The aim of this paper is to estimate the direct solar radiation on a horizontal plane in five regions of Chad using the Liu and Jordan’s model in view of the installation of a thermo-solar power plant. For this purpo...The aim of this paper is to estimate the direct solar radiation on a horizontal plane in five regions of Chad using the Liu and Jordan’s model in view of the installation of a thermo-solar power plant. For this purpose, the HelioClim-3 Data Base of Solar Irradiance V5’s is used. All the results presented in this paper were obtained using Microsoft Excel software 2015. These results show that compared to the other regions considered for this study, the direct solar radiation on a horizontal plane in Moundou is less.展开更多
Thatch fibres grow in large quantity in the Adamawa region of Cameroon. During the long dry season, these fibres cause numerous fire incidents, which not only devastate large areas of cash crops, but also contribute t...Thatch fibres grow in large quantity in the Adamawa region of Cameroon. During the long dry season, these fibres cause numerous fire incidents, which not only devastate large areas of cash crops, but also contribute to increase emissions of greenhouse gases into the atmosphere. This article aims to show how fibres could be used with compressed clay bricks to manufacture an insulating material used in building. Four fibre contents 1%, 2%, 3% and 4% made up the sample studied. The asymmetric hot plate methodology was used to determine the thermophysical properties of these composite materials. The volumetric heat capacity and the thermal effusivity of these materials were estimated. These two parametres were used to determine their apparent thermal conductivities. The results obtained show that the thermal conductivity decreases as the volume of fibres in the mixture increases. It is 0.689 W·m-1·K-1 for simple compressed clay bricks and 0.510 W·m-1·K-1 for a dosage at 3% of thatch fibres. In a bit to validate the results of the pilot study of the apparent thermal conductivity, the heat mass capacity of this composite material was achieved through the use of the dehydration method. The relative difference obtained with the results of the volumetric heat capacity carried out with these two methods was good. All results showed that the use of fibres in compressed laterite brick gives a more insulating composite material that respects Civil Engineering Norms.展开更多
This paper presents a numerical characterization of copper-indium-gallium-diselenide thin film solar cells using one dimensional simulation program （SCAPS-1D）. We have performedan optimization of the performances of...This paper presents a numerical characterization of copper-indium-gallium-diselenide thin film solar cells using one dimensional simulation program （SCAPS-1D）. We have performedan optimization of the performances of the standard Mo/Cu（In, Ga）Se2/CdS/ZnO solar cells using current-voltage and quantum efficiency methods. With a CuIn..7Ga0.3Se2 absorber, we have investigated the buffer layer thickness, temperature, series and shunt resistances effects on the open-circuit voltage, short-circuit current density, fill factor, conversion efficiency and quantum efficiency. The simulated results show good performances when the thickness of the buffer layer is in the range of 10-40 um due to the reduction of absorption in the short wavelenghts （380-500 nm）. High performances of the model is obtained when the series and shunt resistances is in the range of 0.1-1 Ω·cm^2 and 1,000 Ω·cm^2, respectively. Under these conditions, the cell can theoretically operate under an ambiant temperature of 370 K without any loss of its performances.展开更多
The quantitative interpretation of gravity anomalies due to shallow structures needs separation between long wavelength anomalies(regional anomalies) and short wavelength anomalies(residual anomalies).The regional-res...The quantitative interpretation of gravity anomalies due to shallow structures needs separation between long wavelength anomalies(regional anomalies) and short wavelength anomalies(residual anomalies).The regional-residual field separation can be carried out using the polynomial method.In this case, the so-called regional field of order n is treated as a polynomial of degree n.The present study shows that the degree n must vary between a smallest value n_(min) and a maximum value n_(max).This article presents a method to process gravity data that allows determination of n_(min) and n_(max) for a given study area.We apply the method to gravity data of the South-West Cameroon zone.In this chosen study area, we find that regional anomaly maps of orders ranging from 1 to 9 and residual anomaly maps of orders ranging from 1 to 8 can be used for suitable interpretation.The analyses show that one may need residual anomaly maps of several orders to perform satisfactory quantitative interpretation of the different intrusive bodies found in a given area.展开更多
Cameroon lives in the era of great infrastructures in order to reach the economic emergence by 2035. These infrastructures require a solid framework of energy provisions from many natural energy sources and resources ...Cameroon lives in the era of great infrastructures in order to reach the economic emergence by 2035. These infrastructures require a solid framework of energy provisions from many natural energy sources and resources that the country possesses. Speaking of natural energy resources, the country is particularly gifted by solar energy potential in the far north. This region of the land is densely populated but much of the populations do not have access to electricity since they live in remote areas far from national electricity grid. Solar thermal energy appears then as real potential to fulfill the growing demand of energy and reduce fossil fuel use dependence. Moreover, it would also be a grandiose opportunity for hospitals in these regions to provide hot water for Sterilization. As the design of a solar thermal plant strongly relies on the potential of direct solar irradiance and the performance of a solar parabolic trough collector (PTC) estimated under the local climate conditions, in this paper, we annually compute direct solar radiation based on monthly average Linke turbidity factor and various tracking modes in two chosen sites in the far north region of Cameroon. Also, a detailed two dimensional numerical heat transfer analysis of a PTC has been performed. The receiver has been divided into many control volumes along his length and each of them is a column consisting of glass, vacuum, absorber and fluid along which mass and energy balance have been applied. Direct solar irradiation, ambient temperature optical and thermal analyses of the collector receiver takes into consideration all modes of heat transfer and the nonlinear algebraic equations were solved simultaneously at each instant during a day of computation using Engineering Equation Solver (EES). To validate the numerical results, the model was compared with experimental data obtained from Sandia National Laboratory (SNL). It has shown a great concordance with a maximum relative error value of 0.35% and thermal efficiency range of systems about 66.67% - 73.2%. It has also been found that the one axis polar East-West and horizontal East-West tracking with 96% and 94% of full tracking mode respectively, were most suitable for a parabolic trough collector throughout the whole year in the two towns considered.展开更多
The gravity maps display, in Bipindi zone, local oval culminations of low anomalies indicative of a presence of intrusive light body in a subsurface but the nature, the form and the position of this body are still unk...The gravity maps display, in Bipindi zone, local oval culminations of low anomalies indicative of a presence of intrusive light body in a subsurface but the nature, the form and the position of this body are still unknown. The analyses of established gravimetric anomaly maps, the multi-scale evaluation of maxima of gradients and the quantitative interpretation of residual anomalies by 3D modelling permit characterizing the intrusive light body situated at Bipindi. The multi-scale evaluation of maxima of gradients shows that the modelling of the intrusive light body of Bipindi can be done without the problem of interference of anomalies from different sources. The 3D model of Bipindi zone shows two dissymmetrical blocks of the same type of rock with a density contrast of -0.095 g·cm-3 in comparison with the density of the surrounding metamorphic rocks. The two blocks are at a distance about 3 km from one to another. The upper surfaces of these blocks lie at a depth between 1 and 2 km. Their lower surfaces have two landings;one lies at a depth of about 8 km and another at a depth about 14 km. A consideration of the density of the modelled body, of the ranges of densities of specific rocks present in the general region indicates that the body may be composed of nepheline syenites. The intrusive body of Bipindi is situated in a senestral shear zone. The area situated between the two blocks of this intrusive body may be indicated for a detail study in the domain of mineral research.展开更多
文摘The aim of this paper is to estimate the direct solar radiation on a horizontal plane in five regions of Chad using the Liu and Jordan’s model in view of the installation of a thermo-solar power plant. For this purpose, the HelioClim-3 Data Base of Solar Irradiance V5’s is used. All the results presented in this paper were obtained using Microsoft Excel software 2015. These results show that compared to the other regions considered for this study, the direct solar radiation on a horizontal plane in Moundou is less.
文摘Thatch fibres grow in large quantity in the Adamawa region of Cameroon. During the long dry season, these fibres cause numerous fire incidents, which not only devastate large areas of cash crops, but also contribute to increase emissions of greenhouse gases into the atmosphere. This article aims to show how fibres could be used with compressed clay bricks to manufacture an insulating material used in building. Four fibre contents 1%, 2%, 3% and 4% made up the sample studied. The asymmetric hot plate methodology was used to determine the thermophysical properties of these composite materials. The volumetric heat capacity and the thermal effusivity of these materials were estimated. These two parametres were used to determine their apparent thermal conductivities. The results obtained show that the thermal conductivity decreases as the volume of fibres in the mixture increases. It is 0.689 W·m-1·K-1 for simple compressed clay bricks and 0.510 W·m-1·K-1 for a dosage at 3% of thatch fibres. In a bit to validate the results of the pilot study of the apparent thermal conductivity, the heat mass capacity of this composite material was achieved through the use of the dehydration method. The relative difference obtained with the results of the volumetric heat capacity carried out with these two methods was good. All results showed that the use of fibres in compressed laterite brick gives a more insulating composite material that respects Civil Engineering Norms.
文摘This paper presents a numerical characterization of copper-indium-gallium-diselenide thin film solar cells using one dimensional simulation program （SCAPS-1D）. We have performedan optimization of the performances of the standard Mo/Cu（In, Ga）Se2/CdS/ZnO solar cells using current-voltage and quantum efficiency methods. With a CuIn..7Ga0.3Se2 absorber, we have investigated the buffer layer thickness, temperature, series and shunt resistances effects on the open-circuit voltage, short-circuit current density, fill factor, conversion efficiency and quantum efficiency. The simulated results show good performances when the thickness of the buffer layer is in the range of 10-40 um due to the reduction of absorption in the short wavelenghts （380-500 nm）. High performances of the model is obtained when the series and shunt resistances is in the range of 0.1-1 Ω·cm^2 and 1,000 Ω·cm^2, respectively. Under these conditions, the cell can theoretically operate under an ambiant temperature of 370 K without any loss of its performances.
文摘The quantitative interpretation of gravity anomalies due to shallow structures needs separation between long wavelength anomalies(regional anomalies) and short wavelength anomalies(residual anomalies).The regional-residual field separation can be carried out using the polynomial method.In this case, the so-called regional field of order n is treated as a polynomial of degree n.The present study shows that the degree n must vary between a smallest value n_(min) and a maximum value n_(max).This article presents a method to process gravity data that allows determination of n_(min) and n_(max) for a given study area.We apply the method to gravity data of the South-West Cameroon zone.In this chosen study area, we find that regional anomaly maps of orders ranging from 1 to 9 and residual anomaly maps of orders ranging from 1 to 8 can be used for suitable interpretation.The analyses show that one may need residual anomaly maps of several orders to perform satisfactory quantitative interpretation of the different intrusive bodies found in a given area.
文摘Cameroon lives in the era of great infrastructures in order to reach the economic emergence by 2035. These infrastructures require a solid framework of energy provisions from many natural energy sources and resources that the country possesses. Speaking of natural energy resources, the country is particularly gifted by solar energy potential in the far north. This region of the land is densely populated but much of the populations do not have access to electricity since they live in remote areas far from national electricity grid. Solar thermal energy appears then as real potential to fulfill the growing demand of energy and reduce fossil fuel use dependence. Moreover, it would also be a grandiose opportunity for hospitals in these regions to provide hot water for Sterilization. As the design of a solar thermal plant strongly relies on the potential of direct solar irradiance and the performance of a solar parabolic trough collector (PTC) estimated under the local climate conditions, in this paper, we annually compute direct solar radiation based on monthly average Linke turbidity factor and various tracking modes in two chosen sites in the far north region of Cameroon. Also, a detailed two dimensional numerical heat transfer analysis of a PTC has been performed. The receiver has been divided into many control volumes along his length and each of them is a column consisting of glass, vacuum, absorber and fluid along which mass and energy balance have been applied. Direct solar irradiation, ambient temperature optical and thermal analyses of the collector receiver takes into consideration all modes of heat transfer and the nonlinear algebraic equations were solved simultaneously at each instant during a day of computation using Engineering Equation Solver (EES). To validate the numerical results, the model was compared with experimental data obtained from Sandia National Laboratory (SNL). It has shown a great concordance with a maximum relative error value of 0.35% and thermal efficiency range of systems about 66.67% - 73.2%. It has also been found that the one axis polar East-West and horizontal East-West tracking with 96% and 94% of full tracking mode respectively, were most suitable for a parabolic trough collector throughout the whole year in the two towns considered.
文摘The gravity maps display, in Bipindi zone, local oval culminations of low anomalies indicative of a presence of intrusive light body in a subsurface but the nature, the form and the position of this body are still unknown. The analyses of established gravimetric anomaly maps, the multi-scale evaluation of maxima of gradients and the quantitative interpretation of residual anomalies by 3D modelling permit characterizing the intrusive light body situated at Bipindi. The multi-scale evaluation of maxima of gradients shows that the modelling of the intrusive light body of Bipindi can be done without the problem of interference of anomalies from different sources. The 3D model of Bipindi zone shows two dissymmetrical blocks of the same type of rock with a density contrast of -0.095 g·cm-3 in comparison with the density of the surrounding metamorphic rocks. The two blocks are at a distance about 3 km from one to another. The upper surfaces of these blocks lie at a depth between 1 and 2 km. Their lower surfaces have two landings;one lies at a depth of about 8 km and another at a depth about 14 km. A consideration of the density of the modelled body, of the ranges of densities of specific rocks present in the general region indicates that the body may be composed of nepheline syenites. The intrusive body of Bipindi is situated in a senestral shear zone. The area situated between the two blocks of this intrusive body may be indicated for a detail study in the domain of mineral research.
