Design and Implementation of a Hybrid (Solar-Wind) Power System

TABLE OF CONTENTS

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF PLATES

LIST OF ABBREVIATIONS

LIST OF SYMBOLS

ABSTRACT

CHAPTER ONE: INTRODUCTION
1.1 Background of Project
1.2 Objective of Project
1.3 Scope of Project
1.4 Significance of Project
1.5 Justification of Project

CHAPTER TWO: LITERATURE REVIEW
2.0 Introduction
2.1 Hybrid Power System
2.2 Solar Panels
2.2.1 Types of Solar Panel
2.3 Wind turbines
2.3.1 Types of wind turbine
2.3.2 Output power of wind turbines
2.4 Review of Past Works and Studies of Hybrid Power Systems
2.5 Review of Wind Energy Characteristics and Potential in Nigeria
2.6 Review of Solar Energy Characteristics and Potential in Nigeria

CHAPTER THREE: METHODOLOGY
3.0 Introduction
3.1 Project Overview
3.2 Description of the Components
3.2.1 Solar panel for the project
3.2.2 Wind turbine for the project
3.2.3 Charge controller
3.2.4 Battery
3.2.5 Inverter
3.3 Mounting of the Hybrid System

CHAPTER FOUR: RESULTS AND DISCUSSION
4.0 Introduction
4.1 Wind turbine Testing
4.2 Analysis and Discussion of Wind Turbine Test Results
4.3 Solar Panel Testing
4.4 Discussion of Solar Panel Test Results
4.5 Total Power Output of the Hybrid System

CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
5.0 Introduction
5.1 Conclusion
5.2 Recommendations

REFERENCES

APPENDIX

LIST OF TABLES

3.1 Solar Panel Specifications

4.1 Data Collected from Wind Turbine during the Morning Session

4.2 Data Collected from Wind Turbine during the Afternoon Session

4.3 Data Collected from Wind Turbine during the Evening Session

4.4 Data Collected from Solar Panel during Morning, Afternoon and Evening Session

LIST OF FIGURES

2.1 Stages of Development of a PV System

2.2 Monocrystalline Silicon Solar Panel

2.3 Polycrystalline Silicon Solar Panel

2.4 Thin-Film Solar Panel

2.5 Horizontal-Axis Wind Turbine

2.6 Vertical-Axis Wind Turbine

3.1 Block Diagram of the Project

3.2 Setup of the Hybrid System

3.3 Components of Horizontal-Axis Wind Turbine

3.4 Circuit Diagram for Charge Controller

4.1 Graph of Wind Speed Vs Time of the Day

4.2 Graph of Voltage Output Vs Wind Speed

4.3 Graph of Turbine Power Output Vs Wind Speed

LIST OF PLATES

3.1 Monocrystalline Silicon Solar Panel used for the Project

3.2 Horizontal-Axis Wind Turbine used for the Project

3.3 DC Motor for the Wind Turbine

3.4 Charge Controller used for the Project

3.5 Battery used for the Project

3.6 Inverter used for the Project

3.7 The Complete Hybrid Power System

LIST OF ABBREVIATIONS

Abbildung in dieser Leseprobe nicht enthalten

LIST OF SYMBOLS

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ABSTRACT

Nowadays, one of mankind’s greatest desire was to have reliable and sustainable electricity. Over the years, conventional, non-renewable energy resources (e.g. coal, nuclear) had been harnessed to generate electricity. However, this resources were depleting with constant usage. This had initiated a switch in attention to renewable energy sources like wind, solar, tidal energy etc. The objective of this project, therefore, was to design and implement a portable hybrid power system that combines two of these renewable energy sources, that is, wind and solar energy, to generate reliable and sustainable electricity.

To achieve this, a wind turbine was constructed to convert wind energy to electric energy, while a solar panel converts solar energy to electric energy. A hybrid charge controller was also included to “multiplex” the inputs from the turbine and solar panel and deliver an output voltage sufficient the 12 V battery. The DC output of the battery was also converted to the usable AC form by an inverter. This made it possible for the system output to be used to power domestic appliances.

The results showed that the wind speed in Ile-ife was relatively low, ranging from 0.5 m/s to 3.7 m/s during the period testing. In fact, it was lower than what is required by the turbine to produce the 12 V DC output to power the system. On a brighter note however, the results obtained from testing the solar panel showed that the solar panel was more than capable of producing of generating at least 12 V for many hours especially during the day.

The study concluded that, although, the 12 V DC input required by the system to function would not be available at all times in a day, the use of a 12 V battery as an auxiliary power source increased the length of time for which the system was available. Thus, it could be concluded that objective of the project was achieved.

CHAPTER ONE: INTRODUCTION

1. 0 Introduction

One of the greatest needs in mankind’s day to day life is electricity . There are basically two ways of generating electricity. These two ways are explained in this chapter along with examples. The chapter also highlights the objective of the project at hand, the scope, significance and justification of the project.

1. 1 Background of Project

Generation of electric power is no doubt a sine qua non for any country gearing towards industrialization and higher echelons of technological advancement. Constant supply and availability of electricity is unarguably an important need that must be filled to make day to day living more comfortable and enjoyable. Thus, provision of constant electricity is a goal to which several countries of the world press forward.

According to Ingole and Rakhonde (2015), there are two ways of electricity generation; either by conventional/non-renewable energy resources or non-conventional/renewable energy resources. Nowadays, electricity is generated from conventional energy resources. These energy resources include geothermal, tidal, wind, solar etc. On the other hand, non- conventional resources include wind, solar, tidal energy etc. These non-conventional energy resources usually pollution-free and economical. They are also naturally replenished, thus, unlike the conventional energy resources, they are inexhaustible.

As stated above, Wind is one of the various non-conventional energy resources that can be put to use to generate electricity. It is used in many advanced or developed countries of the world to generate electric power. This power from the wind is generated using airflow through wind to mechanically power generators for electricity. These generators then convert the mechanical energy induced to electrical energy. Wind power, as an alternative to burning fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation and uses little land (Fthenakis & Kim, 2009).

Wind power has been used for a long time in the generation of electric power. The first windmill used for the production of electricity was built in Scotland in July, 1887 by Professor James Blyth of Anderson’s College, Glasgow (Price, 2005). However, with the development of electric power, wind power found new applications in lighting buildings remote from centrally generated power. Today, wind power generators operate in every size range between tiny stations for battery charging at isolated residences, up to near-gigawatt sized wind farms (group of wind turbines in the same location used for production of electricity) that provide electricity to national electrical networks.

Furthermore, according to Jacobsen (2016), as of 2015, Denmark generates 40 percent of its electricity from wind and at least 83 other countries around the world are using wind power to supply their electricity grids (Sawsin et al., 2011). In addition, the World Wind Energy Association, in its 2014 half-year report stated that, yearly wind energy production is growing rapidly and had reached around 4 percent of worldwide electricity usage. All these facts show that generation of electricity from wind energy has become more influential since its inception.

Another form of non-conventional energy resource harnessed for generation of electric power is the Solar energy. Generation of electric power from solar energy can be achieved by the conversion of sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power (CSP). The International Energy Agency projected that in 2014 that under its “high renewable” scenario, by 2050, solar photovoltaics and concentrated solar power would contribute about 16 and 11 percent, respectively, of the worldwide electricity consumption, and solar would be the world’s largest source of electricity. The photovoltaic systems use solar panels either on rooftops or in ground mounted solar farms, to convert sunlight directly to electric power. Photovoltaics convert sunlight into electricity using the photovoltaic effect. The photovoltaic effect is the creation of voltage or electrical current in a material upon exposure to light and it is a physical and chemical phenomenon. Solar energy is present on the earth continuously and in abundance. It is also affordable in cost and has low maintenance cost (Ingole & Rakhonde, 2015).

It is very common to use these two aforementioned sources to generate electricity independently i.e. solar power acting alone or wind power alone. Sometimes, though, it is desired that two of these renewable energy resources are combined together to generate electricity. When this is done, the type of system that results is called a Hybrid Power System. Hybrid power systems, as the name implies, combine two or more modes electricity generation together usually using renewable technologies such as solar photovoltaic (PV) and wind turbines. Hybrid power systems therefore, provide increased system efficiency and greater balance in supply of energy.

1. 2 Objective of Project

The objectives of this project include the following,

- To design and implement a solar-wind hybrid power system .
- To use the complete system domestically to provide sustainable electricity irrespective of changes in weather conditions.
- To ensure that the system is available for use throughout the day.

1. 3 Scope of Project

As mentioned earlier, the project involves the design of a hybrid power system made up of wind and solar power. This implies that the project will initially be divided into two parts; the design and implementation of a functional wind turbine to harness the wind energy while the second part involves the design and implantation of a solar power system.

A charge controller is also included in the hybrid systems. This circuit receives the two direct current (DC) outputs of solar and wind systems and outputs a DC voltage that is just suitable to charge the battery and this controller is also controls the charging process of the battery by supplying just the right amount of voltage needed to prevent over-charging.

Furthermore, an inverter is also included in the system convert the DC voltage of the battery to alternating current (AC). Thus, AC loads e.g. incandescent light bulbs or ceiling fans can be powered through the output of the inverter. However, DC loads can be directly connected to the output terminal of the battery.

1. 4 Significance of Project

Every device we use in our day-to-day life such as mobile phone electronic appliances, computers, washing machines etc. require electric power supply to function continuously. Advancement in technology has also increased the usage of electrical and electronic appliances. Thus, undoubtedly, there is a growing need for energy in the world. Nowadays, electrical energy is generated from conventional sources which have been discussed earlier.

However, in Nigeria these sources have failed to yield desirable results. In fact, according to Sambo (2006), despite the abundance of energy resources in Nigeria, the country is still short in supply of electrical power. He added that, only about 40 percent of the nation’s over 140 million has access to grid electricity. Even electricity supply to consumers that are connected to the grid is erratic.

How then can this problem of poor, unsustainable and unreliable electricity supply be solved? New sources of energy are needed and according to Ingole et al. (2015), the new sources should be reliable, pollution-free and economical. They also added that non- conventional energy sources should be a good alternative energy sources for the conventional energy sources. Therefore, there is a need to harness renewable energy potential (such as wind and solar) for reliable power supply in this country. There is also growing concern about global warming and continuous apprehensions about nuclear power around the world (Agbetuyi et al., 2012).

However, renewable energy resources acting as stand-alone or as an independent unit will only produce the required energy when that particular resource is available. For example, wind energy will only be obtainable when wind is blowing while solar energy will only available when sun is shining. Hence, there is a potential problem of low availability (probability of performing required function at a particular time) if only one of these renewable energy resources are harnessed at a time. For example, if a solar panel were to be used alone for the generation of electric power, such a system will not perform its required function on a rainy/stormy day and at night as well. In fact, such a stand-alone system will do very little or nothing in the bid to satisfy the desire for sustainable, reliable electricity in Nigeria.

Therefore, to maximize the available resources and provide stable and consistent electricity supply, hybrid systems that combine two renewable energy resources have been designed. The project at hand is to combine energy from wind and solar energy together to generate electricity. One source will serve as the complement of the other and thus ensure that there is always energy to be harnessed and converted to electrical power. The system is also equipped with a battery to store the power obtained from the wind and solar energy. This means that, if both wind and solar energy happen to be unavailable at the same time, we can still have electricity. Hence, the project at hand has the potential to solve the problem of unreliable, unsustainable and erratic power supply in Nigeria.

1. 5 Justification of Project

Conventional energy resources have been harnessed to good effect to generate electricity and they are still in use today. However, the main drawback of these sources is that they produce waste like ash in coal power plant, nuclear waste in nuclear power plants and taking care of these wastes is very costly and it also damages nature (Ingole & Rakhonde, 2015). Furthermore, these conventional resources are non-renewable, hence, there is danger of complete depletion and consequential unavailability on the long run.

On the other hand, though, non-conventional resources are, plentiful, renewable and naturally replenished. Hence, they are inexhaustible will always be available for use. Furthermore, they are clean and produce no greenhouse gas emissions, thus, they do not contribute to environmental pollution. The cost of maintenance is also very minimal.

The project at hand is to harness two renewable/non-conventional energy resources, hence, it is relatively cheap/economical, pollution-free and requires very little maintenance. Finally, the peak operating times of the two energy resources that will be harnessed occur at different time of the day and year, therefore, they can successfully act as complements of each other.

CHAPTER TWO

LITERATURE REVIEW

2. 0 Introduction

In the preceding chapter, it was made clear that the aim of this project is to design and implement a hybrid solar-wind power system. Numerous scholars have participated in either a study or project involving this type of system and a review of their studies/works are briefly highlighted this chapter. The chapter also presents a description of the important subsystems in the hybrid system.

2. 1 Hybrid Power System

Hybrid power systems are systems that combine two or more renewable sources of energy together to provide increased system efficiency as well as greater balance in energy supply. A very common example of a hybrid power system is that involving the combination of solar and wind energy.

In this system, a photovoltaic array is coupled with a wind turbine. This creates more output from the wind turbine in the cold season, whereas during the hot season, the solar panel produces its peak output. Generally, hybrid energy systems often yield greater economic and environmental returns than wind, solar or geothermal stand-alone systems by themselves.

Before reviewing the past works and studies involving hybrid power systems as a whole, it is vital to describe the key subsystems in the hybrid system at hand, the solar panel and wind turbine.

2. 2 Solar Panels

A solar panel simply refers to a panel designed to absorb the rays from the sun as a source of energy for generating electricity or heating. A photovoltaic (PV) module is a packaged assembly of typically of 6×10 photovoltaic solar cells.

The solar cell is the basic building block of a PV power system. However, it is rarely used individually because it is not able to supply an electronic device with enough voltage and power. Thus, many photovoltaic cells are connected in parallel or series in order to achieve as higher voltage and power output as possible. Figure 2.1 shows how unit solar cells are developed into larger PV systems. Cells connected in series increases the voltage output while cells connected in parallel increase the current (Geetha Udayakanthi, 2015).

Each PV cell is made up of semi-conductor material, such as silicon, which is currently the most commonly used element in the semiconductor industry. Basically, when the light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This absorbed energy knocks semiconductor electrons loose from the atoms in the semiconductor material, allowing them to flow freely.

PV cells have one or more electric fields that act to force electrons that are freed by light absorption to flow in a certain direction. The flow of these electrons brings about electric current and by placing metal contacts at the top and bottom of the PV cell, the electric current can be drawn for external use. This current together with the cell’s voltage which is a result of the built-in electric field, define the power that the solar cell can produce. Therefore, PV modules use light energy (photons) from the Sun to generate electricity through the photovoltaic effect as explained above. Some special forms of PV modules include concentrators in which light is focused by lenses or mirrors onto smaller cells. This facilitates the use of cells with high cost per unit area in a cost-effective way.

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Figure 2.1 Stages of Development of a PV System

2.2.1 Types of Solar Panel

Almost all the world’s photovoltaics today are based on some variation of silicon. The silicon used in photovoltaics takes many forms. The main difference between these forms is the purity of the silicon. The more perfectly aligned the silicon molecules are, the better the solar cell will be at converting solar energy to electricity. Like semiconductors, solar photovoltaics need purified silicon to get the best effici ency and the price behind PV solar manufacturing is often determined by the crystalline silicon purification process (Pickerel, 2015)

There are three basic types of solar panels. These are,

- Monocrystalline Silicon Solar panels
- Polycrystalline Silicon Solar panels
- Thin-film Solar panels

- Monocrystalline Silicon Solar panels

According to Maehlum (2015), these solar cells that make up thus types of solar panels are easily recognizable by an external even colouring and uniform look which indicates high-purity silicon as shown in figure 2.2. The solar cells are made out of silicon ingots which are cylindrical in shape. Furthermore, to optimize performance and lower costs of a single monocrystalline solar cell, four sides of the cylindrical ingots to make silicon wafers, which gives monocrystalline panels their characteristic look.

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Figure 2.2 Monocrystalline Silicon Solar Panel

Source: http://www.ledwatcher.com/solar-panel-basics-and-types-of-solar-panels-used-in- flood-lights/

The advantages of this type of solar panels includes the following;

i. They have the highest efficiency rates since they are made out of the highest- grade silicon. The efficiency rates of monocrystalline solar panels are typically 15-20%.
ii. Monocrystalline silicon solar panels are space-efficient. Since they yield the highest power output, they require the least amount of space compared to any other type of solar panel.
iii. Monocrystalline solar panels live the longest. Most manufacturers put a 25-year warranty on their monocrystalline solar panels.
iv. Monocrystalline silicon solar panels tend to perform better than similarly rated polycrystalline solar panels at low-light conditions (Maehlum, 2015).

The disadvantages of monocrystalline silicon solar panels include,

i. Monocrystalline solar panels are the most expensive
ii. If the solar panel is partially covered with shade, dirt or snow, the entire circuit can break down.

- Polycrystalline silicon solar panels

The solar cells that make up this type of solar panels are made by first, melting raw silicon and pouring it into a square mold which is cooled and cut into perfectly square wafers as shown in figure 2.3. A good way to separate mono- and polycrystalline solar panels is that polycrystalline solar cells look perfectly rectangular with no round edges. This point can be confirmed by comparing the solar panel in figure 2.2 with that in figure 2.3.

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Figure 2.3 Polycrystalline Silicon Solar Panel

Source: http://m.en.ofweek.com/Product/215W-Polycrystalline-SIlicon-Solar-Panel-TSP215- prod-65942-920700.html

One advantage of polycrystalline solar panels over monocrystalline solar panels lies in their relative ease of production. The process used to make polycrystalline silicon is simpler and costs less. The amount of waste silicon is less compared to monocrystalline.

However, polycrystalline solar panels also have their own disadvantages. These include;

i. They are not as efficient as the monocrystalline solar panels. They have efficiency of about 13-16%. This is because of the lower silicon purity compared to that of monocrystalline solar panels.
ii. They have lower space-efficiency. This implies that larger space will have to be covered to have the same electrical power as would be obtainable from a solar panel made of monocrystalline silicon.
iii. Monocrystalline and thin-film solar panels tend to be more aesthetically pleasing since they have a more uniform look compared to the speckled blue colour of the polycrystalline silicon (Maehlum, 2015).

- Thin-film solar panels

The solar cells that make up this type of solar panels are manufactured by depositing one or several thin layers of photovoltaic material unto a substrate. Figure 2.4 shows a typical thin-film solar panel. These types of solar panels have reached efficiencies between 7-13%. There are different types of thin-film solar cells and they are categorized by which photovoltaic material is deposited on the substrate. The various types include;

- Amorphous silicon (a-Si)
- Cadmium telluride (CdTe)

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Figure 2.4 Thin-film Solar Panel

Source: http://www.energyinformative.org/best-solar-panel-monocrystalline- polycrystalline-thin-film/

- Copper indium gallium selenide (CIS/CIGS)
- Organic photovoltaic cells (OPC)

The advantages of thin-film include the following;

i. Mass-production is simple. This makes it potentially easier to manufacture than crystalline-based solar cells.
ii. They have a homogenous appearance that makes them look more appealing.
iii. They can be made flexible, which opens up new applications.
iv. High temperature and shading have less impact on the performance of the solar panel.

Like other solar panels already considered, thin-film solar panels also have disadvantages if their own. These are;

i. They are generally not useful in most residential situations. Although they are cheap, they require a lot of space.
ii. Low space-efficiency also means that the cost of the supporting equipment will also increase.
iii. Thin-film solar panels tend to degrade faster than the mono- and polycrystalline solar panels. They thus have shorter warranty

2.3 Wind Turbine

A wind turbine is a device that converts the wind’s kinetic energy into electrical. The wind turbine works by converting the kinetic energy of the wind to rotational kinetic energy in the turbine and then electrical energy that can be supplied through the grid. The energy available for conversion mainly depends on the wind speed and swept area of the turbine blades. The wind turns the blades, which in turn, spins a shaft which is connected to a DC generator. This generator thus, converts the mechanical energy produced by the spinning effect of the shaft, to electrical energy.

Arrays of wind turbines are known as wind farms and these are becoming an increasingly important source of intermittent renewable energy and are used by many countries as part of a strategy to reduce their reliance on fossil fuels.

2.3.1 Types of Wind Turbine

Wind turbines can rotate about either about a horizontal or vertical axis, giving rise to the main types of wind turbines available i.e. the horizontal axis and the vertical axis wind turbine. The horizontal axis wind turbine is older and more common and generally more powerful than the vertical axis turbines.

- Horizontal-axis wind turbines (HAWT) have a main rotor shaft and electrical generator at the top of a tower and must be pointed into the wind. A simple wind vane is used to point small turbines in the direction of the wind while large wind turbines generallyuse a wind sensor coupled with a servo motor. A typical HAWT is shown in figure 2.5. Most HAWT have a gear box which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.
- Vertical-axis wind turbines (VAWT) have the main rotor shaft arranged vertically. A typical VAWT is shown in figure 2.6. A major advantage of this arrangement over that of HAWT is that, the turbine does not need to be pointed in the direction of the wind to be effective, which is an advantage where the wind direction is highly variable. Furthermore, the generator and the gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, thus improving the accessibility for maintenance purposes.

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Figure 2.5 Horizontal-Axis Wind Turbine

Source: http:1/www.gogreengrid.com/2016/08/09/electricity-from-the-wind-how-wind­ turbines-work/

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