Heat exchange – Regenerator – Heat collector
Reexamination Certificate
2002-09-12
2004-01-13
McKinnon, Terrell (Department: 3743)
Heat exchange
Regenerator
Heat collector
C165S104210, C165S045000
Reexamination Certificate
active
06675872
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to flywheel energy storage systems, and more particularly to devices, and methods for dissipating the heat energy developed during operation of such flywheel energy storage systems, which systems use a vacuum environment to reduce windage losses.
BACKGROUND OF THE INVENTION
The ability of flywheels to accept and release energy over relatively short time periods has been known for many years and energy storage flywheels have been used, or proposed for use, in a variety of applications. Such proposed and actual use applications include motor vehicle applications and stand alone supplemental energy sources.
There is shown in
FIG. 1
a simplified view of a conventional flywheel energy storage system
100
used for storing kinetic energy. The conventional flywheel system
100
includes a flywheel assembly
104
disposed in a flywheel housing
102
. Further, the flywheel housing is configured and arranged so such flywheel assemblies
104
are run under vacuum, in order to avoid drag on the flywheel. The systems are evacuated with standard vacuum pumps, e.g. turbo pumps, and then sealed, preferably by pinching off and then fusing the end of a copper tube, thus forming an all metal seal, which is impervious even to argon. The materials that make up the flywheel system, however, may entrain or evolve substantial quantities of materials which may be released within the system when under a vacuum, thus causing a reduction of the vacuum during operation. To partially deal with that problem, a drag pump
106
for example, is incorporated into the flywheel assembly
104
for pumping gases from the flywheel housing
102
into a separate gas storage chamber
108
.
The typical flywheel assembly
104
includes a flywheel, a shaft to which is secured the flywheel and one or more bearings or bearing assemblies that rotatably support the shaft. Traditionally, flywheels have been made of metal, e.g., high strength steel. More recently, flywheels have been fabricated using fiber composite materials, e.g., fiberglass or carbon wound with a resin binder, thereby making flywheels that are lighter in weight and capable of operating at higher speeds than the traditional metal flywheel assemblies operate.
Because the rotatable supporting of the rotating flywheel results in the production of heat energy in the bearings or bearing assemblies, as well as the production of heat energy by a number of other components of the conventional flywheel energy storage system
100
such as for example, the motor; the flywheel assembly
104
as well as the operational life of the flywheel energy storage system
100
is dependent upon the ability of the flywheel energy storage system to dissipate the heat energy being developed. One conventional technique to dissipate the heat energy involves the use of the supporting structure(s) for the flywheel, motor and the bearings or bearing assemblies as a thermal conduction path to conduct the heat energy of the bearings to the flywheel housing
102
. The heat energy is thence communicated to the external environment or heat sink via the flywheel housing
102
. If heat energy cannot be dissipated in the desired amounts to the heat sink, then the component temperature within the flywheel energy storage system
100
will not be maintained within optimal or desired limits thereby shorting the operational life of these components and thus reducing the operational availability of the flywheel energy storage system.
In some applications, such as when the flywheel energy storage system
100
is being used as an uninterruptible power supply (UPS), the flywheel energy storage system is located below grade (i.e., underground). In this way, a structural failure of the system or its components, no matter how unlikely, would be contained below grade. This arrangement also makes siting of the flywheel energy storage system
100
easier because the space above-ground does not have to be dedicated or reserved for the system. In addition, the end user's cabinet or structure does not have to be designed around the physical space requirements for the flywheel energy storage system. The physical space requirements for a conventional flywheel energy storage system would involve for example, a space area about 3 ft. high and about 2 ft. in diameter, which may be larger than the typical dimensions of an end user's cabinet.
One prior art technique for dissipating heat energy in such cases, involves providing a below grade structure, having a chamber in which is disposed the flywheel energy storage system
100
. This structure also is configured so that the chamber is in fluid communication with the atmosphere, whereby heat energy generated by the flywheel energy storage system
100
is dissipated directly to atmosphere, which acts as the heat sink. This arrangement, however, requires the below grade structure to be configured or designed to include one or more above-grade or at grade openings that are sufficiently sized so there is a sufficient flow of air from within the chamber to the atmosphere and from atmosphere back into the chamber so a desired amount of heat energy is thereby dissipated. Such openings, however, also must be configured and designed to provide a barrier to infestation, such as by insects or animals, or provide a barrier so as the openings do not form an attractive nuisance to children or people. Further, the openings have to be designed to preclude environmental effects, such as those caused by the weather or other natural causes, from affecting the operation of the flywheel energy storage system or shortening its operational life. Also, the structures forming the openings would involve considerations of siting (e.g., visible nuisances), which negate in part some of the perceived advantages of locating the flywheel energy storage system
100
below grade.
In another technique the structure forms a closed chamber where the heat energy dissipated from the flywheel energy storage system
100
into the closed chamber is ultimately communicated to the ground or soil surrounding the structure (i.e., earth, ground or soil comprises the heat sink. Alternatively, the flywheel energy storage system
100
is disposed in the ground or soil without a surrounding structure so the heat energy is dissipated from the storage system directly to the surrounding earth, ground or soil. The earth, ground or soil conditions in some cases, however, do not provide good heat conductivity, consequently there is poor heat energy dissipation into the soil. In such a case, the desired or needed amounts of the heat energy being generated by the flywheel energy storage system cannot be effectively dissipated into the earth, ground or soil. Consequently, component temperatures cannot be maintained at optimal values, thereby shortening the expected operational life of the component and the mean-time-between-failure (MTBF) for the flywheel energy storage system. Thus, as a practical matter this technique is limited for only those cases where earth, ground or soil conditions are optimal for the dissipation of such heat energy. Consequently, in such cases, the chamber of the below grade structure is put into fluid communication with atmosphere as described above.
It thus would be desirable to provide a new device, apparatus or method for dissipating heat energy of a flywheel energy storage system (FESS) to the surrounding environment particularly when the capabilities of the heat sink proximal the FESS are not optimal to dissipate such heat energy. It would be particularly desirable to provide such a device, apparatus and method whereby at least some of the generated heat energy is communicated to a second heat sink, the second heat sink being remote from the FESS and having desirable heat transfer characteristics (e.g., heat transfer characteristics better than those of the heat sink proximal the FESS). It also would be particularly desirable to utilize such a second heat sink as a source of useable heat energy or to provide a mechanism for stor
Ebert Todd A.
Lewis Eric
Beacon Power Corporation
Conlin David G.
Daley, Jr. William J.
Edwards & Angell LLP
McKinnon Terrell
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