(12) Patent Application Publication (10) Pub. No.: US 2011/0175371 A1 Gray (43) Pub

(12) Patent Application Publication (10) Pub. No.: US 2011/0175371 A1 Gray (43) Pub

US 2011 0175371 A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2011/0175371 A1 Gray (43) Pub. Date: Jul. 21, 2011 (54) FLYWHEEL SYSTEM Publication Classification (51) Int. Cl. (75) Inventor: Bill Gray, San Francisco, CA (US) HO2NHO2K 7/18I/00 (2006.01) (52) U.S. Cl. .......................... 290/1 R; 318/116; 310/300 (73) Assignee: Yets INC., San Francisco, (57) ABSTRACT A flywheel system has an approximately toroidal flywheel rotor having an outer radius, the flywheel rotor positioned (21) Appl. No.: 13/008,292 around and bound to a hub by Stringers, the stringers each of a radius slightly smaller than the outer radius of the flywheel rotor. The hub is Suspended from a motor-generator by a (22) Filed: Jan. 18, 2011 flexible shaft or rigid shaft with flexible joint, the flywheel rotor having a mass, Substantially all of the mass of the fly wheel rotor comprising fibers, the fibers in large part movable Related U.S. Application Data relative to each other. The motor-generatoris Suspended from a damped gimbal, and the flywheel rotor and motor-generator (62) Division of application No. 11/995,539, filed on Mar. are within a chamber evacuatable to vacuum. An electrostatic 14, 2008, now abandoned, filed as application No. motor/generator can also be within the same vacuum as the PCT/US08/50670 on Jan. 9, 2008. flywheel. 21 Patent Application Publication Jul. 21, 2011 Sheet 1 of 26 US 2011/0175371 A1 Patent Application Pu blication Patent Application Publication Jul. 21, 2011 Sheet 3 of 26 US 2011/0175371 A1 Fig. 3 Patent Application Publication Jul. 21, 2011 Sheet 4 of 26 US 2011/0175371 A1 42C Patent Application Publication Jul. 21, 2011 Sheet 5 of 26 US 2011/0175371 A1 42 Fig. 5 Patent Application Publication Jul. 21, 2011 Sheet 6 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 7 of 26 US 2011/0175371 A1 Fig. 7 Patent Application Publication Jul. 21, 2011 Sheet 8 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 9 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 10 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 11 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 12 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 13 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 14 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 15 of 26 US 2011/0175371 A1 Fig. 15 Patent Application Publication Jul. 21, 2011 Sheet 16 of 26 US 2011/0175371 A1 41C (ss O Patent Application Publication Jul. 21, 2011 Sheet 17 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 18 Of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 19 Of 26 US 2011/0175371 A1 Fig. 19 Patent Application Publication Jul. 21, 2011 Sheet 20 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 21 of 26 US 2011/0175371 A1 S. SSSSSSSSSSSS 8. Saa ***************************** -----xxx-xx-xs saxxx y ax Patent Application Publication Jul. 21, 2011 Sheet 22 of 26 US 2011/0175371 A1 31 / 34 -Y m A. y 35 J 153b N39 38g / 36t AS 37C 1 33 1. 35c - 53c \ 39C 38c 36C N A. / Fig. 22 Patent Application Publication Jul. 21, 2011 Sheet 23 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 24 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 25 of 26 US 2011/0175371 A1 Patent Application Publication Jul. 21, 2011 Sheet 26 of 26 US 2011/0175371 A1 US 2011/0175371 A1 Jul. 21, 2011 FLYWHEEL SYSTEM frequency regulation and short term emergency power backup. Excepting the invention disclosed in this document, CROSS REFERENCE TO RELATED no flywheel energy storage system that the inventor is pres APPLICATIONS ently aware of is able to provide storage economically enough to be of widespread utility as a bulk energy storage solution. 0001. This application is a divisional of U.S. patent appli 0007. The economic viability of a flywheel system is a cation Ser. No. 11/995,539, filed on Jan. 9, 2008, which function of many factors. Of these, the most important are application is incorporated herein by reference for all pur capital costs of construction, conversion efficiency of the poses. “spin up' and “draw down processes, and the coasting effi ciency or how much energy is lost while the flywheel is in a BACKGROUND charged State but power is neither being applied to or drawn 0002. It is highly desirable to be able to store electrical from it. energy for later use. 0008. The kinetic energy stored in the flywheel is /2Ico 0003. There are many technologies that are able to store where I is the moment of inertia of the flywheel and () is the and regenerate electrical energy, but few of these methods are angular velocity of the flywheel. In order to maximize this able to do so cheaply enough to be economically useful in equation per unit cost, it is generally desirable to form the applications that are connected to large scale system such as flywheel rotor material into a shape that maximizes the utilities electricity grids. All the few currently available tech moment of inertia for a given amount of material. One of the nologies that are able to perform economically are limited in most efficient flywheel rotor shapes then is a ring or hoop of their usefulness by various geographical, geological, and/or material. topological requirements that limit their ultimate achievable 0009. There are a multitude of design issues that must be capacity, and their proximity to potential users. considered in the construction of a flywheel. Those include, 0004. The inexpensive storage of large quantities of elec but are not limited to material cost, fabrication cost, dynamic trical power can allow generators, transmitters, distributors, stability, internal friction, bearing technique and arrange and users of electricity to Smooth large Swings in their power ment, motor/generator technique and arrangement, and requirements allowing for significant increases in fuel and enclosure. capital efficiency. Beyond this purely economical value of (0010. One known flywheel system is the “flexible fly inexpensive electricity storage, a very large environmental wheel system described and partially tested by Vance and value has become apparent. CO produced by fossil-fuel Murphy (the “Vance flywheel'), described in J. M. Vance and based electricity generation is a major contributor to the prob B. T. Murphy, “Inertial Energy Storage For Home or Farm lem of global warming. While there are numerous generation Use Based on a Flexible Flywheel”, 1980 Flywheel Technol technologies in the marketplace that can produce large quan ogy Symposium, October, 1980, Scottsdale, Ariz., cospon tities of usable electricity without producing CO and other sored by U.S. Department of Energy, American Society of pollutants as a byproduct, none of the currently known and Mechanical Engineers, Lawrence Livermore National readily expandable solutions is able to arbitrarily increase or Library, Pages 75-87. This design suspends a doughnut decrease its output to match user demand. Technologies shaped bundle of rope (serving as a flywheel) by means of a based on wind, Solar, and tidal energy conversion are only number of Supporting ropes from a motor which is itself able to generate electricity when these energy sources are Suspended from a special non-axially symmetric damped available. Nuclear power is notoriously hard to rapidly gimbal system. The Vance system was found to have various increase and decrease, running far more efficiently when desirable properties. operated at a steady-state output. Because of these temporal 0011 When this system is accelerated by the motor rap limitations, these technologies are only able to serve a small idly so that the supporting ropes “twist up’ on themselves to portion of total electricity demand, and must rely on fossil form a sort of flexible shaft, the system is found to be entirely fuel generation to provide power at critical times. In order for self-balancing and self-stabilizing. This is a major advantage these technologies to economically grow as a percentage of over most other described flywheel systems. total system generation capacity they require very large 0012. Additionally, because the individual fibers of the increases in the capacity to store and regenerate electricity. Vance flywheel rotor are not bound to one another in a rigid 0005 Much attention has been given in recent years to the matrix, the flywheel rotor does not suffer from the large notion of using a flywheel for Such storage. The goal is to use internal stresses and internal friction that limit many other electrical energy via a motor to accelerate a flywheel thereby flywheel designs. In a rigid flywheel made out of isotropic converting the electrical energy into kinetic energy stored in materials, a composite fiber/resin matrix, or any other rigid or the momentum of the flywheel. Once the electrical energy has semi-rigid material/materials, hoop stresses form as a result been converted into kinetic energy one can optionally to of the angular acceleration experienced by the flywheel rotor permit time to pass during which the flywheel spins freely. material when the flywheel rotor is at speed. These stresses Later, energy can be drawn down from the system by allowing are considerably larger at the periphery of the flywheel rotor the momentum of the flywheel to drive a generator or alter than at locations closer to the axis of rotation.

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