System Sizing of Solar Energy Requirement for an “All-Direct Current” Stand-alone Telecommunication System
Nyaga, Muriithi Symon
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Solar photovoltaic (PV) energy has been widely used for decades especially where connection to a national grid is seldom possible and other sources such as fossil fuel and others are either unavailable or uneconomical. Solar PV energy owing to its free, natural availability and environmental friendliness has found demand for use in industries, homes and institutions. However, very little research has been carried out to precisely establish its effectiveness, reliability and adequacy. In this research work, an investigation to system size a PV telecommunication system was carried out for three consequtive months (June, July and August) considered to be the poorest in terms of irradiance by the Kenya Meteorological Department in the year 2012. The study was based on the power rating of a typical telecommunication system which is 1,222VA. However, the set-up was modeled to a typical telecommunication system by scaling down the actual load by a factor of 16 which gave 76.37VA. A standard stand-alone PV power supply unit to power the simulated telecommunication system was mounted in an open area away from any shading outside the solar energy laboratory of University of Nairobi. Voltage, current and hence the power data were measured daily using a data logger for the three months from the PV power supply unit. The irradiance data was also measured using a pyranometer for the same duration of time as that of voltage and current. The irradiance data collected and power harnessed by the installed PV system varied from month to month with July recording the lowest and August the highest. The highest and lowest irradiance fell on sunny day and cloudy day respectively. The daily average irradiance for June, July and August were 452.40W/m2, 422.43W/m2 and 510.67W/m2 respectively. The corresponding daily average power harnessed from modules for June, July and August were 76.10 VA, 75.37 VA and 85.93 VA respectively. There was a direct correlation between the irradiance and module power output. The irradiance and power harnessed was used to determine the number of modules and batteries required to fully support the Telecommunication PV System. For the month of June the number of modules and batteries were found to be 38, 200W modules and 62, 175Ah batteries. For the month of July they were 38, 200W modules and 62, 175Ah batteries and for the month of August 32, 200W modules and 62, 175Ah batteries respectively. The month that gave the highest number of modules and batteries (poorest month in terms of irradiance and power) was used as reference to size the Telecommunication PV system and in this case it was the month of July. The finding reported in this research work is of great importance to telecommunication campanies as it serves as a guide as to the approximate number of modules and batteries that should be put in place to support the PV telecommunication systems. It also forms the basis for sizing, as can be used to scale down other PV systems to be installed in areas whose average irradiance is known.