Abstract:
A flywheel energy storage system for a vehicle, comprising a first shaft, a second shaft operatively coupled to the first shaft and to the vehicle&#39;s drivetrain, a flywheel operatively coupled to the first shaft, and a motor operatively coupled to the first shaft and electrically coupled to a power source, the motor being adapted to receive energy from the vehicle&#39;s electrical system and the flywheel energy storage system being adapted to transfer energy to the vehicle&#39;s drive system.

Description:
BACKGROUND 
       [0001]    The shrinking supply and rising cost of automobile fuel has stimulated development of technologies for increasing the fuel efficiency of motor vehicles. Such development has not only led to highly efficient internal combustion engines, but also to hybrid-drive vehicles that are powered by an electric motor at low speeds. In such vehicles, the electric motor is powered by a battery pack, while an internal combustion engine assists the electric motor when the vehicle encounters heavy load situations such as fast acceleration, high speed or hill climbing, or when the charge is depleted. The battery pack in such vehicles may be recharged by the internal combustion engine, or by energy recovery methods such as regenerative braking. 
         [0002]    Other automotive technologies designed to maximize fuel efficiency include electric-drive cars, wherein an electric motor directly drives the vehicle using energy from a battery pack, while an internal combustion engine may power a generator that provides energy to the electric motor when the battery pack is depleted. In such cars, the battery pack may be recharged using an external charging station, or by energy recovery methods such as regenerative braking. 
         [0003]    While advances in battery technology have led to more efficient, durable, and higher-capacity energy storage cells, inefficiencies are still inherent in converting mechanical energy into chemical energy for battery storage, and vice versa. Furthermore, electric motors are ill suited for driving situations having high or varying power loads. A means for storing energy while minimizing energy loss and providing rapid response to high-load situations is therefore needed. 
       SUMMARY 
       [0004]    According to at least one exemplary embodiment, a flywheel energy storage system is disclosed. The flywheel energy storage system may include an electric motor, a flywheel, a flywheel shaft, and a crankshaft. The electric motor and flywheel shaft, as well as the flywheel shaft and crankshaft may be coupled via gearsets. The crankshaft of the flywheel energy storage system may be coupled to the drivetrain of the vehicle. In operation, the flywheel energy storage system may store energy, providing it as necessary to the vehicle&#39;s drivetrain under certain conditions, for example, under rapid acceleration. The system may also recover energy from the drivetrain under certain conditions, for example, during regenerative braking. The flywheel energy storage system may thus serve to minimize energy loss and optimize power output in gasoline-powered, hybrid, and electric vehicles. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is an exemplary diagram of a flywheel energy storage system. 
           [0006]      FIG. 2  is an exemplary diagram of a vehicle including a flywheel energy storage system. 
       
    
    
     DETAILED DESCRIPTION 
       [0007]    Aspects of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the spirit or the scope of the invention. Additionally, well-known elements of exemplary embodiments of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention. Further, to facilitate an understanding of the description discussion of several terms used herein follows. 
         [0008]    As used herein, the word “exemplary” means “serving as an example, instance or illustration.” The embodiments described herein are not limiting, but rather are exemplary only. It should be understood that the described embodiment are not necessarily to be construed as preferred or advantageous over other embodiments. Moreover, the terms “embodiments of the invention”, “embodiments” or “invention” do not require that all embodiments of the invention include the discussed feature, advantage or mode of operation. 
         [0009]    Turning to  FIG. 1 , in one exemplary embodiment, a flywheel energy storage system  100  is provided. System  100  may include electric motor  102 , flywheel  104  coupled to flywheel shaft  106 , and crankshaft  108 . Electric motor  102  may include driving gear  110  coupled thereto. Also coupled to flywheel shaft  106  may be input gear  112  and output gear  114 . Crankshaft  108  may have crankshaft gear  116  coupled thereto. Driving gear  110  and input gear  112  may be coupled via a first chain  118  while output gear  114  and crankshaft gear  116  may be coupled via a second chain  120 . In one embodiment, driving gear  110  may be coupled directly to input gear  112 , and output gear  114  may be coupled directly to crankshaft gear  116 . 
         [0010]    Driving gear  110  and input gear  112  may be sized such that driving gear  110  is larger than input gear  112 . In one embodiment, the amount of gear teeth on driving gear  110  and the amount of gear teeth on input gear  112  may be related in a 2:1 ratio. For example, driving gear  110  may have  40  gear teeth, while input gear  112  may have 20 gear teeth. Output gear  114  and crankshaft gear  116  may be sized such that output gear  114  is larger than crankshaft gear  116 . In one embodiment, the amount of gear teeth on output gear  114  and the amount of gear teeth on crankshaft gear  116  may be related in a 2.52:1 ratio. For example, output gear  114  may have 48 gear teeth, while crankshaft gear  116  may have 19 gear teeth. Consequently, every complete revolution of driving gear  110  may result in 5.04 revolutions of crankshaft  108 . Therefore, for example, to spin crankshaft  108  at 750 revolutions per minute, electric motor  102  may spin at 149 revolutions per minute. The above-described ratios may therefore reduce energy consumption by electric motor  102 . 
         [0011]    In one exemplary embodiment, flywheel  104  may have a diameter approximately within the range of 10 to 12 inches, and a weight approximately within the range of 10 to 75 pounds. By varying these parameters, a desired angular moment of inertia for flywheel  104  may be achieved. The operating parameters of electric motor  102  may also be varied as desired; for example, in one embodiment, electric motor  102  may generate horsepower approximately within the range of 0.33 horsepower to over 2.25 horsepower. Motor  102  may also have a maximum revolutions-per-minute limit approximately within the range of 1800 rpm to 5500 rpm. 
         [0012]    In one exemplary embodiment, the coupling between input gear  112  and flywheel shaft  106  may be a one-way overrunning-type clutch. Consequently, when the rotational speed of flywheel  104  and flywheel shaft  106  is greater than the rotational speed of motor  102  and driving gear  110 , damage to motor  102  may be avoided. In another exemplary embodiment, flywheel  104  may be coupled to flywheel shaft  106  via a clutch that may be engaged when transmission of power to or from the flywheel is desired. As a result, energy loss due to friction between the components of flywheel energy storage system  100  may be minimized. In another exemplary embodiment, flywheel  104  may reside within a vacuum chamber to further minimize energy loss due to air resistance between flywheel  104  and the environment. 
         [0013]    Turning to  FIG. 2 , flywheel energy storage system  100  may then be coupled to drive system  202  of vehicle  200 . In one embodiment, flywheel energy storage system  100  may be coupled to drive system  202  of the vehicle in a linear fashion. For example, crankshaft  108  may be coupled to the driveshaft  204  of engine  206 . Engine  206  may be an internal combustion engine, an electric motor, or a hybrid drive system. Coupling  208  between crankshaft  108  and engine  202  may include a friction plate clutch-type apparatus, a fluid coupling such as a torque converter, or any other coupling known to one having ordinary skill in the art. Additionally, coupling  208  may include transmission  210 , which may be a standard manual transmission, a planetary-gear automatic transmission, a continuously variable transmission, or any other power transmission system known to one having ordinary skill in the all. In one embodiment, transmission system  210  may manage the proportion of power transferred to drive system  202  of vehicle  200  by flywheel energy storage system  100 . Flywheel energy storage system  100  may also be operatively coupled to chemical energy storage system  212 , which may consist of any battery technology known to one having ordinary skill in the art. Additionally, chemical energy storage system  212  may be recharged by alternator  214  or regenerative braking system  216 . 
         [0014]    In operation, motor  102  may spool up flywheel  104  such that the rotational speed of flywheel  104  is within a desired speed range. For example, electric motor  102  may operate at approximately 500 rpm, which may translate to flywheel  104  rotating at approximately 1000 rpm, may result in crankshaft  108  rotating at approximately 2,520 rpm. At this rate, vehicle  200  may be traveling at approximately 70 mph, depending on the final drive ratios of the vehicle. In one embodiment, motor  102  may be powered by electrical current from battery system  212 . Motor  102  may also be powered by electrical current generated by alternator  214  or regenerative braking system  216 . Powering the motor directly from alternator  214  or regenerative braking system  216  presents an advantage as it may avoid the energy loss and detriment to battery health inherently present when the battery is subjected to charge and discharge cycles. In another embodiment, motor  102  may include a turbine  218  for partially or completely facilitating the rotation of motor  102 . Turbine  218  of motor  102  may be powered by compressed air generated by a belt-driven impeller or the like. Turbine  218  may be coupled to motor  102  via a gearset designed to maximize power transferred to motor  102 . 
         [0015]    Once flywheel  104  is rotating at the desired rotational speed, flywheel energy storage system  100  may be engaged, via transmission  210  or other coupling  208 , to transmit power to drive wheels  220  of vehicle  202 . Engagement may be facilitated at driver request or via an engine-management computer or the like. For example, in a hybrid or electric-powered vehicle, flywheel  104  may be engaged when there is a sudden demand for increased power. Flywheel  104  thereby assists the electric engine in propelling vehicle  200  and minimizes peak power loads on the electric engine and facilitating efficient operation of the electric engine. In another embodiment, system  100  may be engaged to assist a vehicle&#39;s internal combustion engine, providing additional power to the drive system while facilitating keeping the internal combustion engine at an efficient operating speed. 
         [0016]    The foregoing description and accompanying figures illustrate the principles, preferred embodiments and modes of operation of the invention. However, the invention should not be construed as being limited to the particular embodiments discussed above. Additional variations of the embodiments discussed above will be appreciated by those skilled in the art. 
         [0017]    Therefore, the above-described embodiments should be regarded as illustrative rather than restrictive. Accordingly, it should be appreciated that variations to those embodiments can be made by those skilled in the art without departing from the scope of the invention as defined by the following claims.