This manuscript is about a theoretical modelling of conversion efficiency improvement of a typical polycrystalline Si solar cell in 1D assumptions. The improvement is brought by the increase of the collection of the minority carriers charge in excess. This increase is the consequence of the influence of an electric field provided by the use of the open circuit photovoltage of another silicon solar cell. We assume that it is integrated two silicon solar cells to the system. The first solar cell provides the open circuit photovoltage which is connected to two aluminum planar armatures creating a planar capacitor. The second solar cell is placed under the uniform electric field created between the two aluminum armatures. This work has shown an improvement of the output electric power leading to the increase of the conversion efficiency. We observe an increase of 0.7% of the conversion efficiency of the second silicon solar cell.

The COVID-19 pandemic has significantly disrupted TB services, particularly in low resource settings. In Burkina Faso, a cross-sectional ‘before and after’ study was conducted to assess the impact of COVID-19 on access to TB services. Data was collected in two phases (Phase 1: December 2017–March 2018, and 2: October–December 2020) to estimate and compare various patient and system delays among TB patients before and during COVID-19 and explore changes in treatment seeking behaviors and practices. 331 TB patients were recruited across the two phases. A significant increase in median time between first symptom and contact with TB service (45 days vs. 26 days; p < 0.01) and decrease in median time between first contact and diagnosis, and treatment initiation, respectively, during COVID-19 compared to before. Fewer patients reported using public health centers and more patients reporting using private facilities as the point of first contact following TB symptom onset during the COVID-19 period compared to before. These findings suggest that COVID-19 has created barriers to TB service access and health seeking among symptomatic individuals, yet also led to some efficiencies in TB diagnostic and treatment services. Our findings can be help target efforts along specific points of the TB patient pathway to minimize the overall disruption of COVID-19 and future public health emergencies on TB control in Burkina Faso.

Aims: This paper is about a solar collector made of hemispherical concentrators. This collector is sun tracking free, and used for natural convection. Lenses are used on top of each concentrator to improve its efficiency. Study Design: The Solar collector is made of hemispherical concentrators with Fresnel lenses axially-centered to those concentrators and placed on top of each one of them. Those concentrators are covered with a 4 mm glass for a greenhouse effect. The concentrators generate hot spots that heat the inside air. There is no need for receivers at the hot spots. Methodology: from Inlet to outlet, temperatures are measured as well as inlet air speed, which allow the efficiency evaluation. Results: Although those measurements were conducted in a cloudy period, temperature difference from the inlet to the outlet was around 55°C to 65°C. This result is superior to previous studies of the same system without lenses which gave temperature difference around 35°C to 45°C. It is sharply superior to that of usual black-painted convective system with fined plates that gives a temperature difference of around 20°C to 25°C. Conclusion and Perspectives: The global efficiency calculated using measurement values reaches 56%. This is far greater compared to previous black plate systems’ efficiency of 29%, giving an efficiency increase of 93%, but expected knowing that we are using a concentration system for convection.

This technology is used in drying, domestic water heating or in the production of electricity. However, it uses a solar tracking system that is too complex and expensive for countries with less equipment and high solar potential. In this study, we are interested in the experimentation and thermal analysis of a stationary hemispheric concentrator. The numerical resolution of the caustic equations of a spherical concentrator allowed to determine the dimensions and the position of the receiver, necessary for the design of the physical model and the assembly of the experimental device. The results of the 3D numerical simulation with the Comsol5.3a software allowed to highlight the ray tracing and the profile of the flow concentrated on the receiver. The results obtained experimentally show that the receiver and the air inside reached a maximum temperature of 224°C and 97.6°C respectively. The solar concentration device studied is therefore technically favorable for thermal applications requiring intermediate temperatures.

The energy demand in buildings sector is always increasing due to the climate, the economic growth, and also the need for thermal comfort. The aim of this paper is to find a way that can significantly reduce the energy demand for a building through an improvement of the design of its thermal envelope. Within this work, we utilized the thermophysical properties of four building materials: three local materials (compressed earth block (BTC), lateritic block (BLT), and raw earth), and one modern (Hollow cement). The numerical optimization of the building design has been performed dynamically by Comsol 5.3a software: the case study is Ouagadougou and the surface is 100m2. Also, the temporal variations in the inside of the room, as well as the internal and external temperatures of the walls and the ceiling with four different materials, have been determined. The result of the simulation shows that, for BLT, the maximum of ambiante temperature is obtained 308K around 22h, for Adobe it is 308.8K around 21h, for BTC it was 309.2K at 19h30, and finally for cement block it is 310K around 17. We can safely say that BLT is the material leading to the lowest average daily indoor temperature variation, thus leading to the reduction of air conditioning load and the need for thermal comfort and around the order of 4KW of energy saving can be obtained.