Review on Diffuser Augmented Wind Turbine (DAWT)

Wind energy technology is one of the fastest growing alternative energy technologies. However, conventional turbines commercially available in some countries are designed to operate at relatively high speeds to be appropriately efficient, limiting the use of wind turbines in areas with low wind speeds, such as urban areas. Therefore, a technique to enhance the possibility of wind energy use within the range of low speeds is needed. The techniques of augmenting wind by the concept of Diffuser Augmented Wind Turbine (DAWT) have been used to improve the efficiency of the wind turbines by increasing the wind speed upstream of the turbine. In this paper, a comprehensive review of previous studies on improving or augmentation power of Horizontal Axis Wind Turbines (HAWT) have been reviewed in two categories, first related with relative improvement of energy by improving the aerodynamic forces that affecting on HAWT in some different modifications for blades. Second, reviews different techniques to the augment the largest possible amount of power from HAWT focusing on DAWTs to gather information,helping researchers understand the research efforts undertaken so far and identify knowledge gaps in this area. DAWTs are studied in terms of diffuser shape design, sizing of investigation and geometry features which involved diffuser length, diffuser angle, and flange height. The conclusions in this work show that the use of DAWT achieves a quantum leap in increasing the production of wind power, especially in small turbines in urban areas if it properly designed. On the other hand, shrouding the wind turbine by the diffuser reduces the noise and protects the rotor blades from possible damage

CFD Investigation of Empty Flanged Diffuser Augmented Wind Turbine

Enclosing a wind turbine within a Flanged diffuser is an innovative mean to increase the power harvested by turbine blades and it is among the most effective devices for increasing wind turbine energy. The geometric parameters of the empty flanged diffuser contribute efficiently to increase mass flow in the diffuser, hence improve the turbine performance. The study presents developed models of the geometrical parameters of an empty flanged diffuser that suitable for a scaled-down (1-6.5) horizontal axis wind turbine, the geometry parameters were involved the diffuser length, diffuser angle, flange height and flange angle. The geometrical models were verified and CFD investigated in 2-D and 3-D domains. Results obtained from CFD simulations show that when using a compact size of flanged diffuser within optimum geometrical parameters can give well acceptable for flow velocity increase at suggested place for the turbine rotor install where the increase in flow velocity is due to lower pressure at the outlet of the diffuser. As there is also a significant effect of the flange angle on increasing the flow velocity inside the diffuser where the rate of increase in wind velocity at turbine position was calculated for two flange angles (0 ÌŠ and 5 ÌŠ ) . In another hand, the results also provided information on the velocity contours and velocity streamlines around diffuser geometry

Engineering and Technology (A High Impact Factor

ABSTRACT: The effect of the addition of wind break wall upstream the wind flow is studied numerically. The separation distance between the trough and wind break, and the wind break elevation as well as the wind flow velocity will be the variables of the present work. The computational work done by use a 5.0 COMSOL Multiphysics code to solve the problem. The results show a general decrease in the drag forces on the trough as well as the heat loss. The extreme values of separation distance and wall elevation causes an opposite defect results

THERMAL LOSSES REDUCTION FOR A TROUGH SOLAR COLLECTOR: PART 1 FLUID FLOW

The flow of the wind near an absorber of a trough collector is analyzed. Since this absorber loss useful heat into the ambient, it is necessary to reduce that heat. The common strategy of reduction is the use of a vacuum tube. The maintaining of vacuum is difficult due to air leak or glass fracture led to find another replacement for this strategy. The idea of the present work is to put a half circular disc in front of the receiver in order to reduce the air velocity near the tube and reduce the heat transfer process. The flow is analyzed in the area to find the streamlines of flow and the behavior of air for a different air velocities and trough orientations. The analysis is done by using COMSOL Multiphysics program V4.4. The data show that the overall air velocity is reduced near the receiver as predicted

Performance of cylindrical solar still with hemispherical cover: CFD simulation study

Solar distillation collectors are the device that runs on freshwater products. The solar still is one solar thermal technology for purification of water. This technique is employed to convert saline water into freshwater. At this time, the human being increased freshwater required consumption because of the increasing population density. The thermal analysis of a new design of cylindrical solar still (CSS) with hemispherical cover has been studied. A computer simulation model was improved to investigate its performance. The 2D symmetry simulation models of cylindrical solar still have been validated. The simulation model can emulate the temperature value of different points inside the CSS. The simulation results confirm an acceptable agreement with the experimental result was reported in the literature. From this simulation, it was noted that the freshwater product from the cylindrical solar still obtains the maximum daily productivity of 6.1 kg/m2 as compared to a traditional single slope solar still SSS as 3.18 kg/m2 during the day

CFD investigation of empty flanged diffuser augmented wind turbine

Enclosing a wind turbine within a flanged diffuser is an innovative mean to increase the power harvested by turbine blades and it is among the most effective devices for increasing wind turbine energy. The geometric parameters of the empty flanged diffuser contribute efficiently to increase mass flow in the diffuser, hence improve the turbine performance. The study presents developed models of the geometrical parameters of an empty flanged diffuser that suitable for a scaled-down (1-6.5) horizontal axis wind turbine, the geometry parameters were involved the diffuser length, diffuser angle, flange height and flange angle. The geometrical models were verified and CFD investigated in 2-D and 3-D domains. Results obtained from CFD simulations show that, using a compact size of flanged diffuser within optimum geometrical parameters can give well acceptable for flow velocity increase at suggested place for the turbine rotor install. The increase in flow velocity is due to lower pressure at the outlet of the diffuser. As there is also a significant effect of the flange angle on increasing the flow velocity inside the diffuser where the rate of increase in wind velocity at turbine position was calculated for two flange angles (0 ̊ and 5 ̊). In another hand, the results also provided information on the velocity contours and velocity streamlines around diffuser geometry