Determining the optimum voltage level for A DC home system

Abstract

The reduction in the cost of renewable energy technologies, the efforts of governments to encourage the use of these technologies and the high cost of grid extensions in the rural areas of most African countries has resulted in the increased use of DC solar home system in rural electrification. However, with the absence of proper standards for such systems, different voltage levels are used when developing these DC based systems. This research designs four PV powered DC home systems each with a system voltage of 12V, 24V, 48V and 120V respectively. The systems are designed depending on the load profile of a Rwandan rural household and the meteorological conditions of Rugarika, a sector in Kamonyi district which is in the Southern Province of Rwanda. The performance of these four systems are analyzed and compared with the aim of determining the optimum voltage level for the system. The analysis considers the cost, efficiency, voltage regulation, and the ease of compatibility of the system with the loads available to rural communities of Rwanda. The system with a nominal voltage of 120V, which was determined as the optimum voltage, is compared to the conventional 220V AC system on availability of the system by studying the average outages per year and cost of energy. The research found that the 120V DC home system provides a cheaper cost of electricity whereas the 220V AC system had a higher availability rate. All the operation analysis in this research was done using MATLAB/Simulink simulations whereas the comparison between the DC home system at the optimum voltage level and the conventional 220V AC system was done using HOMER Pro Software.