oer | Ambrose Alli University

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This study presents the modelling and optimization of a Hybrid Energy System (HES) for GSM Base Transceiver Station (BTS) sites in emerging cities. The aim is to ensure reliable and cost-effective power supply, considering the availability, dynamism and viability of energy sources.

Theoretical approach is applied in the modelling, simulation and validation of the developed HES, which consists of the utility grid, wind and solar photovoltaic (PV) as primary energy sources incorporating a super-capacitor/battery storage and power conversion unit. The complexity in optimizing continuous variables of the HES informed the use of a hybrid Genetic Algorithm and Pattern Search (h-GAPS) technique. The optimization problem is treated as a single objective function by considering all objectives in terms of cost while constraining the HES to satisfy the load demand safely according to the reliability criteria defined by the energy management strategy. The h-GAPS based optimization model simulated for the peripheral node GSM BTS sites in Abuja, Benin City, Enugu, Ikeja, Maiduguri and Sokoto utilized long-term (22-years) meteorological data sets collected from the Nigerian Meteorological agency and the National Aeronautics and Space Administration. The performance index of various developed and existing energy systems is evaluated based on economy or Cost of Energy (COE), power system reliability, energy throughput, and emission reduction targets.

Simulation results showed that Sokoto is the most favourable site for utilizing the proposed HES. Abuja and Benin City are the least favourable locations for utilizing the grid-connected (Grid/PV/Wind) and the off-grid (PV/Wind) configurations respectively. The optimum size of grid-connected HES consisting of 2 kW wind turbine, 7.09 m2 PV array inclined at 150, 0.053 kWh super-capacitor and 10.8 kWh (48V, 225Ah) battery banks, and 1,484.60 kWh of energy drawn from the grid per annum enabled reliable (negligible power loss) and cost-effective energy supply in Sokoto. The off-grid configuration reduced the COE by 72.81% (N24.75 to N6.73 per kWh) but with larger PV array size (12.68 m2) and reliability of 99.02%. In comparison with current practice of using grid/diesel systems, the proposed off-grid configuration has the best performance index, with an average energy throughput of 0.076 kWh per naira, in Nigeria. A reliable and cost effective energy option will not only reduce the per-unit cost of mobile services in Nigeria, but also reduce the greenhouse gas emission level from GSM BTS sites by an average of 98.34% thereby making the environment much more friendly and safe. This research would be useful for mobile service providers, consultants, regulatory agencies, policy makers, and the society.


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The development of any nation and its economy at large is centred on reliable and efficient power supply. Many developing nations are yet to actualise this feat, and therefore, there is need to strategize to meet the ever-rising demand for energy. Battery-based inverter systems have over the years provided additional power supply to critical loads, in the absence of public power supply. However, high peak charging/discharging power demands results in the degradation of the battery. Hybrid combination of batteries and other technologies such as super-capacitors can help to provide a single power system with both high energy and power densities. The aim of this project is the design and performance evaluation of a battery/super-capacitor hybrid storage system for renewable energy applications as this can provide an energy source with high power density and high energy density. The paralleling of the battery and the super-capacitor to obtain a single source was established using an Automatic Switching System. Results showed that considerable amount of initial transient current was supplied by the super-capacitor. The peak current drawn from the battery is reduced, which increases the lifetime and performance of the battery. This results in high cost saving as well as improved reliability, which has become increasingly necessary in the alternative power technology.


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The study investigates the electrical surge effects and remedy in Ajaokuta Power System Network located in Kogi State in the North Central of Nigeria, to identify various causes of lightning strokes and highlight various associated effects and to determine surge intensity and magnitude, collection of surge data on distribution and transmission network. The approaches adopted is to develop a preliminary data collection that will address the identified data gap and to review comprehensively the electrical surge related losses and address the potential impact of electrical surge protective devices in mitigating these losses. Experimental investigations will be carried out and collation of available data associated with electrical surges and their impacts. The result of the data recording based on existing power system network revealed that the vast majority of the lightning strikes were less than 30kA. In the three years of monitoring six residences with 15 lightning surge events, only two lightning strikes were severe enough to cause damage at current values of 1.27kA and 1.09kA in 2013 and 2015 respectively. In this thesis causes of over voltages in Ajaokuta power system network are internal and external. Instances of extended high voltages are rare, but when they occurred significant damages are done. Therefore to maintain high quality power, wiring, grounding, bonding and installation of surge protective devices are necessary to prevent over voltages from this power system network.

 


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The economic growth of any country is hinged on reliable and efficient power supply. Many developing countries have not attained sufficiency in energy generation. Hence, there is a need to strategize to meet the ever-rising demand for energy. The micro-grid system can provide a way of escape from this problem as it harnesses the strengths and weaknesses of different energy sources to attain stability in energy provision. The overall aim of this research is the design and operation strategy for a grid-connected micro-grid system for reliable and cost effective energy utilisation. The designed micro-grid, which is made up of three power sources (solar photovoltaic, grid and fossil-fuelled generator), utilises a microcontroller based system to reliably organise the flow of the hybrid power mix from energy sources and battery bank in a cost-effective manner. The microcontroller was programmed to monitor the DC voltage levels of the battery to decide which of the sources powers the load. Results showed that the developed operation strategy proffers appreciable techno-economic benefits especially in areas of energy savings and power supply availability. The developed strategy yielded a grid energy savings of 66.7% and a reliability improvement of 6.5% compared to the conventional strategy. The high energy saving as well as improved power supply reliability of developed strategy has become increasingly necessary especially in the face of exorbitant power supply rates of the various electric power distribution companies in Nigeria.

 


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Power factor is related to power flow in electrical systems and measures how effective an electrical power system is used. In order to efficiently use a power system, the power factor should be as close to unity as possible. This implies that the flow of reactive power should be kept to a minimal. Maintaining a high power factor is crucial to obtaining the best possible economic advantage for both Utilities and Industrial users. Operating a power system at a low power factor is a concern for both electrical utility and industry since it increases the magnitude of current in the system which may damage or shorten the life span of the equipment and also increase copper loss which is capable of lowering the system efficiency due to increase in reactive power. Industrial loads are mostly inductive and hence operate at low power factor. Several methods can be used for improving power factor in order to reduce the reactive power (kVA) demands of the load and power loss from the power supply system. Therefore the study of the power factor impact on the electrical installations of Ajaokuta power system is to analyze the effect of improving power factor of its electrical installation network beyond 0.8 being the power factor of various induction motors as investigated using the recirculating system No. 3 (Pump House No 3). The research approach used to implement this study is through simulation and calculations considering the use of bank of capacitors because it is the most common method of power factor correction. The result of the three investigations carried out shows that when power factor is improved there will be a reduction in the energy charges to the Ajaokuta steel plant. The plant was able to save 2 million one hundred and seventy five thousand five hundred and fifty eight naira (2,175,558) only. This amount was just for one substation out of 400 substations in the plant.

 


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