http://hdl.handle.net/10174/37668 2026-07-16T22:57:05Z http://hdl.handle.net/10174/42359 Title: Modeling and Simulation of GaSb/GaAs Quantum Dot Solar Cells in SILVACO TCAD Authors: Haque, Md Ekramul; Ahmed, Md Tofael; Tlemçani, Mouhaydine Abstract: GaSb/GaUtilizing type-II band alignment to increase sub -bandgap absorption and possibly exceed the Shockley–Queisser efficiency limit, quantum dot solar cells (QDSCs) offer an attractive solution for third - generation photovoltaics. In this work, a GaSb QD-embedded GaAs p-i-n solar cell structure is mathematically modeled using the SILVACO TCAD Atlas simulator. An effective medium approximation is used to describe the quantum dot area, and modified Shockley–Read–Hall recombination parameters are used to model intermediate band states. Under AM1.5G illumination, the effects of QD layer count, dot density, and doping concentration on J_SC, V_OC, fill factor, and total power conversion efficiency are carefully examined. Deltadoping and surface passivation have been suggested as mitigation techniques, and results confirm increased infrared photocurrent collection together with a V_OC deficit ascribed to interface recombination. Standard empirical models are used to incorporate temperature-dependent material properties to guarantee physical accuracy under all operating situations. For the experimental design of high-efficiency GaSb/GaAs QDSCs, the simulation framework provides a solid basis. 2026-07-07T23:00:00Z http://hdl.handle.net/10174/42358 Title: Review of different types of solar cooling system for photovoltaic panel Authors: Olarewaju, Taiwo Olatowale; Ahmed, Md Tofael; Tlemçani, Mouhaydine Abstract: Photovoltaic panels generate electrical energy from sunlight, but they lose efficiency as the temperature exceeds 25°C (STC). For each degree Celsius rise, they may lose efficiency by 0.4-0.5%. This paper reviews various solar cooling technologies used in photovoltaic panels, their models, impacts of temperature on them, and efficiency increases according to some studies done recently. The main purpose of this paper is to compile information that could be used to develop extensive research on solar cooling technologies for photovoltaic panels. Passive cooling does not use any additional energy and is economical and straightforward to deploy. Some examples are radiative cooling by using special paint that dissipates heat into space, evaporative cooling by using water evaporation (effective in arid areas), natural convection cooling using fin-based or heat sinkbased systems, and phase change material (PCM), which absorbs and releases heat to maintain temperature control. However, passive cooling technologies have fewer cooling capabilities under extremely high temperatures. The active cooling system works with the help of pumps or fans to improve the cooling process. The water-based PV/T (hybrid cooling) system utilizes the flow of water behind or at the back side of the panel in order to generate both electrical and hot water. This approach may lead to electrical efficiency of up to 10- 20% and thermal efficiency of up to 50-60%. Moreover, there are other active cooling methods including forced air flow, spraying/jetting impingement and nanoparticle-based fluid cooling (nanofluid, Al2O3 or CuO). The hybrid andadvanced cooling systems include thermoelectric, floating PV panels, microchannel or heat pipe methods. Higher temperatures cause lower voltage and power output of the PV modules. Several studies show that effective cooling helps to decrease the panel's temperature of 10-49°C, resulting in increasing electrical efficiency of 5-47%. Hybrid PV/T systems are widely used due to generating both electricity and heat with efficiency being more than 60%. Modeling of the system is typically carried out via application of energy balance equation, CFD analysis or with TRNSYS or MATLAB software programs. Important parameters are solar radiation, ambient temperature, flow rate and material properties. The cooling techniques can significantly improve the efficiency and life of solar PV panels. The passive cooling technique is appropriate for cheap cases whereas the active and hybrid types have higher efficiency. Further studies for obtaining low cost, durability, and efficiency in different climatic regions is also conducted. 2026-07-05T23:00:00Z http://hdl.handle.net/10174/42357 Title: Sensor Placement Strategy to Maximize Coverage and Early Detection of Forest Fires Authors: Gussule, Milton; Rashel, Masud Rana; Ahmed, Md Tofael; Tlemçani, Mouhaydine Abstract: Forest fires represent a significant threat to ecosystems, causing extensive damage to vegetation, fauna, and local communities. In this context, wireless sensor networks (WSNs) constitute a promising solution for the early detection of fires through the continuous monitoring of environmental parameters such as temperature, humidity, smoke presence, and sound spectrum. However, the implementation of these systems in large forest areas present challenges related to network coverage, connectivity, and energy efficiency. This work proposes an optimization methodology for planning a wireless sensor network applied to the early detection of fires in the Serra de São Mamede Natural Park, as it presents topographic and ecological characteristics that significantly increase its vulnerability to forest fires. The methodology includes the generation of a risk map and a numerical risk map of the study area, the determination of the number and optimal positioning of sensors, as well as the evaluation of network connectivity considering the presence of natural obstacles. Additionally, clusters and Cluster Heads (CHs) are defined in strategic locations in the forest, with the aim of improving communication efficiency and energy management of the network. Finally, a comparative analysis of energy consumption and WSN coverage performance was carried out for different Cluster Head configurations. It is expected that the results will contribute to the development of more robust, energy-efficient monitoring systems capable of ensuring adequate coverage of areas with the highest fire risk. 2026-07-07T23:00:00Z http://hdl.handle.net/10174/42356 Title: Modeling and Analysis of a Solar-Driven Absorption Chiller with Nanofluids Using GNU Octave: energy, economic and environmental study Authors: Priori, Matteo; Ahmed, Md Tofael; Tlemçani, Mouhaydine Abstract: Absorption chillers combined with renewable energy sources are considered a promising alternative to conventional vapor-compression cooling technologies. Previous studies have already shown that performance can be enhanced by adding small quantities of nanoparticles into the working cycle: the selection of the nanoparticle type and its concentration improve the thermophysical properties of the working fluid. In order to investigate the influence of these parameters under realistic operating scenarios for a medium-scale absorption chiller, a numerical model will be presented and developed in GNU Octave. This cooling system is designed to operate in a typical summer climate for Portuguese latitudes and is coupled with thermal energy storage and a flat plate collector as a primary energy source. Various types of nanoparticles will be investigated and studied at different concentration in order to assess their influence on the Coefficient of Performance (COP). Particular attention then is focused on the environmental and economic impact associated with the proposed configuration: it will obtain detailed information about the variation of carbon dioxide emissions, payback period and Net Present Value (NPV). 2026-07-07T23:00:00Z