ABSTRACT
The essence of this work was to reduce energy cost from the conventional methods (BEDC and Generators) of electricity supply, and to improve reliability and efficiency of power supply with the use of Photo-voltaic (PV) systems in UBTH distribution network. The aim of this project was to design a photovoltaic system for critical loads in UBTH distribution network and implement its prototype. An energy survey of the electrical distribution network of UBTH was carried out where the critical loads were identified as loads in continuous operation for 24hours period and which impact on patient’s health was sacrosanct. A load audit was conducted to determine the energy demand by these critical loads in the network and thus, the critical loads in the accident and emergency (A&E) operating theatre were selected as a case study. The loads recorded from the A&E operating theatre were used in the design of the photovoltaic system and its prototype based on existing theories. The main and prototype photovoltaic system were designed by sizing of the essential components such as the photovoltaic panels, batteries, charge controllers, inverters, circuit breakers and cables. The prototype photovoltaic system design was subjected to performance based test that was carried out hourly from 8am to 6pm on the 1st November, 2019 to 7th November, 2019 in the University of Benin, Benin-City, Edo state. The parameters recorded from their required electrical measuring equipment were the ambient temperature, open circuit DC voltage of the solar panels and battery, the charging current from the solar panel, the open circuit inverter voltage, the on-load DC battery voltage and current, the ampere-hour reading from the battery, on-load AC voltage and current. A comparative analysis between the running life cycle cost of photovoltaic system design and the conventional method (BEDC electricity and the generator) of supply was examined mathematically and graphically for 25 years. The test results from the prototype PV system design were tabulated and analyzed graphically. From the comparative analysis, the Net Present Value of the PV system design was ₦0.137 per Wh for 25years life cycle, as against the BEDC & 50kVA diesel generators which was calculated to be ₦0.164 per Wh. Furthermore, the graphical representation of the incremental costs spreading over the 25 years was depicted and thus, revealed a clear idea of how much savings was to be made by UBTH and that the perceived high initial installation cost negated the running cost of the PV system. From the graphical analysis of the test results in the prototype photovoltaic system design, it was observed that the on-load DC voltage and the open-circuit DC voltage was fairly constant throughout the period of testing. The average temperature ranged from 25°C to 31°C which led to a gradual increase in the open-circuit DC voltage. Finally, there were the inverse proportionalities between the on-load AC voltage and on-load AC current, and also between the on-load DC voltage and on-load DC current respectively. Consequently, the illustrations showed huge significance in the efficiency of the photovoltaic system.
