Wind Energy
Ali Khaleghi; hadi bayat
Abstract
The noise generated by a blade is assumed as one of the most central acoustic generation sources in a turbine. The sound induced by the movement of turbulent fluid over the turbine blade and its interaction with the surrounding environment causes the presence of vortices of different sizes in the turbulent ...
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The noise generated by a blade is assumed as one of the most central acoustic generation sources in a turbine. The sound induced by the movement of turbulent fluid over the turbine blade and its interaction with the surrounding environment causes the presence of vortices of different sizes in the turbulent flow. These vortices are considered as the major sources of acoustic waves in a wide range of frequencies. In the present study, the acoustic field induced by turbine blades is simulated by the aid of numerical simulation. In this respect, the flow_field around the blades is solved by using the flow governing equations and then the acoustic solution of flow is modeled by using the Ffowcs Williams-Hawkings acoustic model. The main objectives of the present study include investigations of sound propagation at different distances of turbine axis, the extent of sound propagation along the blade direction, and the effect of the cavity implemented over the blade on acoustic results. The obtained results reveal that the sound pressure level generally decreases as the observer’s distance increases. Furthermore, based on the obtained results, one can infer that the reduction in the sound pressure level is triggered by the presence of larger vortices with higher energy close to the blade (a larger sound pressure level) and smaller vortices at a further distance from the blade (a lower sound pressure level). Numerical simulations indicate that adding a cavity to the turbine blade does not reduce noise but instead increases the acoustic generation level.
TITU THOMAS
Abstract
Highly unstable absorber layers along with costly Hole Transport Materials(HTMs) have been the main problems in the perovskite-based photovoltaic industry recently. Here in this study, we intend to meet both these problems by introducing a non-toxic cesium-based absorber layer and low-cost material, ...
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Highly unstable absorber layers along with costly Hole Transport Materials(HTMs) have been the main problems in the perovskite-based photovoltaic industry recently. Here in this study, we intend to meet both these problems by introducing a non-toxic cesium-based absorber layer and low-cost material, Graphene Oxide (GO) as the Hole Transporting Layer (HTL). We use the Solar Cell Capacitance Simulator Program (SCAPS) to study the various output parameters of the device with the structure GO/Cs2TiBr6/TiO2. Physical properties like the thickness of the absorber and hole transporting layers, the role of the layer interfaces, the effect of electron affinity, optical properties like the band gap of the absorber and hole transporting layer, electrical properties like the parasitic resistance, and finally the influence of operating conditions like the temperature on the working of the device was found out. The results show that a thickness of 1 μm for absorber and 0.1 μm for HTL is suitable. Also, the optimum value for front and back interface layers were 1010 cm-3 and 1016 cm-3 respectively. Resistance values were fixed at 2 for series and 40 for shunt resistance. The electron affinity doesn’t seem to have much effect on the device performance while with the increase in temperature the performance of the device deteriorated. The highest efficiency that we obtained from the optimized device was 15.3%. In short, this unprecedented work shows that Cs2TiBr6 - GO based devices are suitable candidates to achieve highly efficient, eco-friendly, all-inorganic perovskite solar cells.
Solar Thermal Engineering
A.R. Shateri; I. Pishkar; Sh. Mohammad Beigi
Abstract
Trombe walls and solar chimneys have been widely used by the construction industry for many years to heat buildings. In this study, the heat conductance of a Trombe wall was simulated and studied. The equations related to energy and momentum were solved numerically by use of the technique of control ...
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Trombe walls and solar chimneys have been widely used by the construction industry for many years to heat buildings. In this study, the heat conductance of a Trombe wall was simulated and studied. The equations related to energy and momentum were solved numerically by use of the technique of control volume. The equations were solved simultaneously using the Simple algorithm. At first, a base case was defined and simulated. A sensitivity analysis study was then performed to investigate the parameters affecting the performance of the wall. Based on the results, an optimized geometry was suggested which maximized the performance of the Trombe wall. In addition, the effect of the presence of the fins on the surface of the absorber wall was studied. In order to obtain the best geometry, the fins were assumed to have different shapes but a constant area. The results showed that the Trombe wall with rectangular fins demonstrated the best performance compared to the other fin geometries studied in this paper. The presence of rectangular fins can increase the room temperature by 1.24% compared to other fin geometries.