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Urban areas’ energy consumption accounts for almost three fourths the global energy use with 70% of the related emissions. Therefore, cities play a meaningful role in decoupling economic growth from greenhouse gases (GHGs) emissions. This study presents a system dynamic approach to model the energy efficiency impact on the Togolese capital city’s residential electricity consumption and carbon dioxide emissions reduction. The time spans from 2000 to 2050. An assessment of household appliances, such as lighting, refrigeration, cooling, and ventilation, was conducted along with monitoring electricity consumption of used and newly bought televisions, refrigerators, and freezers. Then, using Stella software, Lomé’s residential electricity consumption model was built based on the following variables: (1) population, (2) the number of existing households with access to electricity, (3) new homes having access to electricity, and (4) per capita electricity consumption. The model was calibrated and validated using data for the years 2000 to 2016. Afterward, this previous knowledge was used to evaluate three efficient energy policies: 1) business-as-usual scenario, 2) new policies scenario, and 3) sensitivity scenario. Lomé’s households present a predominantly low efficient appliances percentage. Therefore, the study found that substituting inefficient electric appliances with new and efficient models can lead Togo to substantial energy savings and reduce CO2 emissions of about 680 GWh and 350 kt in the horizon of 2050, respectively. Additionally, the findings of this study could stimulate policymakers to audit other sectors to implement related energy efficiency policies and/or set up corresponding energy management strategies in neighboring emerging countries. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the effect of barium (Ba) doping on the optical, morphological and structural properties of ZnO nanoparticles. Undoped and Ba-doped ZnO have been successfully synthesized via sonochemical method using zinc nitrate, hexamethylenetetramine (HMT) and barium chloride as starting materials. The structural characterization by XRD and FTIR shows that ZnO nanoparticles are polycrystalline with a standard hexagonal ZnO wurtzite crystal structure. Decrease in lattice parameters from diffraction data shows the presence of Ba in the ZnO crystal lattice. The morphology of the ZnO nanoparticles has been determined by scanning electron microscopy (SEM). Incorporation of Ba was confirmed from the elemental analysis using EDX. Optical analysis depicted that all samples exhibit an average optical transparency over 80%, in the visible range. Room-temperature photoluminescence (PL) spectra detected a strong ultraviolet emission at 330 nm and two weak emission bands were observed near 417 and 560 nm. Raman spectroscopy analysis of Ba-doped samples reveals the successful doping of Ba ions in the host ZnO. [ABSTRACT FROM AUTHOR]