Dimensioning of hybrid solar-battery-grid micro-energy power systems to alleviate domestic power outages in urban Zimbabwe: A reliability-cost approach

Abstract

Power outages are rampant in most of Southern African countries due to inadequate electricity generation capacity by the utilities in these countries. This situation results in direct and indirect costs to both the consumers of electricity- those that are lucky to be connected to the electricity grid- and to the utilities themselves. In a region endowed with abundant solar resource, hybrid solar-battery-grid micro-power systems are an attractive option to alleviate the power outage problems, resulting in improved electricity supply reliability at reasonable cost of energy. In this study, an approach to the dimensioning of these hybrid power systems, for domestic consumers in Zimbabwe is presented. For a given hourly load profile, and for a desired level of electricity supply reliability, a combination of solar photovoltaic (PV) array and storage battery can be specified in a fairly general way (i.e. independent of size of daily load) by use of dimensionless component size parameters, A/Ao and Bcap/Lday, respectively, and defined in the study. A “home-made” Excel program is utilized for performing the necessary simulation of the systems. A plot of the dimensionless battery size parameter, Bcap/Lday, versus the PV array size parameter, A/Ao, maps the locus of points of system-component combinations resulting in a desired level of electricity supply reliability. Least levelized cost of energy (LCOE) is then used as the objective function to select among systems delivering the same level of reliability. Properly dimensioned hybrid solar-battery-grid micro-energy systems are found to be much cheaper than the commonly used approach to alleviating power outages by use of an auxiliary petroleum fuel generator.