Design And Construction Of A Solar Power Inverter

ABSTRACT

This work is on design and construction of a solar power inverter. Solar power 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      OBJECTIVE OF THE PROJECT

1.3      SCOPE OF THE PROJECT

1.4      PURPOSE OF THE PROJECT

1.5     SIGNIFICANCE OF THE PROJECT

1.6      PROBLEM OF THE PROJECT

1.7      LIMITATION OF THE PROJECT

1.8      DEFINITION OF TERMS

1.9      PROJECT ORGANISATION

CHAPTER TWO

2.0     LITERATURE REVIEW

2.1      OVERVIEW OF THE STUDY

2.2      REVIEW OF AVALIABLE TECHNOLOGY

2.3      REVIEW OF THE RELATED STUDY

2.4      KNOWLEDGE GAP

2.5      HISTORITICAL BACKGROUND OF PHOTOVOTAIC CELL

2.6         THEORETICAL REVIEW OF SOLAR CELL

2.7      REVIEW OF SOLAR CELL EFFICIENCY

2.8      REVIEW OF SOLAR CELL MATERIALS

2.9      REVIEW OF EARLY INVERTERS

CHAPTER THREE

3.0     CONSTRUCTION

3.1      BASIC DESIGNS OF A SOLAR INVERTER

3.2      BLOCK DIAGRAM OF THE SYSTEM

3.3      DESCRIPTION OF SOLAR INVERTER UNITS

3.4      SYSTEM CIRCUIT DIAGRAM

3.5      CIRCUIT OPERATION

3.6      DESCRIPTION OF COMPONENTS USED

3.7      HOW TO CHOOSE THE BEST INVERTER BATTERY

3.8      DESIGN CALCULATION

CHAPTER FOUR

RESULT ANALYSIS

4.0      CONSTRUCTION PROCEDURE AND TESTING

4.1      CASING AND PACKAGING

4.2      ASSEMBLING OF SECTIONS

4.3      TESTING OF SYSTEM OPERATION

4.4      COST ANALYSIS

4.5      PROBLEM ENCOUNTERED

4.6      PRECAUTIONS

4.7      CONSRUCTION OF THE CASING

4.8      ECONOMIC OF THE PROJECT

4.9     PROJECT VIABILITY

4.10   PROJECT RELIABILITY

4.11   PROJECT MAINTAINABILITY

4.12      PROJECT EVALUATION

CHAPTER FIVE

5.1      CONCLUSION

5.2      RECOMMENDATION

5.3      REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

solar inverter converts 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 balance of system (BOS)–component in a photovoltaic system, allowing the use of ordinary AC-powered equipment. Solar power inverters have special functions adapted for use with photovoltaic arrays, including maximum power point tracking and anti-islanding protection[1].

The solar panel used in solar inverter produces 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[2] [3].

An inverter produces square waves or a sine wave which can be used for running lights, televisions, lights, motors etc. However these inverters also produce harmonic distortion[2].

1.1                                         BACKGROUND OF THE PROJECT

Solar technology isn’t new. Its history spans from the 7th Century B.C. to today. We started out concentrating the sun’s heat with glass and mirrors to light fires. Today, we have everything from solar-powered buildings to solar-powered vehicles. Here you can learn more about the milestones in the historical development of solar technology, century by century, and year by year. You can also glimpse the future. From the 3rd Century BC when Archimedes fought off Roman ships by concentrating the suns rays at them with brass shields (they burst into flame), through work by some of the best known figures in the history of science, harnessing the power of the sun has long been a goal of human innovation. Let’s look at some of the highlights:

In 1767 Swiss physicist, alpine explorer, and aristocrat Horace de Saussure is credited with inventing the first working solar oven, amongst other discoveries. Constructed from 5 layers of glass and measuring around 12 inches across, the oven worked by allowing light to pass through the glass before being absorbed by the black lining and turned into heat. The heat is then reflected by the glass, therefore heating the space inside the box up to 87.5 degrees Celsius [4][5].

Also in 1839 Edmond Bequerel, born in Paris in 1820, discovered that when two electrodes were placed in an electrolyte (electricity-conducting solution), a voltage developed when light fell upon the electrolyte. The basic principles of solar power had been uncovered [4].

Many people using solar power these days which prove that its necessity has been increased in the current years. A Solar inverter is similar to a normal electric inverter but uses the energy of the Sun, that is, Solar energy. A solar inverter helps in converting the direct current into alternate current with the help of solar power. Direct power is that power which runs in one direction inside the circuit and helps in supplying current when there is no electricity. Direct currents are used for small appliance like mobile e phones, MP3 players, IPod etc. where there is power stored in the form of battery. In case of alternative current it is the power that runs back and forth inside the circuit [4] [5]. The alternate power is generally used for house hold appliances. A solar inverter helps devices that run on DC power to run in AC power so that the user makes use of the AC power. If you are thinking why to use solar inverter instead of the normal electric one then it is because the solar one makes use of the solar energy which is available in abundant from the Sun and is clean and pollution free.

Solar inverters are also called as photovoltaic solar inverters. These devices can help you save lot of money.  The small-scale grid  one have just two components i.e. the panels and inverter while  the off grid systems are complicated and consists of batteries which allows users to use appliances during the night when there is no Sunlight available.  The solar panel and the batteries that are placed on rooftops attract Sun rays and then convert the Sunlight into electricity. The batteries too grab the extra electricity so that it can then be used to run appliances at night [4].

1.2                                             OBJECTIVE OF THE PROJECT

The main objective of this project is to design and construct a solar power generating device that can collect an input dc voltage (12, 24, or 48vdc) from the solar panel and convert it to 220vac output which can be use to power an ac appliances. The output power of this device is AA with frequency of 50Hz.

1.3                                                 SCOPE OF THE PROJECT

The main function of solar inverter is to convert battery’s Direct Current (DC) into pure sine wave Alternative Current (AC) to feed home compliances.

Solar power inverter system is consisted of solar panels, charger controllers, inverters and rechargeable batteries, while solar DC power system is not included inverters. The inverter is a power conversion device, which can be divided into self-excited oscillation inverter and external excited oscillation inverter.

1.4                                              PURPOSE OF THE PROJECT

The purpose of this work is to build a power generating device that transforms direct current (DC) generated by a PV system into alternating current (AC), which can be sent into AC appliances. Solar inverter converts DC (from solar panel ) to AC for consumption purposes [9].

1.5                                         SIGNIFICANCE OF THE PROJECT

Solar inverter is useful in making appliances work at residential and industrial levels, such as:

• A Solar Inverter is better optimised for solar power than the regular one. For example, it will prioritise power supply from the solar panels. This means that when the energy from the Sun is adequate like during afternoons, the inverter will draw power entirely from the solar panels to power your home or office even if public power supply is available. This can lead to huge savings on power bills [7].
• Similarly, a Solar hybrid inverter will prioritise charging from solar panels, enabling your batteries to charge via the PV panels even when public power supply is on, leading also to savings on your power bills.
• Solar inverter has always helped in reducing global warming and green house effect.
• Also use of solar inverter helps in saving money that would have used for buying fuel for conventional generator
• Some solar inverters will allow you prioritise charging to solar panels or power grid depending on the battery level. Some solar inverters are even intelligent enough just to take just as much deficit current from the grid as is required [7].
• A solar inverter helps in converting the Direct current in batteries into alternative current. This helps people who use limited amount of electricity.
• There is this synchronous solar inverter that helps small homeowners and power companies as they are large in size.
• Then there is this multifunction solar inverter which is the best among all and works efficiently. It converts the DC power to AC very carefully which is perfect for commercial establishments.
• Solar inverters are the best way and they are better than the normal electric ones. Also their maintenance does not cost much money.
• Solar Inverters can work when there is no Sunlight but provided their battery is charged fully with the help of Sunlight [7].

1.6                                              PROBLEM OF THE PROJECT

• Initially you need to shell out a lot of money for building a solar inverter
• It will work effectively and produce direct current only when the Sunlight is strong.
• The solar panels that are used for the design to attract Sunlight requires lots of space
• The device can work efficiently only if the presence of the Sun is strong.
• Maintenance and replacement may require more effort. In the event of a problem, a technician will need to access the roof to make repairs. Depending on your maintenance plan and warranty, this may cost you money [8].

1.7                                           LIMITATION OF THE PROJECT

• This device is rated 1000w that means any load more than 1000w should for no reason applied to this device.
• The intensity of the Sun varies throughout the day. This creates an over-charging problem if the panels are connected to the battery directly, and It should also be able to tell you when you connect the panels wrongly (i.e. positive to negative, etc) and also provide protection against short-circuit. For this reason a charge controller must be used to offer protection from high voltage and current from the panels [5].
• The inverter frequency is rated at 50hz
• Iron casing and good heat sink is been used for heat absorption
• In spite of the construction of an inverter and its noiseless and pollution free nature unlike other alternative sources of the generating electricity, there is a need for charging and recharging the battery from time to time.
• The inability of the circuit to provide a pure sine wave output from gives room for further improvement. This is because it is quite expensive to design a pure wave inverter circuit.
• Again, lack of financial assistance incapacitated the project to achieve its accuracy and reliability as well its appearance (packaging).

1.8                                                  DEFINITION OF TERMS

Terms related to this work are defined as below:

Power Factor (PF) Control: Sets the ratio of real power to apparent power, allowing for sourcing or sinking of VARs to maintain voltage and increase efficiency in the power system.

Utility-scale PV plant: It is a installation that is ground-mounted. The plant owner sells energy directly to the electric utility. The interconnection occurs on medium or high voltage level.

Utility-scale inverter: Inverter which is used in an Utility-scale installation

Maximum input voltage (Vdcmax): allowed maximum voltage at the inverter input

Minimum input voltage (Vdcmin): minimum input voltage for the inverter to energize the utility grid, independent of mode of operation

Start-up input voltage (Vdcstart): input voltage at which the inverter starts energizing the utility grid rated input voltage (Vdc,r) input voltage specified by the manufacturer, to which other data sheet information refers

Maximum MPP voltage (Vmppmax): maximum voltage at which the inverter can deliver its rated power.

Minimum MPP voltage (Vmppmin): minimum voltage at which the inverter can deliver its rated power.

Maximum input current (Idcmax): maximum current at which the inverter can operate. If the inverter has multiple MPP inputs, Idcmax is related to each single input.
Maximum grid voltage (Vacmax): maximum voltage at which the inverter can energize the grid.

Minimum grid voltage (Vacmin): minimum voltage at which the inverter can energize the grid.

Rated grid voltage (Vac,r): utility grid voltage to which other data sheet information refers.

Maximum output current (Iacmax): maximum output current that the inverter can deliver.

Rated power (Pac,r): the active power the inverter can deliver in continuous operation
rated frequency (fr): utility grid frequency at which the inverter performs as specified.
Maximum frequency (fmax): maximum frequency at which the inverter can energize the grid.

Minimum frequency (fmin): minimum frequency at which the inverter can energize the grid.

Power factor of operation range: range of power factor for the range operation of the inverter.

Inverter: electric energy converter that changes direct electric current to single-phase or polyphase alternating current
Isolated inverter: an inverter with at least simple separation between the mains and PV circuits

Multiple mode inverter: an inverter that operates in more than one mode, for example having grid-interactive functionality when mains voltage is present, and stand-alone functionality when the mains is de-energized or disconnected
Stand-alone inverter: an inverter or inverter function intended to supply AC power to a load that is not connected to the mains.

MPPT (Maximum Power Point Tracking): Control strategy of operation at maximum power point or nearby.

PCC (Point of Common Coupling): Point of a power supply network, electrically nearest to a particular load, at which other loads are, or may be, connected.

Maximum MPP voltage: Maximum voltage at which the EUT can convert it’s rated power under MPPT conditions.

Dry cell: A battery cell that does not contain any liquid but instead has a solid or paste electrolyte.

Duty cycle: The percentage of time that a machine or system is active. If a backup generator is used for 48 hours a year its duty cycle is 0.55%.

Deep cycle battery: A battery that is designed to be deeply discharged regularly and suffer less degradation than a normal battery of its type when doing so. Usually only used to describe lead-acid batteries and the depth of discharge they are designed for generally ranges from 45-75%.

Depth of discharge: How much of a battery’s total capacity is depleted before it is recharged again, expressed as a percentage.

Dielectric: A material that is dielectric is an electric insulator. The plastic coating around electrical wiring is an example.

Diode: An electronic component. A semiconductor that only allows the flow of electricity in one direction like the valves in your heart only allows blood to flow in one direction.

Direct current (DC): Electricity that flows in only one direction. Solar panels produce direct current. Before it can be used in our homes it has to be converted into alternating current by an inverter. Batteries can only be charged with direct current.

Discharge: When a battery outputs electrical energy it discharges and the energy stored inside it decreases. When a battery is fully discharged there is no usable energy left.

Discharge rate: How rapidly a battery is discharged.  This can be measured by C-rate.

Cathode: This is the electrode in a battery which positively charged cations move towards and negatively charged anions moves away from.

Central inverter: usually refers to a large (MW scale) inverter that thousands of solar panels will be connected to in a very large commercial or utility-scale installation.

Charge: usually this refers to putting energy into a battery.

Charge controller: A device that regulates the charging and discharging of batteries. They generally operate to maximize battery life and prevent the depth of discharge being too great and prevent overcharging.

Charging: Putting energy into a battery.

Circuit: A loop that electricity travels through. A circuit can have one or many electrical components on it.

Conductance: How well something conducts electricity. How poorly something conducts electricity is resistance.

Conductor: Something that carries electric current.

Cost-effective: If something is worth the money you spent on it, it is cost-effective. The accounting methods businesses use to determine if something is cost-effective vary and can be quite complex.

Cost Of money: When you borrow money from a bank or other financial institution they will want you to pay interest.

Cut in: The point at which a controller activates a device.

Cut off voltage: As a battery becomes discharged the voltage of the current it supplies decreases. The cut off voltage is either the voltage at the point where the battery is fully discharged, or when a charge controller stops the discharge at a pre-set point. Most home energy storage systems have cut off voltages which prevent their batteries from being fully discharged to prolong their lives.

Current: A flow of electricity.

DC Converter: This is a device that changed DC current from one voltage to another.  A battery DC converter can allow batteries to be connected to a rooftop solar system.

DC Coupling: When there is one inverter used for both the solar and batteries. DC from the solar panels is used to charge the batteries via a DC charger.

Battery: A specially constructed case containing potential chemical energy. When a chemical reaction occurs electricity is generated and can be used to do work. In disposable batteries the chemical reaction cannot be easily reversed, so avoid using them. In rechargeable batteries the chemical reaction can be reversed by supplying electrical energy.

Battery capacity: The total amount of electrical energy a battery can provide before it is completely discharged. Battery capacity is often higher than usable capacity because many types of batteries will be damaged if they are completely discharged.

Battery case: The tough protective case that protects the battery cell or cells inside.

Battery cell: A battery can be made up of many individual units called cells. Or a battery can be a single cell, such as the small batteries you might put in a remote control or toy.

Battery cycle life: This is the number of times a battery can be fully discharged before it becomes so degraded it can only operate at 80% of its original capacity.

Battery enclosure: A cabinet or structure that holds batteries. This is important for lead-acid batteries used for home energy storage as they can take up a lot of space, require a lot of cabling, and both children and batteries operate better when kept separate from each other. Modern home energy storage systems normally do not require an enclosure as they are designed to be less dangerous and less infested with cabling.

Battery inverter: An inverter designed for use with batteries.  This is required for home energy storage if the solar inverter is not a multimode solar inverter that is compatible with the batteries used.

Battery management system (BMS): The software and electronics that control how a battery charges and discharges.

Alternating current (AC): The type of current that is used in our homes and most transmission lines.

Alternative energy: Sources of energy that are an alternative to using fossil fuels or nuclear power. The big three are solar, wind, and hydroelectricity. Other types are geothermal, biomass, tidal, and wave power.

Ampere (A): The unit of electrical current which refers to the rate of flow of electricity.

Ampere-hour (A·h or A h or Ah): A current of one ampere produced for one hour. Lead-acid batteries used for home energy storage often have their capacity measured in ampere-hours. To determine its capacity in kilowatt-hours, multiply the ampere-hours by its voltage and then divide by 1,000. So a 100 ampere-hour 12 volt battery can output a maximum of 1.2 kilowatt-hours.

1.9                                          APPLICATION OF THE PROJECT

Solar inverter is used for powering devices such as LED night lights, a cell phone charger, fridge, TV, Laptop and other sensitive equipment for domestic, office, workshop or commercial uses.

1.10                                     ORGANISATION OF THE PROJECT

This work is organized in such a way that every reader of this work will understand how solar power inverter is been made. Starting from the chapter one to chapter five focused fully on the topic at hand.

Chapter one of this work is on the introduction to solar power inverter. In this chapter, the background, significance, objective, aim, purpose, application, limitation and problem of solar power inverter were discussed.

Chapter two is on literature review of solar power inverter. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.

CHAPTER FIVE

5.1                                                        CONCLUSION

In the context of renewable energy, a solar inverter is a device that will convert  DC battery/solar panel voltage into mains type AC power; suitable for use in your home or business.

Without this conversion from DC to AC, special appliances or adapters often need to be purchased – and DC appliances are often more expensive than their AC counterparts.

The above two types of batteries are popular inverter batteries. Before buying the inverter and the battery, ask your dealer which suits your requirement better.

5.2                                               RECOMMENDATION

This project is designed to be used in our homes, offices and industries where the need for 24hrs supply is needed. And should be used and maintain by a qualified personnel.