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1 Faculty of Science and Technology, University Cheikh Anta Diop, Dakar-Senegal 2 Mining School of Niamey-Niger 3 Ecole Supeieure polytechnique de Daar-Senegal 4 Ecole Polytechnique of Thies, EPT, Thies, Senegal 5 Faculty of Science and Technology, University Cheikh Anta Diop, Dakar-Senegal 6 Ecole Supeieure polytechnique de Daar-Senegal 7 Faculty of Science and Technology, University Cheikh Anta Diop, Dakar-Senegal

Abstract In Senegal, soil is used in construction with a misunderstanding of the thermal and mechanical properties. The lifespan of building considerably depends of the mechanical properties of construction materials used. The thermal properties of construction materials have considerable influence on the energy performance of the building. This work deals with the determination of thermal and mechanical properties of soil bricks stabilized with cement produced by five handicraft manufacturers. For the mechanical characterization, we determine the compressive strength of bricks using a mechanical press. The thermal characterization is to determine thermal capacity and thermal conductivity of bricks by asymmetrical transient Hot Plate method. The results show that vibrated bricks have a compressive strength of about 1.6 MPa and a thermal conductivity of about 0.8 W.m-1.K-1. The compressed bricks have better compression strength of about 2 MPa and a thermal conductivity of about 0.7 W.m-1.K-1.

A theoretical and experimental study of a conventional boost converter is presented. Based on the real behavior of the components, the conventional boost converter model dealing with both inductive and capacitive losses as well as switching losses is introduced. From this model, the detailed analytical expressions of the voltage gain factor and the conversion efficiency are established taking into account the losses due to parasitic resistances and switching losses. The behavior of the converter is then analyzed by simulating the voltage gain factor and the conversion efficiency as a function of the duty cycle. The converter prototype was manufactured and a set of experimental measurements was made; these measurements made it possible to demonstrate that the proposed theoretical models were reliable for a large range of duty cycle for the boost converter.

Traditional technologies for clay brick burning are often confronted with firing problems. The produced brick is of poor quality due to poor combustion inside the kiln. So that, cooking plays an important role because it determines the quality of the final product. Therefore, this work presents a transient computational fluid dynamic (CFD) study of firing clay bricks in the traditional oven. The heat transfer modeling in the furnace mainly is made from hydrodynamic equations and combustion reactions. Therefore, numerical simulation is done using ANSYS-Fluent software, using the standard k-ε turbulence model and the Eddy Dissipation turbulent combustion model. The results focused on the flow field, evolution of temperature, and O2 mass fraction to verify the combustion process inside the kiln. The results show that the kiln reaches the maximum temperature is in order of 900 °C and therefore verification process occurs. Moreover, the results revealed that the O2 mass fraction has the highest values at the inlet and it decreases gradually inside the kiln which gives good evidence about combustion process propagation.

AbstractThis paper presents a decentralized management system of a hybrid agent paradigm-based electrical system. The management strategy aims at quantifying and controlling production sources to adapt the energy consumed by consumption sources to that supplied by the system renewable production sources while reducing the operating cost of the system. A multi-agent system, where each production and consumption source is modeled by an agent, is proposed to represent the electrical system. The suggested strategy, which is based on an economic model designed to control the energy produced by the production sources and that required by the consumption sources, made it possible to reduce the system production cost. It optimizes the production cost for the operator and improves the energy use without compromising the user's energy needs and comfort.

According to existing literature, there are no conclusive results on the impact of stirring on hydrothermal carbonization (HTC); some studies report a significant impact on the product's properties, while others indicate no influence. This study investigates the influence of stirring rate on several responses and properties of HTC products, including solid mass yield, solid carbon fraction, surface area, surface functional groups, morphology, and the fate of inorganic elements during HTC. Waste biomass was introduced as a feedstock to a 2 L HTC reactor, where the effects of temperature (180-250 °C), residence time (4-12 h), biomass to water (B/W) ratio (1-10%), and stirring rate (0-130 rpm) were investigated. The findings of this study conclusively indicated that the stirring rate does not influence any of the studied responses or properties of hydrochar under the selected experimental conditions used in this study. Nevertheless, the results indicated that a low-stirring rate (5 RPM) is enough to slightly enhanced the heating-up phase of the HTC reactor. For future research, it is recommended to examine the impact of stirring rate on the HTC of other types of biomass using the methodology developed in this study.

Solar irrigation pumps are considered as an alternative to the use of diesel and electric pumps due to the high cost of energy. These pumps are now increasingly used in the Niayes area. Thus, a more in-depth knowledge about the components of a solar pumping system and their characteristics available on the market as well as prices can be beneficial. This study was conducted to have an idea on the baseline of the use of solar irrigation pumps in this area. To perform this study, surveys were conducted among 12 suppliers and 10 service providers located in Dakar, Thies, Louga and Saint-Louis region and among 53 users located in Potou area which is in Louga region. Results show a wide range of pump brands and characteristics. Brands found were Lorentz, LIKOU, SHIMGE, Grundfos, Solar pump, Feili, Difful, JUQIANG, Solar tech, and Asaman. The pumps’ flow rate varies between 2.5 m3/h and 45 m3/h, the pressure ranges from 15 m to 160 m and the power is between 0.072 kW and 10 kW. The price of these pumps varies depending on the brand used and their characteristics. In addition, other materials are available, such as panels with power ranging from 80 W to 330 W and electric cables. The price of these components varies according on the type used. Thus, the investment cost for implementation varies between 640 euros (420,000 CFA) and 25,087 euros (16,455,919 CFA). The cost of installation varies between 76.3 euros (50,000 CFA) and 1219.6 euros (800,000 CFA). Concerning maintenance, it is generally free during the warranty period when the equipment is supplied and installed by the same company. However, the cost of maintenance varies between 152.5 euros and 457.4 euros/year or is estimated at 45.7 euro/maintenance after the warranty years. Investigations conducted among users show that farmers in general do not perform pump maintenance due to a lack of knowledge and financial means. Thus, according to farmers, factors that impact pumps operation are the low sunshine that occurs between December and January and the iron in the water and low well discharge.

This study presents a theoretical study of a vertical parallel junction solar cell under multispectral illumination in steady state. Based on the diffusion equation, the excess minority carrier's density is expressed and both photocurrent density and photovoltage are determined. For all these parameters we showed the effect of external temperature with respect to the operating point of the solar cell through the junction recombination velocity.