Assessment of Radon Concentrations inside Residential Buildings and Estimation of the Dose in the City of Kaya, Burkina Faso

Colorless, incessant radon gas is notably the second most important cause of lung cancer after smoking in smokers and the first cause in non-smokers. Having little effect in the atmosphere, radon gas accumulates in confined spaces. Therefore, the determination of radon concentrations inside residential buildings is very important to improve the health of the inhabitants. The objective of this research is to measure the concentration of radon in indoor air in residential areas of the city of Kaya and to assess the absorbed dose, the effective dose and the relative risk of lung cancer. In this study, the CORENTIUM AIR THINGS digital radon detector is used to determine the radon concentration in twenty-one houses in Kaya. The CORENTIUM AIR THINGS digital radon detector has been placed in each residential building for a minimum period of one week and the concentration values are read every 24 hours. This research revealed that the average concentration of radon was 28.47 Bq/m3 in the residential areas of Kaya. The radon concentration in a house has been found to exceed 100 Bq/m3, which is the level authorized by the World Health Organization (WHO). In the long term, the absorbed dose varies from 0.118 mSv to 4.975 mSv and the effective dose is between 0.229 mSv and 12.002 mSv. In the short term, the absorbed dose varies between 0.095 mSv to 5.001 mSv and the effective dose is between 0.283 mSv to 11.935 mSv. The mean lung cancer relative risk (CPRR) from indoor exposure was 1.026. There is a need to raise awareness among the population of the city of Kaya on this issue and to take measures to reduce radon in homes when the concentrations are above the limit recommended by the WHO.

Evaluation of Water Losses by Evaporation in the Nakanbe Basin

A numerical approach to heat and mass transfer in a large water reservoir is presented. This water reservoir is likened to a parallelepiped reservoir whose vertical and lower walls are adiabatic and impermeable. The equations that govern natural convection in water are solved by the finite volume method and Thomas’salgorithm. The adequacy between the velocity and pressure fields is ensured by the SIMPLE algorithm. We are going to evaluate the water losses by evaporation from three dams in the Nakanbé basin in Burkina Faso for a period of thirty years, that is to say from January 1, 1991, to March 15, 2020. The three dams have a rate of evaporation greater than 40% of the volume of water stored. Indeed the rate of evaporation in each dam increases with the water filling rate in the reservoir: we have observed the following results for each dam in the Nakanbé basin;for the date of 02/27/1988 to 03/13/2020., the Loumbila dam received a total volume of stored water of 22.02 Mm3 and 10.57 Mm3 as the total volume of water evaporated at the same date. At the Ouaga dam (2 + 3), it stored a water volume of 4.06 Mm3 and evaporated 2.03 Mm3 of its storage volume from 01/01/1988 to 05/07/2016. Finally, with regard to the Bagré dam, it stored 745.16 Mm3 of water and 365.13 Mm3 as the volume of water evaporated from 01/01/1993 to 03/31/2020.

Optimization of Mo/Cu(In,Ga)Se2/CdS/ZnO Hetero-Junction Solar Cell Performance by Numerical Simulation with SCAPS-1D

The paper presents a one-dimensional simulation study of chalcopyrite Cu(In,Ga)Se2(CIGS)solar cells,where the effects of the variation of CIGS,CdS,and ZnO layers are presented.Additionlly the influence of the variation of doping and the defects density of shallow uniform donors and acceptors types are also presented.The analyse of the simulation results shows that recombination inside the space charge region(SCR)decrease more our CIGS solar cell model performance.We also found that the electrical parameters increase with increasing CIGS absorber doping density exception of JSC values that reach their maximum at 1016cm-3 and decrease due to recombination of charge carriers in the p-n junction particularly the recombination inside the SCR.We also stressed the fact that the effects of shallow uniforme donor density is very low on the performance of our CIGS solar cell model is important because it will allow to control the width of space charge region from shallow uniform acceptors defect density that has a strong influence on the different electrical parameters.Yet,good optimization of performance of the CIGS-based solar cell necessarily passes though a good control of the space charge region width and will constitute a boosting perspective for the preparation of our next paper.We contact that the results obtained of the numerical simulation with SCAPS-1D show a good agreement comparatively of the literature results.The simulation of our CIGS solar cell presents best performances if the values of the absorber layer thickness is in the range of 0.02 to 0.03μm,the buffer layer thickness is in the range of 0.02 to 0.06μm and the defects density of shallow uniform acceptors types is in the range of 1015 to 1017cm-3.

Modeling of Residential Photovoltaic (PV) System Connected to Low Voltage (LV) Network: Application to Public Distribution Network of Burkina Faso

Residential photovoltaic (PV) systems connected to the grid are used for self-consumption. Any surplus production is fed into the grid and contributes to improving the voltage. Several techniques are developed to model their connection. However, studies on methods of injecting energy production into the Low Voltage (LV) network are nowadays a problem. This paper proposes a mathematical model to determine the current to be injected and calculate each node’s voltage. The current equation is a recurrence relation with an initial condition. This initial condition is for the case of a single PV system connected to the LV grid. The equation can also be written in matrix form. Similarly, the voltage solution is a recurrence relation. It also has an initial condition for the first node. Both mathematical formulae with the proposed initial conditions are consistent and can be used for the determination of the current and voltage of the different nodes in the grid.

2D Modeling of Solar Cell p-n Radial Junction: Study of Photocurrent Density and Quantum Efficiency in Static Mode under Monochromatic Illumination

A theoretical study of a polysilicon solar cell with a radial junction in static regime under monochromatic illumination is presented in this paper. The junction radial solar cell geometry is illustrated and described. The carriers’ diffusion equation is established and solved under quasi-neutral base assumption with boundaries conditions and Bessel equations. New analytical expressions of electrons and holes photocurrent density and quantum efficiency are found. The wavelength and structural parameters (base radius, base thickness and wavelength) influences on photocurrent density and quantum efficiency are carried out and examined.

Effect of Defects at the Buffer Layer CdS/Absorber CIGS Interface on CIGS Solar Cell Performance

This scientific paper presents a study investigating the effects of defects at the CdS/CIGS and CdS/SDL interfaces on the performance of CIGS solar cells. The objective of this study is to analyze the influence of defects at the interface between the CdS buffer layer and the CIGS absorber, as well as the surface defect layer (SDL), on CIGS solar cell performance. The study explores three key aspects: the impact of the conduction band offset (CBO) at the CdS/CIGS interface, the effects of interface defects and defect density on performance, and the combined influence of CBO and defect density at the CdS/ SDL and SDL/CIGS interfaces. For interface defects not exceeding 1013 cm-2, we obtained a good efficiency of 22.9% when -0.1 eV analyzing the quality of CdS/SDL and SDL/CIGS junctions, it appears that defects at the SDL/CIGS interface have very little impact on the performances of the CIGS solar cell. By optimizing the electrical parameters of the CdS/SDL interface defects, we achieved a conversion efficiency of 23.1% when -0.05 eV < CBO < 0.05 eV.

Influence of Defect Density, Band Gap Discontinuity and Electron Mobility on the Performance of Perovskite Solar Cells

In this manuscript, we used the SCAPS-1D software to perform numerical simulations on a perovskite solar cell. These simulations were used to study the influence of certain parameters on the electrical behavior of the cell. We have shown in this study that electron mobility is strongly influenced by the thickness of the absorber, since electron velocity is reduced by thickness. The influence of the defect density shows that above 1016 cm-3 all the electrical parameters are affected by the defects. The band discontinuity at the interface generally plays a crucial role in the charge transport phenomenon. The importance of this study is to enable the development of good quality perovskite solar cells, while taking into account the parameters that limit solar cell performance.

High Performance for Cu(In,Ga)Se2 Quaternary System-Based Solar Cells with Alternative Buffer Layers

In this study, the authors investigated the performance of different buffer layers through the electrical parameters such as Jsc, Voc, QE and η of the quaternary system Cu(In,Ga)Se2 solar cells. The performance of Cu(In,Ga)Se2solar cells has been modeled and numerically simulated by using the SCAPS- 1D device simulation tool. The cells with a ZnSe, Zn(O,S) and (Zn,Mg)O buffer layers were compared with the reference CdS buffer layer. The investigation of ZnSe, Zn(O, S) and (Zn,Mg)O-based cells to substitute the traditional CdS in the future shows that the ZnSe-buffer layer is a potential material to replace CdS, which revealed the best efficiency of 20.76%, the other electrical parameters are: JSC = 34.6 mA/cm2, VOC = 0.76 V and FF = 79.6%. The losses as a function of the temperature are estimated at 0.1%/K, among all kinds of buffer layers studied. We have also shown that the use of a high band-gap buffer layer is necessary to obtain a better short-circuit current density JSC. From our results, we note that the chalcogenide solar cells with Zn-based alternative buffer layer have almost the same stability thatthe traditional CdS buffer layer solar cells have.

Equilibrium Composition of a Plasma in the Low Voltage Air Circuit Breaker Contaminated by the Vapor of AgSnO2 Alloy Electrical Contacts

When the circuit breaker cuts the electric current, an electric arc is created between its electrodes. The success or failure of breaking the electric current by the circuit breaker depends strongly on the physico-chemical properties of the electric arc created, such as the composition of which depends on the material of the electrical contacts. In this work, we determine the equilibrium composition of the electric arc in the low voltage air circuit breaker with silver tin dioxide alloy contacts, in a temperature range from 500 K to 15,000 K and at atmospheric pressure. We use the Gibbs free energy minimization method and develop a computer code to determine the equilibrium composition of the created plasma. The analysis of the results obtained shows that O2 particles with a dissociation energy of 5.114 eV, NO with a dissociation energy of 6.503 eV, and N2 dissociation 9.756 eV dissociate around 3500 K, 5000 K, and 7500 K, respectively. We note that the electro-neutrality is established between the electrons and the cations: Ag+ and NO+, for temperatures lower than 6500 K. For temperatures higher than 6500 K, the electro-neutrality is established between the electrons and the cations: N+, O+, and Ag+. The numerical density of the electrons increases when the proportion of the vapor of the electrical contacts increases in the mixture, in particular for temperatures lower than 11,000 K.

Impact of Languages and Accent on Perceived Speech Quality Predicted by Perceptual Evaluation of Speech Quality (PESQ) and Perceptual Objective Listening Quality Assessment (POLQA): Case of Moore, Dioula, French and English

Perceptual Objective Listening Quality Assessment (POLQA) and Perceptual Evaluation of Speech Quality (PESQ) are commonly used objective standards for evaluating speech quality. These methods were developed and trained on native speakers’ speech sequences of some western languages. One can then wonder how these methods perform if they are applied to other languages or if the speaker is non-native. This paper deals with the evaluation of PESQ and POLQA on languages that were not been considered when setting up these methods, with emphasis on Moore and Dioula, two local languages of Burkina Faso. Another aspect is the evaluation of these two methods in the case of non-native speakers. For this purpose, in the one hand, the Mean Opinion Score-Listening Quality Objective (MOS-LQO) of PESQ and POLQA, computed for Moore and Dioula, are compared to those of French and English. On the second hand, the MOS-LQO scores of French and English are compared for native and non-native speakers, to evaluate the effect of the accent of speakers.

Water Dynamics under Drip Irrigation to Proper Manage Water Use in Arid Zone

The water resources reduction due to climate changes and also population increase, have contributed to increasing the constraint on water disponibility and accessibility. In the agricultural field, we need moderate soil and water resources management. This work aims to simulate water dynamics in soil under drip irrigation system in arid regions to better manage irrigation water. Simulations are done with soil physical properties of Burkina Faso. We assess maize plant water requirements for the whole growing season. With Hydrus 2D, we simulate water supply in the soil column. We assign atmospheric conditions on the top of the domain, zero flux of water on the lateral sides, and free drainage on the bottom boundary domain. We perform many irrigation events to analyze wetting pattern distribution around the emitter, which allowed us to contain the amount of irrigation water applied, only around the area dominated by roots, and then reduce water losses that roots cannot uptake. According to the different growing stages of the maize crop, we choose proper irrigation duration and frequency, and suggest irrigation schedule for the whole growing season.

Hydromechanical Behavior of Low-Swelling Soils Compacted at Low Water Content: Laboratory Study

Fine unsaturated soils are used in many applications, particularly in road infrastructure and in construction. These materials undergo deformations according to the stresses to which they are subjected. The purpose of this paper is to study the influence of hydromechanical stresses on the behavior of low swelling soils compacted at low water content in accordance with the French standard GTR 92 (Guide des Terrassements Routiers). Then, various experimental tests on an oedometer were carried out in the laboratory. Two types of low swelling soil sampled in Nasso on the outskirts of the town of Bobo Dioulasso (Burkina Faso) were used. After shuffling, each sample was moistened to its optimum water content and then compacted to 90% and 95% of its optimum density. Behavior tests show that these soils deform very little when subjected to hydromechanical stresses. However, these deformations are swelling in nature for low mechanical stresses and when the stresses are high, they tend to collapse. When these soils are subjected to a vertical stress of 420 kPa, the primary consolidation time is of the order of one minute for NH2 (a silty soil) and about ten minutes for NH3 (a silty-clayed soil).

Comprehensive Analysis of CuIn_1-xGa_xSe₂Based Solar Cells with Zn_1-yMg_yO Buffer Layer

The development of cadmium-free CIGS solar cells with high conversion efficiency is crucial due to the toxicity of cadmium. Zinc-based buffer layers seem to be the most promising. In this paper, a numerical analysis using SCAPS-1D software was used to explore the Zn(Mg,O) layer as an alternative to the toxic CdS layer. The effect of several properties such as thickness, doping, Mg concentration of the Zn(Mg,O) layer on the current-voltage parameters was explored and their optimal values were proposed. The simulation results reveal that the optimal value of the ZMO layer thickness is approximately 40 nm, the doping at 1017 cm-3 and an Mg composition between 0.15 and 0.2. In addition, the effect of Gallium (Ga) content in the absorber as well as the Zn(Mg,O)/CIGS interface properties on the solar cell’s performance was examined. The results show that contrary to the CdS buffer layer, the best electrical characteristics of the ZMO/CIGS heterojunction are obtained using a Ga-content equal to 0.4 and high interface defect density or unfavorable band alignment may be the causes of poor performances of Zn(Mg,O)/CIGS solar cells in the case of low and high Mg-contents.

Required CIGS and CIGS/Mo Interface Properties for High-Efficiency Cu(In, Ga)Se<SUB>2</SUB>Based Solar Cells

In this work, we have modeled and simulated the electrical performance of CIGS thin-film solar cell using one-dimensional simulation software (SCAPS-1D). Starting from a baseline model that reproduced the experimental results, the properties of the absorber layer and the CIGS/Mo interface have been explored, and the requirements for high-efficiency CIGS solar cell were proposed. Simulation results show that the band-gap, acceptor density, defect density are crucial parameters that affect the performance of the solar cell. The best conversion efficiency is obtained when the absorber band-gap is around 1.2 eV, the acceptor density at 1016 cm−3 and the defect density less than 1014 cm−3. In addition, CIGS/Mo interface has been investigated. It appears that a thin MoSe2 layer reduces recombination at this interface. An improvement of 1.5 to 2.5 mA/cm2 in the current density (Jsc) depending on the absorber thickness is obtained.

Renewable Energies in Africa, Context and Socio-Economic Challenge

In this paper, we have shown that Africa has an enormous wealth of renewable energy resources among the most important in the world such as the strong sunshine, Congo and Nile Rivers respectively among the most powerful and the longest in the world. We have underlined the presence of important forests, rich subsoil in mineral elements, and strong winds. In addition to a rapidly growing human capital, Africa, therefore, has at its disposal all the factors enabling it to initiate sustainable and inclusive socio-economic development. We have shown that the transformation of these renewable energies is an opportunity for Africa to reach its socio-economic challenges. The development of renewable energies in Africa will be a source of many financial benefits and advantages both in terms of improving living conditions and carrying out activities. The electrical supply of rural areas of Africa represents a considerable issue, which can be a propellant factor in long-term socio-economic development if the conditions of use of clean fuel and cooking technologies, especially sanitary are taken into account. The provision of modern energy services can contribute to the creation of jobs for young people upstream. Among other things, we can note the development of local skills, the creation of income-generating activities, and the improvement of hygiene and health measures which are necessary conditions for family and social well-being. This requires a policy focused, on research in general and in particular on semiconductors that participate in the transformation of photovoltaic solar energy. We have stressed that Africa which is currently experiencing a period of economic growth and sustained transformation must be very looking at in its energy policy and give pride of place to renewable energies to initiate sustainable socio-economic development, equitable and inclusive different social strata both in rural areas and urban areas.

Water Dynamics Combined with a Supply of NPK Solutes and Urea in a 3-Layer Soil Profile under Drip Irrigation

The intensive and inappropriate use of water, fertilizers and phytosanitary products is sources of water and soil pollution. It is thus necessary to improve the management of irrigation water in order to optimize its use and productivity, especially in regions where water resources are becoming increasingly scarce. The water flow and non-reactive solutes’ transport simulation under drip irrigation were carried out in a 3-layered soil profile distributed from top to bottom i.e., sandy, sandy-silty, silty-sandy-clay. The aim of this study was thus, to provide a good practice of water management associated with solutes’ application, in order to retain as much solute as possible in the root zone, which will increase the residence time of the solutes. Three treatments of water flux corresponding to 100% ETc, 75% ETc, 50% ETc, combined with 100 mmol /L/ m2 of NPK and 246 mmol/L/m2 of urea applicable in two doses, were carried out over a period of 110 days corresponding to the duration of the cropping cycle for the intermediate variety of maize. The 100% ETc and 75% ETc treatments cause more loss of water and solutes, because of the sandy texture of the soil. However, a 50% ETc water flux would reduce more water loss through drainage, and solutes’ loss due to leaching beyond the root zone, which would increase the residence time of solutes in the soil profile. Application tests of the NPK solute on different days before the 15th day after sowing were also carried out according to the technical itinerary for maize production in Burkina Faso, in order to find a favorable day for application of the solute. For the different dates of solute’s application, there was more loss of the solute as we approach the 15th day after sowing. To limit this loss and increase the residence time of the NPK solute, one could apply the solute without first supplying water, the day before and the day after the date of solute’ injection. Or, one could amend the soil with organic matter to improve its retention capacity of water, and the solutes’ residence time in the soil.