ABSTRACT
All nations of the world depend on fossil fuels for their energy needs. However the obligation to reduce Carbon dioxide and other gaseous emissions is the reason behind which countries turn to non-polluting renewable energy sources. Hot water heated by the sun is used in many ways, in residential settings to provide domestic hot water, also has industrial applications, e.g. to generate electricity. Designs suitable for hot climates can be much simpler and cheaper, and can be considered an appropriate technology for these places. Hot water use represents a large proportion of energy needs in hostels. This energy need accounts for a large portion of the total annual energy consumption in hostels and therefore a reasonable amount of the university income is spent on electricity bills used for heating water for bathing in hostels. A solar water heater was designed, simulated, fabricated and tested. The design, simulation, fabrication and performance tests of a thermosyphon solar water heater were carried out successfully for a block in Postgraduate hostel of Ahmadu Bello University Zaria. the fabrication was carried out using locally available materials. The solar water heater has the ability to heat 200 liters of water from a temperature of 25oC to a temperature of 500C,. The design was purposely for students to use the water for bathing in order to totally discourage the use of electric heating devices in the hostel which on several occasions has been the reason of fire outbreaks in the hostel. The system factors such as costs and sizing were taken into consideration which assisted in the choice of materials and the design. The average solar radiation data was obtained from typical meteorological year (TMY) of Zaria which was used to determined the month with the least solar radiation. From the analysis of the typical meteorological year (TMY) data of Zaria the month of August has the least energy ratio which point it out as the month with the least solar radiation and it was used as the design month.The optimization of the system components was also carried out using MATLAB to determine the optimum system size. After the fabrication of the system the performance was evaluated by comparing the simulation results obtained from the model (solar data processor, Type 109 of TRNSYS) and the results obtained from the experiment using Microsoft Excel and standard deviation, Nash-Sutcliff coefficient statistical tools were used to validate the predictive power of the model. From the result obtained from the research it can be concluded that the thermosyphon solar water heater of collector area of 2.6m2 has the ability to heat 200 litre of water to a temperature of 500C in the month that has the least solar radiation in Ahmadu Bello University Samaru, Zaria.The statistical tools used for the validation of the simulation model confirm that the model is valid and can be used in the estimation of the actual characteristics of a real system. The relative error is very minimal for all the measured parameters and Nash-Sutcliff coefficient shows that the degree of fitting is very high which shows that the simulation model has high accuracy, also the standard deviation shows that the deviation of the experimental parameters from the simulated is very low and therefore it is negligible.The results show little deviation of predicted values from actual values with a good level of fit, thereby validating the model used for simulating the solar water heating system.
TABLE OF CONTENTS
DECLARATION………………………………………………………………………………………………………….. iii
CERTIFICATION ………………………………………………………………………………………………………….iv
DEDICATION ……………………………………………………………………………………………………………… v
ACKNOWLEDGEMENT ……………………………………………………………………………………………….vi
ABSTRACT ………………………………………………………………………………………………………………… vii
LIST OF FIGURES ……………………………………………………………………………………………………….. xi
LIST OF TABLES ……………………………………………………………………………………………………….. xii
LIST OF APPENDICES ……………………………………………………………………………………………….. xiii
NOMENCLATURE …………………………………………………………………………………………………….. xiv
CHAPTER ONE……………………………………………………………………………………………………………. 1
INTRODUCTION …………………………………………………………………………………………………………. 1
1.1 Background to the Study ………………………………………………………………………………………….. 1
1.2 Statement of the Problem …………………………………………………………………………………………… 2
1.3 The Present Work …………………………………………………………………………………………………….. 3
1.4 Aim and Objectives of the Work …………………………………………………………………………………. 4
1.5 Significance of the Research ………………………………………………………………………………………. 4
CHAPTER TWO …………………………………………………………………………………………………………… 6
LITERATURE REVIEW ……………………………………………………………………………………………….. 6
2.2 Passive and Active Solar Water Heater ………………………………………………………………………… 6
2.2.1 Passive solar water heater ………………………………………………………………………………………. 6
2.2.2 Active solar water heater …………………………………………………………………………………………. 8
2.3 Components of a Solar Water Heater …………………………………………………………………………. 10
2.3.1 Hot water storage tanks ……………………………………………………………………………………….. 10
2.3.2 Solar collector ……………………………………………………………………………………………………… 11
2.3.2.1 Types of solar collectors used for domestic water heating …………………………………………. 12
2.3.2.2 Solar collector orientation…………………………………………………………………………………… 16
2.3.3 Absorber plate……………………………………………………………………………………………………… 18
2.3.4 Transparent cover ………………………………………………………………………………………………… 19
2.3.5 Collector casing ………………………………………………………………………………………………….. 19
2.3.6 Insulation ……………………………………………………………………………………………………………. 19
2.4 Application of Solar Heated Water …………………………………………………………………………….. 20
2.5 Selecting and Sizing a Solar Heating System ……………………………………………………………….. 20
2.6 Siting Your Solar Water Heating System…………………………………………………………………….. 22
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2.7 Review of Past Research Work …………………………………………………………………………………. 22
2.8 Theoretical Background …………………………………………………………………………………………. 28
2.8.1 Thermal radiation …………………………………………………………………………………………………. 28
2.8.2 Optical Analysis…………………………………………………………………………………………………… 28
2.8.3 Estimation of Absorptance of Absorber Plate ……………………………………………………………. 33
CHAPTER THREE ……………………………………………………………………………………………………… 36
MATERIAL AND METHOD ……………………………………………………………………………………….. 36
3.1 Solar Water Heater Description and Operation ……………………………………………………………. 36
3.2 Working Principle of the Solar Water Heater ………………………………………………………………. 37
3.3 Solar Resources and Weather Data …………………………………………………………………………….. 37
3.4 Material Selection ……………………………………………………………………………………………… 37
3.5 Design Analysis ……………………………………………………………………………………………………… 39
3.5.1.1 Total Radiation on Tilted Surfaces ……………………………………………………………………….. 39
3.5.1.2 Absorbed Solar Radiation …………………………………………………………………………………… 41
3.5.1. 3 Extraterrestrial solar radiation …………………………………………………………………………… 41
3.5.1.4 Terrestrial irradiation ………………………………………………………………………………………… 42
3.5.1. 5 Declination (δ) …………………………………………………………………………………………………. 43
3.5.1.8 Collector energy losses ………………………………………………………………………………………. 44
3.5.1.12 Collector useful energy…………………………………………………………………………………….. 47
3.5.1.13 Heat Removal Factor ……………………………………………………………………………………….. 48
3.5.2 Determination of the Design Month ………………………………………………………………………… 50
3.5.3 Optimum Geometrical Parameters …………………………………………………………………………… 51
3.5.3.2 Optimum tube to tube distance and collector tube diameter ………………………………………. 52
3.5.3.3 Orientation angle of tilt ………………………………………………………………………………………. 52
3.5.3.4 Absorber plate thickness …………………………………………………………………………………….. 53
3.5.3.5 Number of glass cover ………………………………………………………………………………………… 53
3.5.3.6 Collector absorber plate distance from the glazing material ……………………………………… 53
3.5.3.7 Shading ……………………………………………………………………………………………………………. 54
3.6 Design Consideration ………………………………………………………………………………………………. 54
3.7 Design Assumptions ……………………………………………………………………………………………….. 55
3.8.1 Determination of total solar radiation absorbed by the collector ……………………………………. 55
3.8.2 Design calculation of heat loss in the collector ………………………………………………………….. 57
3.8.3 Heat transfer through the storage tank component ……………………………………………………… 58
3.8.3 Heat transfer through the storage tank component ……………………………………………………… 59
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3.9 Simulation and Validation of the Solar Water Heater…………………………………………………….. 59
3.10 Fabrication, Costing and Testing. …………………………………………………………………………….. 64
3.10.1 Fabrication ………………………………………………………………………………………………………… 65
3.10.2 Cost of Solar Water Heater …………………………………………………………………………………… 67
3.10.3 Testing of solar water heater…………………………………………………………………………………. 69
CHAPTER FOUR ……………………………………………………………………………………………………….. 72
4.0 RESULTS AND DISCUSSION …………………………………………………………………………… 72
4.1 Meteorological and Simulated Solar Data for Zaria and Solar Water Heater Design Parameter 72
4.2 Collector Tilt Angle (𝜷) ……………………………………………………………………………………… 76
4.3 Collector Tube Diameter and Centre to Centre Distance. ……………………………………………… 77
4.4 Collector Absorber Plate Thickness ………………………………………………………………………. 78
4.5 Collector Number of Glazing ………………………………………………………………………………. 79
4.6 System Optimum Parameters and Simulation …………………………………………………………… 80
4.8 Comparison of experimental results with result obtain from simulation and determining the Authenticity of the simulation software (TRNSYS 16) ……………………………………………………….. 84
4.8.1 Comparison and Validation of simulated ambient temperature with experimental ambient temperature ………………………………………………………………………………………………………………… 84
4.8.2 Comparism and Validation of simulated Solar Radiation with experimental Solar Radiation 87
4.8.3 Comparism and Validation of simulated Collector outlet Temperature with experimental Collector outlet Temperature. ………………………………………………………………………………………… 91
4.8.4 Comparison and Validation of simulated Collector Inlet Temperatures with experimental Collector Inlet Temperatures. …………………………………………………………………………………………. 94
CHAPTER FIVE …………………………………………………………………………………………………………. 99
5.0 SUMMARY, CONCLUSION AND RECOMMENDATIONS ……………………………………… 99
5.1 Summary ………………………………………………………………………………………………………………. 99
5.2 Conclusion…………………………………………………………………………………………………………… 100
5.3 Recommendations…………………………………………………………………………………………………. 101
REFERENCES ………………………………………………………………………………………………………….. 102
20,2012 from http//:www.redscreen.net …………………………………………………………………………….. 103
APPENDIX B …………………………………………………………………………………………………………… 109
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CHAPTER ONE
INTRODUCTION
1.1 Background to the Study
The sun has produced energy for thousands of years. Solar energy is the sun‘s rays (solar radiation) that reach the earth. This energy can be converted into other forms of energy, such as heat and electricity. Radiant energy from the sun has powered life on earth for thousands of years. In the 1830s, the British astronomer, John Herschel, famously used a solar thermal collector box (a device that absorbs sunlight to generate heat) to cook food during an expedition to Africa (Soteris, 2004). Solar energy is the most capable of the renewable energy sources. Despite this hopeful evaluation of the potential of solar energy, considerable technical and economic problems must be solved before utilisation of solar energy can occur (Ahmad, 2010). The solar power development will depend on how a number of serious constraints are dealt with, including scientific and technological problems, marketing, financial limitations and political challenges. In addition, the education of engineers will have to change its focus from non-renewable fossil-fuel technology to renewable power sources. There has been a general agreement that the most significant of the renewable energy sources is solar radiation (Ahmad, 2010).
When a dark surface is placed in sunshine, it absorbs solar energy and heats up. A solar energy collector working with sun facing surfaces will transfer energy to the water that flows through it. To reduce heat loss to the atmosphere and to improve its efficiency, one or two sheets of glass are usually placed over the absorber surface. This type of thermal collector suffers from heat losses due to radiation and convection. Such losses increase rapidly as the temperature of the working fluid increases. Improvement such as the use of
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selective surfaces, evacuation of the collector to reduce heat losses, and the special glass is used to increase the efficiency of the collector. Solar water heating (SWH) is a proven and famous renewable energy technology and has been used in many countries of the world. The SWH system consists of mainly three parts, namely a solar collector, a storage tank and a circulating pump. A solar water heating system has been the famous application that uses solar radiation as an energy source that uses thermal conversion.
Hot water heated by the sun is used in many ways, in residential settings to provide domestic hot water, also has industrial applications, e.g. to generate electricity. Designs suitable for hot climates can be much simpler and cheaper, and can be considered an appropriate technology for these places. The global solar thermal market is dominated by China, Europe, Japan and India (Dobson, 2008). Water heating accounts for a substantial portion of energy use in many residential, commercial, institutional and federal facilities. Worldwide, approximately 18% of energy use in residential buildings and 4% in commercial buildings are for water heating. Solar water heating systems, which use the sun’s energy rather than electricity or gas to heat water, can efficiently serve up to 80% of hot water needs—with no fuel cost or pollution and with minimal operation and maintenance (O&M) expense. (Walker, 2012).
1.2 Statement of the Problem
It is now widely accepted that human activities have contributed to a noticeable average global warming in the twentieth century. However, there are differential impacts of this global trend on regional climate, agriculture, storm damage, and other effects in different parts of the world. This complicates both the assessment of global effects of atmospheric emissions and international negotiations over requisite changes in fossil fuel use.
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Burning fossil fuels for the generation of energy, especially coal is a dirty process. Incomplete combustion of coal and oil produces particulate matter. Heavier particulates produce an annoying dirty grit, and lighter particulates can be inhaled deeply and become a health hazard. In addition, impurities such as sulphur also burn and produce potentially dangerous oxides. Since the air is made about 80% nitrogen, nitrogen is combusted along with the fuel at high temperatures, releasing nitrogen oxides (Christopher, 2010). Since fossil fuels are composed mainly of carbon by weight. All fossil fuels produce carbon dioxide when burned. In the atmosphere, the sulphur and nitrogen oxides produce sulphuric acid and nitric acid, respectively, which can lead to acid rain. The carbon dioxide helps trap heat in the atmosphere contributing to the warming of the earth‘s atmosphere. Hot water use represents a large proportion of energy needs in hostels. This energy need accounts for a large portion of the total annual energy consumption in hostels and therefore a reasonable amount of the university income is spent on electricity bills used for heating water for bathing in hostels. Also students are involved in all kinds of illegal electrical connections of electrical boiling rings, which had resulted in many fire outbreaks in the hostels all in the quest of warming bathing water.
1.3 The Present Work
This research involves design, simulation, construction and performance tests of a solar domestic hot water heating thermosyphon system for Ahmadu Bello University Samaru, Zaria, Nigeria, located on latitude 11.2o N and longitude 7.8oN to generate 200liter hot water at 500C using passive single glazed solar water heater for a block of postgraduate hostel in Ahmadu Bello University Zaria, When the preliminary viability was established, system performance was evaluated and generate more precise engineering data, optimal system parameter. The system was simulated using hourly simulation software, for this
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task Transient system simulation (Trnsys) software was used. The system was constructed based on the final optimal result of the system parameters obtained from the optimisation result and the system performance test was carried out based on standard test procedure of ISO 9806-3:1995 (ISO, 1995b) to validate the simulation results.
1.4 Aim and Objectives of the Work
The aim of the study is to design, construct, test and simulate a solar water heater for the postgraduate hostel in Ahmadu Bello University, Zaria. The specific objectives of the study are:
i. to determine the optimal system size, through a design analysis
ii. to construct the solar water heater
iii. to test and simulate the performance of the system.
iv. to estimate the cost of the solar water heating system.
1.5 Significance of the Research
i. Installation of solar water heater in the hostels is economically very paramount because it will reduce the cost of electricity and maintenance charges on the university income.
ii. The use of solar water heating systems in the hostel will dramatically lead to decrease in frequent fire outbreaks in the hostels and illegal electrical connections.
iii. Solar water heater use renewable energy, as it is renewable, it will never run out.
iv. Solar water heater produces little or no waste products such as carbon dioxide or other chemical pollutants, so has minimal negative impact on the environment.
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v. Solar heater systems can easily operate 20 years or more without needing any serious maintenance. Very little service or maintenance is required for the life of the system.
vi. Simple and Easy Installation. Once installed, the system is fully automated.
vii. High return on investment, compared to all other alternative energy options, solar energy is the most economical renewable energy (Ahmed 2010).
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