Patent Publication Number: US-2011068648-A1

Title: Energy storage and generation system for an electrically powered motorized vehicle

Description:
CLAIMS OF PRIORITY 
     Benefit is claimed under 35 U.S.C. 119(e) to U.S. Provisional Application Ser. No. 61162238, entitled “FLYWHEEL POWER SYSTEM IN AN ELECTRIC VEHICLE” by Anil Ananthakrishna, filed on Mar. 20, 2009, which is herein incorporated in its entirety by reference for all purposes. 
    
    
     FIELD OF TECHNOLOGY 
     Embodiments of the disclosure generally relate to the field of electrically powered motorized vehicles, and more particularly to an energy storage and generation system in an electrically powered motorized vehicle. 
     BACKGROUND 
     The need to conserve non-renewable energy resource and clean-running vehicles has been echoing for many years. This is due to constant increase in gasoline fuel prices, the exhaustion of the gasoline fuel resources and also other environmental effects by internal combustion exhaust. In general, the need to conserve natural resources, to avoid contamination of the environment as well as economic factors, has led to an increasing emphasis on the efficient use of energy, its collection and storage from renewable sources and making pollution-free operation of on road vehicles and other powered equipments. In the automobile industry, many attempts have been made in this regard to develop an effective free-ranging electrically powered motorized vehicle, however, the success rate in achieving the same is very low due to certain limitations. 
     In a conventional electrically powered motorized vehicle, the use of rechargeable storage batteries restricts the available power output and range of the vehicle due to dead weight of such batteries. Moreover, the costs of batteries are relatively high which in turn increases the cost of the vehicle. Further, the battery life is another concern as it impacts the economy of the battery powered vehicle, as the replacement cost of the battery is another essential factor. 
     In addition, the conventional flywheels used in the electrically powered motorized vehicles which stores energy mechanically in the form of kinetic energy have low specific energy. There are safety concerns associated with said flywheels due to their high speed rotor and the possibility of it breaking loose and releasing all its energy in an uncontrolled manner. The conventional flywheels are a less mature technology than chemical batteries and the current cost is too high to make them competitive in the market. 
     However, the flywheels are the best energy storing device which can be employed in regenerative braking systems. The approach conventionally taken has been to add a flywheel device to a drive system is prone to said limitations. In addition, the conventional materials like iron cast, steel and other metal alloys used for manufacturing flywheels and also the coupling of the flywheel separately to the vehicle crankshaft amounts to adding weight to the vehicle. Hence, this may lead to increase in the cost of assembling the vehicle, its maintenance and also decrease in the efficiency. 
     SUMMARY 
     This Summary is provided to comply with 37 C.F.R. §1.73, requiring a summary of the invention briefly indicating the nature and substance of the invention. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 
     An energy storage and generation system for an electrically powered motorized vehicle is disclosed. In one aspect, an energy storage and generation system for an electrically powered motorized vehicle includes a stator having field coils and one or more sensors which are provided on the inner periphery of the stator. The energy storage and generation system further includes a rotor having permanent magnets with N and S poles arranged alternately in a circumferential direction on the outer periphery to face the inner periphery of the field coils. Further, rotor houses batteries of the electrically powered motorized vehicle. The plurality of batteries is housed in the rotor for adding a rotational mass to the rotor. 
     The energy storage and generation system also includes a drive control unit connected to one or more sensors for obtaining feedback information on the magnetic field polarity of the permanent magnets of the rotor and to the field coils for generating magnetic field in the field coils of the stator in response thereto to rotate the rotor. The rotation of the rotor stores rotational kinetic energy due to the dead weight of the plurality of batteries which is applied to the power wheels of the electrically powered motorized vehicle to propel the electrically powered motorized vehicle. 
     In another aspect, a flywheel assembly for generating a rotational kinetic energy using a plurality of batteries of an electrically powered motorized vehicle includes a shaft defining an axis of rotation, and a fixed member having field coils and one or more sensors which are provided on the inner periphery of the fixed member. Further, the flywheel assembly includes a rotary member carried on the shaft. The rotary member carries permanent magnets with N and S poles arranged alternately in a circumferential direction on the outer periphery to face the inner periphery of the field coils. The rotary member also houses the plurality of batteries of the electrically powered motorized vehicle. The plurality of batteries is housed in the rotor for adding a rotational mass to the rotor. 
     The flywheel assembly also includes a drive control unit connected to one or more sensors for obtaining feedback information on a magnetic field polarity of the permanent magnets on the rotary member and to the field coils for generating magnetic field in the field coils of the fixed member in response thereto to rotate the rotary member. The rotation of the rotary member stores rotational kinetic energy due to the dead weight of the plurality of batteries which in turn is applied to the power wheels of the electrically powered motorized vehicle to accelerate the electrically powered motorized vehicle to a speed equal to a predetermined vehicle speed from a standing start. 
     Other features of the embodiments will be apparent from the accompanying drawings and from the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE VIEW OF THE DRAWING 
         FIG. 1  illustrates cross-sectional views of an energy storage and generation system for an electrically powered motorized vehicle, according to one embodiment. 
         FIG. 2  illustrates a schematic diagram of a combinational system implemented in an electrically powered motorized vehicle, according to one embodiment. 
         FIG. 3  illustrates a schematic diagram of an exemplary powering system to the combinational system of  FIG. 2 , according to one embodiment. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     An energy storage and generation system for an electrically powered motorized vehicle is disclosed. The following description is merely exemplary in nature and is not intended to limit the present disclosure, applications, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
       FIG. 1  illustrates cross-sectional views of an energy storage and generation system  100  for an electrically powered motorized vehicle, according to one embodiment. The energy storage and generation system  100  includes a stator  102 , a shaft  104 , a rotor  106  carried on the shaft  104 , and a drive control unit  116 . The stator  102  consists of field coils  108  provided on the inner periphery of the stator  102 . The stator  102  is mounted on the chassis of the electrically powered motorized vehicle and may be electric powered. 
     The rotor  106  consists of permanent magnets  112  with N and S poles arranged alternately in a circumferential direction on the outer periphery of the rotor  106  to face the inner periphery of the field coils  108 . The inner portion of the rotor  106  houses batteries  114  for the electrically powered motorized vehicle. For example, the batteries  114  may be single chemistry batteries or hybrid chemistry batteries which stores chemical potential energy. The batteries  114  housed by the rotor  106  are having predetermined geometrical shapes and dimensions in order to achieve an agglomerate mass. This agglomerate mass contributes to the rotating mass of the rotor  106 . 
     The stator  102  and the rotor  106  are mounted on a common axis. Further, the rotor  106  is mounted for rotation within the stator  102  in such a way that the field coils  108  of the stator  102  encircle the permanent magnets  112  of the rotor  106 . In the energy storage and generation system  100 , sensors  110  are placed in a fixed position on the inner periphery of the stator  102  and adjacent to the path of rotation of the rotor  106  for sensing alignment of N and S poles of the permanent magnets  112  of the rotor  106  with the field coils  108  of the stator  102 . For example, the sensors  110  may be optical sensors or magnetic sensors of a Hall effect type. 
     The sensors  110  are coupled to the drive control unit  116  for providing feedback information of the magnetic field polarity of the permanent magnets  112  on the rotor  106 . The magnetic field polarity of the permanent magnets  112  is determined based on the alignment of the N and S poles with the field coils  108  of the stator  102 . The drive control unit  116  is connected to the field coils  108  for generating magnetic field in the field coils  108  based on the signals from the sensors  110 . The magnetic field in the field coils  108  results in commutation of the permanent magnets on the rotor  112  thereby rotating the rotor  106 . The drive control unit  116  and the field coils  108  are powered using the power supplied by an external power source or the batteries  114 . The external power source may be a power grid connected to a 110, 220V wall socket with suitable power converters. 
     In operation, the drive control unit  116  rotates the rotor  106  up to a predetermined maximum vehicle speed by energizing the field coils  108  of the stator  102 . Once the predetermined maximum vehicle speed is attained, the electric power is cut-off, thereby allowing the rotor  106  to free wheel. The rotor  106  free wheels for longer period of time due to the dead weight of the batteries  114 , thereby storing large amounts of rotational kinetic energy. 
     The rotational kinetic energy stored in the spinning rotor  106  is utilized to overcome inertial forces and to propel the electrically powered motorized vehicle. In other words, the rotational kinetic energy thus stored supplies tremendous amount of initial torque to the power wheels to accelerate the electrically powered motorized vehicle to a predetermined vehicle speed from the standing start. It is appreciated that, the rotational kinetic energy is transformed to a transmission system (e.g., a fixed ratio transmission system or a continuously variable transmission system) and then to the power wheels via a differential mechanism as will be illustrated in  FIG. 2 . 
     The rotational kinetic energy generated using the dead weight of the batteries  114  eliminates need for instantaneous starting current required for acceleration and thus conserves the chemical potential energy of the batteries  114 . Thus, the energy storage and generation system  100  described herein serves to absorb the peak power requirements, thereby leveling the load on the batteries  114 . 
     Once speed of the electrically powered motorized vehicle becomes equal to the predetermined vehicle speed, the chemical potential energy from the batteries  114  is supplied to drive the electrically powered motorized vehicle. Further, the stator  102  and the rotor  106  can also function as a generator mechanism with required electrical and electronic circuitry configured within the drive control unit  116 . In one embodiment, when the rotor  106  is spinning without being connected to provide output mechanical traction, the generator mechanism may generate electrical power. The electric powered thus generated by the generator mechanism can be used to recharge the batteries  114 . 
     In another embodiment, when the electrically powered motorized vehicle is intended to reduce speed, the generator mechanism depletes the kinetic energy from the rotor  106  and generates electric power which in turn recharges the batteries  114 . In other words, the generator mechanism generates electrical power based on inertia of the power wheels generated on requirement of reducing speed and hence stores chemical potential energy in the batteries using the electrical power. It can be noted that, during operation of the electrically powered motorized vehicle, when the rotor  106  is up to speed, the rotational kinetic energy is primarily applied to the power wheels for propulsion rather than to charge the batteries  114  using the generator mechanism. 
       FIG. 2  illustrates a schematic diagram of a combinational system  200  implemented in an electrically powered motorized vehicle, according to one embodiment. The combinational system  200  includes the energy storage and generation system  100 , drag and draw compensation mechanisms  202  and  204 , a clutch actuation mechanism  206 , a transmission system and differential mechanism  208 , and an electric hub motor  210  in power wheels  212 . 
     As shown in  FIG. 2 , the rotational kinetic energy stored in the energy storage and generation system  100  is transmitted to the electric hub motor  210  in the power wheels  212 . The rotational kinetic energy to the electric hub motor  210  is transmitted through the clutch actuation mechanism  206  and the transmission system and differential mechanism  208  as will be described in greater detail below. 
     The energy storage and generation mechanism  100  is coupled to a set of drag and draw compensation actuators  214  and  218  which consists of the drag and draw compensation plates  216  and  220  on either sides. The drag and draw compensation actuator  218  is coupled to the clutch actuation mechanism  206 . The clutch actuation mechanism  206  can be electric powered, hydraulic powered or pneumatic powered and is connected to the clutches  222 . The clutches  222  are connected to the differential gears through a continuous variable transmission system or a fixed ratio transmission system. 
     The combinational hybrid of the transmission system and differential mechanism  208  and the electric hub motor  210  is embedded in the power wheels  212  to maximize regenerative braking and cope with road load requirements while driving. The transmission system and differential mechanism  208  is made up of gears, belts, pulleys, spheres, hydraulic system, or pneumatic system embedded into any or all the power wheels  212  of the electrically powered motorized vehicle or mounted separately and connected to the driven power wheels. 
     In general, the combinational system  200  provides power to the electrically powered motorized vehicle using the transmission system and differential mechanism  208 . It is appreciated that, the transmission system and differential mechanism  208  provides multiple torque ratios at varied gradients and load conditions so that the torque and speed of the electrically powered motorized vehicle are maintained at optimal levels. It can be noted that, the batteries  114  in the rotor  106  are supported through a dynamic stabilizing platform that takes care of drag and draw forces of the energy storage and generation system  100 . 
     The drag and draw forces may occur when there is a change in directional path of the electrically powered motorized vehicle. The drag and the draw compensation mechanisms  202  and  204  contain ball bearings, spheres and rollers with dampers to achieve stabilization by controlling the drag and draw forces. In one embodiment, the combinational system  200  achieves stabilization by positioning the drag and draw compensation plates  216  and  220  in the desired position of opposition to control draw or drag forces. The combinational system  200  thus optimizes energy surge requirements during an initial startup of the electrically powered motorized vehicle. 
       FIG. 3  illustrates a schematic diagram of an exemplary powering system  300  to the combinational system  200  of  FIG. 2 , according to one embodiment. When the electrically powered motorized vehicle is stand still, the drive control unit  116  is powered initially by a power grid  302  which is connected to a 110, 220 V wall socket with suitable power converters. Using this power, the rotor  106  is being rotated till a predetermined vehicle speed is attained. As described above, the rotor  106  containing the batteries  114  is then allowed to free wheel. 
     As a result of free wheeling, the rotor  106  stores a large amount of rotational kinetic energy due to dead weight of the batteries  114 . The rotor  106  acts as a flywheel utilizing the battery mass and store large amounts of rotational kinetic energy as well as chemical potential energy. The rotational kinetic energy is utilized for initial propulsion of the electrically powered motorized vehicle. For instance, an electric car may be propelled forward by releasing the clutch and transferring the kinetic energy from the flywheel to power wheels  212  of the car. 
     It can be noted that, initial propulsion of the electrically powered motorized vehicle may not drain the batteries  114 , instead would use the rotational kinetic energy stored using the mass of the batteries  114 . Thus, the high instantaneous starting current normally required for acceleration would be avoided and improve the battery performance. The utilization of the kinetic energy during initial start up eliminates the power requirements from the batteries  114  which aids in maintaining the batteries  114  from discharging of heavy currents in a short span of time. 
     One can envision that, the above-described energy storage and generation system  100  can be implemented as a flywheel assembly in the electrically powered motorized vehicle for storing kinetic energy using the dead weight of the batteries and chemical potential energy of the batteries. Also, one can envision that, the above-described energy storage and generation system  100  can be used in any motive power application. 
     In various embodiments, the energy storage and generation system  100  described in  FIGS. 1 through 3  enables storing of rotational kinetic energy and chemical potential energy. Thus, the combinational system  200  helps optimize energy storage for a pure electric drive and integrated electric hybrids. The combinational system  200  also helps optimize energy surge requirements during an initial startup of the electrically powered motorized vehicle. Further, the powering of the field coils  108  of the stator  102  at appropriate required conditions helps maintain the battery performance at optimum levels. Moreover, in the energy storage and generation system  100 , it is possible to withdraw large amount of energy in a far shorter time than with traditional chemical batteries. 
     The above-described energy storage and generation system  100  have high turn-around efficiency and the potential for very high specific power compared with the batteries. In addition, the above-described energy storage and generation system  100  have very high output potential and relatively long life and are relatively unaffected by temperature extremes. 
     It will be recognized that the above described invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the disclosure. Thus, it is understood that, the invention is not to be limited by the foregoing illustrative details, but it is rather to be defined by the appended claims.