Sizing a standalone photovoltaic electrical solar system for domestic consumption
Mukere, Moffat Kiruthu
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The performance of a stand-alone photovoltaic (PV) system depends on the solar radiation and behavior of each PV system component; size of PV array, battery capacity and charge controller. Therefore, the correct sizing plays an important role on the reliability of the stand-alone PV systems. This research presents an experimental numerical method for determining the optimal sizing of a standalone PV system in terms of optimal sizing of PV array, battery capacity and size of charge controller. A standalone domestic PV system was first developed and then measurement of current, voltage and irradiance at the site was done. Current and voltage from the stand-alone PV system was measured daily over a period of three months. Measurement of these parameters was done using a data logger capable of recording data per second for accuracy and precision. Total average power harnessed; hourly, daily and monthly was calculated. The study sought to determine the size of a PV system that can adequately and reliably cater for a domestic power system in a Kenyan rural home. In applying the formulas for optimal sizing of PV array, battery and charge controller rating, the data measured at the site was used. Using July 2012, the month with the least solar irradiance, the optimal components for the simulated PV system was found to be; 3 PV modules (40W), 3 deep cycle batteries (12V/75Ah) and a charge controller rated 12V/20A. Based on the results of the designed simulated domestic PV system installed in Chiromo, Nairobi; the proposed method gives satisfactory optimal sizing results.