Abstract:
An auxiliary power supply includes a battery, a motor-generator and an inertial energy storage mass. The motor-generator draws power from the inertial energy storage mass to drive the motor-generator thereby creating electricity. As inertial energy is depleted from the drive mechanism during use, a battery recharges the inertial energy storage mass. The inertial energy storage mass includes a series of flywheels each having smaller disks contained therein. The disks translate radially with respect to the flywheels working with gravity to provide drive power to the motor-generator.

Description:
TECHNICAL FIELD 
       [0001]    The present invention pertains to auxiliary power supply systems, and more particularly to auxiliary power supply systems having a plurality of energy storage devices where at least one of the energy storage devices stores inertial energy. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are numerous applications that exist for auxiliary power sources that can operate in the event that conventional utility power has been interrupted. For example, computer systems need to be isolated from short-term drop-outs and switching noise that commonly occur on utility power lines. Homeowners require backup systems to power furnaces or air conditioners. Office buildings also require backup power to maintain various systems in the event of a utility power outage. Hospitals are yet another example where auxiliary power is critical to maintaining life support equipment. 
         [0003]    One type of auxiliary power source includes large multi-cell DC batteries that typically have a limited backup time measured in units of hours depending on the size of the connected load. Another type of auxiliary power source utilizes electromechanical systems that include an engine connected to an electrical generator. These electromechanical devices require fuel to keep the engine rotating resulting in a system that produces harmful exhaust gases. These systems may also generate a significant amount of noise undesirable for many situations. The amount of time that any of these systems may operate without being recharged or refueled is relatively limited. 
         [0004]    What is needed is an auxiliary power supply that can supply power for an extended period of time without the detriment of both noise and air pollutants, and the expense of costly fuels. The embodiments of the subject invention obviate the aforementioned difficulties by providing a highly efficient auxiliary power supply that operates from the kinetic energy stored in an inertial energy storage device. 
       BRIEF SUMMARY 
       [0005]    A flywheel is a heavy rotating disk used as a repository for angular momentum. Flywheels can be used by small motors to store up energy over a long period of time and then release it over a shorter period of time, temporarily magnifying its power output for that brief period. The kinetic energy stored in a rotating flywheel is represented by the equation 
         [0000]        E= ½ Iω   2    
         [0000]    where I is the moment of inertia of the mass about the center of rotation and ω (omega) is the angular velocity in radian units. A flywheel is more effective when its inertia is larger, as when its mass is located farther from the center of rotation either due to a more massive rim or due to a larger diameter. The similarity of the above formula will be noted to that of the kinetic energy formula E=½mv 2 , where linear velocity v is comparable to the rotational velocity and the mass is comparable to the rotational inertia. 
         [0006]    In accordance with the embodiments of the invention an auxiliary power supply system supplies electrical power to an associated load and includes a power monitoring device that can regulate the transmission of electrical power to the associated load. An associated external power supply, such as power supplied from conventional power lines, is also communicated to deliver power to the associated load through the power monitoring device. The auxiliary power supply system may also include first and second energy storage devices communicated to the power monitoring device, wherein the power monitoring device cycles between supplying auxiliary power from the first energy storage device and the second energy storage device. 
         [0007]    In one embodiment of the subject invention the first energy storage device may store electrical energy and may comprise a battery having one or more cells. Additionally, the second energy storage device may store a different type of energy from that of the first energy storage device, which may be inertial energy. 
         [0008]    One aspect of the embodiments of the subject invention may include a generator, which may be connected between the second energy storage device and the power monitoring device. The generator may be a motor generator operable to function in one mode as an electrical generator and in another mode as an electrical motor. 
         [0009]    Another aspect of the embodiments of the subject invention may include a transmission operatively connected between the second energy storage device and the power monitoring device, wherein the transmission may include a gearbox having one or more planetary gears. 
         [0010]    In yet another aspect of the embodiments of the subject invention may the second energy storage device may include a frame, an inertial energy storage portion having a fixed mass M operatively connected to the frame and an output shaft rotatably connected with respect to the frame, the output shaft being coupled to the inertial energy storage portion, which may include one or more flywheels having a plurality of disks rollingly connected with respect to each of the flywheels. 
         [0011]    In one embodiment the flywheels may have an offset center of gravity with respect to an axis of rotation caused by the placement and/or movement of the disks within the flywheels respectively. 
         [0012]    One aspect of the auxiliary power supply system according to the embodiments of the subject includes a power monitoring device that may cycle between supplying auxiliary power from the first energy storage device and the second energy storage device when the second energy storage device falls below a threshold level of inertial energy and more particularly below a threshold rotational speed. 
         [0013]    Still another aspect of the auxiliary power supply system according to the embodiments of the subject includes a first energy storage device that is operable to recharge the second energy storage device. 
         [0014]    According to the embodiments of the subject invention an inertial energy storage device may include a frame, an output shaft rotatably connected with respect to the frame, an inertial energy storage portion having a fixed mass M coupled to the output shaft, wherein the inertial energy storage portion includes, at least a first flywheel fixedly connected with respect to the output shaft and a plurality of disks rollingly connected with respect to the at least a first flywheel. 
         [0015]    One aspect of the inertial energy storage device according to the embodiments of the subject invention includes at least a first flywheel having one or more slots fashioned on an interior of the at least a first flywheel that respectively receive the disks. 
         [0016]    Another aspect of the inertial energy storage device according to the embodiments of the subject invention includes at least a first flywheel that comprises at least a first pair of flywheels, where each of the plurality of disks includes an axle fixedly connected to the disks respectively, wherein the axles are rollingly connected with respect to the at least a first pair of flywheels. 
         [0017]    Yet another aspect of the inertial energy storage device according to the embodiments of the subject invention includes a plurality of brake members fixedly connected with respect to at least a first flywheel for arresting motion of the rollingly connected disks. 
         [0018]    Still another aspect of the inertial energy storage device according to the embodiments of the subject invention includes the plurality of flywheels that is phase shifted with respect to the remaining flywheels. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a schematic representation of a power supply system for supplying power to a load according to the embodiments of the invention. 
           [0020]      FIG. 2  is a perspective view of an inertial energy storage device according to the embodiments of the invention. 
           [0021]      FIG. 3  is an end view of the flywheel of the inertial energy storage device according to the embodiments of the invention. 
           [0022]      FIG. 4  is a perspective view of a disk according to the embodiments of the invention. 
           [0023]      FIG. 5  is a side view of a flywheel according to the embodiments of the invention. 
           [0024]      FIG. 6  is a side view of a flywheel according to the embodiments of the invention. 
           [0025]      FIG. 6   a  is a side view of a flywheel according to the embodiments of the invention. 
           [0026]      FIG. 7  is a schematic representation of a power monitoring device for controlling the supply of power to a load according to the embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the invention only and not for purposes of limiting the same,  FIG. 1  shows an auxiliary power supply system  1  for supplying electrical power as depicted within the dashed lines. The power supply system  1  may comprise a series of subsystems  2  interconnected to function in the presently described manner. The subsystems  2  may include a first energy storage device  4 , which may be an inertial energy storage device  4 ′. By inertial energy storage device it is meant a repository that stores energy in the form of a moving mass. The inertial energy storage device  4 ′ may be interconnected to an electrical generator  8  through a transmission  6 , which in one embodiment may be a planetary gear box  6 ′. The inertial energy storage device  4 ′ may alternatively be connected to the electrical generator  8  via other torque-speed converting means including but not limited to torque converters and fixed ratio gear boxes. However, any means may be used to connect the inertial energy storage device  4 ′, the transmission  6  and the generator  8  as is appropriate for use with the embodiments of the subject invention. Power may be drawn from the inertial energy storage device  4 ′ as during a power outage and directed to the electrical generator  8 . The generator  8  will produce electrical power for supplying energy to a second energy storage device  13  and/or a designated load depicted generally at  15 . The second energy storage device  13  may comprise one or more electrical energy storage cells as may be found in a battery  13 ′, of which the battery  13 ′ may also be connected to the load  15 . 
         [0028]    In this manner, electrical power may be supplied by the power supply system  1  to a load  15  from the battery  13 ′ and/or the generator  8 . In other words, power supplied to the load  15  may be drawn from either of the first or second energy storage devices. The battery  13 ′ may be connected in parallel to a primary power source  18 . Such power sources  18  are readily known in the art and may include electrical energy supplied from a utility power company through conventional transmission lines. In the event that primary power has been interrupted, a power monitoring device  22  may be incorporated to switch power sources thus maintaining a continuous supply of power to the load  15 . In one embodiment, the power monitoring device  22  may engage the battery  13 ′ and/or the generator  5  in regulating the flow of energy between the devices and the associated load  15 . In particular, the power monitoring device  22  may monitor the amount of energy remaining in each source and selectively engage the battery  13 ′ and/or the generator  5  to regulate the flow of energy from the power supply system  1 . Accordingly, the power supply system  1  may draw power from one energy storage device and charge the other energy storage device, while supplying power to the load  15 , as will be discussed in detail in a subsequent paragraph. 
         [0029]    With reference now to  FIG. 2 , the inertial energy storage device  4 ′ may include a series of flywheels  20  mounted within a flywheel housing  21 , where each flywheel  20  has a characteristic mass M. The flywheels  20  may be fixedly connected to a shaft  23  extending through a center of the flywheel  20 . One shaft  23  may connect all of the flywheels  20  together into a single rotating unit. Accordingly, the single rotating unit will have a mass equal to the sum of the masses of the individual components, i.e. the flywheels  20  and shaft  23 . The shaft  23  may subsequently be rotatably connected with respect to the flywheel housing  21  via bearings  25 . In one embodiment, the bearings  25  may be magnetic bearings  25 ′, which incorporate non-contacting technology. The shaft  23  may be received within the magnetic bearings  25 ′ and may rotate therein without substantial frictional losses thereby helping to preserve the inertial energy stored in the mass of the flywheels  20  for conversion by the generator  8  as will be described further in a subsequent paragraph. While the aforementioned embodiment discusses the use of bearings  25  and in particular magnetic bearings  25 ′, it is to be construed that any means may be chosen to rotatably connect the shaft  23  to the flywheel housing  21  that significantly limits the loss of inertial energy stored in the flywheels  20 . In addition to the use of magnetic bearings  25 ′, the housing  21  may be evacuated of air and/or other gases to limit losses due to windage. A person of ordinary skill in the art will understand the resistance caused by an object moving through ambient conditions, and more specifically the density of air at a particular elevation level. Accordingly, the housing  21  may be hermetically sealed substantially preventing air from entering the vacuum of the housing  21 . 
         [0030]    With continued reference to  FIG. 2  and now to  FIGS. 3 and 4 , the flywheels  20  may be laterally spaced along the length of the shaft  23  in pairs or sets  30  each containing two flywheels  20 . Each set  30  may function as supports for a plurality of disks  50  rotatably connected between the pair of flywheels  20 . The disks  50  may each be fixedly mounted to an axle  52  that spans the distance between the pair of flywheels  20 . As such, the length of the axles  52  may correspond to the spacing of the flywheels  20 . Any length may be selected with sound engineering judgment as is appropriate for use with the embodiment of the subject invention. It will be readily seen that the disks  50  add to the mass of the inertial energy storage device  4 ′ thereby increasing the amount of inertia that can be stored in the power supply system  1 . In this manner, each pair of flywheels  20  may include a set of disks  50  connected therebetween. In one embodiment, the inertial energy storage device  4 ′ may include eight (8) flywheels thus comprising four (4) pairs or sets of flywheels  20 . To facilitate rotation of the disks  50  between the sets of flywheels  20 , the flywheels  20  may be fashioned having one or more races  60  onto which the respective ends  53  of the axles  52  may roll as will be discussed in detail below. In this manner, the disks  50  are connected to rotate with respect to the flywheels  20  and the shaft  23 . The disks  50  may be fashioned having guide ends  55  that align the axles  52  onto their respective races  60 . In one embodiment, the guide ends  55  may be tapered to keep the disk from moving laterally with respect to the flywheels  20 . 
         [0031]    With continued reference to  FIGS. 3 and 4  and now to  FIGS. 5 and 6 , a flywheel  20  may be constructed having a plurality of slots  62  fashioned on an interior of the flywheel  20 . The slots  62  may have a generally elliptical shape, having a major and a minor axis, with curved surfaces that may function to receive an axle  52 . In this manner, the curved surfaces of the slots  62  may form races  60  on which a disk  50  may rotate. In one embodiment, the flywheels  20  each include seven (7) slots  62  spaced equidistantly around the interior of the flywheel  20  and seven (7) corresponding disks  50 . While the current embodiment describes the flywheels  20  having seven (7) slots  62 , any number of slots  62  and any angular orientation of the slots  62  may be included as are appropriate for use with the embodiments of the subject invention. As the flywheels  20  rotate with the shaft  23 , the disks  50  may translate or roll along the races  60  as the flywheels  20  rotate. In other words, upon reaching a specific point in the cycle of the rotating flywheel  20 , a disk  50  will be pulled downward by gravity thus initiating the rotation of that particular disk  50 . In this manner, gravity causes the disks  50  to move downward in an arcuate trajectory as guided by the configuration of the slots  62 . For example,  FIG. 6  depicts point masses M 1 -M 7  in each of the respective slots  62  representing each of the disks  50 . It is to be understood that the point masses represent each of the disks respectively and are used in the examples for illustrative purposes. A disk  50 , represented by point mass M 1 , is positioned at one end of the corresponding slot  62 . It will be readily seen that as the flywheel  20  is rotating in the direction R 1 , work is being done against gravity by the flywheel  20 . The disk  50  in this position is stationary with respect to the flywheel  20 . As the flywheel  20  continues to rotate, the slot  62  crosses a horizontal plane. This position is depicted by point mass M 2 , representing another disk  50 . As such, gravity pulling the disk  50  downward, initiates the movement of the disk  50  along the arcuate trajectory A as guided by the slot  62 . The disk  50  continues along this trajectory, exemplified by point mass M 3 , until it reaches the distal end of the slot  62 , shown by point mass M 4 . Once the disk  50  reaches this position momentum continues to rotate the disk  50  seated in the vertex of the slot  62  until the angle of the slot  62  once again allows gravity to pull the disk  50  downward further rotating the disk  50  in the direction R 2 . It is noted here that the races  60  and the guides  55  of the axle  52  may be fashioned having smooth surfaces so as to minimize frictional losses between the axle  52  and the flywheel  20 . In one embodiment, the surface finish of the slots  62  and the guides of the axles  52  may be substantially 15. However, any surface finish may be used that minimizes frictional losses as chosen with sound engineering judgment. Thus, as the flywheel  20  rotates, in the direction R 1 , each of the successive disks  50  will be drawn upward by the flywheel  20  through approximately one quadrant of the cycle and downward by gravity through the remainder of the cycle. It will be appreciated by a person of ordinary skill in the art that rotation of the flywheels  20  will produce a centrifugal force that drives the disks  50  radially outward. If the radially outward force is sufficiently large enough, the disks  50  will be prevented from rolling along their respective races  60 . As such, a rotational speed of the flywheels  20  may be chosen such that the centrifugal force against the disks  50  is small enough to allow the disks  50  to roll through their respective slots  62 . In one embodiment, the designated rotational speed of the flywheels may be less than 30 RPMs. More specifically, the designated rotational speed may be between 20 and 30 RPMs and more particularly may be substantially 25 RPMs. 
         [0032]    With reference to  FIGS. 4 through 6   a , as mentioned above, disk  50  upon reaching the distal end of the slot  62 , as exemplified by point mass M 4 , may spin in place until the flywheel  20  rotates further to the point where the disk  50  once again is drawn by gravity along the slot  62 . A friction reducing device such as a bearing  67  may be placed proximate to the end  65  of the slot  62  so as to receive the guide  55  of the disk  50 . In this manner, as the disk  50  is rotating in the position at the end  65  of the slot  62  the bearing  67  may receive the guide  55  thereby allowing the disk  50  to spin with reduced friction. It is to be construed that each end  65  of each of the slots  62  on all of the flywheels  20  may include bearings  67  positioned in the aforementioned manner. However, any configuration bearings  67  with respect to the ends  65  of the slots  62  may be chosen with sound engineering judgment. The bearings  67  may be roller bearings having multiple bearing members or contacting surfaces for receiving the respective guides  55  of the disks  50 . Alternatively, the bearings  67  may be magnetic bearings or any other type or configuration of friction reducing device as is appropriate for use with the embodiments of the subject invention.  FIG. 6   a  depicts the bearings  67  fastened onto a side of the flywheel  20  having a retainer  68 . Two bearings  67  may be included per flywheel  20 ; one on each side for each of the respective slots  62 . It is noted that the depicted configuration of bearing  67  is for illustrative purposes and as such other configurations, placement and installation of the bearings  67  may be utilized without departing from the intended scope of coverage for the embodiments of the subject invention. 
         [0033]    With continued reference to  FIG. 5 , the flywheels  20  may include brakes  70  which arrest the rotating motion of the disks  50 . In one embodiment, the brakes  70  may be respectively affixed proximate to the end of the slots  62  at the rim  24  of the flywheel  20 . The brake  70  may comprise a friction pad  70 ′ that engages the axle  52 . As mentioned above, at various points in the cycle, the disks  50  will be rolling along each respective race  60  as the flywheels  20  rotate. When the disk  50  reaches the end of the slot  62  at the rim  24  of the flywheel, it contacts the brake  70  bringing the rotating disk  50  to a stop thereby translating the inertial energy of the rotating disk  50  to the flywheel  20 . The disk  50  will remain stationary through that portion of the cycle until it reaches an angle that once again allows the disk  50  to begin rotating along the slots  62  in a manner as previously described. Thus, it will be readily seen that each successive rotating disk  50  will transfer its inertia at prescribed intervals correlating to the configuration of the slots  62 . In one embodiment, a disk  50  may contact each respective brake  70  at approximately every 51.4 degrees throughout the revolution of one set of flywheels  20 . Each set of flywheels  20  may be substantially identical to the others. However, each set of flywheels  20  may be shifted in their angular orientation around the shaft  23 . In one embodiment, the sets of flywheels  20  may be phase shifted approximately 12.8 degrees with respect to each other thus enabling at least one disk  50  to contact its respective brake  70  every 12.8 degrees continuously throughout each revolution of the shaft  23 . While the present embodiment describes the power supply system  1  having four sets of flywheels and seven disks per set of flywheels, it is to be construed that any number of the flywheels and any number of disks may be used in the inertial energy storage device  4 ′ as chosen with sound engineering judgment. In this manner, all of the disks  50  may be substantially equidistantly spaced around the circumference of the shaft  23 . However, any radial position or spacing of the disks  50  around the circumference of the shaft  23  may be chosen as is appropriate for use with the embodiments of the subject invention. 
         [0034]    As the flywheels  20  rotate, output power is available from the shaft  23  proportionate to the speed of rotation of the shaft  23  and the mass of the flywheels  20  of the inertial energy storage device  4 ′. As previously mentioned, the inertial energy storage device  4 ′ may be connected, via shaft  23 , to a transmission  6  thereby conveying the inertial energy stored in the flywheels  20  to a generator  8  for converting the inertial energy into electrical energy. In one embodiment, the transmission  6  may function to convert the output speed, and consequently the torque as well, of the shaft  23  to a speed suitable for driving the rotor of the generator  8 , which may range from 1500 to 2500 RPMs. In this manner, the transmission  6  may comprise a gear reducer having one or more sets of planetary gears, not shown. However any gear reducing means for converting the speed and torque of the inertial energy storage device may be chosen with sound engineering judgment. 
         [0035]    With continued reference to  FIGS. 1 and 2 , the output of the transmission  6  or planetary gear box  6 ′ may be coupled to the generator  8 . In one embodiment, the generator  8  may be a reversible motor-generator  8 ′, which functions as a motor or a generator depending on the particular mode of operation as will be discussed in detail in the following paragraphs. The motor-generator  8  may be an AC or DC generating device having a rotor and a stator, neither shown, that work in conjunction with each other to produce either an electrical power output or mechanical power output having parameters of angular velocity and torque. The motor-generator device has two principal components: a field winding and an armature winding. A field, or excitation, winding is a coil or group of coils through which an electrical current is passed. The excitation current sets up a magnetic field in the vicinity of the coil and includes what is commonly referred to as “lines of magnetic flux”. An armature winding is a coil, separate from the excitation coil, which cuts through the lines of magnetic flux created by the field winding and excitation current. This cutting action results in an induced electromotive force (EMF) on the armature winding according to well-established principles of electromagnetic theory. When an electrical load is connected to the armature winding, an electrical current will be made to flow because of the induced EMF. Thus an output voltage and current are generated by the generator  8  when mechanical input is applied to the rotor. As such, the rotor is the rotating part of the motor-generator  8 ′ that may be coupled to the output of transmission  6 . As the rotor turns within the magnetic fields of the stator, current flow will be induced in the windings of the rotor for use by the power supply system  1 . In the opposite mode of operation, current may be supplied to the armature winding thus producing a torque that drives the rotor. In that the operation of motors and generators are well known in the art, no further explanation will be offered at this time. 
         [0036]    With reference again to  FIGS. 1 and 7 , the power supply system  1  may include a power monitoring device  22  as previously mentioned, which may incorporate a switchgear  34  for switching and controlling power through the power supply system  1 . The switchgear  34  may be an automatic type switchgear that transfers power to the load  15  between an external power source  18  and the power supply system  1 . One example of an external power source  18  may be power delivered over standard transmission lines from a local power company. When power from the external power source  18  is interrupted, the power monitoring device  22  may sense the interruption and switch power to the load  15  from the external power source  18  to the power supply system  1 . In this manner, the power supply system  1  may be alternate or auxiliary source of power ready for immediate use in the event of a power outage. Thus, the power monitoring device  22  may sense and automatically transfer the connection of power to the load  15  between an external power source  18  and the power supply system  1 . 
         [0037]    With reference to  FIG. 7 , in one embodiment, the switchgear  34  may comprise one or more components including a power switching device  36  to shift the load circuits to and from the power supply system  1  and a transfer controller  39  to monitor the status of the external power source  18  and the power supply system  1 . The power switching device  36  may utilize a “circuit breaker” or a “contactor” type switch to transfer the loads between the external power source  18  and power supply system  1 . In one embodiment, solid state circuitry may be incorporated, such as that found in Silicon Controller Rectifiers (SCR). However any type and/or configuration of devices may be used to transfer power between the power supplies. As the load  15  may require a specific type electrical power, for example DC power as opposed to AC power, the power from the generator  8  may need conditioned or rectified. For example, the load  15  may require 24 VDC power whereas output from the generator  8  may provide AC power. Accordingly, the power supply system  1  may include power converters  38  for conditioning the power. Additionally, the magnitude and frequency of the power may also need converted. Power converters  38  may include transformers, rectifiers, variable frequency devices and/or other solid state circuitry, e.g. DC to DC power converters, that functions to condition the power as needed. 
         [0038]    With continued reference to  FIG. 7 , the transfer controller  39  may provide logic based circuitry that tells the power switching device  36  under what conditions the power connection is to be switched between the sources of electrical power. Logic-based processors such as microprocessors may be used to perform logic functions based on feedback signals generated by sensors within the power supply system  1 . In one embodiment, power supply system  1  may utilize torque and/or speed sensors that monitor the speed of the shaft  23 . Additionally, the power supply system  1  may incorporate current and/or voltage sensors that detect power levels in the external power source  18 , the load  15  and the output from the generator  8  and the battery  13 ′. It is to be construed that any type, quantity and configuration of sensors may be chosen with sound engineering judgment for use with the embodiments of the subject invention. In this manner, the transfer controller  39  may provide supervisory circuits to constantly monitor the condition of the power sources and thus provide the intelligence necessary for the switchgear  34  to adjust the power output accordingly. 
         [0039]    With reference again to  FIG. 1 , the second energy storage device  13  may be a multi-cell battery  13 ′. The battery  13 ′ may have sufficient storage capacity to supply power for a given period of time up to a maximum load. Power for the load  15  may be supplemented by inertial energy converted from the inertial energy storage device  4 ′. Each of these two energy storage devices  4 ′,  13 ′ may function in conjunction to provide an auxiliary source of power to the load  15  as regulated by the power monitoring device  22 , which will be discussed further in a subsequent paragraph. In one embodiment, the power supply system  1  may be configured to supply power at a rate of up to 30 kW to a prescribed load. 
         [0040]    With reference once again to  FIG. 1 , the operation of the power supply system  1  will now be described. The power supply system  1  may be connected to a load  15 , such as that found in residential or commercial buildings. Well known electrically operated devices may be connected to draw power from the power supply system  1  including for example copiers, lights, compressors, heating units and the like. External source power  18  may also be connected to the load  15  and may function as a primary source of electrical power for use by the load devices. In one embodiment, the external power source  18  may be connected to the load  15  through the power monitoring device  22  in a manner consistent with the above described embodiments of the subject invention. When the power flow from the external power source  18  is interrupted, the power monitoring device  22  may sense the drop in voltage and/or current and automatically switch the connection of the power to the load  15  from the external power source  18  to the power supply system  1 . 
         [0041]    In one embodiment, when supply power for the electrically operated devices, i.e. load  15 , is switched to the power supply system  1 , the load  15  may be directly connected to battery  13 ′ through a power converter  38  or any power conditioning circuit as may be required. For example, power from the battery  13 ′ may be drawn as DC electrical power and converted to  115  VAC power by a transformer and other circuitry for use by the load  15 . While power is being supplied to the load  15  via battery  13 ′, electrical power may be supplemented by the inertial energy storage device  4 ′ as converted by the generator  8  and supplied to the load  15  in a parallel circuit as controlled by the power monitoring device  22 . Therefore power from each of the first and second energy storage devices  4 ′,  13 ′ may be electrically communicated to the power monitoring device  22 . In this manner, electrical power from the power supply system  1  may be supplied from two dissimilar sources of stored energy, namely an electrical energy source and a kinetic energy source. It will be realized by a person of ordinary skill in the art that as kinetic energy from the flywheels  20  is drawn from the inertial energy storage device  4 ′ the rotational speed of the shaft  23  and the flywheels  20  will decrease thereby reducing the inertial energy stored therein. The power monitoring device  22  may sense the decrease in rotational speed and automatically shi ft the supply of power to the load  15  from both the battery  13 ′ and the inertial energy storage device  4 ′ to power supplied from only the battery  13 ′. Thus, the load  15  will temporarily be supplied by electrical power from a single source of stored energy. In conjunction, the power monitoring device  22  may shift operating modes of the motor-generator  8 ′ from converting the inertial energy stored in the flywheels  20  to supplying energy from the battery  13 ′ to speed up the flywheels  20 . In this mode of operation, power from the battery  13 ′ may supply power not only to the load  15  but also to the motor-generator  8 ′ thus recharging the inertial energy storage device  4 ′. When the inertial energy storage device  4 ′ reaches its designated rotational speed, the power monitoring device  22  may once again shift operating modes of the motor-generator  8 ′ thereby supplying power to the load  15  from both sources of stored energy  4 ′  13 ′. The frequency at which the power monitoring device  22  shifts between operating modes may depend on a threshold rotational speed of the shaft  23  of the inertial energy storage device  4 ′. In one embodiment, the threshold speed of shaft  23  may be within a range equal to the designated rotational speed less 5 RPMs. In other words, the threshold speed may be between 20 and 25 RPMs. More particularly, the threshold speed may be substantially 23 RPMs. The threshold speed represents a minimum value that the inertial energy storage device  4 ′ may rotate while operating the motor-generator  8 ′ in generator mode. Accordingly, the frequency of switching between modes of operation may depend on the load  15 . A larger load may draw energy from the power supply system  1  at a faster rate. The converse also holds true. 
         [0042]    In summary, the power supply system  1  may control the supply of power to the load  15  from between two sources of stored energy  4 ′  13 ′. The power monitoring device  22  may shift between modes of operation where both sources of stored energy, i.e. the battery  13 ′ and inertial energy storage device  4 ′, supply power to the load  15  to one source of stored energy, i.e. the battery  13 ′, supplies power to the load  15 , As the inertial energy storage device  4 ′ drops to a minimum threshold energy level, the power monitoring device  22  triggers the operating modes of the motor-generator  8 ′. When the motor-generator  8 ′ is shifted into motor mode, power supplied to the motor-generator  8 ′ from the battery  13 ′ will produce an output torque transferred through transmission  6  to the inertial energy storage device  4 ′ until the shaft  23  is rotating again the designate operating speed. When the motor-generator  8 ′ is shifted into generator mode, power from the inertial energy storage device  4 ′ is supplemented with power from the battery  13 ′ to meet the demands of the load  15 . Thus, an efficient power supply system  1  is provided that can supply electrical power for an extended length of time during a power outage. 
         [0043]    It will be appreciated by persons of ordinary skill in the art that the power supply system  1  contains a finite amount of stored energy. Once the subject power outage has ended, the power supply system  1  may be configured to draw power from the external power source  18  to recharge the battery  13 ′ and/or the inertial energy storage device  4 ′ for use at a future time. In this manner, the power supply system  1  maintains a constant state of readiness to supply power in the event of a power outage. 
         [0044]    The invention has been described herein with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alternations in so far as they come within the scope of the appended claims or the equivalence thereof.