Abstract:
A rotating device for multi-megawatt, fast response frequency regulation for the electric grid. The device generally has a main shaft coupled to a motor-generator, a main spring concentric to the main shaft, and several radially-symmetric arms, each connected to the main spring via a four-bar mechanism. As the rotational speed of the device increases, centrifugal force acting on the arms causes them to rise, the four-bar mechanism compresses the main spring, and energy is stored in the device as a combination of kinetic rotational energy, elastic potential energy, and gravitational potential energy. The device can be configured with additional springs, which can be compression springs, tension springs, or a combination thereof, in order to increase the amount of energy produced. Symmetrically-spaced gliding masses can be arranged on the arms as well.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The invention relates to electric power generation, and, more specifically, to large scale electric power energy storage and fast response frequency regulation. The electric grid is continuously attempting to balance the load (demand) with the power capacity (supply) connected to the grid. A perfect balance between supply and demand is impossible without the use of energy storage, load banks, flexible power sources and fast response supply systems. Grid operators manage these supply demand discrepancies by forecasting capacity requirements several days in advance, but, inevitably, there are errors in the forecast or gaps in the planned supply. Therefore, the grid requires fast response multi-megawatt energy storage and delivery systems that can react to the grid&#39;s requirements in real time. This has been an elusive requirement. The most successful type of system in use today is pumped storage, but it is costly and difficult to build and contains significant inertia, so its response is relatively slow and better suited for non-real time applications. High speed flywheels have been used for this purpose, but high costs and lack of multi-megawatt capabilities have significantly limited their adoption. The present invention addresses these challenges. 
         [0003]    2. Description of Prior Art 
         [0004]    Energy storage systems for electric power frequency regulation have increased in importance with the introduction of intermittent power sources, including wind and solar plants. In order to work properly and address the needs of the electric grid, these storage systems need to be capable of storing or delivering several megawatts of electric power for relative short periods of time on the order of 4 to 20 seconds, with a round trip efficiency (RTE, defined as the average ratio of power output versus power input over a period of ˜24 hours) greater than 70%, and capital costs in $/KW installed lower than the cost of adding new capacity, and a service life greater than twenty years. Because the currently-available and/or proposed energy storage systems fail to meet these requirements, inefficient and dated gas turbine power plants, or reciprocating engines known as “peakers”, have seen a sharp increase in demand in recent years. These peaker power plants are relatively compact and easily deployed, but, because of their inefficiency and their use of fossil fuels, they offset the renewable benefits of the intermittent solar and wind farms. 
         [0005]    The currently available and/or energy storage devices for electric power generation include compressed gas systems, battery based systems, pumped storage systems and high speed flywheels. For example, Nakhamkin, (US Publication 2010/0251712) describes a compressed air energy storage system with a relatively low RTE of 65% and high capital costs to implement. Manz (US Publication 2011/0137481) describes a battery-based energy storage system for wind farms, but the upfront costs of this system remain high and its service life inadequate. Ley (U.S. Pat. No. 3,405,278, 1965) describes a pumped storage system for hydroelectric plants; such systems represent the bulk of the energy storage and frequency regulation systems in use today, but their use is limited due to high capital costs, difficulty in finding proper sites, and the extensive permitting required. Hockney (U.S. Pat. No. 6,614,132, 2003), Gray (US Publication 2010/0237629), Han (US Publication 2010/0231075) and Palmer (US Publication 2011/0120806) all describe high speed flywheels, with a combination of vacuum chambers and magnetic levitation to minimize friction, hollow shafts and flexible materials to minimize structural stresses at higher speeds, and multiple flywheel systems. However, these flywheel systems are either too costly or cannot provide multi-megawatt capacity to the grid. In fact, the Hockney patent was owned by Beacon Power, a flywheel energy storage company that recently filed for bankruptcy due to the inadequate economics of these systems. 
         [0006]    The present invention provides large scale multi-megawatt real time frequency regulation with round trip efficiencies of approximately 80% and above by using gravitational and elastic potential energy along with rotational kinetic energy storage. The embodiments involve energy storage in the form of rotational kinetic energy and potential energy in the form of compression and tension in springs, along with gravitational potential energy of a mass. Several other inventions have been described in applications unrelated to large scale electric power energy storage and frequency regulation. For example, Easton (U.S. Pat. No. 373,061, 1887) and Hitt (U.S. Pat. No. 424,418, 1890) describe clock winding mechanisms using a torsional spring. Korfhage (U.S. Pat. No. 1,952,030, 1931) describes an automatic clock winding mechanism that stores potential energy in both a torsional spring and in the rise/fall of several masses. Dennis (U.S. Pat. No. 3,986,580, 1975) describes an energy storage device that can be used in mechanical transmissions, in which energy stored in several linear springs is arranged as an equivalent torsional spring. Yang (U.S. Pat. No. 5,269,197, 1993) describes an air-stream activated energy storage device, in which energy is stored in springs that are compressed through centrifugal forces acting on inertial masses. Fielder (U.S. Pat. No. 7,127,886, 2006) describes a self-winding electric generator that provides consistent power from wind and other intermittent energy sources by incorporating the use of a torsional spring similar to that used in self-winding clocks. While the above inventions incorporate the use of springs to store energy and, in the case of Yang, a centrifugal force that acts upon a spring, none of them are designed for use as a fast response multi-megawatt frequency regulation device for the electric grid, independent of the energy source. 
       SUMMARY OF THE INVENTION 
       [0007]    Briefly, the present invention relates to a method and apparatus of large scale, multi-megawatt, fast response frequency regulation for the electric grid. The device is characterized by having main shaft that is coupled to a motor-generator, a main linear spring that is concentric to the main shaft, and several radially-symmetric swinging arms that are each connected to the main spring via a four-bar mechanism consisting of four linkages and one degree of freedom, as defined by Gruebler&#39;s equation. This four-bar mechanism converts the swinging arms&#39; rotational movement about a horizontal plane to a linear movement that compresses the main spring as the arms are raised due to the centrifugal forces acting on them as the rotational speed of the device increases. 
         [0008]    In accordance with an aspect of the invention, the main shaft can either be directly coupled to the motor-generator known as direct drive, or it can be coupled first to a gear box, which, in turn, is connected to the motor-generator, which is known as geared drive. 
         [0009]    In accordance with an aspect of the invention, the motor-generator unit consists of an alternating current induction motor that can be used as a motor when the grid signal requires the device to store electric energy or as a generator when the grid signal requires that the device deliver energy to the grid. 
         [0010]    In accordance with a further aspect of the invention, the motor-generator unit consists of a direct current motor that can be used as a motor when the grid signal requires the device to store electric energy or as a generator when the grid signal requires that the device deliver energy to the grid. The direct current motor-generator would then be electrically connected to an inverter to convert alternating current from the grid to direct current and vice versa. 
         [0011]    In accordance with a further aspect of the invention, the connection between the main shaft and the motor-generator unit or gearbox can be equipped with a flexible joint that allows the device to seek a dynamic equilibrium as it rotates; such a joint normally has three degrees of freedom and is known as a “universal joint” by those familiar with the art. In any case, either with or without the use of a flexible joint, a main bearing is used in the device such that the loads along the main shaft can be transmitted and supported by the main structure of the apparatus. 
         [0012]    In accordance with a further aspect of the invention, the main structure that supports the device can be made of reinforced concrete, structural steel, wood, rock or a combination thereof, depending on the availability of these materials at the point of use and the configuration that minimizes the overall costs of the system. The structure can be installed below or above ground, depending on the needs and space restrictions at the site, but the structure would be equipped with proper access doors for maintenance. 
         [0013]    In accordance with a further aspect of the invention, to smooth any spikes in the loads on the main shaft and on the elements attached to it, a flexible shaft and/or a slip clutch can be directly coupled to the main shaft and act as a mechanical “fuse” in order to protect the device or its components in case of extreme torque or flexion loads. 
         [0014]    In accordance with a further aspect of the invention, the device can be built without any springs and configured only with swinging arms that are concentric to the main shaft and are symmetrically arranged about the shaft in order to achieve a dynamic balance; such arms rise and fall as the rotational speed increases and decreases, respectively. 
         [0015]    In accordance with a further aspect of the invention, in order to minimize any asymmetric forces and moments induced by the rising or lowering of the radial arms, complexity, and parts count, the main spring that is concentric to the main shaft is a single spring. Alternatively, in order to ease assembly or manufacturing, instead of utilizing one main spring, several smaller springs can be connected in series and concentric to the main shaft. 
         [0016]    In accordance with a further aspect of the invention, instead of a main concentric spring, smaller radially located concentric and symmetrically spaced springs can be used in conjunction with smaller, but more numerous, radial arms, symmetrically spaced about the center of the main shaft, with the smaller radially distributed springs being connected in parallel and having an equivalent spring constant as a main spring. 
         [0017]    In accordance with a further aspect of the invention, the swinging radial arm can be equipped with a linear spring that is parallel and concentric to the arm which, in turn, is coupled to a mass that is symmetrically spaced about the arm in order to minimize unwanted moments and can glide along the arm with the use of a bushing or bearing to minimize friction. This mass accelerates as a result of the net acceleration along the arm, which is the result of the radial acceleration of the mass along the arm and the centrifugal acceleration about the center of rotation when using cylindrical coordinates to describe the motion. 
         [0018]    In accordance with a further aspect of the invention, energy is stored in the proposed invention as a combination of kinetic rotational energy, which is proportional to the moment of inertia of the device and the square of the rotational speed, elastic potential energy, which is proportional to a spring&#39;s elastic coefficient and the square of its deformation, and gravitational potential energy, which is proportional to the vertical height increase of a mass. 
         [0019]    In accordance with a further aspect of the invention, a significant amount of the energy stored in the device will be of the kinetic rotational type, which will increase as speed increases and which also increases drag induced losses with the surrounding air, but is limited by the increase in the moment of inertia resulting from the rise of the swinging arms as they extend as the speed increases. Inevitably, the kinetic energy stored decays due to both drag forces and frictional losses in the main bearing, whereas potential energy does not decay since conservative forces are involved. In order to minimize the decay of the kinetic energy stored, the device is equipped with the ability to store potential energy in springs and in masses as they rise. While the potential energy stored accounts for a smaller percentage of the total energy accumulated in the device, it delays the rate of kinetic energy decay and thus increases the round trip efficiency and economics of the device because the potential energy stored is quickly converted to kinetic energy and vice versa, on a real time basis. 
         [0020]    In accordance with a further aspect of the invention, the device can be placed in a sealed enclosure that can be located above or below ground and from which air is extracted by means of a vacuum pump in order to reduce the air density in the enclosure and, therefore, reduce the drag losses of the system. 
         [0021]    In accordance with a further aspect of the invention, the vacuum pump used to reduce drag can be either be driven with electricity from the grid or by direct coupling to the main shaft via a gear box or pulley belt/chain system. 
         [0022]    In accordance with a further aspect of the invention, the arms, shaft and springs are all made of strong materials, including high tensile strength steel. 
         [0023]    In accordance with a further aspect of the invention, the gliding masses that may be attached to each arm can be made of many types of materials, such as steel, lead, dirt, rock, and any other readily available material that minimizes cost without compromising the performance of the device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a side elevational view of the support structure holding the present invention, partially broken away to show the simplest embodiment thereof, with a four-bar mechanism. 
           [0025]      FIG. 2  is a side elevational view, partially broken away, of the support structure holding an embodiment of the present invention, which incorporates a main spring with the four-bar mechanism. 
           [0026]      FIG. 3  is a partial side elevational view of an alternate embodiment of the present invention, which incorporates a plurality of springs arranged in parallel. 
           [0027]      FIG. 4  is a partial side elevational view, partially broken away, of an alternate arrangement for coupling the shaft of the present invention to the motor-generator. 
           [0028]      FIG. 5  is a side view of an alternate embodiment of one of the arms of the present invention, which incorporates a slidable mass and a spring. 
           [0029]      FIG. 6  is a side elevational view of an alternate support structure for the present invention, one which utilizes a vacuum pump. 
           [0030]      FIG. 7  is a side elevational view, partially broken away, of the support structure holding the present invention, the support structure being disposed underground. 
           [0031]      FIG. 8  is a side elevational view, partially broken away, of the support structure holding an alternate embodiment of the present invention, which incorporates a compression spring and a tension spring. 
           [0032]      FIG. 9  is a partial side elevational view of an alternate embodiment of the present invention, which incorporates a plurality of paired springs disposed between fixed and slidable plates, all parallel to the main shaft. 
           [0033]      FIG. 10  is a partial side elevational view of an alternate embodiment of the present invention, which incorporates two or more compression springs. 
           [0034]      FIG. 11  is partial side elevational view of an alternate embodiment of the present invention, which uses a bearing to keep the shaft centered. 
           [0035]      FIG. 12  is a partial side elevational view of an alternate embodiment of the present invention, which combines additional springs for energy storage. 
           [0036]      FIG. 13  is a partial side elevational view of an alternate embodiment of the present invention, which combines springs with a coupled geared spline for uniform travel of masses. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
       [0037]    The present invention relates to devices for fast response frequency regulation for large scale electrical power. In its simplest form shown in  FIG. 1 , the device  10  is mounted to and enclosed by support structure  12 . The device  10  is driven by a motor-generator  14 , which is mounted on a motor support  16  on top of support structure  12 . The motor-generator  14  is directly coupled to a main shaft  18 , which, in turn, is connected to a fixed plate  20 . An end of each swinging arm  22  is pivotally connected to the outer edge, or circumference, of the fixed plate  20  at pivot point  24 . Linkages  35 , each having a first end connected to a swinging arm  22  at pivot point  36 , have a second end connected to an outer edge of sliding plate  32  at pivot point  37 , thereby coupling the sliding plate  32  to the swinging arms  22 . The linkages  35  can be designed as rigid bars or can be high tensile strength cables, in order to reduce weight and cost. Each linkage  35  can be connected to the swinging arm  22  at any of a variety of pivot points  36 , as long as the pivot points  36  are identical for all the linkages  35  of a particular device for proper balance. Sliding plate  32 , which has a central opening with a bearing  33 , allows the sliding plate  32  to slide upwards and downwards along the main shaft  18 . A stopper  34  at the lower end of the main shaft  18  prevents the sliding plate  32  from falling off the main shaft  18 . During energy storage, the motor-generator  14 , acting as a motor, drives the main shaft  18 , which rotates inside bearing  28 , thereby rotating the fixed plate  20  with the attached swinging arms  22 . As the swinging arms  22  rotate, centrifugal forces acting on the swinging arms  22  cause the free ends  26  of the swinging arms  22  to pivot upwards until they are aligned with the fixed plate  20 , thereby storing both kinetic and potential energy. In the case of energy delivery, the device  10  transmits power to the motor-generator  5 , acting as a generator, via the main shaft  18 . As energy is transferred, the rotational speed of the device  10  decreases, and the free ends  26  of the swinging arms  22  fall when the centrifugal force component acting in the vertical direction is lower than the weight of the swinging arms  22 . 
         [0038]    The device  30  shown in  FIG. 2 , which utilizes a main compression spring  31 , is a preferred embodiment of this invention. The device  30  is driven by a motor-generator  14 , which is mounted on a motor support  16  on top of a support structure  12 . The motor-generator  14  is directly coupled to a main shaft  18 , which, in turn, is connected to a fixed plate  20 . The concentric main compression spring  31  is disposed around the main shaft  18  between the fixed plate  20  and a sliding plate  32 , which has a central opening with a bearing  33 , which allows the sliding plate  32  to slide upwards and downwards along the main shaft  18 . A stopper  34  at the lower end of the main shaft  18  prevents the sliding plate  32  from falling off the main shaft  18 . Linkages  35 , each having a first end connected to a swinging arm  22  at pivot point  36 , and a second end connected to an outer edge of the sliding plate  32  at pivot point  37 , couple the sliding plate  32  to the swinging arms  22 . The combination of the swinging arms  22 , the linkages  25 , the sliding plate  32 , and the main shaft  18  constitute the basic elements of the four-bar mechanism that converts the rotational movement of the swinging arms  22  to linear motion of the sliding plate  32  used to compress the main spring  31 . The linkages  35  can be designed as rigid bars or can be cables, in order to reduce weight and cost. Each linkage  35  can be connected to the swinging arm  22  at any of a variety of pivot points  36 , as long as the pivot points  36  are identical for all the linkages  35  of a particular device. During energy storage, the motor-generator  14 , acting as a motor, drives the main shaft  18 , rotating the fixed plate  20  with attached swinging arms  22  and sliding plate  32 . As the swinging arms  22  rotate, centrifugal forces acting on the swinging arms  22  cause the free ends  26  to pivot upwards, thereby also raising the sliding plate  32 , which compresses the main compression spring  31  against the bottom of the fixed plate  20 . Energy is stored as kinetic energy from the device&#39;s  30  rotating moment of inertia and potential energy in the main compression spring  31  as it is deformed and the mass of the swinging arms  25  as they pivot upwards. 
         [0039]      FIG. 3  shows a device  40  similar to that shown in  FIG. 2 , utilizing a plurality of compression springs  41  instead of a single main compression spring  31 . In this embodiment, both the fixed plate  42  and the sliding plate  43  have much larger radii. The compression springs  41  are symmetrically arranged so that each is parallel to the main shaft  18 , each spring  41  having one end attached to the fixed plate  42  and a second end attached to the sliding plate  43 . The sliding plate  43  has a bearing  44  which allows it to slide upwards and downwards along the main shaft  18 . A stopper  45  prevents the sliding plate  43  from falling off the main shaft  18 . An end of each swinging arm  22  is pivotally connected to the outer edge of the fixed plate  42  at pivot point  24 . Linkages  35 , each having a first end connected to a swinging arm  22  at pivot point  36  and a second end connected to an outer edge of the sliding plate  43  at pivot point  37 , couple the sliding plate  43  to the swinging arms  22 . When the main shaft  18  rotates, the fixed plate  42  with attached swinging arms  22  and sliding plate  43  also rotates, and centrifugal forces acting on the swinging arms  22  cause the free ends  26  to pivot upwards, thereby raising the sliding plate  43 , which compresses the plurality of compression springs  41  against the bottom of the fixed plate  42 . The amount of potential energy stored in the compression springs  41  increases with the number of such springs  41  used. 
         [0040]      FIG. 4  shows an alternate arrangement for equipment used to drive the devices  10 ,  30 ,  40 . A motor-generator  50  is directly coupled to a gear box  51 , which, in turn, is coupled to a flexible shaft  52  that acts as a mechanical “fuse” to absorb torsion and flexion loads. The flexible shaft  52 , in turn, is connected to a universal joint  53  that allows the device  10 ,  30 ,  40  to achieve a dynamic balance as it rotates. Alternatively, a slip clutch can be used instead of or in addition to the flexible shaft. 
         [0041]      FIG. 5  shows an alternate embodiment of a swinging arm  55 . A first stopper  56  encircles the swinging arm  55 , then a spring  57  is disposed on the swinging arm  55 , then a mass  58  with a central bushing or bearing (not shown) is slid onto the swinging arm  55 , and, finely, a second stopper  59  is affixed to the swinging arm  55 . The swinging arm  55  is pivotally affixed to an outer edge of a fixed plate  20 , as described, supra. As the swinging arm  55  rotates and rises, the mass  58  is accelerated due to net radial forces that act upon it, and the spring  57  is compressed. The result is an increase in the amount of potential energy stored in the spring  57 , while taking advantage of the radial forces acting on the mass  58 . 
         [0042]    As shown in  FIG. 6 , any of the embodiments of the present invention can be placed within an enclosure  60 . A vacuum pump  61  can be used to reduce air density within the enclosure  60 , thereby reducing the drag losses of the device. The vacuum pump  61  can be driven by electric current from the grid or by direct mechanical coupling to the main shaft (not shown). 
         [0043]    As shown in  FIG. 7 , any of the embodiments of the present invention can be enclosed in a support structure  63 , which is located underground in order to protect the surrounding areas in the event of a structural failure. For example, the device  30  (shown in  FIG. 2 ), will still be driven by a motor-generator  14 , which is directly coupled to a main shaft  18 , which, in turn, is connected to a fixed plate  20 . The concentric main compression spring  31  is disposed around the main shaft  18  between the fixed plate  20  and a sliding plate  32 , which has a central opening with a bearing  33 , which allows the sliding plate  32  to slide upwards and downwards along the main shaft  18 . A stopper  34  at the lower end of the main shaft  18  prevents the sliding plate  32  from falling off the main shaft  18 . Linkages  35  couple the sliding plate  32  to the swinging arms  22 . During energy storage, the motor-generator  14 , acting as a motor, drives the main shaft  18 , rotating the fixed plate  20  with attached swinging arms  22  and sliding plate  32 . As the swinging arms  22  rotate, centrifugal forces acting on the swinging arms  22  cause the free ends  26  to pivot upwards, thereby also raising the sliding plate  32 , which compresses the main compression spring  31  against the bottom of the fixed plate  20 . Energy is stored as kinetic energy from the device&#39;s  30  rotating moment of inertia and potential energy in the main compression spring  31  as it is deformed and the mass of the swinging arms  25  as they pivot upwards. 
         [0044]    The alternate embodiment of the device  65 , shown in  FIG. 8 , incorporates a tension spring  66 , acting in concert with a compression spring  31 . The main shaft  18 , is connected to a fixed plate  20 , and the compression spring  31  is disposed around the main shaft  18  between the fixed plate  20  and a sliding plate  32 , which has a central opening with a bearing (not shown), which allows the sliding plate  32  to slide upwards and downwards along the main shaft  18 . Linkages  35  couple the sliding plate  32  to the swinging arms  22 . A tension spring  66  is affixed to the bottom of the sliding plate  32 , and a second fixed plate  67  is affixed to the lower end of the tension spring  66 . The rotation of the main shaft  18  causes the swinging arms  22  to rotate, and centrifugal forces acting on the swinging arms  22  cause the free ends  26  to pivot upwards, thereby also raising the sliding plate  32 , which compresses the main compression spring  31  against the bottom of the fixed plate  20 , while extending tension spring  66 , resulting in a larger amount of energy being stored in the springs. 
         [0045]    Smaller diameter springs tend to have higher spring constants but lower energy storage capabilities, making it likely that multiple springs will be required in some applications.  FIG. 9  shows how multiple springs could be positioned in such an embodiment. Like the embodiment shown in  FIG. 3 , the device  70  utilizes a plurality of compression springs  41  instead of a single main compression spring  31 . The compression springs  41  are symmetrically arranged so that each is parallel to the main shaft  18 , each spring  41  having one end attached to the fixed plate  42  and a second end attached to the sliding plate  43 . The sliding plate  43  has a bearing  44  which allows it to slide upwards and downwards along the main shaft  18 . An end of each swinging arm  22  is pivotally connected to the outer edge of the fixed plate  42  at pivot point  24 . Linkages  35 , each having a first end connected to a swinging arm  22  at pivot point  36  and a second end connected to an outer edge of the sliding plate  43  at pivot point  37 , couple the sliding plate  43  to the swinging arms  22 . A plurality of tension springs  71  are affixed to the bottom of the sliding plate  43 , and a second fixed plate  72  is affixed to the lower ends of the tension springs  71 . A stopper  73  prevents fixed plate  72  from losing contact with the main shaft  18 . Since the length to diameter ratio of the compression springs  41  is high, buckling will occur unless a tube  74  is placed around each compression spring  41 . If tubes  74  are used, the lower side of the fixed plate  42  will be fitted with complementary slots (not shown) so that the tubes  74  are not compressed and ride freely in oscillating vertical motion. Alternatively, to avoid buckling, each of the compressions springs  41  could have a rod or an internal tube (not shown) inserted inside it, with complementary slots in the lower side of the fixed plate  42 . 
         [0046]    Yet another embodiment is shown in  FIG. 10 . This device  75  uses two (or more) compression springs  31 . The main shaft  18 , is connected to a fixed plate  20 , and the first compression spring  31  is disposed around the main shaft  18  between the fixed plate  20  and a sliding plate  32 , which has a central opening with a bearing (not shown), which allows the sliding plate  32  to slide upwards and downwards along the main shaft  18 . Linkages  35  couple the sliding plate  32  to the swinging arms  22 . A second compression spring  80  is disposed around the main shaft  18  between the second fixed plate  77  and the second sliding plate  78 , which has a central opening with a bearing (not shown), which allows the sliding plate  78  to slide upwards and downwards along the main shaft  18 . The two sliding plates  32 , 78  are connected by tension members  76 . A stopper  79  at the lower end of the main shaft  18  prevents the sliding plate  78  from falling off the main shaft  18 . 
         [0047]    The embodiment  80  in  FIG. 11  is similar to that shown in  FIG. 2 , but it is supported in order to keep the main shaft  18  centered. As shown in  FIG. 11 , the compression spring  31  is disposed around the main shaft  18  between the fixed plate  20  and a sliding plate  32 . Linkages  35  couple the sliding plate  32  to the swinging arms  22 . A bearing  81  on the ground or other support  82  is used to keep the main shaft  18  centered. 
         [0048]      FIG. 12  shows an embodiment of the present invention that combines several of the embodiments described supra, along with additional springs. The device  85  can be hung from a universal joint  84  and can incorporates a tension spring  66 , acting in concert with a compression spring  31 . The main shaft  18 , is connected to a fixed plate  20 , and the compression spring  31  is disposed around the main shaft  18  between the fixed plate  20  and a sliding plate  32 , which has a central opening with a bearing (not shown), which allows the sliding plate  32  to slide upwards and downwards along the main shaft  18 . Linkages  35  couple the sliding plate  32  to the swinging arms  55 . A tension spring  66  is affixed to the bottom of the sliding plate  32 , and a second fixed plate  67  is affixed to the lower end of the tension spring  66 . A first stopper  56  encircles each of the swinging arms  55 , then a spring  57  is disposed on each of the swinging arms  55 , then a mass  58  with a central bushing or bearing (not shown) is slid onto each of the swinging arms  55 , and, finely, a second stopper  59  is affixed to each of the swinging arms  55 . The swinging arms  55  are pivotally affixed to an outer edge of a fixed plate  20 . A third fixed plate  86  is affixed to the lower end of the main shaft  18 . To increase the amount of energy storage, additional side springs  87  can be used, with a first end of each side spring  87  attached to a swinging arm  55  at pivot point  88  and a second end of each side spring  87  attached to the outer edge of plate  86  at pivot point  89 . 
         [0049]      FIG. 13  shows an embodiment that uses a combination of interlinked mechanical parts to enhance the energy produced by the device  90 . As shown, the device  90 , which is driven by a motor-generator  14  is suspended from a support bearing  91 . The main shaft  18  is coupled to the motor-generator  14 , with a universal joint  84  therebetween. Attached to the main shaft  18  is a fixed plate  92 , under which is a common central gear  93 , which drives spline gears  94 , which are mounted on a spline gear carrier  95 . A plurality of arms  96  are pivotally mounted onto the circumference of the fixed plate  92  at pivot point  97 . A plurality of spiral splines  98  are each joined to the spline gear carrier  95  by universal joint  99 . A sliding mass  100  is mounted onto the spline  98  with a spline rider  101 , separated by bearing  102 . Each arm  96  has an L-shaped portion  103 , and a compression spring  104  is mounted between the upper side of the L-shaped portion  103  of the arm  96  and the lower side of the sliding mass  100 . An end of each linkage  105  is pivotally connected to each arm  96  at pivot point  106 , while the other end of each linkage  105  is connected to the sliding plate  107 , which had been slidably mounted onto the main shaft  18 , at pivot point  108 . Compression spring  109  is disposed concentric to the main shaft  18  between the bottom side of the spline gear carrier  95  and the top side of the sliding plate  107 . An extension spring  110  is disposed concentric to the main shaft  18  between the bottom side of the sliding plate  107  and the top side of second fixed plate  111 , which is affixed to the lower end of the main shaft  18 . A first end of a second extension spring  112  is affixed to the L-shaped portion  103  of arm  96 , with the second end of the second extension spring  112  pivotally connected to the outer edge, or circumference, of second fixed plate  111  at pivot point  113 . The device  90  shown in  FIG. 13  provides a method a maintaining system dynamic balance for multiple arms  96  with sliding masses  100 , specifically by providing a method of linking the sliding masses  100  to provide for their uniform deployment. Each of the sliding masses  100  is keyed to its respective spiral spline  98 , and all the splines  98  are interlinked through gearing to a common central gear  93  so that the splines  98  rotate uniformly. The masses  100 , which slide on the rotating splines  98 , move uniformly on the arms  96  as the rotational speed of the device  90  changes, whether accelerating or decelerating. 
         [0050]    It will be understood by those skilled in the art that the embodiments of the present invention are not described with reference to any particular source of energy feeding the electric grid, but can be used with any source of power, including wind, solar and fossil fuels.