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A Proposal for Implementation of Wind Energy Harvesting System in Trains

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A Proposal for Implementation of Wind Energy Harvesting System in Trains
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  A Proposal for Implementation of Wind Energy Harvesting System in Trains Sindhuja.B Department of Electrical and Electronic Engineering RMD Engineering College Chennai, India meetsinduja@gmail.com  Abstract  -–Energy resources in our modern fast paced techno-world is fast depleting. Hence a renewable energy source is much required at the moment. Thus researching new and innovative systems in renewable energy sector is an indispensable prerequisite. This paper attempts to propose a model for generating clean energy by harnessing the power of wind in moving trains. The scope of this paper concentrates on a new approach to harvest wind power by installing a conical shaped ducted turbines on the roof of the trains which are coupled to a generating unit. Another auxiliary system is also installed that sucks in air through a tunnel like shroud and compresses it. The compressed air is stored in pressure conduits or an agitation tank that maintains the turbine speed at the desirable rate during fluctuations in train speed or wind potential at the inlet turbine. To complement this approach, CFD simulated results are used to investigate the design profile of the proposed model. The conclusion thus obtained proves the efficiency of the system to harness large scale power in a sustainable manner.  Key words-train power; clean energy; electricity; alternate energy; ducted turbines; wind energy etc. I.   L IST OF SYMBOLS USED   Symbol Meaning Unit    Mass flow rate of air (kg/s)     Wake velocity (m/s)     Free stream velocity (m/s)     Induced velocity (m/s)      power (watt)     Power output from air stream (watt)     Swept area of rotor         Radius of the turbine (m)    Diameter of the turbine (m) .   Kinetic energy (J)  ρ   Density of air (Kg/     )    Tip speed ratio    Turbine resistance coefficient δ   Pressure coefficient C   P    Power coefficient C  T Torque coefficient C  V Velocity coefficient II.   I  NDTRODUCTION  The world is a resident for about 7 billion people which will be 9 billion shortly.1/3rd of the population i.e., 2.3 billion  people have no access to electricity. Moreover, world’s fuel needs are largely met by fossil fuels that are costly, finite and non eco-friendly as it pollutes the environment and are exhausting at a very faster rate. Hence conservation and tapping of energy from new sources is a much needed aspect all over the world. Renewable energy systems on a large scale are an important step for keeping national and international infrastructures intact, it's also important to understand the scalability of renewable energy solutions. It is widely known and accepted that wind and solar power are the most sustainable energy sources that is available in abundance. New improved innovative methods to harness their  power are much appreciated in the present decade. The major  predicament in extracting the power from wind is its variations in velocity. This paper explains a novel concept plan that harvests the wind power from moving trains. The idea of large scale energy harvesting from trains is very fascinating. India has about 63000 route kilometers of railways and 14,300 trains running every day. Indian railways can generate 1,481,000  MW    powers every day according to calculations [2], the alternative  pattern of wind energy produced around the train is very unique, if the wind is properly directed towards the blades, optimum energy can be generated. III.   P OWER POSSIBLITIES IN TRAIN  The train is an entire hub of energy source that can be harvested to supply power to the grid, distributed systems, standalone load supply or to power up the supply head for local trains and to meet the daily power requirements of the railway system. Indian railways spend 17 percent revenue on the fuel head which is roughly 15000 Crores (150 billion) per annum. There are three possible methods to produce power in a moving train, namely wind, solar and human excreta. When the train runs at an average speed of 50-60 km/hr  , it creates an air  pressure in the opposite direction. It compresses the air in the front of it and pushes it to its sides, thereby creating a vacuum at its rear and sides as it moves forward. To fill up this vacuum a mass of air flow rushes into the sides and rear of the train. The kinetic energy thus created by the wind flow induced by the train can be effectively utilized to generate power on a larger scale [1] [2]. 2014 International Conference on Control, Instrumentation, Energy & Communication 978-1-4799-2044-0/14/$31.00©2014IEEE 781   Next method is to integrate solar modules into traditional roof materials of train in order to generate clean energy [2]. Although this method promotes effective use of roof space, it does have its own disadvantages like dust deposition, high capital investment, extensive maintenance etc. The third method is to utilize the vast quantity of human waste to  produce energy instead of disposing it along the tracks. Bio degradable waste undergoes a process of anaerobic digestion after which they are subjected to induction heating. This  produces methane gas which can power the methanol fuel cells. This paper technically concentrates on power production by utilizing the wind velocity in moving trains by using set of wind turbines and air suction system to complement their standby operation at varying speeds of wind. IV.   B ASIC THEORY OF WIND TURBINE  W.J.M. Rankine and W E Fraude established simple momentum theory for application in the shipped propeller. Later, A.Betz of the institute of Gottingen used their concept to the windmill [4]. When wind flows across a wind mill, the flow is retarded in the downstream side of the windmill. The flow velocity through the windmill is usually called induced velocity and the flow velocity in the downstream is called wake velocity. V  ∞   According to Newton’s second law of motion the thrust developed in the axial direction of the rotor is equal to the rate of change of momentum i.e. Axial thrust  =  (     −       ) (1)  Where m is the mass of the air flowing through the rotor in unit time. Therefore the power produced is given by Ρ = m   (     −       )       (2) The rate of kinetic energy change in the wind is, ∆./  (    −    ) ( 3) Equating (2) and (3),                 (4) After simplifying equation (4), we obtain           (5) Gauert determined the identical expression in his actuator disc theory. Here the flow is assumed to occur along axial direction of the rotor and velocity is uniform over the swept area,  A  of the rotor. Since,      From the equation (2), Power extraction at the rotor,           (6)   Where,  ρ  is the density of air, substituting the value of    from equation (5) in the equation (6)                      (8) This can be rewritten as,   1     1          (9)           =    Therefore equation (9) becomes,     11    (10)  Now differentiating   of the equation (10) with respect to   and setting it to zero for maximum power, one obtains          (11) By simplifying, the expression for maximum power is obtained as,         (12)       ·    (13)     0.59 for ideal turbine   Here mass of air flowing through the blades has been assumed to be ideal. A German physicist Albert Betz concluded in 1919 that no wind turbine can convert more than 59.3% of the kinetic energy of the wind into mechanical energy to turn a rotor. This is known ad Betz limit [7].This is called power coefficient  C   P  .   V  a  A V  W 2014 International Conference on Control, Instrumentation, Energy & Communication 782  The C   P    value is unique to each turbine type and is a function of wind speed that the turbine is operated in. Hence we need to concentrate on improving the power efficiency or  power coefficient factor to improve the available maximum  power that can be converted into usable electricity.  A.   Wind power calculations without shrouds The energy available at the turbines at the cut in speed can  be calculated as follows   12  ·    Let’s assume the density of air  ρ  at 20 ◦ c  at sea level, 1.2 /     A =  л  R 2   =3.14×0.25 2 = 0.19 m 2   When the train runs at an average speed of 60 Km/hr.  V ∞   =16.7 m/sec  Hence by substituting the above values, we get the maximum work output as   314    By the time we take into account the other factors in a complete wind turbine system e.g. the gearbox, bearings, generator, and mechanical loading effect and so on, the power available is further reduced. In this paper we shall concentrate on improving the efficiency of the system by using ducted turbine, better gearbox system to reduce the mathematical loading effect on the turbine. V.   S YSTEMATIC DIAGRAM OF THE PROPOSED MODEL  When the train starts to move, the turbine starts to rotate, the converging section of the conduit increases the actual induced velocity of the wind over the blades. With the additional wind velocity and improved turbine design, there is a significant increase in the power that can be extracted from the turbine from the suggested design as shown in Fig. no.1. Figure 1. Proposed model The ducted and multi-bladed turbine overcomes many difficulties that are faced by the conventional models. This rotation is then transferred to a specially designed gearbox system that steps down the speed and increases the mechanical torque of the system to avoid mechanical loading effect over the turbine. This is then coupled to the rotor shaft of the alternator. Another feature of the proposed model is the  boosting system. The train speed is never a constant, it varies with places hence to have a constant input speed, and we use an auxiliary system that sucks the air, compresses it with a set of impellers and stores it in an agitation tank. When the speed of the train or the major input speed is below the desired level then a governor sets the boosting system to inject high pressure air through a gun nozzle over the turbine to maintain the speed of the turbine rotation. Hence large amount of power can be  produced, which can be connected to the grid or power up local loads. In the next section, the ducted turbine design, gearbox designs are detailed. VI.   W IND TURBINE DESIGN  The proposed model uses vertical axis wind turbine (VAWT). Reasons for selecting VAWT over horizontal axis turbine (HAWT) are given below. •   HAWT type turbines installed over the train obstructs the train’s forward motion by exerting a force against their propelling. •   HAWT also loads the generating system and cannot easily function at high velocities of the moving train. •   High thrust developed over horizontal axis turbines develops fatigue loads. •   The wind energy developed excessively during train’s  propulsion is concentrated on the surface thrust of horizontal axis turbines, so the useful power input is lost. •   The self starting capability and starting torque of VAWT is high •   One of the major advantages of VAWT in train implementation is that it can work on wind force from any direction, even when the train goes on reverse direction. Whereas HAWT requires shifting blades according to the direction of the wind, hence a system needed for this direction change is excluded in case of VAWT. Improvisation in technology has made VAWT designs much efficient and easy. Fig no. 2 shows the different VAWT turbines that can be used. Figure 2. Different VAWT turbine types proposed. We know that the total power obtained is governed by the    factor. BOOSTING SYSTEM To maintain the speed of the turbine by injecting compressed air DUCTED  TURBINE   AIR    TRAIN at 50-60  Km/hr    GEARBOX To step up torque ALTERNATOR   2014 International Conference on Control, Instrumentation, Energy & Communication 783             is the power coefficient that affects usable potential at the turbine. Hence the prime objective of this study is to improve this factor so as to increase the efficiency by using different turbine design. The remarkable feature of this paper is the use of encasing for the turbines called ducts or otherwise known as shrouds. A conical shaped duct is installed in the upstream inlet junction so as to obtain increased wind velocity at turbine inlet. An optimum multi-bladed convergent inlet, divergent outlet shrouded wind turbine design has aerodynamic advantages than the conventional bladed ones. A converged inlet duct is used to accelerate wind speed, this high dynamic pressure is exerted over the turbine blades and the high cut in pressure is incorporated with a diverged tail section along the downstream for adjusting the turbine exit pressure to get high input. The simulated results of pressure variation and air flow dynamics inside a shroud are shown in Fig no. 3. Figure 3. Simulation results of pressure variation and air flow dynamics inside a duct. The numerical and experimental results have proved that ducting decreases torque fluctuation of the vertical axis turbine significantly, especially at high tip speed ratio [6]. Frankovic and vrsaloric estimated that the efficiency of the ducted wind turbine could be raised 3.5 times while the area of the inlet was 3 times of minimum section. Hence researches, experimental and stimulated analysis study have been made to improve the    [8]. Power extracted from the air stream is given by               (14) Differentiating equating (1) with respect to     gives the maximum conditions.      3   15  Substituting in equation (1) gives maximum power output     3√ 3     16   We know     ·            (17)   Therefore the power coefficient is given by    √        (18)   The power output component is therefore a function of the duct velocity coefficient (    , the operating area and free stream velocity of the wind  ∞ .Experimental analysis [9] has shown    to be close to 1.0 Hence we find that ducting the turbine significantly increases the    factor thus increasing the power output of the turbine. The graphical representation is shown in Fig. no.4. Figure 4. Variation of power coefficient with pressure coefficient An optimum multi-bladed system is provided to increase the efficiency of the turbine effectively. It increases the starting torque, reduces cut in speed and provides better blade area to transfer the downstream wind [5]. Hydro dynamic experiments of ducting a vertical axis turbine shows that it can significantly increase the power output of the turbine by about 70% increase in power coefficient. Fluid dynamics remain same for hydro and aero dynamics. An important factor that contributes to the turbine design for implementing in train is the tip-speed ratio (   λ  ).  For any wind turbine, the tip-speed ratio is defined as the ratio of the speed at the tip of the turbine blade, to the wind speed. TSR is denoted by  λ , in terms of rotational speed (    ) of the turbine blade, wind speed (   ∞  )  and rotor radius  R . 2/60    Arifujjman calculated a model for C   P   as a function of λ   and generated a curve [10]. Statistical analysis showed that  predicted model for C   P   with fitted coefficient was acceptable. The resulting equation was found to be,   0.00044  0.012  0.097  0.20.1   Figure 5. Variation of Power coefficient with TSR 00.511.50 0.5 1 1.5 2 2.5 C   P δ   2014 International Conference on Control, Instrumentation, Energy & Communication 784  Hence plotting the values of  λ  will resulin Fig no.5. Therefore to obtain higher powewe chose the  λ  value for greater value of turbine, according to the generator’s requireSheng-Huuan Wang and Shih-Hsiung their study by computational fluid dynamiincreasing the number of blades increases the but plays a reducing role over the pAppropriate blade design is needed to m performance and power requirement. coefficient is found to decrease because of lowering of blade entrance velocity. As we uit is possible to avoid the blockage by effedesign process. Figure 6. Variation of C   T    and C  P    with  λ  for differe  The incident and stragger angle of the fidesigning an optimum incident angle of thecreating side space to allow more wind pduct as shown in Fig no.7. Thus we can  power coefficient and torque coefficiedesigning of the ducted turbine. Figure 7. Example of incident wind flow into th The opposing wind force that hinders tshaft is neglected with the help of the dealters the path of the wind flow. The simulcross-section where the wind flows at a t the curve shown r efficiency factor C   P    to design the ent. hen concluded in cs technique, that torque coefficient ower coefficient. tch the generator ere the power the blockage and se a ducted design   ctive and efficient ent number of blades. can be varied by duct conduit and ssing through the obtain maximum t by intelligent VAWT turbine he rotation of the lector duct which ated image of the velocity of 1m/s laminar flow in Ansys workbno.8. Figure 8. Simulated wind flow i VII.   M AXIMUM POWER AVAI Shrouding the turbine increthe incident induced velocity his study concludes that the pthe turbine resistance coefficie                     12        4 1    Therefore that the powconsiderably increased. We have increased the incand the power coefficient C   P     bincreasing the potential availabVIII.   G EA  The proposed model uses design to step down the availathe mechanical torque. If the tgeneration system, the electrichave a mechanical impact odirection, a blocking torqueindispensible to design a geatorque input to the rotor shaft. Figure 9. Gearbox design The design of the gearbox torque. Let’s assume that we this is given to a 4’’ diameter   ench software is shown in Fig the system (Wind velocity 1 m/s  ) LABLE AT THE DUCTED TURBINE  ases the velocity and pressure of     at the blades. C.J Lawn in essure coefficient is high when t K is low [11]. r output at the turbine is ident velocity at the turbine V  a   y efficient design process, thus e. BOX DESIGN  a special gearbox system that is le rotational speed and step up rbine is directly coupled to the al loading on the generator will er the turbine in the reverse will be produced so it is rbox system that steps up the showing their diameter ratios is very unique that steps up the obtain a high rpm prime input, ear and it is coupled to another DIAMETER   RATIO 2014 International Conference on Control, Instrumentation, Energy & Communication 785
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