<abstract> <p>Population expansion and increased industrialization are driving up global energy demand. Similarly, the most populous African country, Nigeria generates and transmits electricity far less than is required to meet her basic residential and industrial demands. Alternative means such as fossil fuel-powered generators to complement these demands are still not sufficient to meet these demands with notice to their limitation such as high lifecycle cost and carbon dioxide emission. Renewable energy resources are suitable substitutes for existing electricity sources to fulfil growing demand. Extensively in this paper, a review on the research progress of Hybrid Renewable Energy Systems (HRESs) and Integrated Renewable Energy Systems (IRESs) in the different continents of the world was presented considering methodologies, approaches, and parameters such as technical, economic, and emission limitation in determining the optimal renewable energy system in their present locality. According to the study's findings, about 63% and 22% of the research were conducted in Asia and Africa respectively, from which the research is mostly conducted in rural and remote areas of these continents.</p> </abstract>

<abstract> <p>A hybrid solar power system (HSPS) is an alternate method of supplying electricity that can reduce fuel usage while maintaining power supply security. In this study, the efficiency of HSPS, which consists of Grid Supply (GS), Diesel Power Generation (DPG), Solar-Photovoltaic (SPV), and Battery Storage (BS) systems, was evaluated in two economic activity areas (EAAs) in Southern Nigeria. The cross-sectional research design was used, and the research was based on Behera's energy-led growth theory. Urban-residential and Health were the EAAs considered and chosen using a stratified random sample technique. Southern Nigerian states of Oyo and Lagos provided the samples, which were combined and used for the study. Electricity consumption was calculated using electricity load demand for the two EAAs from 2008 to 2017. For each EAA, an Integrated Renewable Energy Mini/Microgrid Model (IREMMM) based on power load demand and solar irradiation was constructed. Levelized Cost of Electricity (LCOE) (/kWh), and Net Present Cost (NPC) (M) were calculated for one hybrid configuration, SPV-DPG-BS-GS, and two standalone configurations, DPG and SPV-BS. Configurations with SPV integrated had lower LCOEs than DPGs in both EAAs. In Southern Nigeria, solar PV combinations with battery storage provided the highest performance for a hybrid power system. In the medical contexts, a hybrid power system achieves higher overall performance.</p> </abstract>