Wind Turbine Generation System (WTGS) is a vehicle
mounted wind turbine system that is used to generate electricity. This paper
focuses on designing a horizontal axis wind turbine and simulating its
performance and showing its output results. This paper shows power extracted by
the turbine from the wind and its different parameters (attack angle, drag
co-efficient, wind speed) relation with extracted power. It’s assumed that
there is no external air flow. Thus vehicle speed is assumed to be air speed.
And if there is any external air flow, it will be added to the air velocity.
Values of some constants like Mach number, Reynolds number, Ncrit are
considered for a certain testing environment.

Keywords: Wind energy, wind turbine, electric vehicle,
power, simulation

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Introduction

Renewable energy sources
offer limitlessresource and environment friendly operation compared
toconventional energy sources. There are several forms ofrenewable energy such
as solar energy, wind energy,geothermal energy, tidal energy, hydro energy
andbioenergy.However, wind energy is the most valuable, safe and fastest
growing renewable energy. At the end of2016, wind energy has served
approximately 49%electricity of South Australia (GWEC, 2017). Moreover, it is
low cost(0.12/kWh) (Ravi et al., 2009), low carbon footprints (<5CO2/kWh), minimum sound pressure level (50-60 dBfrom 100 feet) and easy integration with other energy sources. However, commercial wind turbine (WT) is notsuitable for small scale application as it requires big land,high installation cost, lack of energy storage and notportable. Additionally, in some places wind speed is notsufficient to run a commercial or domestic WT. Hence, amodified WT system is necessary which can be efficientunder this kind of circumstances. Consequently, the ideaof mobile WT for vehicle came along for small scaleenergy harvesting (Christian, 1975). Several attempts are taken to produce electricity by vehicle as a number of literatures are already exists (Sham, 2011; Ferdouset al., 2011). However, these proposals never meet the threshold of the practicalimplementation. In most cases, these proposed modelseither too inefficient or directly affect the aesthetic appeal of the vehicles (Jean, 1983; Jose, 2013; Cecil, 2012;Andrew, 2013; Peter, 2013; Keith, 1979; Tran, 2011). Therefore, electricity harvesting from vehicle is still an active area to explore. From these motivations, this paper proposes amodified, portable and distributed wind turbine system for vehicles. It is possible to increase the incoming wind speed for a mounted WT artificially by using the vehicle speed. Wind energy and power Wind energy is available in the form of kinetic energy which can be transformed to energy by mechanical conversion. As it is required to use wind energy to produce electrical energy, hence the conversion is mainly from the mechanical to electrical. So the wind is the primary source of energy and it is different from usual wind turbine as it will be mobile.   The kinetic energy in wind can be expressed by,                 (1) Here V is the speed of air,? is the air density, A is the area of the air parcel and T is the time needed for air parcel to move through the plane. Now wind power can be expressed as Pw =                                          (2) For the cross sectional area the available wind power Pw =                                                         (3) The power captured by wind is as follow Pout=Cp  Pin                                                                 (4) Here Pout is the actual output captured by the wind turbine, Cpis the power co-efficient and Pinpower flows through the wind turbine. The power co-efficient represents a fraction of power captured by the wind turbine and has a theoretical maximum of 0.55(David Richard et al 1993). The power co-efficient can be expressed by a typical formulaas (5) Here ? is the tip speed ratio of the wind turbine and ? is the pitch angle of the blade. The tip speed ratio ? can be expressed as                                                        (6) Here ? is the angular velocity of turbine.   This is our proposed model of electric vehicle with the diffuser shroud augmented turbine. A diffuser shroud is used as it increases the wind speed at the rotor plane. Thus greater generated power for the same air speed for the turbine having shroud. According to velocity distribution around a moving car, the velocity distribution of air is highest at the top of the roof. And at the front top, its highest. Two turbines are used only for more power generation purpose. Description of the Different Elements Used in the VMWT System: Horizontal Axis Wind Turbine (HAWT): Horizontal axis wind turbines are the most common type used. All of the components (blades, shaft, and generator) are on the top of the tower, and the blades face into the wind. In case vehicle there is no tower. The shaft is horizontal to the ground. The wind hits the blades of the turbine that are connected to a shaft causing rotation. The shaft has a gear on the end which turns a generator (sometimes there is no gear; just the shaft is connected directly with the generator). The generator produces electricity and sends the electricity into the power grid (in our case DC generator is used and the produced power is saved into battery). The wind turbine also has some key elements that add to efficiency. Inside the Nacelle is an anemometer, wine vane and controller that read the speed and direction of the wind (in our case direction of the vehicle is considered as the direction of the air). In case of extreme winds the turbine has a break that can slow the shaft speed and/or isolate the shaft from the generator. This is to inhibit any damage to the turbine or generator in extreme conditions   Rotor: Rotor collects energy from the wind. The rotor consistsof two or more blades which rotate about an axis (horizontal or vertical).Rotational speed of the rotor is determined by the wind speed and the shape of the blades. The blades are attached to the hub, which in turn isattached to the main shaft. So rotor is consists of hub and blades. Description of the Turbine: 1. Airfoil: An airfoil or aerofoil is the shape of a wing, blade (of a propeller, rotor, or turbine), or sail as seen in the cross section. That is airfoil is the cross sectional curve of the turbine blade. The lift on an airfoil is primarily the result of its angle of attack and shape. When oriented at a suitable angle, the airfoil deflects the oncoming air, resulting in a force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force and can be resolved into two components: lift and drag. The lift component is responsible for the rotation of the turbine. Airfoil design is major part in turbine designing. NACA developed some airfoils. The NACA airfoils are airfoil shapes developed by the National Advisory Committee for Aeronautics (NACA). The shape of the NACA airfoils is described using a series of digits following the word "NACA". Several types of NACA airfoils are: Four-digit series, Five-digit series, 1-series, 6-series, 7-series, and 8-series. We used NACA 2412 airfoil. The airfoil has a maximum camber of 2% located 40% (0.4 chords) from the leading edge with a maximum thickness of 12% of the chord. From Fig 4, we can see with increase in angle of attack alpha (?), lift coefficient Cl increases up to a certain point. Then it decreases. And from Fig 5, drag coefficient Cd decreases with increase in alpha (?).From Fig 6, we can see angle of attack of around 8 degree is optimum where Cl/Cd has a highest value. So angle of attack of 8 degree should be maintained.   2. Blade design: We used QBlade v0.963 to primarily design the blade and simulate its performance. We assumed Reynolds number 50000, Mach number 0,  Ncrit 9 and air density (?) 1.225 kg/m3. Blade in designed for simulation in QBlade: From Fig 9, we see for a rotational speed of around 1200 rpm the blade can extract highest power; about 60 W from the wind. From Fig 10, we see with increase in TSR, power co-efficient Cp increases at a certain point and then decreases. In this case optimum TSR is 4.5. Conclusions A convenient system for energy harvesting from wind to charge the battery of the electric vehicle is proposed in this paper. The architecture and the design of the wind turbine have been discussed in detail. The wind turbine mounted in the electric vehicles have many attractive features including increasing rpm and torque compared to the conventional vehicles, along light weight, small size and easy to install. From experiment the wind turbine mounted on the vehicle can produce 200W (at speed of 80Km/h) with proper conversion technology it can be stored for future use. Nevertheless, it produces some drag force which is the great challenge in this field. Moreover, this wind turbine can be used for producing electricity in small scale for electrical vehicles or some house hold. Introducing hybrid car is a great future agenda.                            Brief Description of Design and Analytical Approach Conventional electrical vehicles have the problem with charging because the charging and discharging time are equal to each other. So if only the vehicle could be charged in its motion state that would be a great alternative for the charging of electric vehicles. The wind energy is a great source of energy and the speed of vehicle will produce a great deal of wind which can be used to produce electrical energy. This research paper proposes a design of wind turbine to produce electrical energy to charge the battery of electric vehicles during motion and an algorithm to get optimum power for charging the battery of the vehicles.

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