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Numerical Study of Mixed Convection in a Photovoltaic Trombe Wall Channel Coupled with a Solar Chimney Integrated into a Building for Habitats Passive Cooling

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Open Journal of Applied Sciences 2020年第12期10卷 844-863页

作者： Yawovi Nougbléga Koffi Sagna Hodo-Abalo Samah Kodjo Kpode laboratoire Sur l’energie solaire /Groupe Phénomène de Transfert et Energétique Université de Lomé Lomé Togo laboratoire Sur l’energie solaire/Chaire UNESCO sur les energies Renouvelables Université de Lomé Lomé Togo département de Physique Université de Kara Kara Togo

The solar chimney can generate airflow through the living space of the building to provide cooling. Hence, solar energy represents the best renewable, environmentally friendly source of energy that can be used for heating and cooling of houses. The present paper reports the numerical study of the performance of the mixed convection in the associated hybrid Photovoltaic/Thermal chimneys integrated into building for natural habitat ventilation. The front side glass plate of the chimneys is heated by a non-uniform daily solar radiation flux. Air is considered to be the cooling fluid. The stream fucntion-vorticity formulation with a finite difference numerical discretization solution scheme has been adopted. The system of algebraic governing equations is solved by Thomas algorithm method. The aim of the present paper is to study and to predict the dynamic fields and particularly of the mass flow rate of the air thermosiphon drawing in the associated hybrid Photovoltaic-Thermal chimneys integrated into a building for passive cooling in the habitats. The effects of the governing parameters, namely Reynolds number (30 ≤ Re ≤ 200), Rayleigh number (103 ≤ Ra≤ 105), the integrated chimney width on the fluid flow and the heat transfer characteristics, are studied in detail. The local Nusselt number, streamlines, isotherms, PV cells electrical efficiency and the outlet velocity at the top of the channels are the results represented versus the above controlling parameters.

关键词： Trombe Wall Passive Cooling Associated Chimneys Electrical Efficiency Thermal Comfort

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Modeling of Coupled Heat and Mass Transfer in a Trapezoidal Porous Bed on a Grid

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Open Journal of Fluid dynamics 2023年第1期13卷 1-15页

作者： Kokou N’Wuitcha Gagnon Koffi Apedanou Yendoubé Lare Kossi Napo laboratoire sur l’energie solaire Groupe Phénomènes de Transfert et Energétique (LES-GPTE) Faculté des Sciences Université de Lomé Lomé Togo laboratoire sur l’energie solaire Chair Unesco Faculté des Sciences Université de Lomé Lomé Togo

We investigate heat and mass transfer in an isosceles trapezoidal cavity, filled with charcoal considered as a granular porous medium. The darcy-Brinkman-Forchheimer flow model is coupled to the energy and mass equations with the assumption of non-thermal equilibrium. These equations are discretized by the finite volume method with an offset mesh and then solved by the line-by-line method of Thomas. The coupling between pressure and velocity is obtained by Semi-Implicit Method for Pressure Linked Equations. (SIMPLE) algorithm. The results show that the temperature in the cavity increases when the inclination angle of the sides walls decreases. The 15° inclination is selected as being able to offer better thermal performance in the cookstove combustion chamber.

关键词： Heat and Mass Transfer Isosceles Trapezoidal Cavity Porous Medium Finite Volume Method SIMPLE Algorithm

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Numerical Study of Mixed Convection in an Isosceles Trapezoidal Cavity with Several Outlets: Application for Primary Air draft in ASUTO Charcoal Stove

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Modern Mechanical Engineering 2022年第2期12卷 45-61页

作者： Gagnon Koffi Apedanou Kokou N’wuitcha Yendoubé Lare Kossi Napo laboratoire sur l’energie solaire Chair Unesco Faculté des Sciences Université de Lomé Lomé Togo laboratoire sur l’energie solaire Groupe Phénomènes de Transfert et Energétique (LES-GPTE) Faculté des Sciences Université de Lomé Lomé Togo

Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintained in natural convection while the lower horizontal wall is adiabatic. These conditions reflect the air draft zone of the ASUTO charcoal stove. The governing two-di- mensional flow equations have been solved by using the finite difference method and Thomas’s algorithm. The investigations are conducted for different values of Richardson (Ri), Reynolds number (Re) and inclination angles of sidewalls. The results are presented in terms of streamlines, isotherms, moisture contours. It was found that for Reynolds number (Re) equal to 100, the flow pattern is strongly dependent on the inclination angle and Richardson number. Thus, for high Richardson number (Ri) values (10, 100), the dominance of natural convection over the flow structure decreases with the decreasing of the inclination angle of sidewalls of the cavity. For Ri = 1, an optimum air draft corresponds to an inclination angle in the vicinity of 22° while for Ri = 10 or 100 (in dominance of natural convection), the optimum inclination angle for air draft is in the vicinity of 15°.

关键词： Mixed Convection Heat and Mass Transfer Trapezoidal Cavity ASUTO Charcoal Stove Richardson Number Several Outlets

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Numerical Modeling and Simulation of CIGS-Based Solar Cells with ZnS Buffer Layer

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Open Journal of Modelling and Simulation 2017年第4期5卷 218-231页

作者： Adama Sylla Siaka Touré Jean-Pierre Vilcot laboratoire d’energie solaire Université Félix Houphou&euml t Boigny Abidjan Cote d’Ivoire Institut d’Electronique de Microélectronique et de Nanotechnologie (IEMN) UMR CNRS 8520. Laboratoire Central Villeneuve d’Ascq Cedex Lille France

Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our work focuses on this type of CIGS-based solar cells where CdS is replaced by a ZnS buffer layer. In this contribution, AFORS-HET software is used to simulate n-ZnO: Al/i-ZnO/n-ZnS/p-CIGS/Mo polycrystalline thin-film solar cell where the key parts are p-CIGS absorber layer and n-ZnS buffer layer. The characteristics of these key parts: thickness and Ga-content of the absorber layer, thickness of the buffer layer and doping concentrations of absorber and buffer layers have been investigated to optimize the conversion efficiency. We find a maximum conversion efficiency of 26% with a short-circuit current of 36.9 mA/cm2, an open circuit voltage of 824 mV, and a fill factor of 85.5%.

关键词： Cu(In1-xGax)Se2 Thin-Film Solar Cell Numerical Modeling AFORS-HET Simulation Optimization

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determination of Natural Radioactivity of the Hibiscus sabdariffaLinn (Roselle) Used in Côte d’Ivoire (Ivory Coast)

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Advances in Materials Physics and Chemistry 2021年第3期11卷 59-66页

作者： Agbo djoman djama Alfred djagouri Koudou Brigui Olkalé Jean-Claude laboratoire des Sciences de la Matière de l’Environnement et de l’Energie Solaire (LASMES) of Felix Houphouet Boigny University Abidjan C&#244 te Felix Houphouet Boigny University Abidjan C&#244 te d’Ivoire Ecole Normale Supérieure of Abidjan C&#244 te d’Ivoire Laboratoire des Sciences de la Matière de l’Environnement et de l’Energie solaire (LASMES) of Felix Houphouet Boigny University Abidjan C&#244 te d’Ivoire

In this work, ten medicinal and nutritional leaves samples of Hibiscus sabdariffa Linn imported from Mali and Burkina Faso in Côte d’Ivoire and sold on the market were collected. The analysis of these plants using High Purity Germanium detector (HPGE) gamma spectrometry showed the activity concentrations of 226Ra, 232Th, and 40K varied respectively in the range of (1.74 - 0.11) × 10−3 Bq/kg, (6.72 - 0.61) × 10−4 Bq/kg and (4.65 - 0.54) × 10−3 Bq/kg1 in the leaves of H. sabdariffa. The Average Annual Committed Effective dose (AACEd) values from leaves this plant varied from 251.492 × 10−6 to 68.133 × 10−6 mSv/y. These values found are below 0.30 mSv/y, the world average value for an individual. These results show that there is no radiological risk in consuming “bissap” leaves.

关键词： Natural Radioactivity HPGe Gamma Spectrometry Activity Concentration Medicinal and Nutritional Plant Côte d’Ivoire

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Experimental Study of a Modified Icaro Solar dryer: The Case of Coffee drying

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Journal of Power and Energy Engineering 2023年第7期11卷 36-48页

作者： Auguste Oscar Mackpayen Aloys Martial Ekoe A. Akata Vinci de dieu Bokoyo Barandja Kossi Napo laboratoire d’Energétique Carnot (L.E.C) University of Bangui Bangui Central African Republic laboratoire sur l’energie solaire (L.E.S) University of Lomé Lomé Togo Energy Systems Technology Laboratory (ESTL) University of Douala Douala Cameroon

Food losses in the developing country are thought to be 50% of the fruits and vegetables grown and 25% of harvested food grain. Food preservation can reduce wastage of a harvest surplus, allow storage for food shortages, and in some cases facilitate export to high-value markets. drying is one of the oldest methods of food preservation. drying makes produce lighter, smaller, and less likely to spoil and helps to minimize the moisture content in coffee beans as high moisture content during storage is certain to ruin the taste and appearance of coffee. This work presents the results of an experimental study of forced convection drying of coffee cherries in a modified Icaro solar dryer. The study aims to validate the numerical models developed for further research. The experimental tests envisaged also aim to determine the mass loss curves of the product by fixing or calculating its initial mass (1 kg), its initial water content (70%), the ambient temperature, the drying airflow (0.02 m3.s-1 to 0.09 m3.s-1) and the exchange coefficients. The influence of these aerothermal parameters on the drying time of a most commercialized coffee variety (Robusta) was studied. Finally, the results revealed an increase in the efficiency of the heat transfer air and a reduction in the water content of the coffee cherry from 70% to 9.87%, after 30.2 hours.

关键词： Solar dryer Icaro Experimental Validation Moisture Content Coffee Tem-perature

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Minority Carrier diffusion Coefficient d*(B,T): Study in Temperature on a Silicon Solar Cell under Magnetic Field

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Energy and Power Engineering 2017年第1期9卷 1-10页

作者： Richard Mane Ibrahima Ly Mamadou Wade Ibrahima datta Marcel S. douf Youssou Traore Mor Ndiaye Seni Tamba Grégoire Sissoko laboratoire des Semi-conducteurs et d’energie solaire Facult&eacute des Sciences et Techniques Universit&eacute Cheikh Anta diop Dakar S&eacute né gal Ecole Polytechnique de Thiè s Thi&egrave s S&eacute né gal

This work deals with minority carrier diffusion coefficient study in silicon solar cell, under both temperature and applied magnetic field. New expressions of diffusion coefficient are pointed out, which gives attention to thermal behavior of minority carrier that is better understood with Umklapp process. This study allowed to determine an optimum temperature which led to maximum diffusion coefficient value while magnetic field remained constant.

关键词： Solar cell diffusion Coefficient Temperature Magnetic Field

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Energy Efficiency of Briquettes derived from Three Agricultural Waste’s Charcoal Using Two Organic Binders

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Journal of Sustainable Bioenergy Systems 2019年第2期9卷 79-89页

作者： Pali Kpelou damgou Mani Kongnine Saboillié Kombate Essowè Mouzou Kossi Napo department of Physics Laboratoire sur l’Energie Solaire-Université de Lomé Lomé Togo department of Physics Laboratoire de Physique des Matériaux et des Composants à Semi-conducteurs Université de Lomé Lomé Togo

Waste management could contribute significantly to reducing environmental degradation. Studies showed that briquetting provides with or without binder helps to manage wastes as energy fuels. However, the properties of many binders are not investigated extensively. This work investigated the effect of two organic binders’ low rate on energy efficiency of Briquettes produced from charcoals of Tender Coconut Husks (TCH), Palm Kernel Shells (PKS) and Corn Cobs (CC). Bombax Costatum calyx (B) and Cissus Repens barks (C) were used separately as binders to elaborate briquettes. The briquettes were compared based on their energy efficiency parameters with wood charcoal as control. Energy efficiency parameters such as water boiling time (WBT), mass of biomass used (MB), burning rate (BR), temperature rise rate (TR) and maximum temperature in the furnace (Tmax) were measured from each biomass charcoal briquette and wood charcoal combustion. Water boiling test was applied to determine briquettes thermal properties. The results of WBT, BR, TR and Tmax were respectively within the ranges 3.4 - 12.3 min, 2.90 - 7.71 g/min, 4.63°C/s - 16.10°C/s and 623°C - 900°C. Corn Cobs charcoal briquettes with Bombax binder took the shortest time to boil water and also presented a high temperature rise rate and the highest maximum temperature. The lowest burning rates were obtained for Tender coconut husks charcoal briquettes with Cissus binder. They showed good material conservation for bombax bound briquettes. The results of our investigations showed that binders content increasing enhanced the thermomechanical stability and affected negatively the energy efficiency parameters of the studied briquettes.

关键词： Biomass Charcoal Briquette Binder Energy Efficiency

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Modeling of the Global daily Horizontal Solar Radiation data over Togo

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Energy and Power Engineering 2021年第12期13卷 403-412页

作者： Yendoubé Lare Kanlanféi Sambiani Kokou Amega Moyème Kabe laboratoire sur l’energie solaire Département de Physique Université de Lomé Lomé Togo West African Science Service Centre on Climate Change and Adapted Land Use (Wascal) University Abdou Moumouni of Niamey Niamey Niger

Solar photovoltaic appears to be the most interesting renewable energy in developing countries where its deposit is abundant. Unfortunately, the lack of precise knowledge of solar radiation deposit and its limited data hinder optimal exploitation of solar installations. This study presents a performing model for daily global horizontal solar radiation for the five regional capitals in Togo: Lomé, Atakpamé, Sokodé, Kara and dapaong. The data used for the study were obtained from the General directorate of National Meteorology of Togo, for five years. The model developed combines linear and nonlinear methods with harmonic and exponential terms taking into account climatological parameters such as location latitude, daily relative humidity, daily ratio of sunshine duration and daily mean temperature. Statistical errors of the model were compared to those of two previous models elaborated for Togo and Nigeria. The results showed that the model is more efficient to predict global horizontal solar radiation over the five main cities in Togo. The comparison of estimated data and measured ones showed a good agreement between them.

关键词： Horizontal Solar Radiation Modeling Non-Linear Regression Statistical Errors

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detection of Rice Yellow Mottle at the Asymptomatic Stage by Hyperspectral Fluorescence and Reflectance Spectroscopies

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Optics and Photonics Journal 2023年第4期13卷 63-78页

作者： Amara Kamate Penetjiligué Adama Soro Emma Georgina Zoro-diama Kedro Sidiki diomandé Adjo Viviane Adohi-Krou laboratoire des Sciences de la Matière de l’Environnement et de l’Energie Solaire (LASMES) Université Félix Houphouët-Boigny Abidjan Côte d’Ivoire Centre National de Recherche Agronomique (CNRA) Adiopodoumé Côte d’Ivoire

Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is no research devoted to the spectral detection of rice yellow mottle virus (RYMV) infection, especially in the asymptomatic or early stages. This work proposes the use of hyperspectral fluorescence and reflectance data at leaf level for the detection of this disease in asymptomatic stages. A greenhouse experiment was therefore conducted to collect hyperspectral fluorescence and reflectance data at different stages of infection. These data allowed to calculate nine vegetation indices: one from fluorescence spectra and eight from reflectance spectra. A t-test made it possible to identify, from the second day after infection, four relevant reflectance vegetation indices to discriminate healthy leaves from those infected: these are Photochemical Reflectance Index (PRI), Transformed Chlorophyll Absorption in Reflectance Index (TCARI), Structure Intensive Pigment Index (SIPI) and Simple Ratio Pigment Index (SRPI). The fluorescence index was less sensitive in detecting infection. The four significant vegetation indices for the detection of RYMV were then used to build and evaluate models for discriminating plants according to their health status by the supervised classification of support vector machine (SVM) at different stages of infection. The maximum overall accuracy is 92.5% six days after inoculation (6 dAI). The sixth day after inoculation would be the adequate day to detect RYMV. This plants discrimination was validated by the mean reflectance spectra and by the histograms showing the differences between the average reflectance vegetation indices values of the two types of plants. Our results demonstrate the feasibility of differentiating RYMV-infected samples. They suggest that support vector machine learning models could be developed to diagnose RYMV-i

关键词： Rice Yellow Mottle Virus Fluorescence Spectra Reflectance Spectra Vegetation Indices SVM Classification Savitzky Golay Filtering

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