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Due to increase in energy demand along with environmental awareness, the attention is shifting towards renewable energy sources. A wind turbine developed from Banki water turbine is used in this study as it starts at low-wind speeds and has high starting torque. Experimental investigations are carried out on a test rig equipped with open jet wind tunnel with wind velocity varying from 7 to 11 m/s. Later, 3D steady-state numerical analyses are performed using ANSYS CFX for better understanding of the flow physics of cross flow VAWT. The experimental investigations revealed that cross flow VAWT has a good self-starting ability at relatively low-wind speeds. A peak power coefficient (Cp, max) value of 0.059 is observed for the tip speed ratio (λ) of 0.30. As the tip speed ratio is raised further, the Cp value is observed to decrease gradually. The numerical simulations reveal the reason for the drop in Cp value. This is due to lessening of positive interaction between the flow and cross flow VAWT blades at higher λ due to vortex formation. The torque coefficient is found to decrease almost linearly from a peak value of around 0.49 at λ = 0 to a value of 0 around λ = 0.60. Polar plot between angle and torque shows that torque output of the turbine is nearly same in all directions which reinforce the potency of cross flow VAWT to be omni-directional as it produces the same performance regardless of wind directions.

Vortex-induced vibration is one of the predominant fundamental concepts for forced oscillation which attracts considerable practical engineering application for energy conversion. In this work, an oscillation of a mast arising as a result of wind force is utilized for energy conversion. The paradigm for energy conversion from vortex-induced vibration in the mast is the bladeless wind turbine. It consists of a rigid mass known as a mast, fixed in the spring of stiffness (k) and allowed to oscillate along the direction of the flow. In this work, four different types of mast have been fabricated and tested. The first is uniform tapered hollow conical mast (MAST1), the cross-section of the second is uniform tapered plus symbol (MAST2), the third is uniform tapered inversed plus symbol (MAST3) and the fourth is uniform tapered simple rectangular cross-section (MAST4). All the masts were fabricated using fiber carbon. The experiments were conducted in a versatile small wind turbine testing facility of Hindustan Institute of Technology and Science, Chennai. This test facility contained an open jet wind tunnel with variable frequency drive and other measuring instruments. The vibration sensor was located in the mast where it experienced a large oscillation in a free stream. In this experiment, an increase in wind velocity led to a terrible change in the amplitude of vibration. A vigorous oscillation was experienced in this mast at this critical frequency, when the natural frequency of the mast was synchronized with the frequency of the vortex shedding and the frequency of the oscillation of the mast. The total force in this oscillation was a summation of the body force due to the mass of the mast and vorticity force that is mainly which was the result of the shedding of the vortices. In this work, extensive studies have been carried out for Reynolds number ranging from 2.5 × 105 to 5.0 × 105. The mast length to diameter ratio of 13 was exposed to various speeds of wind and response was measured. The occurrence of the maximum oscillation in a simple rectangular mast was seen where vortex shedding due to the bluff body was large for constant mass and spring stiffness. The frequency of the oscillation at maximum amplitude of the rectangular cross-section mast was equal to the natural frequency, due to vortices shedding at critical velocity. This demonstrated the appropriateness of the simple rectangular cross-section for harnessing the low rated wind energy and its suitability for renewable energy conversion in the small bladeless wind turbine.

The objective of this present work is to investigate numerically the effect of converging conical hole on blade cooling at leading edge. Diameter ratio of the converging conical holes is maintained as two with a converging angle of 20°. Cylindrical geometry used by Lee et al. [5] for the experimental investigation is taken as base reference for this present numerical investigation. Turbulence model study is carried out with three different models and kω-SST is found to give closer result with the experimental data. Subsequent investigations are carried out using kω-SST turbulence model. The target surface for the present study is 19.05 cm in radius and the diameter of the impingement hole is 1.30 cm, 2.15 cm 3.40 cm. The jet hole to the target surface spacing is varied as R/4, R/2 and 3R/4. The steady-state Reynolds Averaged Navier Stokes equations are solved for different impingement hole diameters at Reynolds number of 11000, 23000 and 50000. The target surface is maintained at constant heat flux of 10000 W/m2. Numerically computed Nusselt number and temperature distribution for the convergent conical hole and cylindrical hole are compared. Around 186% increase in Nu and 13% decrease in surface temperature is observed at the stagnation point for the optimum case in this present study i.e, jet spacing R/2, converging conical hole diameter 2.15 cm and Re 23000. The converging conical hole configuration increases the fluid velocity in the potential core region and enhances the heat transfer. It is followed by 185% increase in Nu and 15.58% reduction in target surface temperature for Re 11000 and 170% increase in Nu and 7.28% reduction in temperature for Re 50000.

The importance of renewable energy has increased continuously in the recent years due to the growth in the energy demand and a decrease in the fossil fuel resources. Harnessing the low rated wind energy is the promising source so that the wind turbine can be used all year round. Deploying sequence of small turbine is efficient than single bigger size turbine in extracting the low rated wind energy. Hence, in this work, sequence of small vertical axis wind turbine is arranged in the tree like structure and named it as wind tree. The vertical axis type of turbine would be able to perform more efficiently at minimum wind velocity. So, the Helical Savonius vertical axis rotor is deployed in the wind tree which gives the relatively high torque and self-starting even at low wind speeds. The main aim of this work is to analyze numerically the cluster of vertical axis wind turbine in order to improve the average output of the wind tree. In this study, the vertical axis turbines are arranged in the branches of the tree at different plane, so that the wake of one turbine will not affect the turbine in the downstream. The numerical simulation has been studied by using commercially available software ANSYS CFX©. The single helical vertical axis wind turbine is fabricated and tested in the open jet wind tunnel and this experimental result is used for validating the numerical results. In addition to the validation, sensitive study for the grid and the turbulence model has been carried out to improve the simulation quality. Vertical axis wind can accept wind from any direction without any yaw mechanism, so the average performance of this type of turbine in cluster is analyzed by changing the flow (α = 0°, 45° and 90°) of the wind turbine cluster. It is observed from this study that the average power coefficient of the cluster of turbine at the flow angle of 45° has better performance than the other pattern. Moreover, its average power coefficient is 2.3 times higher than the isolated vertical axis wind turbine. These results of the cluster simulation are used to develop an efficient wind tree to harness the low rated wind energy.