ABSTRACT
The aim of this study is to design and simulate a hybrid energy system for reliable and cost – effective power supply to mobile telecommunication sites in developing cities. The Hybrid optimization model for electric renewable (HOMER) software was utilized to design the wind-solar hybrid energy system. Long-term wind speed and solar radiation data were collected for the study location in Nigeria from the archives of the Nigerian Meteorological agency and the Nations Aeronautics and Space Admiration respectively. Simulations were carried out for one-year period, by making energy balance calculations based on HOMER software using long-term meteorological data and the load profile of a practical mobile telecommunication site load installed at Agbor, Delta State. Simulation results showed that the optimized wind-solar-battery hybrid system, which consists of 14 kW PV arrays, 15 kW wind turbine generators, 5 kW power electronic converter and 110.98 kWh battery bank, gives the lowest cost of US$ 0.165 (N51.23) per kWh of energy consumed but with 3% annual capacity shortage compared to diesel-alone US$ 0.479 per kWh (N 148.73 per kWh), wind-diesel-battery (N 65.83 per kWh), solar-diesel-battery (N 78.56 per kWh), and solar-wind-diesel-battery hybrid systems (N 51.85 per kWh). In addition, the application of the designed hybrid energy system could eliminate the greenhouse gas emissions of mobile telecommunication sites resulting from the use of diesel generators and thereby making the environment greener and safer.
TABLE OF CONTENTS
| Declaration | iii | ||
| Certification | iv | ||
| Dedication | v | ||
| Acknowledgements | vi | ||
| Table of contents | vii | ||
| List of Abbreviation | ix | ||
| List of Tables | x | ||
| List of Figures | xi | ||
| Abstract | xiii | ||
| CHAPTER ONE: INTRODUCTION | 1 | ||
| 1.1 | Background to the Study | 3 | |
| 1.2 | Statement of the Problem | 4 | |
| 1.3 | Objectives of the Study | 4 | |
| 1.4 | Scope of the Study | 4 | |
| 1.5 | Research Methods | 5 | |
| 1.6 | Significance of the study | 5 | |
| 1.7 | Thesis arrangement | 6 | |
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CHAPTER TWO: LITERATURE REVIEWÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
2.1 Renewable Energy Source (Res)Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 7
2.2 Photovoltaic Energy System                                                                                               7
2.2.1 Photovoltaic Arrangement                                                                                                8
2.2.3 PV Cell                                                                                                                            9
2.2.4 PV Array                                                                                                                        10
2.2.5 Working of PV Cell                                                                                                        10
2.2.6 Modelling of Pv Cell                                                                                                      11
2.2.7 Okundamiya et al. Model                                                                                               16
2.3 Wind Energy and Power                                                                                                   16
2.3.1 Wind Turbine                                                                                                                 18
2.4 Hybrid Power Systems                                                                                                      21
2.4.1 HPS Design                                                                                                                          24
2.4.2 HPS design optimization                                                                                                      24
2.5 HOMERÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 26
2.5.1 What does HOMER do?                                                                                                      27
2.5.2 HOMER and NPCÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 27
CHAPTER THREE: RESEARCH METHODSÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 29
3.1 Study Location and Meteorology                                                                                            29
3.2 Data Collection Analysis                                                                                                         30
3.2.1 Load Data                                                                                                                             30
3.2.2 Meteorology Data                                                                                                                 30
3.2.3 Technical and Economic Data                                                                                              30
3.3 Design and Simulation of the Wind-Solar Hybrid Energy System                                         36
CHAPTER FOUR: RESULTS AND DISCUSSIONÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 38
4.1 Results                                                                                                                                     38
4.2 Discussion                                                                                                                                40
4.3 Findings                                                                                                                                   41
CHAPTER FIVE: CONCLUSION Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 43
5.1 Conclusion                                                                                                                               43
References
LIST OF ABBREVIATIONS
PV                  –          Photovoltaic
HOMER        –          Hybrid Optimization Model for Electrical renewable
NIMET          –          Nigeria Meteorological
NASA            –          Nations Aeronautics and Space Admiration
RES                –          Renewable Energy sources
VOC              –          Voltage of cell
HPS                –          Hybrid Power System
AC                 –          Alternating Current
DC                 –          Direct Current
SSC                –          System Supervisory Control
WTG              –          Wind Turbine Generator
DG                 –          Diesel Generator
CAPEX          –          Capital Expenses
OPEX            –          Operation Expenses
NPC               –          Net Present Cost
TAC               –          Total Analyzed Cost
SV                  –          Salvage Costs
R D               –          Research and Development
LIST OF TABLES
Table 2.1: Parameters of the PV array at 25oC, 1000w/m2 16
Table 2.2: Overview of simulation tools 25
Table 3.1: Geographical coordinates of the study location 29
Table 3.2: Energy consumption a functional mobile telecommunication site at Agbor 30
Table 3.3: Main characteristics of datasets collected from the Nigerian Meteorological
agency (Okundamiya et al., 2014b) 31
Table 3.4: Technical/Economic parameters for sizing the wind-solar hybrid energy
system 34
Table 4.1:Â Â Â Â Â Â Â Simulation results of the possible configurations of the designed hybrid energy
system based on the net present cost 38
Table 4.2: Electrical characteristics of proposed (wind-solar-battery) hybrid system 39
Table 4.3: Summary of total net present cost of the designed wind-solar hybrid system
components 39
Table 4.4: Comparison of pollutant emissions from diesel generator source with various
hybrid system options at study location 40
LIST OF FIGURES
Figure 2.1: Overall block diagram of PV energy system 8
Figure 2.2: Structure of PV Cell
9
Figure 2.3: Photovoltaic system
10
Figure 2.4: Working of PV cell
11
Figure 2.5: Equivalent circuit of Single-diode modal of a solar cell 11
Figure 2.6: Representation of PV module 14
Figure 2.7: I-V and P-V characteristics of PV module 15
Figure 2.8: Air moving with velocity V m/s towards area A m2 17
Figure 2.9: Drawing of the rotor and blades of a wind turbine (courtesy of ESN) 19
Figure 2.10: Power curve of a typical wind turbine 20
Figure 2.11: Basic topology of a hybrid power system 21
Figure 2.12: HPS possibilities (Manwell and McGowan, 2002). 22
Figure 2.13: Solar-wind hybrid power system 24
Figure 3.1: Map of the study location
29
Figure 3.2: Seasonal load profile of the studied mobile telecommunication site 30
Figure 3.3: 20-years (1986–2005) monthly average daily solar resources (radiation and
clearance index) for study site 32
Figure 3.4: 10-years (2003–2012) monthly average daily wind speed (measured at a
height of 10 m above sea level) for study site. 33
Figure 3.5: Power profile of Wind Turbine Generator used in this study (Okundamiya and
Omorogiuwa, 2016) 33
Figure 3.6: Architecture of the designed wind-solar hybrid energy system 36
Figure 4.1: Average monthly electrical production of the designed wind-solar hybrid
system
CHAPTER ONE
INTRODUCTION
- Background to the Study
The rising costs of energy and carbon footprint of operating mobile telecommunication sites in the developing countries have increased research interests in renewable energy technology. The renewable energy system design usually integrates renewable energy mix, such as biomass, wind and solar energy. Nevertheless, large area of land, water usage, and social impacts often characterize the electricity production from biomass, and this requires further study to verify the techno-economic viability of its power generation (Okundamiya, 2015). Consequently, it may be required to shift demand to other energy sources, such as wind and solar. Wind and solar energy are ubiquitous and freely available. These are used sources for renewable energy generation because are both technically and environmentally viable options.
Wind energy is one of the most viable and promising sources of renewable energy globally. Accurate estimate of wind speed distribution, selection of wind turbines, and the operational strategy and management of the wind turbines are essential factors that affect the wind energy potential. The first steps a utility company considers when deploying wind as an energy source is to examine the available wind speed (Okundamiya and Nzeako, 2013). The next step is to adjust the wind speed data at anemometer height to wind turbine hub height using appropriate conversion ratio. The adjustment of the wind profile is necessary to account for the effects of the wind shear inputs. Moreover, accurate assessment of wind power potential at a site requires detailed knowledge of the wind speeds at different heights (AI Abbadi and Rehman, 2009, Rehman and Ai- Abbadi, 2009). Methods are available in the literature for improving the estimate of the hub height wind resource (Lackner et al, 2010). The solar photovoltaic (PV) system is a clean source of power, which does not emit greenhouse gasses.
The performance of the photovoltaic conversion system is highly dependent on its orientation and period of service (Yang and Lu, 2007). The orientation of the PV surface is described using its tilt angle and the azimuth, both relate to the horizontal. This creates the problem of designing the optimum tilt angle for harvesting solar energy at fixed latitudes, as this is essential for effective harnessing and utilization of global solar radiation (Okundamiya et al, 2014a). In general, there are two steps in determining the available solar energy when supplying a remote load. The first step involves the determination of the amount of solar radiation that arrives on the earth at the PV panel’s location. The next step is modelling of the panel itself, considering its efficiencies, losses and physical orientation. Each step requires a model that deals with many variables, and inputs into the second stage of the model utilize the results of the first step. Using the available solar radiation at the tilted PV surface, the air temperature, and manufacturers data for a PV module as input parameters, the power output of the PV module can be deduced (Markvard, 2000).
There has been outstanding interest in the optimal design and management of stand-alone hybrid energy systems with the aim of achieving energy balance between the maximum energy captured and consumed energy (Kalantar and Mousavi 2010). The fluctuating renewable energy supplies, load demands, and the non-linear characteristics of some components complicate the design of hybrid systems. In addition, the overall assessment of autonomous hybrid energy systems that incorporate renewable and convectional energy sources depends on economic and environmental criteria, which are often conflicting objectives. The technical constraints in hybrid energy systems relate to system reliability. Several reliability indices have been employed for the evaluation of generating systems in the literature. The most technical approaches used for the evaluation of power system reliability are the loss of load probability, loss of load power supply, and loss of power supply probability.
The various methods for fixing hybrid energy systems are classified as follows (Zhou et al., 2010): simulation and optimization software and optimization methods. Hybrid optimization model for electrical renewable (HOMER), a computer- based model is the most widely used simulation software for the design options, which makes it easier to assess the techno-economic benefits of different power system configurations. Unlike other simulation, HOMER allows for comparison with different design options based on technical and economic merits, as a result, (Talebhagh and Kareghar, (2012)), (Teoh et al.2012) and (Okundamiya et al. (2014b)) have used this tool for the design, management and sizing of hybrid energy systems.
- Statement of the Problem
The rapid growth of mobile telecommunications in Nigeria creates a number of problems such as network congestion and poor quality of service delivery. These problems are fast eroding the gains of the Nigeria mobile telecommunication sector (Okundamiya et al. 2014). Lack of a reliable electric power grid and the cost implication of a supplementary energy source are major problems besetting this sector in most developing countries, particularly as network operators strive to expand their communications network to provide global coverage with increased quality of service. Most mobile telecommunication sites in the developing regions rely heavily on the use of fossil-fuel led generations either as supplements to the electric power grid or exclusively in remote locations.
The use of fossil-powered solution at mobile telecommunication sites presents a number of economic, logistical, and environment problems (Okundamiya et al., 2014b). The operation and maintenance of fossil-fueled generators account for about 78% of the total cost of operations (equivalent to about 35% of the cost of ownership) of the mobile telecommunication sites (Adegoke and Babalola, 2011). In addition, studies by ( Kovates et al.
(2005)), VandeWeghe and Kennedy (2007) and Rahmstorf (2008) indicate that the earth’s climatic change is the result of increasing concentrations of greenhouse gases resulting primarily from fossil fuel combustion into the atmosphere, yet Nigeria’s grid electricity supply is characterized by high unreliability index (Ogujor, 2007). Besides, the current and future demand patterns of energy are not sustainable (Oyedepo, 2012). Sustainable energy provides accessible, affordable, and reliable energy service that improve the socio-economic and environmental standards within the overall developmental context of the society while recognizing equitable distribution (Davidson, 2002).
- Objectives of the Study
The overall aim of this study is to design and simulate a wind-solar hybrid energy system for reliable and cost-effective power supply to mobile telecommunication sites in developing cities. The objectives of this study are to:
- design a wind-solar hybrid energy system for mobile telecommunication sites in developing cites;
- simulate and determine the optimum capacity of the wind-solar hybrid energy system for reliable and cost-effective power supply;
- determine the viability of the proposed wind-solar hybrid energy system.
- Scope of the Study
The hybrid energy systems discussed in this study are designed to supply power to outdoor mobile telecommunication sites consuming up to 3KW of power continuously. The outdoor mobile telecommunication sites consume lesser energy compared to traditional sites. It is worthy of note that the use of energy efficient is essential to attaining renewable energy solution.
- Research Methods
The methods proposed to achieve the set objectives for this study are:
- theoretical approach was applied in the design of the wind-solar hybrid energy system. Load data of a typical outdoor mobile telecommunication sites was collected from MTN, Nigeria. Long-term meteorological (wind speed and solar radiation) data were collected for the study location in Nigeria from the archives of the Nigerian Meteorological (NIMET) agency, Oshodi, Lagos State and the Nations Aeronautics and space Admiration (NASA) respectively. The data set was analyzed and evaluated using stochastic methods.
- Hybrid optimization model for electric renewable (HOMER) softer will be utilized to simulate the wind-solar hybrid energy system. The optimum capacity of the hybrid energy system for reliable and lost-effective power supply is determined by making energy-balance calculations based on HOMER.
- The viability of the proposed hybrid energy system will be determined based on sensitivity analysis. Sensitivity analysis isperformed on the system by varying system design parameters. Three key performance indices (power supply reliability, cost of energy, and emission reduction) was applied to evaluate the overall performance of the proposed hybrid energy system over existing diesel energy generation system
- Significance of the study
Renewable technologies are essential components of sustainable development mainly because of the following reason (Okundamiya et al., 2014c). Firstly, these are eco-friendlier than other sources as such extensive utilization of the renewable option will help in making the environment friendlier and safe. Secondly, these are non-exhaustible and if properly utilized in appropriate application, willcan provide a reliable and sustainable supply of energy
almost indefinitely. Thirdly, these favour system decentralization and local solution that are somewhat independent of the electric power grid. This enhances the flexibility of providing enormous benefits to small isolated populations.
The hybrid renewable energy systems are capable of providing the needed energy for sustainable economic development in the mobile telecommunication sectors but critical issues on the enabling technologies are yet to be resolved (Zhou et al., 2010). The intermittent nature of most renewable energy sources creates the problem of designing the optimum configuration for a given location, the use of renewable energy system as an alternative to fossil –powered source can reduce the unit cost of power, but the range of financial benefits depends on the geographical coordinates (Okundamiya and Omorogiuwa, 2015). The reason is that the renewable energy depends highly on weather conditions. Moreover, the viability of a hybrid energy system is a function of the configuration, which depends on the size or allocated capacity, mix of power source and the dispatch strategy. It is worthy of note that the operational specifications of renewable energy systems are location dependent (Okundamiya et al., 2014). Potential investors are at a cross road on the choice of system design configuration, optimum specifications, capacity projections and the techno-economic implications. In addition, renewable energy solutions are not commonly used for powering mobile telecommunication sites in Nigeria presently. Consequently, more research work on hybrid energy systems and the enabling technology for a sustainable economic development is needed
- Thesis Arrangement
Chapter 1 discusses the introduction, aims and objectives of the study. Chapter 2 reviews related literature relevant to this study. The chapter 3 describes the meteorology of the study area, data collection, design and analysis as well as a case study simulation. The results are presented and discussed in chapter 4 while chapter 5 gives the conclusion and recommendations of the study.
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