Patent Application
20120119510
The present technology is directed generally to gearboxes. In particular, the present technology is directed to pneumatic gearboxes with variable speed transmission and associated systems and methods.
Power demand from an electric system can vary considerably throughout the day and between seasons. In order to improve the efficiency of an electric system, it is desirable to store excess and off-peak energy to utilize the stored energy when demand is high. Renewable energy sources (e.g., wind, wave, tidal, etc.) are typically variable (i.e., they supply intermittent and/or variable levels of energy), and can therefore also benefit from energy storage to provide a meaningful contribution to an electric system. There are several available energy storage systems that can accumulate energy for subsequent production of electricity, such as batteries, elevated hydro systems, and compressed air energy storage (CAES) systems.
Compressed air energy storage (“CAES”) systems compress air with a compressor, and the compressed air is stored in a geological formation (e.g., a cavern, aquifer, etc.) or other structure where it can be drawn upon when energy demands require. Typically, the compressed air mixes with natural gas, combusts and expands through a turbine to generate mechanical power that drives an electric generator to generate electricity. Mechanical gearboxes are used to convert the speed and torque from the power source (e.g., a renewable energy source) to interface with the electrical generator. However, mechanical gearboxes require substantial maintenance and tend to deteriorate faster than the systems they support. Direct drive generators can eliminate the need for these expensive mechanical gearboxes, but the complexity and associated maintenance of direct drive generators make them no less of a cost burden.
CAES systems are also constrained by geographic constraints and by the modest fixed volume of geological formations, and therefore typically operate at high variable pressures during energy storage and retrieval. This variable pressure decreases the efficiency of the compressor and the turbine, which operate at an optimal performance at a single design pressure. As a result, there exists a need for efficient and low-cost energy systems for use in CAES systems.
Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The present technology is directed generally to pneumatic gear-boxes with variable speed transmission and associated systems and methods. In several embodiments, for example, a pneumatic gearbox is configured to interface with a low-speed, variable mechanical power system (e.g., systems that derive power from renewable energy sources, such as wind and wave power) and with a high-speed electric generator. The pneumatic gearbox can compress a fluid at a first cyclic frequency, accumulate the compressed fluid in a storage vessel, and expand the compressed fluid upon demand. The fluid can be expanded at a second cyclic frequency different from the first cyclic frequency to interface with an electric generator that delivers electrical power to a grid. As used herein, the term “fluid” can include air, carbon dioxide, supercritical carbon dioxide, and/or any other suitable working fluid. The term “cyclic frequency” can refer to the rate of compression and/or expansion, measured in units of cycles per second (e.g., using a positive-displacement machine), such as a wind turbine, a Wankel engine, piston, and/or other devices that operate in one or more cycles. However, cyclic frequency is not limited to rotary, piston, or turbine devices. In various embodiments, the pneumatic gearbox eliminates the need for expensive gearboxes and/or direct drive systems that convert low-speed power input to a high-speed power output compatible with various electric generators and grids. In other embodiments, the technology and associated systems and methods can have different configurations, modes, components, and/or procedures. Still other embodiments may eliminate particular components or procedures described below with reference to
In other embodiments, the input power source 110 can derive from an electrical power grid (not shown). The system 100 can communicate with the electrical power grid (e.g., via a controller 180) such that electrical power can be drawn from the electrical power grid and stored as compressed fluid energy during off-peak hours (e.g., late evening, early morning), and then recovered during peak hours when energy can be drawn from system 100 to augment baseline power systems (e.g., coal, natural gas, diesel) and/or to sell the power at a premium. Conversely, to reduce the cost during peak power consumption, operation of the system 100 can be reversed such that the system 100 is the baseline power source and the traditional baseline power sources provide additional power during peak times when the load exceeds the supply from the system 100.
In further embodiments, the system 100 can include other suitable sources for input power source 110, including intermittently available power sources and/or sources that may be drawn during low-cost or off-peak hours and sold during more desirable times (e.g., peak electrical load, after the outage of power plant). In still further embodiments, the input power source 110 can derive power from multiple input power sources.
As shown in
The system 100 can convey the compressed fluid from the compressor 120 to a storage vessel 140 for the compressed fluid. In various embodiments, the storage vessel 140 can be a substantially flexible bag, balloon, and/or other conformal fluid storage device that can be ballasted within a body of water or secured to the bottom of the body of water. For example, the storage vessel 140 can be submerged a depth of approximately 60 feet or more underwater in a lake, reservoir, ocean, and/or other suitable body of water. When the storage vessel 140 is flexible, the volume of the fluid contained within can conform isobarically to the amount of fluid compressed and the depth within the body of water. In other embodiments, the storage vessel 140 can be substantially rigid, such as a pipe or tank, and/or it can be positioned under or above water. In further embodiments, the storage vessel 140 can be an underwater device as described in the following U.S. patent applications: U.S. patent application Ser. No. 12/888,971, filed on Sep. 23, 2010, and entitled SYSTEM FOR UNDERWATER COMPRESSED FLUID ENERGY STORAGE AND METHOD OF DEPLOYING SAME; U.S. patent application Ser. No. 12/889,013, filed on Sep. 23, 2010, and entitled UNDERWATER COMPRESSED FLUID ENERGY STORAGE SYSTEM; and U.S. Provisional Application No. 61/309,415, filed on Mar. 1, 2010, and entitled UNDERWATER COMPRESSED AIR ENERGY STORAGE, each of which is herein incorporated by reference in its entirety.
To generate power, the compressed fluid may be transferred to an expander 150 that can expel the fluid into the environment at a generally standard or ambient pressure. In other embodiments, such when the fluid is hazardous to the environment (e.g., carbon dioxide), the fluid outlet 160 can dispel the fluid into a closed chamber where it can be disposed of or recirculated through the system 100. Expansion of the fluid generates mechanical power that may be conveyed to an electrical generator 170 where the mechanical power is converted into electrical power. The electrical generator 170 can be any suitable electrical generator 170. Once the electrical power is generated, it can be conveyed to an electrical power grid and/or other electrically powered devices. The power may be transmitted via DC or NC lines. Accordingly, the system 100 can step up electrical power to provide a high A/C voltage that can be transmitted to a load or grid.
As explained in further detail below, the expander 150 can be a Wankel-type expander, an Archimedes screw-type expander, and/or other suitable fluid expander. In selected embodiments, the compressor 120 and the expander 150 can be combined into a single device (i.e., a compression/expansion device or “C/E” device).
The expander 150 can expand the compressed fluid at a cyclic frequency different from the cyclic frequency at compression. Accordingly, the system 100 can convert the low frequency (e.g., low RPM), low torque power produced by many renewable energy systems (e.g., wind turbines) to interface with electrical generators (e.g., the electrical generator 170) that have high-frequency (e.g., high RPM), and low torque, and therefore the system 100 eliminates the need for expensive mechanical gearboxes and direct drive systems.
The heating associated with compression and the cooling associated with expansion can decrease the efficiency of the system 100. Accordingly, various embodiments of the technology include forced-convection cooling to cool the fluid in the compressor 120, and forced-convection heating to heat the fluid in the expander 150. In embodiments where the storage vessel 140 is at substantially ambient temperature and pressure (e.g., at a depth within a body of water), both cooling for compression and heating after expansion may be performed using the water that surrounds system 100. This allows the system 100 to operate in a substantially isothermal manner that cools the fluid to near ambient during the compression stage(s) and heats the fluid to near ambient during the expansion stage(s). In other embodiments, system 100 can store energy via a controlled heat transfer process to a thermal storage tank (not shown), and energy to heat the fluid after expansion is drawn from the thermal storage tank via pumps or other suitable devices.
Referring still to
The system 100 can have particular applicability in the context of renewable energy sources. In particular, many renewable energy sources (e.g., wind, wave, solar, tidal, etc.) provide energy in a manner that varies over time. The system 100 can provide an efficient mechanism to accumulate energy (e.g., build up and store a reserve of energy) and release energy at a later time. This allows renewable energy sources to operate at variable speeds, rather than at a fixed speed, and therefore increases the amount of power generated and improves the efficiency with which such renewable energy systems operate.
Fluid passageways 222 (identified individually as a first fluid passageway 222a and a second fluid passageway 222b) can connect the compressor 120 and the expander 150 with the submerged storage vessel 140 such that compressed fluid can flow to and from the storage vessel 140. In several embodiments, the compressor 120 and the expander 150 can be combined into a single C/E device 224 (as indicated by the broken lines) such that only one fluid passageway 222 is necessary to couple the C/E device 224 to the storage vessel 140. In further embodiments, the system 200 can include more than two fluid passageways 222. For example, multiple fluid passageways 222 can be coupled to the compressor 120 and/or to the expander 150 to transmit higher volumes of compressed fluid to and from the storage vessel 140. In other embodiments, additional compressors 120 and expanders 120 with corresponding fluid passageways 222 can be added to the system 200.
The rigidity or flexibility of the fluid passageways 222 can be selected depending upon whether the surface unit (e.g., the compressor 120, the expander 150, etc.) attached to the fluid passageways 222 is floating or affixed to the seafloor 218. In deeper waters, for example, renewable energy harvesting schemes typically use a floating platform that is anchored to the seafloor 218 such that wind, wave, or other elements may move the platform until the anchor lines are tensioned. To accommodate this movement, flexible tubes or other flexible fluid passageways 222 may be used. Conversely, rigid fluid passageways 222, such as pipes, are well suited for more stationary surface units. In other embodiments, more rigid fluid passageways 222 can be used with anchored surface units and configured such that the deflection strain over the length of the fluid passageways 222 is within its structural limits.
As power is introduced into the system 200 (e.g., via renewable energy sources), the compressor 120 can compress a fluid, and the first fluid passageway 222a can transfer the compressed fluid to the storage vessel 140. When energy loads 225 demand additional energy from a grid 226, the expander 150 can draw the compressed fluid from the storage vessel 140 via the second fluid passageway 222b and expand the fluid to drive the electrical generator 170. The separate compressor 120 and expander 150 configuration shown in
The system 201 can optionally include a thermal storage vessel 232 (e.g., a tank, pipe, flexible bag, etc.) coupled to the compressor 120 and the expander 150 via the pump 228 and configured to extract energy (i.e., heat) during compression and supply energy during expansion. In various embodiments, the thermal reservoir 232 can be sufficiently large such that thermal stratification occurs therein. This allows hot water to be drawn from the upper portion of the thermal reservoir 232, and cold water to be drawn from the lower portion of the thermal vessel 232. For example, during compression, cold water for cooling can be drawn from the lower portion of the thermal reservoir 232 to the compressor 120. The water is heated during compression and fed back into the thermal reservoir 232 where it settles in the upper portion for use during expansion and/or other operations requiring heat. In lieu of the thermal reservoir 232, relatively cold water can be extracted from lower depths of the body of water and relatively warmer water can be extracted proximate to the surface of the water. Accordingly, the system 200 can operate in an isothermal mode, or in an adiabatic mode, with intercooling wherein cold water is supplied to the compressor 120 between compression stages and/or interwarming wherein hot water is supplied to the expander 150 from the thermal storage vessel 232 during expansion.
As shown in
In various embodiments, electro-chlorination can reduce or prevent biofouling when seawater is introduced into the system 200 (e.g., for cooling and heating). Electro-chlorination can be performed as the seawater enters the system through an electrolysis process that produces sodium and chlorine ions in excited states that act as a temporary biocide (e.g., 15-30 minutes) against buildup of organisms on the surfaces of a heat exchanger or like structure. A short time after electro-chlorination, the seawater returns to a ground state such that no long-lasting biocides are added to the seawater. In other embodiments, DC or AC pulsed electricity can be used through metallic walls of a heat exchanger at regular intervals to reduce the buildup of organisms.
In operation, several embodiments of the system 200 can eliminate or at least reduce the high cost of a mechanical gearbox, while enabling the effective coupling of a low-rpm energy device to a high-rpm electrical generator. The low cyclic frequency device compresses the fluid, optionally storing it for later use, while the expander takes pressurized air and drives a higher frequency generator. Accordingly, the system 200 can provide efficient and inexpensive generation of electricity.
As further shown in
Referring now to
At the base of the wind turbine 334, the compressed fluid moves to the storage vessel 140. When power is needed, the compressed fluid can be piped to an onshore expander 150 and electric generator 170 to produce electrical power. These onshore power generation components can eliminate costs associated with offshore setup and operation of the expander 150 and the electrical generator 170. Like the system 300 discussed above, the system 301 shown in
The systems 300 and 301 described with reference to
An input power source (e.g., a renewable energy system, motor, etc.) can drive the screw device 436 (e.g., the shaft 444 and the outer cylinder 445) such that it rotates about the underground support 438. The screw device 436 can be configured to rotate as a whole such that the spiral 446, the shaft 444 and the outer cylinder 445 rotate together to provide a simplified compressor with only one moving part. Unlike conventional Archimedes screws that pump fluids upwards, the screw device 436 in the illustrated embodiment is configured as a compressor that pumps slugs of fluid and water downward from the first end portion 448 to the second end portion 452 under hydrostatic equilibrium at incremental depths of the screw device 436. As the screw device 436 rotates through 360°, it captures both air and water via the first opening 454a to form a bubble of air in a portion of the circumference surrounded by water within the screw device 436. The spiral 446 drives the air down toward the second end portion 452 at an angle, causing each air bubble to shrink and compress as they descend.
The screw device 436 can include one or more features to compensate for the shrinking air bubbles and maintain compression throughout the length of the screw device 436. For example, in selected embodiments, the pitch of the spirals 446 can be decreased (i.e., the spirals 446 can be positioned closer together) as the compression increases (i.e., toward the second end portion 452) to decrease the volume within the more compressed portions of the screw device 436. In other embodiments, the diameter of the inner shaft 444 can be increased and/or the diameter of the outer cylinder 445 can be decreased along the length of the screw device 436. In further embodiments, the outer cylinder 445 can include apertures that allow additional water to be entrained in the screw device 436 without releasing air.
The compressed air can be released via the second opening 454b and stored within the storage vessel 140. In various embodiments, the compressed air is at local hydrostatic pressure when it is expelled from the second opening 454b, and therefore the storage vessel 140 or a portion thereof must be positioned above the second opening 454b to capture the rising bubbles. For example, as shown in the illustrated embodiment, the system 400 can include an inverted funnel 442 positioned above the second opening 454b to collect the compressed air bubbles as they rise in the direction of the arrow A. As shown in
In selected embodiments, the screw device 436 can be reversed such that it effectuates expansion of the compressed air. When the compressed air in the storage vessel 140 is at local atmospheric pressure, the second end portion 452 of the screw device 436 can be raised (e.g., via a controller) above the storage vessel 140 to capture out-flowing air (e.g., using an inverted funnel at the second opening 454b). Alternatively, the storage vessel 140 can route the compressed air into the second opening 454b. The compressed air can be allowed to periodically exit the reservoir and drive the screw device 436 in the reverse direction to expand the air and drive the electrical generator 170 at the surface of the water 214.
During compression and expansion, the air bubbles exchange heat with the water entrained within the spiral 446 of the screw device 436 and with the exterior body of water via the outer cylinder 445. For example, as air is drawn downward during compression, the water outside the screw device 436 provides substantial cooling, and the direct contact of the air with the slugs of water within each turn of the spiral 446 can further enhance cooling as a result of the substantially higher heat capacity of the water than air (e.g., 3,000 times higher per unit volume at standard temperature and pressure). Additionally, the rotation of the screw device 436 ensures the exterior cylinder 445 is continuously wetted by the water to further enhance cooling.
The stable stratification of a body of water can also facilitate cooling as the air compresses and warming as the air expands. For example, due to thermal stratification, the upper portions of the screw device 436 are surrounded by relatively higher temperature water proximate to the surface of the water and the lower portions of the screw device 436 are surrounded by relatively lower temperature water proximate to the seafloor 218. During compression, the air bubbles are cooled by the surrounding water as they descend through the screw device 436 such that the temperature of the compressed air is substantially equal to the surrounding water once the air bubbles reach the second end portion 452 of the screw device 436. Therefore, less work must be performed to compress the air and the system 400 increases in efficiency. Similarly, during expansion, the expanding air can be warmed by the surrounding water as it ascends through the screw device 436 to enhance the efficiency of expansion. Accordingly, the enhanced heat exchange of the screw device 436 eliminates the need for an intervening heat exchanger.
In several embodiments, the shaft 444 of the screw device 436 can have a hollow core that defines a cavity 447. During compression, cold water from the depths of the water can be upwelled against the flow of stable stratification of the water using a pump and/or motor. The cold water can move from the second end portion 452 of the screw device 436 to the first end portion 448 via the cavity 447 to enhance cooling. Similarly, warm water from the surface of the water 214 and/or a thermal reservoir can be down-welled from the first end portion 448 to the second end portion 452 to enhance heating during expansion. This additional heating and cooling during expansion and compression, respectively, can increase the efficiency of the screw device 436 and allow more work to be extracted. In further embodiments, a hollow conduit can be positioned around the outer cylinder 445 to further enhance heating and/or cooling.
In the embodiment illustrated in
The tubing 559 is attached to the shaft 444 such that the first opening 454a forms an umbrella or cup shape that captures a semicircle of air as it rotates at an angle to the surface of the water 214. Once captured, the air will rise as a bubble toward the top of the tubing 559, while the water settles underneath. As the screw device 566 continues to rotate and capture more slugs of air, the air bubble will remain positioned toward the top of each rung of the tubing 558 as it spirals downward toward the second end portion 452 of the screw device 566. Accordingly, the air is therefore held at a local maximum as it travels downward through the tubing 559, thus maintaining hydrostatic pressure through compression as the air bubble descends.
In the embodiment illustrated in
As further shown in
Referring to
Turning now to
As discussed above, to further enhance the performance (e.g., power generated) of the screw device 668, propellers and/or other fluid conveyance mechanisms can be coupled to the screw device 668 to convey cold water up a hollow portion of the shaft 444 during compression (i.e., to cool the air), and conveying warm water down from the surface of the water 214 during expansion (i.e., to warm the air).
In selected embodiments, the first end portion 448 of the screw device 668 can be coupled to a linear spring / universal joint to constrain the location of the screw device 668 at the surface of the water 214. For example, the screw device 668 can use such a linear spring-universal joint configuration when it is connected to a ship. This allows for rotational and longitudinal degrees of freedom for the ship in response to surface waves, while still enabling an on-board motor/generator to generate power and mechanical work during charge (i.e., compression) and discharge (i.e., expansion) cycles.
In the embodiments described above with reference to
Embodiments of the pneumatic gearbox system alternately use rotary Wankel-style compressors, expanders, and/or bidirectional C/E devices.
In several embodiments of the disclosure, the system 710 includes a bidirectional compressor/expander, configured to operate as a compressor in a first mode and an expander in a second mode. Depending on the operational mode of the system 710 (e.g., whether it is being run as a compressor or an expander), the first port 726 operates as an inlet port or an outlet port and the second port 728 performs the opposite function, e.g., it operates as an outlet port or an inlet port. For example, in a first mode, in which the system 710 is running as a compressor, the rotor 732 rotates in a first direction, the first port 726 functions as an inlet port (feeding low-pressure working fluid, or flow, into the compression chamber 724), and the second port 728 functions as an outlet port (accepting compressed working fluid and feeding it to the first passageway 714). In the second mode, in which the system is running as an expander, the rotor 732 rotates in a second direction opposite the first direction, the first port 726 operates as an outlet port, the second port 728 operates as an inlet port, and the direction of flow through the system 710 is reversed. In other embodiments, the system 710 operates as a dedicated compressor or expander instead of operating bidirectionally. In particular embodiments, the system 710 can have more than two ports. For example, in some embodiments, the system 710 can have two inlet ports and two outlet ports. The ports 726, 728 can be rectangular with rounded corners or otherwise shaped. The ports 726, 728 are positioned in the chamber housing 718 in manners that differ in different embodiments of the disclosure, as will be described in further detail later. In any of these embodiments, individual ports (e.g., the first port 726 and the second port 728) are separated from each other by a partition 730 of the chamber housing 718.
The system 710 can further include a rotor 732 coupled to and eccentrically rotatable relative to a shaft 734 which runs through a center portion 736 of the rotor 732. An eccentric cam 768 is further coupled to the shaft 734 and is positioned in the center portion 736 of the rotor 732. The rotor 732 can have a plurality of lobes 738. Although the rotor 732 illustrated in
In the illustrated embodiment, both the first port 726 and the second port 728 are radially positioned. In other words, the ports 726, 728 are positioned on a surface 721 of the chamber housing 718 that is generally parallel to the rotational axis RA. As the rotor 732 makes orbital revolutions around the shaft 734, the lobe tips 739 rotate past the first and second ports 726, 728 and cyclically cover and uncover the first and second ports 726, 728.
Seals (e.g., tip rollers 740) on the lobes 738 seal the rotor 732 against the inner wall 720 of the chamber housing 718. The tip rollers 740 can be generally cylindrical and are mounted to the lobes 738 via a roller-mount 741, such as a gear-free wheel-and-axle apparatus or a spherical wheel system. The rollers 740 can be forced against the rotor walls in a modulated manner by springs or other pressure devices (e.g., as disclosed in U.S. Pat. No. 3,899, 272) that provide low-friction contact with the chamber housing inner wall 720 and guide the rotor position. The rollers 740 can also help ensure that pressurized fluid does not escape from a chamber zone 742 bounded by the rotor 732 and the housing inner wall 720. In other embodiments, other tip-sealing features, such as sliding seals, liquid films, and/or a purposefully placed gap space between the lobe 738 and the inner wall 720 of the chamber housing 718 can be used. In one embodiment, for example, a thin film of liquid can be applied to the chamber housing 718 or the lobe tips 739. In some embodiments, the thin film can comprise seawater, freshwater, oil, glycol, glycerin, and/or another material, or a combination of materials. The thin film can provide a higher flow resistance across a gap between the tip 739 and the chamber housing inner wall 720. In other embodiments, air bearings can be applied to the tip 739 to seal the chamber zone 742742 with minimal friction. In at least some embodiments, the inner wall 720 of the pressure-modifying chamber 724 and/or portions of the rotor 732 can include one or more low-friction coatings 744. The coating 744 can include plastic, ceramic, or other materials. In low-temperature applications, a low-friction coating (e.g., Teflon, epoxy, polycarbonate, cross-linked polyethylene, and/or other material) can improve the integrity of the seal, while providing relatively low friction between the rotor 732 and the chamber 724 and without incurring the expense of a high temperature seal.
The separation portion 730 between the first port 726 and the second port 728 can carry a seal, e.g., a variable geometry seal 746. The variable geometry seal 746 can engage with the peripheral boundary 733 of the rotor 732 as the rotor 732 eccentrically rotates in the chamber 724. The variable geometry seal 746, in combination with the rotor periphery 733 and rollers 740 contacting the inner wall 720 of the chamber housing 718, divides the chamber 724 into individual chamber zones 742 having individual zone pressures. In the illustrated position, the chamber 724 has only one chamber zone 742 due to the orbital orientation of the rotor 732. Rotating the rotor 732 alters the size and number of the zones 742.
The orbital position of the rotating rotor 732 with respect to the chamber housing inner wall 720 can determine the size of the chamber zones 742 and the pressure of the fluid within the zones 742. For example, the rotor 732 illustrated in
The system 710 can further include a heat exchanger 758 positioned outside the chamber housing 718. The heat exchanger 758 can include a heat exchanger passageway 756 in fluid communication with one or more of the first and second passageways 714, 716 and/or the chamber 724. In one embodiment, a heat exchanger housing wall 761 positioned between the heat exchanger passageway 756 and the first and/or second passageways 714, 716 channels fluid flow between the heat exchanger passageway 756 and the first and/or second passageways 714, 716. The fluid can be channeled to enhance working fluid contact with the heat exchanger 758. The heat exchanger 758 can be dedicated to providing heating or cooling, or can be bidirectional to cool fluid processed by the chamber 724 during compression and heat the fluid during expansion. In other embodiments, fluid is injected directly into the chamber 724 and/or a passageway 714, 716, or 756 by one or more nozzles 731, such as an atomizing spray nozzle. The injected fluid can be colder or hotter than the working fluid in the chamber 724, and can accordingly cool or heat the working fluid in addition to or in lieu of the heat transfer provided by the heat exchanger 758.
An outer housing 750 can at least partially surround or encase the chamber housing 718, the first passageway 714, and the second passageway 716. The outer housing 750 can have an inner surface 752 and an outer surface 754. The outer housing 750 can be radially spaced apart from the chamber housing 718 to provide room for the passageways 714, 716, 756, the heat exchanger 758, stabilizing features 760 (e.g., standoffs), an insulator material (not shown in
As mentioned above, the inner wall 720 of the chamber housing 718 can have one or more coatings 744 to reduce friction and/or manage wear. The coating 744 can be applied to other surfaces of the system 710 (in addition to or in lieu of the inner wall 720), e.g., other surfaces of the chamber housing 718, the outer housing 750, the rotor 732, the passageways 714, 716, the fluid passageways 756, the heat exchanger 758, the bulkheads 762 and/or the shaft 734, in order to achieve desired functional or material characteristics such as heat resistance or corrosion resistance. For example, when the system 710 is used for combustion engine applications, high-temperature coatings, such as ceramics, can be used to protect the surfaces from hot fluids. In low temperature compressor applications, plastic coatings can be used to improve corrosion resistance and reduce friction at lower cost. Further features of the system 710 are described in U.S. patent application Ser. No. 13/038,345, filed on Mar. 1, 2011, and entitled ROTARY COMPRESSOR-EXPANDER SYSTEMS AND ASSOCIATED METHODS OF USE AND MANUFACTURE, which is herein incorporated by reference in its entirety.
In the embodiment illustrated in
Additionally, compression losses represent an undesirable conversion of energy to heat. Air passing through a small hole or will experience a pressure drop that causes irrecoverable loss of energy. By decreasing the number of compressions per cycle in the system, more degrees of rotation are available, which in turn enables the plenum on the side of the C/E to be larger. Such larger plenums reduce losses and thus improve efficiency.
Moreover, the chamber ports keep the peak-flow speeds reasonable, often less than 50 meters per second, to avoid losses. The volumetric flow is tied to the rotor rotational speed and the eccentricity of the cam, which affects the displacement per rotation. The pressure ratio of the stage affects the location of the edge of the exhaust port. It is generally beneficial to make the ports as large as possible, thus lowering the average exit velocity. One of skill in the art of mechanical design can vary these parameters to optimize the geometry for a given pressure ratio per stage.
From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. For example, several features of the disclosure are discussed in the context of wind-powered systems. Many of these features can be applied in the context of systems powered by other renewable and non-renewable energy sources. Certain aspects of the technology described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, each of the pneumatic gearbox system described above include one power input system and one power output. However, a plurality of pneumatic gearbox systems and components can be combined into a single system with multiple power inputs and/or outputs. Additionally, in an alternate embodiment, an Archimedes screw device may be housed in a bath through which cooling and heating liquid may pass. In such an embodiment, energy from the heat of compression can be extracted and stored (e.g., in a thermal reservoir) such that energy can then be drawn from storage during expansion to heat the Archimedes screw device. Further, while advantages associated with certain embodiments have been described in the context of those embodiments, other embodiments may also exhibit such advantages and not all embodiments need necessarily exhibit such advantages to fall within the scope of the present technology. Accordingly, the present disclosure and associated technology can encompass other embodiments not expressly described or shown herein.
The present application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/364,364, filed on Jul. 14, 2010 and entitled UNDERWATER COMPRESSED AIR ENERGY STORAGE SYSTEM OPERATION AND COMPONENTS, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61364364 | Jul 2010 | US |
