The use of hybrid renewable energy systems among household consumers in sub-Sahara Africa (SSA) is increasingly gaining attention. This is due to low electrification rates in many of the countries in SSA. A hybrid energy system for power generation combines various energy systems, either renewable or a combination of renewable and fossil-powered sources for optimal power extraction and operation. In the era of decarbonization of the electricity grid through the use of renewable energy, hybridization of sources is an essential condition for the production of electricity. Based on current quest for renewable energy (RE) expansion in the global energy mix, optimum conditions for the production and adoption of hybrid renewable energy systems (HRES) at micro-levels are indispensable and must be advocated for. This can be justified based on the perpetually rising cost of energy for socio-economic development. This paper presents a survey of major issues regarding the motivations and specific benefits behind the adoption of HRES. Also presented, is a discussion on different renewable energy sources that can be adopted for HRES application for both grid and off-grid consumers. Furthermore, a discussion on the important issues as it pertains to the design and implementation of HRES is also presented. Finally, a policy discussion on the affordability of HRES in a low-income household is presented.

The ability to measure, understand, manipulate, organize, engineer and control matter on the nanoscale has been opening up the wealth of possibilities that were otherwise non -existent at higher scales. At this scale, basic research principles and tools in biology, physics, chemistry, and engineering converge and have led to all-inclusive applications of nanotechnology. Despite the innovative applications and promising potentials of nanotechnology, there are concerns about its short and long-lasting impacts on humans, nature and the environment. In an attempt to address these concerns, a number of researches have been conducted. Evaluations of studies addressing the issues of nanotechnologies and their impacts are necessary to give insights for further studies that will advance the technology for the true benefit of mankind and nature. This study, thus, provides a detailed review of studies on nanotechnology applications and the positions of stakeholders on the impact of nanotechnology. Among other things, the outcome of this survey shows that there are numerous successful applications of nanotechnology. Public perceptions are pivotal in determining the extent of revolution and transformation that nanotechnology will have on the environment. Religious beliefs and moral concerns; trust in governmental regulatory agencies and the industry; the level of inclusion of the society in the product design, development, and commercialization process is critical to the extent of acceptance of nanotechnology inventions. Expression of objective views concerning the benefits, limitations & risks, and adequate education of the public, risk regulators & all stakeholders are crucial in determining the fate of nanotechnology.

The use of a single criterion in the selection of the most suitable hybrid renewable energy system (HRES) has been reported to be inadequate in terms of sustainability. In order to fill this gap, this study presents a multi-criteria approach for the selection of HRES for a typical low-income household. The analysis is based on two energy demand scenarios viz: consumer demand based on energy efficient equipment (EET) and consumer energy demand without energy efficiency. The optimization of the HRES is performed using hybrid optimization of multiple energy renewables (HOMER) while the multi-criteria analysis is carried out using Criteria Importance Through Intercriteria Correlation (CRITIC) and the Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS). Results show that the optimal HRES alternative returned based on both energy demand scenarios is a PV/GEN/BAT system. The analysis further shows that a reduction of 44.6% in energy demand through EET leads to: 51.38% decrease in total net present cost, 11.90% decrease in cost of energy, 96.61% decrease in ${\mathrm{CO}}_2$ emission and 193.94% increase in renewable fraction. Furthermore, the use of multi-criteria approach for HRES selection has an influence in the selection and ranking of the most suitable HRES alternatives. Overall, the application of EETs is environmentally and economically beneficial while the application of MCDM can help decision makers make a comprehensively informed decision on the selection of the most suitable HRES.