Limited access to electricity in rural areas creates a critical need for decentralized power generation solutions. Solar energy is a particularly promising option. This study addresses the lack of experimental data on the performances of small-scale solar Organic Rankine Cycles for off-grid applications in many developing countries. It is assumed that a solar Organic Rankine Cycle using R245fa as working fluid can achieve satisfactory energy and exergy performance under local climatic conditions of Senegal. The system was simulated with Engineering Equation Solver software and validated experimentally on a dedicated test bench. Results show the technical feasibility of small-scale solar Organic Rankine Cycle, achieving net electrical outputs up to 10  kW, thermal efficiencies from 8.5 % to 11.5 %, exergy efficiency from 44.6 % to 60.2 %, and overall system efficiency up to 6.6 %. Solar collector efficiency increases by 39 % when irradiance rises from 525 W/m2 to 1200 W/m2, and it improves by 7.6 % when ambient temperature increases from 25 °C to 45 °C. Increasing evaporator temperature improves net mechanical power and thermal efficiency, while exergy losses are highest in the evaporator and turbine. Condenser temperature affects exergy flows, slightly reducing overall efficiency. Evaporator insulation decreases required hot water flow. Solar collector area requires nearly 128  m2 for 10 kWel output under typical local conditions. These results provide a scientific support to encourage the deployment of reliable solar Organic Rankine Cycles in isolated rural areas. The analyses emphasize the importance of implementing strategies to optimize the operational conditions of the system and maximize its performances, while confirming the viability of these technologies for sustainable electricity generation in developing countries.

Thin film filed effect transistors (TFTs) have drawn significant attention from scientific community as one of the most attractive for low-cost, large area and flexible electronics.In this context, the development of high-k dielectric materials with additional functional properties is essential for low voltage operating and enhancement of device performance. This work presents the investigation of solution processed Pb(Zn1/3Nb2/3)O3 4.5PbTiO3(PZN PT) perovskite nanoparticles thin films, with and without Mn doping, as gate dielectrics for thin film transistor applications. PZN-PT with 1% Mn doped and undoped PZN-PT films were deposited by spin coating on nanostructured doped n-type silicon substrate to form metal-oxide-semiconductor (MOS) structures with top silver contact. SEM analysis shows Mn doping PZN-PT presents a denser and more homogeneous microstructure compared to undoped. Electrical measurements confirmed transistor operating mode and highlighted the effect of ferroelectric polarization on device behavior.

Solar thermal energy is available in abundance in a country like Senegal where direct solar radiation is on average 1950kWh/m2 per year. Solar thermal treatment is one of the methods to preserve food. Thermal treatment of agricultural products using solar thermal energy utilizes collectors to capture solar irradiation and convert its energy into heat, which is then used for drying, heating, cooking, or cooling the products. This study focuses on thermal treatment using a solar cooker. The work involves performing a numerical simulation of a solar cooker using COMSOL Multiphysics software to analyze the temporal and spatial distribution of physical parameters such as temperature, air velocity, and absolute pressure within the cooker. A theoretical model is made in order to establish the heat balance at the level of the cooker components. A model of the cooker was developed within the software after establishing assumptions and defining boundary conditions. The simulation results show that in the solar cooker, the absorber temperature can reach 123°C, allowing the cooking of many types of food. The isothermal profile reveals a dome-shaped structure evolving from the absorber, where the temperature is highest, towards the glass cover. The pressure is also uniform within the cooker. The pressure is approximately equal to 1.11 104Pa. Similarly, the air velocity inside the cooker is low.

In the current economic, energy and environmental context, the implementation of technologies using renewable energies as a source of power electricity and cooling production is very beneficial insofar as it allows the reduction of pollution and the cost of fossil fuels. Senegal has a sunshine potential well distributed across the country for irradiation varying from South to North between 1850 KWh/m²/year and 2250 kWh/m²/year. It is one of the best solar potentials in the world. Systems operating on the organic Rankine cycle ORC and the absorption cooling system ACS are innovative and sustainable technologies for the exploitation of low enthalpy renewable energy sources. In this present work, the thermodynamic analysis of a combined ORC and ACS system for power electricity and cold production is carried out numerically using the Engineering Equation Solver (EES) software. R245fa and water-lithium bromide mixture are used as working fluid for ORC and ACS respectively. The results obtained at the ACS subsystem level show that the COP of ACS decreases when the absorption temperature increases. This reduction goes from 0.83 to 0.55, i.e. a reduction of 0.28 for a variation of absorption temperature from 27°C to 45°C. The COP has stabilized for generator temperatures above 95°C and is in the range of 0.7 to 0.8. These fluctuations are due to the irreversibility at the level of the components of the system. For the ORC subsystem, the turbine power and ORC condenser power decrease as the ORC condensing pressure increases. Thus, the turbine power goes from 235 kW to 200 kW and the ORC condenser power goes from 80 kW to 60 kW.

The integration of solar cooling system into the food preservation system is an important step towards energy sustainability. Study aims are to design a cooling system combining solar thermal energy, an absorption cooling system and cooling rooms. The cooling rooms studied are containers intended to preserve fish and onions with storage capacities of 1000 kg and 2000 kg respectively. A modeling of the different subsystems was done and the energy balances established. The model simulation is done with Engineering Equation Solver (EES). The results obtained show that for solar thermal collector efficiency between 0.6 and 0.7, the area of the solar thermal field can be optimized to 45 m2 and 70 m2 respectively for the preservation of onions and fish. Similarly, for solar irradiation between 5 KWh/m2 and 6 KWh/m2, the area of the solar thermal field decreases from 100 m2 to 40 m2 and from 160 m2 to 60 m2 respectively for the cold room intended to preserve onions and fish. For thermal loads greater than 50 KWh and 80 KWh respectively for onions and fish, the area of the solar field increases linearly with the increase in thermal loads.

Despite the excellent properties of Pb(Zn1/3Nb2/3)O-3-4.5PbTiO(3) (PZN-4.5PT) single crystals, the greatest difficulty for their application on electronic devices is to make them to thin layers related to the difficulty to make them as ceramic materials. In this paper, we use the combined USAXS/SAXS/WAXS instrument at 9ID beamline at APS-ANL for in situ characterization of PZN-4.5PT inorganic perovskite nanoparticles thin films deposited on nanotextured silicon to understand the phase transitions and determine the observed microcrystals' structure. The sample was annealed from ambient to 1000 degrees C. The results revealed structure changes in the nanoparticles' thin films which could be explained by the new phase that can be assigned to the Pb-3(PO4)2-based component. The peak at 31 degrees indicates the presence of the rhombohedral phase perovskites assigned to the nanoparticles. WAXS characterization permitted to identification of many transitions during thermal annealing like dehydration or dihydroxylation of phosphorus gel -OH bonds and internal water.

Biopolymers obtained from renewable resources became the center of public interest by virtue of their environmental and commercial advantages. Natural polymers such as starch, almond gum, chitosan and arabic gum were investigated to get fully or partially biodegradable dielectric material. Thus, in this article we study the material properties of cashew gum. This biopolymer is an exudate collected from occidental anacardium tree. For this investigation, scanning electron microscopy of powder and thin film cashew gum showed homogenous and slightly rough surface morphology with visible wrinkles. The thermal analyses such as thermogravimetric (TGA) and differential scanning calorimeter were realized. thermogravimetric thermogram shows two distinct stages of decomposition. The first around 150°C is attributed to moisture evaporation with loss in weight of 9.7%. The second transition, between 255°C and 330°C, is related to the decomposition of cashew gum with loss in weight of 50%. UV-visible spectra of the cashew gum thin film show a low absorbance and high transmittance. For this material, we obtained a direct optical band gap around 4.56 eV. In addition, the dielectric and electrical characterizations lead to conclude that cashew gum may be interesting for transistor applications as a gate dielectric.

In this study, we investigate the influence of solvents with different boiling points on the electrical performances of poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) transistors. To dissolve PBTTT for thin-film processing, we used toluene, chlorobenzene (CB), and tetrahydrofuran (THF). The highest obtained field effect mobilities were about 3.42 × 10−2 cm2 V−1 s−1, 1.62 × 10–3 cm2 V−1 s−1, and 1.78 × 10–2 cm2 V−1 s−1, respectively, for PBTTT devices using chlorobenzene, toluene, and tetrahydrofuran and heated respectively at 120 °C, 150 °C, and 120 °C. In order to point out the role of morphological properties, AFM images were performed. We observed liquid crystalline state formation in PBTTT film from THF and toluene which drive the electrical parameters over grain size.

This work is an energy analysis of a simple effect absorption cooling system operating with H2O-LiBr pair in the climatic conditions of Senegal. To achieve this, the energy balance at the level of the various components of the system will be established in order to show the behavior of each component of the system according to the climatic conditions of the study site. To find out if this cooling absorption system is suitable for the Senegalese climate, the effects of the temperature of the absorber and the generator have respectively been seen on the mass flow rates and on the circulation factor. The behavior of the cooling absorption system in the weather conditions of Senegal was predicted using a mathematical model developed with Engineering Equation Solver (EES) software. The simulation results of this present work were compared with those found in the literature. The thermodynamic parameters such as temperature, entropy, enthalpy, mass fraction found at the level of the various components of the system are in agreement with those found by other authors. Similarly, the results obtained show that for better performance of the system, the operating parameters must be optimized taking into account the crystallization limits of lithium bromide. Similarly, modifications must be made to the design of some devices such as the absorber and the generator to better adapt them to local climatic conditions. Beyond the design and modification of the components of the system, it is also necessary to play on the operating conditions for a better functioning of the absorption cooling system in Senegal.

Photovoltaic (PV) modules suffer from a variety of degradation that reduces their long-term performance and reliability. Ten polycrystalline silicon PV modules are exposed to Cologne climate. After 14 years exposure, the defects that occur at PV modules are explored by visual inspection, electroluminescence and infrared thermography. Electroluminescence (EL) characterization techniques have been exploited for the quantification of microcrack, corrosion, breakages, delamination and dark areas, while infrared (IR) has been implemented for the investigation of dark areas, hot spots and electrical losses in the PV modules. The electrical performance of the tested modules is also investigated in order to find a correlation with the visual defects.

The idea to use ferroelectric materials (PZN-PT) came from the fact that the ferroelectric nature could facilitate electric charges accumulation on the interfaces of the solar cell. Thus, it would increase the open circuit voltage Voc which could reach more than 10 V. This would directly impact the efficiency which is proportional to Voc, thus hoping to obtain solar efficiency never equaled by the halide perovskites which are less stable and less resistant in aggressive environments. In this work, the solar cells produced gave an exceptional record efficiency of 39.32% with a very high open circuit voltage (Voc) of 3.50 V, a short-circuit current density (Jsc) of 0.118 mA/cm2 and an FF of 0.72 measured in the positive polarization direction under 3825 lux (5.6 W/m2) lighting. The negative polarization direction under 4781 lux (7 W/m2) lightning gave a current density of 2 mA/cm2, an open circuit voltage of 2.30 V and an FF of 0.35.

Energy and food are very intertwined and important in human life. Cashew juice is a very abundant product in southern Senegal. Unfortunately, due to lack of processing and conservation, this product cannot last 24 hours without being fermented. The aim of this study is to study the heat treatment processes of agri-food products, particularly the pasteurization of cashew fruit juices. Pasteurization often uses heat from fossil fuels. In this heat treatment process of cashew juice, we are interested in the energy source. Thus thermal solar energy is used in this heat treatment. A solar thermal collector with an area of 17.9 m2 and a hot water storage tank with a capacity of 0.1 m3 are used. With the pasteurization model used, the juice circulates in a copper coil immersed in hot water coming from the solar thermal field or the hot water storage tank. A numerical simulation program has been developed on Ansys Fluent 2020 R1 to study the evolution of the temperature of the juice from the inlet to the outlet of the coil. The results obtained give outlet temperatures varying from 70 to 80°C depending on the speed of circulation of the juice. We can also achieve outlet temperatures of 100°C. This means that our system can operate in sterilizer mode.

The ideal band gap for a photovoltaic active layer for the solar spectrum is around 1.3 eV. However oxides with such values are rare. One of the most studied oxides to date as a photovoltaic active layer is the cuprous oxide Cu2O. Its band gap is around 2.1 eV and is therefore not ideal for the solar spectrum. Power Conversion Efficiency generally do not exceed 4 we propose to study an emerging type of solar cell that is based on ferroelectricity. In this type of solar cell, a p-n junction is not necessarily required, unlike conventional solar cells. Interesting conversion efficiencies are beginning to be obtained with this type of cell, however the mechanisms are still not well understood and several material and engineering challenges must be addressed. The objective of this paper is to initiate an innovative photovoltaic technology based on novel inorganic with suitable bandgap widths and organic materials (biopolymer). These oxides are more stables. We synthesized ferroelectric materials that absorb a large part of the solar spectrum with reduced bandgap widths. PZN-4.5PT nanoparticles were dispersed in a biopolymer matrix. Hybrid thin films with these inorganic nanoparticles embedded in a biopolymer have been successfully fabricated by spin coating on ITO substrate. Structural, morphological and electrical properties were investigated. The best Power Conversion Efficiencies measure under a light LED illumination of 3550 lux are respectively 21.83 light exposition with an open-circuit voltage of 5.17 and 5.86 V.

Nature and its biodiversity provide academics with a plethora of research topics, including the development of dielectric layers based on natural compounds that do not require any purification process for use in electronic equipments. Nevertheless, the properties of natural substances must then be investigated, and a suitable low-cost coating technique must be established. This study looks at the physicochemical behavior of khaya gum (KG) which is a biopolymer derived from khaya Senegalese tree exudates. In the form of powder, X-ray diffraction and scanning electron microscopy analyses of khaya gum revealed an amorphous structure and a slightly rough surface morphology with apparent wrinkles, respectively. The presence of oxides such as Al2O3, CaO, SiO2, as well as a high concentration of CuO, were disclosed by X-ray fluorescence data. Furthermore, tiny amounts of strontium, rubidium, molybdenum, chlorine, cadmium, and others elements were detected in KG. Several functionalities were qualitatively identified using Fourier Transform Infrared Spectroscopy. In the form of thin film, the absorption rate is low and the light transmittance exceeds 80%. The optical band gap was found to be around 4.15 eV. In regards of KG film dielectric properties, the capacitance frequency dependence exhibits conventional polar polymer dielectric behavior. At 1 kHz and room temperature, the estimated dielectric permittivity is between 6 and 10. These findings are intriguing, and they can be improved by combining different gum types for various applications in green opto-electronic systems.

The African School of Fundamental Physics and Applications, also known as the African School of Physics (ASP), was initiated in 2010, as a three-week biennial event, to offer additional training in fundamental and applied physics to African students with a minimum of three-year university education. Since its inception, ASP has grown to be much more than a school. ASP has become a series of activities and events with directed ethos towards physics as an engine for development in Africa. One such activity of ASP is the African Conference on Fundamental and Applied Physics (ACP). The first edition of ACP took place during the 2018 edition of ASP at the University of Namibia in Windhoek. In this paper, we report on the second edition of ACP, organized on March 7–11, 2022, as a virtual event.

In this paper, we study the dielectric and material properties of almond gum, a natural biopolymer material collected from almond trees. The dielectric properties are investigated by mean of impedance spectroscopy in the ranges of frequency 40 Hz-10MHz and temperature 300 K-400 K. The resulting responses provided valuable information about the material and revealed that the dielectric parameters are both temperature and frequency dependent. The calculated dielectric constant is around 8 at temperature T = 300 K and frequency f = 1 kHz. UV-visible spectrum of the almond gum thin films recorded from 300 nm to 2500 nm, showed a high transmittance with an optical band gap around 3.4eV. X-ray fluorescence showed that almond gum contained oxides such as CaO, SiO2, K2O, etc, with a significant concentration of CuO (63.72%) and several other chemical elements in trace such as strontium, rubidium, chlorine, cadmium, sulfur, etc. Thermal properties studies such as thermogravimetric analysis and differential scanning calorimetry conducted on almond gum powder revealed two stages of decomposition with a glass transition at 58.5 degrees C. In order to study the surface properties of almond gum thin films, we have carried out contact angle measurements and scanning electron microscopy analysis. The results showed hydrophobic surfaces. Our findings in this study lead to conclude that almond gum may be an interesting candidate for electronic applications especially for gate dielectric and encapsulating layer.

The Pb(Zn 1/3 Nb 2/3 )O3-4.5PbTiO 3 (PZN-4.5PT) single crystals showed very large ferroelectric and piezoelectric properties compared to traditional ferroelectric ceramics (BaTiO 3 and PZT) used presently as active material in medical imaging, detection and sonars. However, despite these excellent properties, the greatest difficulty to use PZN-4.5PT single crystals on electronic devices is to achieve them in thin layers form because of their incongruent melting property. To overcome this difficulty, we deposit them as thin layers by dispersing their nanoparticles in a gel containing a matrix that can maintain at least their bulk properties. After this size reduction at nanoscale and the annealing process following the deposition, changes and structural transformations would occur. We fabricate with success thin films by dispersing these nanoparticles in a gel. The materials show some agglomeration at the surface of the silicon substrate films (from SEM images) and non-identified hexagonal microcrystals, which could be at the origin of their excellent properties.

Solar modules are being built with nearly the same configuration for decades now. The front is covered with a tempered glass pane. The performance of a PV module can be increased by the texturation of the front side. One of the major requirements for front cover glasses is their high optical transmission. One option to boost transmission is texturing the front surface in a similar manner to crystalline solar cell. Another advantage of a textured glass is the fact that the reflected light beam at normal incidence has a second chance of being transmitted to the solar cell. Furthemore, the texturation of front cover glass might collect more dust and soiling than a flat glass surface. Due to this concern, the soiling effect of module covered with textured cover Alberino P glass after long-term exposed will investigated in this work. The modules presented in this work have the same characteristics in STC (i.e short circuit current, open circuit voltage and maximum power point). Electroluminescence, I-V and P-V characteristic are the method used to detect faults on the PV module. The results show a loss of PV performance with textured cover glass is l,72% higher than the reference module in other hand the increase of serie resistance is also observed in both modules

Many authors in the literature have worked on models for producing PV module performance, but the question of a climate-specific model is problematic.Some studies have shown more appropriate models for any PV module technology, while others have highlighted models that are more appropriate for a given climate.The aim of this work is to evaluate our model which is based on the I-V characteristic and their accuracy was assessed versus one-year of ground measurement from a system of PV module at different time resolutions.To predict the performance of PV modules in crystalline silicon in a sahelian climate in Senegal, the results obtained experimentally and those of the model were compared.The monthly nRMSE is 17.33% during the rainy season and 17.46% in dry season.There was a good correlation of the model, with a coefficient of 0.88 in January and 0.94 in September.

The present work relates to a process for silicon surface texturing for preparing large-area, silicon nanotextures on silicon substrates at ambient temperature by assisted chemical etching. A novel strategy comprises of two fundamental steps (metal-assisted chemical etching (MACE) and solution post-treatment) of using the silver catalyst to obtain specific nano- or micro-textures. The strategy is based on metal-induced (Ag) local oxidation and dissolution of a silicon substrate in three different concentrations of aqueous fluoride solution with the post-treatment solution. The etching technique is dependent on the etching time and concentration of aqueous fluoride solution. Therefore, detailed scanning electron microscopy observations reveal specifics shapes as inverted pyramids, cubic nano-microholes, spiroconical nano-microholes and rhombohedral-stared nanosheet bouquets (called Nanobukets), obtained for the first time on a (100) silicon surface by this new variant of the MACE method named Double Etching Method (DEM). Silicon nanostructures are used in many nanotechnology applications such as nano-microelectronics, optoelectronics or biomedical applications. UV-Visible spectrometry measurements carried out made it possible to obtain the lowest reflectance and highest absorbance values who are 3% and 97%, respectively for the rhomboedral-stared nanosheet bouquets on (100) crystalline silicon substrates in the UV-visible-NIR wavelength range from 300 to 1200 nm.