Eduediuyai, Dan , Enyenihi, Johnson , Idorenyin Markson (2019). Analysis of the Effect of Variations in Refractivity Gradient on Line of Sight Percentage Clearance and Single Knife Edge Diffraction Loss. International Journal of Sustainable Energy and Environmental Research, 8(1): 1-9. DOI: 10.18488/journal.13.2019.81.1.9
In this paper, analysis of the effect of variations in refractivity gradient on line of sight percentage clearance and single knife edge diffraction loss is presented. Relevant, mathematical expressions and approaches for the analyses are presented. Sample path profile data of terrestrial line of sight (LOS) microwave communication links operating at C-band 5.5 GHz frequency and Ku-band 11 GHz frequency with 15 Km path length are used in the study to demonstrate the application of the ideas presented in this paper. The results showed that the critical point of minimum LOS percentage clearance occurred at a distance of 8.89 Km from the transmitter. Based on the results regression models were derived for relating the refractivity gradient to the effective earth K-factor, earth bulge, LOS percentage clearance and single knife edge LOS percentage clearance. The implication of the result is that, given that for any location the refractivity gradient varies with the primary atmospheric parameters like temperature, pressure and relative humidity, the amount of diffraction loss posed to the signal in the atmosphere will be varying at different rates depending on the prevailing values of the atmospheric parameters upon which refractivity gradient depends. Also, apart from the reference refractivity gradient of 39.25 N units/km, different frequencies will experience different amount of diffraction loss. The specific impact of the refractivity gradient on different frequencies depends on whether the prevailing refractivity gradient is above or below the reference refractivity gradient of 39.25 N units/km.
Contribution/ Originality
This study is one of very few studies which have investigated the effect of variations in refractivity gradient on line of sight percentage clearance and single knife edge diffraction loss. The ideas presented can easily be used to study the effect of variations in atmospheric parameters on wireless signal quality.
Impact of the Optimal Tilt Angle on the Solar Photovoltaic Array Size and Cost for a 100 kWh Solar Power System in Imo State
Ozuomba, Simeon , Iniobong Edifon Abasi-Obot , Idorenyin Markson (2019). Impact of the Optimal Tilt Angle on the Solar Photovoltaic Array Size and Cost for a 100 kWh Solar Power System in Imo State. International Journal of Sustainable Energy and Environmental Research, 8(1): 29-35. DOI: 10.18488/journal.13.2019.81.29.35
In this paper the impact of adjusting the optimal tilt angle of solar photovoltaic (PV) modules on monthly bases was studied and compared to that of the annually-fixed optimal tilt angle. PVSyst software was used to determine the optimal tilt angle for each month for a given case study site in Imo state in Nigeria. Mathematical models for computing the required PV array power to meet the daily energy demand of 100 kWh were presented. Addition parameters considered in the study were the PV array number of modules as well as PV array area and cost. For the case study 100 kWh daily energy demand, the selected PV module had a peak power rating of 100W, with a unit cost of N 18,000 and with dimensions that gave an area of 0.65945m^2. The results showed that there is about 4 % (annual average) reduction in the required PV array power when the monthly adjustment of the optimal tilt angle is used. December had the highest percentage reduction in the required PV array power. The reduction in the PV array power resulted in the corresponding reduction in the number of PV modules needed to provide the required power, as well as a reduction in PV array area and cost.
Contribution/ Originality
This study is one of the very few studies which have investigated the impact of the optimal tilt angle on the solar photovoltaic array size and cost for the solar power system in Imo state, Nigeria.
Experimental and Numerical Study of Magnetic Field Impact on the Thermal Solar Collectors
S. Sami , F. Quito (2019). Experimental and Numerical Study of Magnetic Field Impact on the Thermal Solar Collectors. International Journal of Sustainable Energy and Environmental Research, 8(1): 10-28. DOI: 10.18488/journal.13.2019.81.10.28
An experimental study has been conducted to determine the impact of magnetic field on the performance of thermal solar collectors. A numerical model has been developed after the mass and energy balances, presented, integrated and coded. The study compared between thermal solar collector’s behavior with or without magnetic field at different solar radiations, magnetic field forces, as well as other conditions. Comparisons were made against data collected at different conditions for validation purposes of the model numerical predictions.
Contribution/ Originality
This study contributes to the understanding of the impact of magnetic field on the heat transfer fluid circulating in thermal solar collectors. In addition, this study enhances our understanding of the behavior of thermal solar collectors and impact of the different solar radiations on the behavior of thermal solar collectors.
Optimal Planning of Energy Hubs Considering Renewable Energy Sources and Battery Energy Storage System
V. V. Thang , Thanhtung Ha (2019). Optimal Planning of Energy Hubs Considering Renewable Energy Sources and Battery Energy Storage System. International Journal of Sustainable Energy and Environmental Research, 8(1): 36-47. DOI: 10.18488/journal.13.2019.81.36.47
In the context of multiple energy loads, the energy hub is introduced as a unit where multiple energy carriers can be converted, conditioned, and stored to enhance the energy efficiency of the system. Therefore, this study presents an optimal planning framework, which aims the selection the invested size and time of equipment based on minimizing the life cycle cost considering renewable energy sources (RES) and battery energy storage systems (BESS). The input energies considered include the electrical energy, natural gas, solar radiation and wind that are converted to supply for output energies consisting of electricity, cooling, and heating. The planning framework with the objective function which is minimizing the life cycle cost of the project consists of the investing and operating cost of equipment, cost for purchasing energy from market (electricity, natural gas), the emission taxes cost and the replacement cost or residual value of equipment at the end of the planning period. The constraints as balance energy types, the size limit of equipment integrated into model together with binary variables make a mixed integer nonlinear programming (MINLP) planning problem. The feasibility of the proposed model and the effectiveness of renewable energy sources and BESS in optimal planning of energy hubs are tested by an assumed energy hub with the high-level algebraic modeling software, general algebraic modeling system (GAMS).
Contribution/ Originality
This study contributes in existing documents a novel planning framework which considers the RES and BESS. A MINLP planning framework with the LCC objective function and constraints proposed allows determining the installed size and time of equipment during the planning period. The different lifetime and uptime of equipment are examined which improve the accuracy and suitability of problem for the practical.
Optimal Design of Hybrid Energy System Drives Small-Scale Reverse Osmosis Desalination Plant
M. Osman , M. A. Farahat , Mohammed Elsayed Lotfy (2019). Optimal Design of Hybrid Energy System Drives Small-Scale Reverse Osmosis Desalination Plant. International Journal of Sustainable Energy and Environmental Research, 8(1): 48-61. DOI: 10.18488/journal.13.2019.81.48.61
Different configurations for a hybrid energy system are presented. This study aims to produce 100 m3/day of freshwater for 120,000 people at Nakhl city, North Sinai, Egypt. This simulation selects the optimal design of the hybrid energy system according to the net present cost (NPC), the cost of energy (COE), the gases emissions (carbon dioxide, sulfur dioxide) and the excess system electricity. The hybrid system consists of photovoltaic panels, wind turbines, storage batteries, and a diesel generator. The operation of five different systems is studied to supply the load at an average rate of 557.22 kWh/day with 35.67 kW peak load. In order to minimize the system total cycle cost, both of the photovoltaic modules sizing, the wind turbine production, the number of battery strings and the diesel generator fuel consumption are studied. Homer Pro software is used to select the optimal system configuration. The results illustrate that the hybrid PV/diesel/RO desalination plant system with storage batteries is sustainable and socially accepted system. It consists of 83.5 kW PV panels, a 36.4 kW converter, seven strings of lead-acid batteries and a 50 kW fixed capacity generator. Also, the system achieves the lowest cost of energy and net present cost.
Contribution/ Originality
This study is one of very few studies which have investigated the optimal hybrid power system configuration to drive a reverse osmosis desalination plant at the Nakhl city, Egypt. This study documents that renewable energy is the effective option to face the fuel energy pollution by reducing the gases emissions from burning fossil fuels.
Using Refined Phosphogypsum to Replace Natural Gypsum in Portland Cement Production in Vietnam
Viet-Thien-An Van , Van-Binh Nguyen (2019). Using Refined Phosphogypsum to Replace Natural Gypsum in Portland Cement Production in Vietnam. International Journal of Sustainable Energy and Environmental Research, 8(1): 62-69. DOI: 10.18488/journal.13.2019.81.62.69
This study assessed the effects of different contents of two refined phosphogypsums (PG1, PG2) on standard consistency, setting times, compressive strength and sulfate resistance of cement. PG2 possesses higher water-soluble impurities such as P2O5, F content than PG1. The results were compared to those of cement containing natural gypsum (NG). The results showed that water demand of cement reduces when the content of the gypsums increases, especially with PG1 and NG. The phosphogypsums prolong the setting times of cement. The higher the gypsum content is, the more the 3-d compressive strength of cement can obtains. The low impurity phosphogypsum (PG1) accelerates the 3-d strength but lowers the 91-d strength of cement compared to the high impurity phosphogypsum (PG2). The strength of cement containing NG is always between those of the phosphogypsums at the ages of 3 and 91 days. There is a suitable content of gypsum to produce the highest strength of the cement at the ages of 28 and 91 days. Deterioration of the cement in sodium sulfate solution (50g/l) is more severely when increasing gypsum content. The sulfate resistance of cement containing PG1 is lower than that of cement containing PG2 or NG.
Contribution/ Originality
This study is one of very few studies in Vietnam to investigatewhich have investigated the potential for using refined phosphogypsum to replace natural gypsum in cement for environmental protection in Vietnam. This study has reported that phosphogypsum content and impurities of P2O5 and F- significantly affect the properties of Portland cement.
Ozuomba, Simeon , Iniobong Edifon Abasi-Obot , Idorenyin Markson 
