightly less efficient but have a slightly better temperature coefficient. That means at elevated temperatures the poly cells become more efficient.

The differences are only slight. It is largely irrelevant. A solar panel with good efficiency and good temperature coefficient is to be used whether it is poly or mono, it does not matter.