WO2011123955A1 - System and method for energy storage and retrieval - Google Patents
System and method for energy storage and retrieval Download PDFInfo
- Publication number
- WO2011123955A1 WO2011123955A1 PCT/CA2011/000405 CA2011000405W WO2011123955A1 WO 2011123955 A1 WO2011123955 A1 WO 2011123955A1 CA 2011000405 W CA2011000405 W CA 2011000405W WO 2011123955 A1 WO2011123955 A1 WO 2011123955A1
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- WO
- WIPO (PCT)
- Prior art keywords
- gas
- compression
- energy storage
- retrieval system
- hydraulic fluid
- Prior art date
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L50/00—Electric propulsion with power supplied within the vehicle
- B60L50/30—Electric propulsion with power supplied within the vehicle using propulsion power stored mechanically, e.g. in fly-wheels
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
- F02C6/00—Plural gas-turbine plants; Combinations of gas-turbine plants with other apparatus; Adaptations of gas-turbine plants for special use
- F02C6/14—Gas-turbine plants having means for storing energy, e.g. for meeting peak loads
- F02C6/16—Gas-turbine plants having means for storing energy, e.g. for meeting peak loads for storing compressed air
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
- F15B1/02—Installations or systems with accumulators
- F15B1/027—Installations or systems with accumulators having accumulator charging devices
- F15B1/033—Installations or systems with accumulators having accumulator charging devices with electrical control means
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
- G05F3/02—Regulating voltage or current
- G05F3/04—Regulating voltage or current wherein the variable is ac
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K99/00—Subject matter not provided for in other groups of this subclass
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- F05D2260/00—Function
- F05D2260/40—Transmission of power
- F05D2260/406—Transmission of power through hydraulic systems
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/16—Mechanical energy storage, e.g. flywheels or pressurised fluids
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- This application relates generally to power conversion and energy storage, and more particularly to systems and methods for and relating to storing and retrieving energy in and from compressed gas.
- the stored energy may then be used to provide most of the drive to gas expansion turbines (like the General Electric LM2500) but because of the thermodynamics of expanding gas from 1000 psi to 15 psi (1 atmosphere) large temperature losses occur within the expanded gas, and to maintain an operational system natural gas must be burned in the gas turbines to provide adequate heat to allow for "reasonable" operating temperatures.
- gas expansion turbines like the General Electric LM2500
- thermodynamics of expanding gas from 1000 psi to 15 psi (1 atmosphere
- large temperature losses occur within the expanded gas, and to maintain an operational system natural gas must be burned in the gas turbines to provide adequate heat to allow for "reasonable" operating temperatures.
- CAES systems There are known problems with known CAES systems, and these relate to two specific areas. First, known systems are not truly “renewable” because they rely on the burning of natural gas (or some other fuel) to provide heat to balance the thermodynamics of the system. Second, they are relatively inefficient with a total efficiency of between 30 and 40 percent (
- Rufer et al. in WO 2008-139267 have identified the ultimate basic efficiencies possible through the use of piston compression and expansion of gas, and in particular through the use of liquid pistons to achieve this compression/expansion.
- Rufer et al. teach the use of a shuttling device to separate hydraulic motor pump fluid from the working fluids of the storage vessel, and about the energy densities, and efficiencies which are attainable with such an apparatus.
- Rufer et al. further teach that heat exchange within the "liquid piston" part of the apparatus will improve the possible energy densities.
- GATSI entitled “Investigation and optimisation of hybrid electricity storage systems based on compressed air and supercapacitors.” (Thesis N 3628 (2006), Swiss Federal Institute of Technology, Lausanne (EPFL Lausanne - Switzerland).
- Van de Ven and Li (Applied Energy 86, 10) teach of the high efficiencies
- thermodynamics may be better managed by limiting the gas compression ratios to approximately 3.2: 1.
- the disclosed apparatus makes use of common commercially-available components to achieve the implementation of hydraulic-pneumatic compression.
- Cavitation is the highly destructive appearance of bubbles formed by entrained gases and usually nucleated around small impurities in the hydraulic fluid. If the expansion of the gas is for example 1000 times, then a bubble that was entrained at a scale of 10 microns expands to 10 mm with the destructive force of a small explosion.
- Adler and Siebert and Van Ven and Li further teach that the liquid pistons easily accommodate heat exchangers in the compression chamber (or cylinder) so that maintaining quasi-isothermal conditions is much more easily achieved than with conventional compressors or expanders.
- a system for storing and releasing energy comprising a generator/motor subsystem; a hydraulic pump for pumping hydraulic fluid between first and second pump ports in response to force applied by the generator/motor subsystem and also capable of imparting force to the generator/motor subsystem in response to hydraulic fluid being caused to flow between the first and second pump ports; a first compression/expansion vessel for exchanging hydraulic fluid with the hydraulic pump via the first pump port; a second compression/expansion vessel for exchanging hydraulic fluid with the hydraulic pump via the second pump port; a gas storage subsystem for selectively storing gas from, or releasing gas to, the first and second gas compression/expansion vessels; an internal heat exchanger within each of the first and second compression/expansion vessels for exchanging heat between the hydraulic fluid and the gas therein, each internal heat exchanger having a very large thermal mass relative to the mass of gas within the first and second compression/expansion vessels; a control subsystem for controlling at least a plurality of gas valves associated with the
- FIG. 1 is a schematic diagram of a system for storing and retrieving energy using compressed gas, according to an embodiment
- Figure 2 is a schematic diagram of connections of a control subsystem with various components of the system of Figure 1 ;
- Figures 3A and 3B are diagrams of a compression/expansion vessel for the system of Figure 1 without an internal heat exchanger, and respective different hydraulic fluid levels therewithin;
- Figures 3C and 3D are diagrams of a compression/expansion vessel for the system of Figure 1 with an internal heat exchanger, and respective different hydraulic fluid levels;
- Figure 4 is a schematic diagram showing components of the system of Figure
- Figure 5 is a schematic diagram showing components of the system of Figure
- Figure 6 is a schematic diagram showing components of the system of Figure
- Figure 7 is a schematic diagram of an alternative embodiment of a gas storage subsystem
- Figure 8 is an alternative embodiment of a system for storing and retrieving energy using compressed gas
- FIG. 9 is a graph showing variation of power output/input of a generator/motor over time
- Figure 10 is a graph showing variation of angular speed of rotation and variation of power output/input of the generator/motor over time
- Figure 1 1 is a graph showing variation of exciter current of the
- Figure 12 is a graph showing the resultant variation of power output/input of the generator/motor over time as a result of variation of exciter current as showing in Figure 1 1 ;
- Figure 13 shows the hydraulic pump volume and flow direction variations with time
- Figure 14 is a schematic circuit diagram of a circuit for conditioning three phase power being applied to (released via) a generator/motor during storing (retrieving) of energy;
- Figure 15 shows output voltage waveform as a result of filtered pulse width modulation
- Figure 16 shows a compression/expansion vessel in cooperation with an isolation cylinder for a two-liquid buffered configuration
- Figure 17 shows a compression/expansion vessel with two layers of liquid therein for a two-liquid un-buffered configuration
- Figure 18 shows two compression/expansion vessels for an alternative embodiment of a two-liquid buffered configuration with a solid piston
- Figure 19 is a schematic diagram of an uninterruptible power supply
- Figure 20 is a schematic diagram of a rectification stage for the uninterruptible power supply of Figure 19;
- Figure 21 is a schematic diagram of an alternative rectification stage for the uninterruptible power supply of Figure 19;
- Figure 22 is a schematic diagram of voltage rectification, smoothing and inverting stages of the uninterruptible power supply of Figure 19;
- Figure 23 is a schematic diagram of the output stage of the uninterruptible power supply of Figure 19;
- Figure 24 is a schematic diagram of one of the sets of insulated gate bipolar transistors of the output stage of Figure 23;
- Figure 25 is a schematic diagram showing the interconnection of multiple secondary power sources along with a primary power source to a power bus, according to an embodiment
- Figure 26 is a schematic diagram showing the interconnection of multiple secondary three-phase power sources along with a primary three-phase power source to a power bus, according to an embodiment
- Figure 27 is a schematic diagram showing interconnection of multiple three- phase loads to a power bus;
- Figure 28 is a schematic diagram showing a voltage switching mechanism;
- Figure 29 is a graph showing voltage variations with primary and secondary power sources.
- Figure 30 is a schematic diagram showing centralized control of multiple power sources and their delivery of power to multiple loads.
- System 5 is controlled by a control subsystem 7 which, in this embodiment is a programmable logic controller (PLC) but which could be implemented alternatively by another device such as a personal computer or the like with appropriate interface hardware.
- System 5 also comprises a generator/motor subsystem that, in this embodiment, comprises a single generator/motor 10 mechanically coupled to a hydraulic pump 12 with a shaft coupler so as to impart rotational force to the hydraulic pump 12 thereby to pump hydraulic fluid 13 between a first port 14 and a second port 16 of the hydraulic pump 12 during energy storing.
- generator/motor 10 and hydraulic pump 12 are mechanically coupled such that hydraulic pump 12 can impart rotational force to the generator/motor 10 in response to hydraulic fluid 13 being pumped between the first and second ports 14, 16 during energy releasing, as will be described.
- generator/motor 10 is a three-phase AC (Alternating
- hydraulic pump 12 has a variable displacement and an over-the-centre configuration, and thereby has a shaft that rotates in only one direction (for example, clockwise), whether hydraulic fluid 13 is flowing from the first port 14 to the second port 16, or from the second port 16 to the first port 14. That is, despite the direction of flow of hydraulic fluid 13, throughout storing and releasing, hydraulic pump 12 rotates in a single direction.
- the hydraulic pump 12 comprises filters, valves and charge pressure circuitry for its operation.
- valve(s) (not shown for ensuring Figure 1 is straightforward to understand) in hydraulic pump 12 are each electronically controlled via signals provided by the control subsystem 7.
- a flywheel 18 is mechanically coupled to the shaft coupler for maintaining rotation during fluid flow through hydraulic pump 12, pressure changes, changes in the direction of flow between ports 14 and 16 of the hydraulic fluid 13, and mode changes (i.e., from energy storing to energy releasing and vice-versa, as will be described).
- the flywheel 18 provides additional angular momentum which may be converted to electrical energy by the generator/motor by means of loss of rpm for the short term, which in this embodiment is between about 1 and 10 seconds.
- a power conditioning module 19 is coupled between the generator/motor 10 and electrical mains (not shown) to control the generator/motor 10 and to condition power from the generator/motor 10 for use in supplying power to electrical mains.
- power condition module 19 is an inverter preceded by rectification diodes and a stiff DC capacitor. Power conditioning in the opposite direction between the mains and the motor aspect of the generator/motor subsystem is of course a similar circuit in reverse - a Variable Frequency Drive.
- the hydraulic pump 12 is in fluid communication with an interior volume of a first compression/expansion vessel 20 via a fluid line 40 that runs from the first port 14, through the exterior wall of the first compression/expansion vessel 20, and terminates near to the bottom of its interior volume. Hydraulic fluid 13 is permitted to flow between the hydraulic pump 12 and the interior volume of first compression expansion vessel 20 via fluid line 40.
- the hydraulic pump 12 is also in fluid communication with an interior volume of a second compression/expansion vessel 30 via a fluid line 50 that runs from the second port 14, through the exterior wall of the second compression/expansion vessel 30, and terminates near to the bottom of its interior volume. Hydraulic fluid 13 is permitted to flow between the hydraulic pump 12 and the interior volume of the second compression/expansion vessel 30 via fluid line 50.
- Fluid lines 40 and 50 are constructed of any material or materials that is/are capable of withstanding pressures imparted to the hydraulic fluid 13 in system 5, such as steel.
- the hydraulic fluid 13 is RYTOX, which is a nonflammable, non-reactive liquid suitable for use with compression of gases that include oxygen, such as air.
- Other suitable hydraulic fluids may be employed.
- the interior volume of the first compression/expansion vessel 20 is also in fluid communication with a gas storage subsystem 100 via a gas line 60 that runs from near to the top of the interior volume of first compression/expansion vessel 20, through its exterior wall, to the gas storage subsystem 100.
- the interior volume of the second compression/expansion vessel 30 is also in fluid communication with the gas storage subsystem 100 via a gas line 70 that runs from near to the top of the interior volume of second compression/expansion vessel 30, through its exterior wall, to the gas storage subsystem 100.
- Gas lines 60 and 70 are constructed of any material or materials that is/are capable of withstanding pressures imparted to the gas in system 5, such as steel.
- At least one liquid level transducer 24 is disposed within the interior volume of the first compression/expansion vessel 20, and generates liquid level signals indicative of the level of hydraulic fluid 13 within the first compression/expansion vessel 20.
- at least one liquid level transducer 34 is disposed within the interior volume of the second compression/expansion vessel 30, and generates signals indicative of the level of hydraulic fluid 13 within the second compression/expansion vessel 30.
- Control subsystem 7 receives the liquid level signals from liquid level transducers 24, 34 for controlling system 5 accordingly. Generally, the control subsystem 7 ensures that hydraulic fluid 13 does not enter gas lines 60, 70.
- the liquid level transducers 24, 34 generate respective signals that can be received by control subsystem 7 outside of the first and second expansion/compression vessels 20, 30. It will be understood that such signals may be provided to control subsystem 7 by wire or by both wire and wirelessly.
- a first internal heat exchanger 22 is also disposed within the interior volume of the first compression/expansion vessel 20, and a second internal heat exchanger 32 is also disposed within the interior volume of the second compression/expansion vessel 30.
- Each of the internal heat exchangers 22, 32 functions to exchange heat between any hydraulic fluid 13 within the compression/expansion vessels 20, 30 and any gas within that is being compressed/expanding within respective compression/expansion vessels 20, 30.
- the heat exchanger exists everywhere within the volume of the compression/expansion modules and is thermally massive (physical density approximately 1 gm/cc) and porous (displacing less than 25% of the available volume).
- the internal heat exchanger is thermally massive relative to the gas, and everywhere, it is difficult for the gas to change temperature much, and the process remains quasi-isothermal. As the liquid of the liquid piston passes in and out of this porous massive internal heat exchanger, it captures the heat trapped within the heat exchanger, so the heat is transferred to the liquid hydraulic fluid.
- a first external heat exchanger 42 associated with the fluid line 40 functions to exchange heat between hydraulic fluid 13 within the fluid line 40 and the ambient atmosphere.
- a second external heat exchanger 52 associated with the fluid line 42 functions to exchange heat between hydraulic fluid 13 within the fluid line 42 and the ambient atmosphere.
- First internal heat exchanger 22, second internal heat exchanger 32, first external heat exchanger 42 and second external heat exchanger 52 generally cooperate to provide heat exchange between the ambient atmosphere outside of the first and second compression/expansion vessels 20, 30 and the gas within the first and second
- United States Patent Application 2007/0258828 discloses that with a liquid piston compressor, it is possible to mount a heat exchanger within the compression chamber of a liquid piston gas compressor. It is also mentioned that passive heat exchange may be possible by partially filling the volume with spheres or plates.
- PCT Application 2010/135658 A2 (Aborn and Ingersoll) disclose that thin cup like structures can be used within the apparatus to catch gas bubbles, and thereby improve the heat exchange.
- United States Patent No. 7,802,426 (Bollinger) discloses that high efficiency near-isothermal compression of gas may be achieved by externally circulating a stream of that gas through an external heat exchanger. It is taught that, if rates of compression and heat exchange flow are chosen appropriately, and the compression rate is sufficiently slow then near-isothermal results may be achieved.
- internal heat exchangers 22 and 32 are identical to each other, and are made of metal foam. It is preferable that the internal heat exchangers 22, 32 are each distributed throughout substantially the entire interior volume of its respective vessel 20, 30 so that access to heat exchange is available nearby (about 1 millimetre or less, preferably) to molecules substantially throughout the entire interior volume. Thus, there is provided a large, available, thermal mass for heat transfer. In this way, quasi-isothermal operation of the system 5 can be best maintained.
- substantially all pores in the metal foam have a size that is less than about 5 cubic millimetres.
- internal heat exchangers 22, 32 may be positioned only near to the top of the interior volume of its respective compression/expansion vessel 20, 30 where molecules' access to heat exchange is most critical for providing quasi-isothermal operation of system 5 due to the rapidity of temperature changes in the gas being compressed or expanding.
- internal heat exchange may similarly be provided by a highly porous sintered plug of metal, and/or by a tightly wound metal coil, and/or by a subsystem of formed tubes or fingers of conductive material.
- Conductive materials such as metals chosen may be copper and/or aluminum.
- Other materials may be used for the internal heat exchangers 22, 32, as desired.
- the internal heat exchangers 22, 32 may be connected to the fluid lines 40, 50, or be integrated with fluid lines 40, 50 in some manner.
- Figures 3A and 3B are diagrams of a compression/expansion vessel 20 or 30 without an internal heat exchanger, and respective different hydraulic fluid levels therewithin.
- Figures 3C and 3D are diagrams of a compression/expansion vessel 20 or 30 with an internal heat exchanger in the form of a tightly wound spiral copper mesh positioned within the interior volume, and respective different hydraulic fluid levels.
- the gas storage subsystem 100 comprises a high pressure gas chamber 1 10 and a low pressure gas chamber 120. Gas line 60 from first
- compression/expansion vessel 20 provides for fluid communication with the high pressure gas chamber 1 10 for the exchange of gas, depending on whether a first high pressure chamber gas valve (FHPcV) 112 is controlled to be open or closed.
- gas line 70 from second compression/expansion vessel 30 provides for fluid communication with the high pressure gas chamber 1 10 for the exchange of gas, depending on whether a second high pressure chamber gas valve (SHPcV) 114 is controlled to be open or closed.
- gas line 60 from first compression/expansion vessel 20 provides for fluid communication with the low pressure gas chamber 120 for the exchange of gas, depending on whether a first low pressure chamber gas valve (FLPcV) 122 is controlled to be open or closed.
- gas line 70 from second compression/expansion vessel 30 provides for fluid communication with the low pressure gas chamber 120 for the exchange of gas, depending on whether a second low pressure chamber gas valve (FLPcV) 124 is controlled to be open or closed.
- FLPcV second low pressure chamber gas valve
- Electrical control of the open/closed states of FHPcV 1 12, SHPcV 114, FLPcV 122 and SLPcV 124, and thereby control for the storing and releasing of gas in gas storage subsystem 100 is provided by control subsystem 7 as will be described herein.
- each of the high pressure and low pressure gas chambers 1 10, 120 are provided and communicate with the control subsystem 7 for providing pressure data for the gas within these components. This pressure data is received by the control subsystem 7 and used during control of the operation of system 5.
- one or more hydraulic liquid pressure transducers (not shown so as to ensure Figure 1 is straightforward to read) for measuring hydraulic fluid pressure in the system 5 is/are provided and communicate with the control subsystem 7 for providing pressure data for the hydraulic fluid in the system 5.
- FIG. 2 is a schematic diagram of connections of the control subsystem 7 in communication with various components of the system 5, to both receive and to transmit control signals to and from pressure transducers, electronic valves, hydraulic pump 12, and so forth.
- Figure 5 is a schematic diagram of components of system 5, when in an initial state. As shown, compression/expansion vessel 20 is at a maximum level of hydraulic fluid 13, and compression/expansion vessel 30 is at a minimum level of hydraulic fluid 13. In this state, the control subsystem 7 has provided signals such that FLPcV 122 is open, FHPcV 1 12 is closed, SLPcV 124 is closed, and SHPcV 114 is open.
- Control subsystem 7 provides signals such that the hydraulic pump 12 is operating as a pump with the flow of hydraulic fluid 13 moving from first port 14 to second port 16. IN this condition, generator/motor 10 is driving the hydraulic pump 12, as is shown in Figure 6. As generator/motor 10 rotates the hydraulic pump 12, hydraulic fluid 13 is pumped from first port 14 to second port 16, overcoming a pressure difference ⁇ between the high pressure gas storage chamber 110 and the low pressure gas storage chamber 120. The electrical energy driving the generator/motor 10 is thereby being converted and stored as potential energy by virtue of the gas pressure differential between the gas storage chambers 110, 120.
- the system 5 can be changed in state from energy storing to energy releasing. This can be achieved by reversing the direction of flow of hydraulic fluid 13 within the hydraulic pump 12, and allowing the hydraulic fluid 13 to impart force to the hydraulic pump 12 so as to rotate its shaft and drive the generator/motor 10, as shown in Figure 5.
- hydraulic pump 12 has an "over the center” configuration, reversing the direction of flow does not change the direction of rotation of the shaft of the hydraulic pump 12. As a result, the angular momentum is not significantly perturbed.
- the settling/transition time for the "over the center” pump to perform this reversal could be on the order of 0.1 second, and during this settling/transition time the angular momentum of the flywheel 18 maintains rotation at a nearly constant angular velocity.
- the generator/motor 10 now operates as a generator, and as electricity produced by the generator/motor 10 is used by an electrical load, the generator/motor 10 provides back torque that resists the rotation of the hydraulic pump 12 and absorbs the mechanical energy being generated from the hydraulic pump 12 (which is, at this point, acting as a motor driven by the gas pressure differential.
- the current "stroke” would end when the level of hydraulic fluid 13 in the first compression/expansion vessel 20 reached at a minimum level, corresponding to level of hydraulic fluid 13 in the second compression/expansion vessel 30 reaching a maximum level, as determined using, in this embodiment, the fluid level transducers. At the end of this stroke the storing could continue upon occurrence of a different transition.
- pressure and temperature sensors can be used for redundancy.
- the hydraulic pump 12 would be controlled by control subsystem 7 to reverse the direction of flow of the hydraulic fluid 13 through the hydraulic pump 12. Furthermore, as described above the shaft of the hydraulic pump 12 would continue to rotate in the same direction due to its over-the-centre configuration, and during this flow direction change the flywheel 18 would smooth the angular momentum of the shaft of the hydraulic pump 12. However, the states of valves 1 12, 1 14, 122, 124 would be carefully reversed.
- the hydraulic pump moves hydraulic fluid 13 from the second compression/expansion vessel 30 to the first compression/expansion vessel 20, thereby compressing the gas therein.
- the gas pressure in the first compression/expansion vessel 20 generally reaches equilibrium with the gas pressure in the high pressure gas storage chamber 110, as determined by the control system 7 responsive to signals from pressure transducers as described above, the FHPcV 1 12 is opened.
- control subsystem 7 opens FLPcV 122 to put first compression/expansion vessel 20 in fluid communication with the low pressure gas storage chamber 120, and flow of hydraulic fluid 13 from pump port 14 to pump port 16 is commenced.
- the SHPcV 1 14 is opened to put high pressure gas storage chamber 1 10 in fluid communication with the second compression/expansion vessel 30.
- next stroke would begin with a command to the hydraulic pump 12 to reverse fluid flow so that the next stroke would commence with fluid flow from pump port 16 to pump port 14, with the hydraulic pump 12 acting as a motor, and the electrical generator/motor 10 acting as a generator.
- the SLPcV 124 would be opened to thereby enabling fluid communication between the low pressure gas storage chamber 120 and the second compression/expansion vessel 30.
- the SHPcV 1 14 would be opened so that differential in the gas pressures would continue to drive the fluid, but in this stroke the drive would be from the pump port 16 to the pump port 14.
- the moment of closure for the valve connecting the high pressure gas storage chamber 1 10 to the second compression/expansion vessel 30 would correspond to the proportion of levels of hydraulic fluid matching the proportion of gas pressures, as similarly described above.
- FIG. 7 is a schematic diagram of an alternative embodiment in which valves between the gas storage subsystem and the compression/expansion vessels can in fact be “doubled” so that lockstep timing of the opening and closing of the valves is not as critical.
- a uni-directional poppet valve will only allow the gas to escape from the vessel under compression when the pressure in the compression vessel equals or slightly exceeds that in the high pressure gas chamber.
- "doubling" of the gas valves is necessary if the electronically controlled valves are uni-directional by design. If the valves are "doubled” then a reversal between storage and retrieval of energy also requires a reversal of which of the pair of valves is electronically selected.
- the above storing/retrieval process can be applied successfully if the hydraulic liquid is an ionic liquid (or a hydraulic liquid that similarly absorbs no gas so that the phenomenon of cavitation cannot happen), or if the pressure differences between the low and high pressure gas storage chambers are maintained at a small ratio, such as 3 or 5.
- a less expensive liquid such as KRYTOX - a fluorinated vacuum pump oil with a density of 2.1 formulated to be non-reactive with oxygen -for the bulk of the liquid, but to also float a small guard layer of true ionic liquid (with a higher density such as 1.4) on top of the KRYTOX to protect the gas/liquid interface.
- the liquid levels would have to be controlled such that the ionic liquid remained entirely within the compression/expansion vessels 20, 30 and was not drained into the hydraulic pump 12. As a result, the strokes would be controlled to be shorter.
- Efficiencies expected from either conventional compression into the buffer reservoir, or expansion through an air engine are expected to be in the range of 30 percent (comparable to conventional compressed air energy storage, or CAES) but the high losses would be confined to the 20 percent of energy available in the "low pressure" compression expansion between 1 atmosphere and 60 atmospheres, so that the total loss is limited to 30 percent (total efficiency of about 70 percent).
- Such a single large reservoir may conveniently be implemented as an assembly of steel tubes, or preferably as carbon fiber composite structures. Where suitable, it can be even more effective as a geological reservoir (either a salt dome, or even a depleted oil well) having a large enough capacity to store significant amounts of potential energy in the form of pressurized gas. Geological reservoirs offer the possibility of storing 100's of megawatt hours and thereby buffering significant wind or solar energy installations. Carbon fiber composite structures, or steel tubes are currently less economical, but may prove effective in providing energy storage at remote sites, or in portable vehicles.
- United States Patent Application Publication No. 2007/0258828 Al discloses the importance of avoiding gas absorption within a liquid piston compressor and a solution that consists of the use of liquids which do not absorb gases.
- the particular liquids proposed are ionic liquids.
- ionic liquids with gas solubility of less than 10 "4 mol/1 bar available such as TFSI (trifluoromethanesulfonimide) based ionic liquids including
- United States Patent No. 5,021, 125 discusses means of dealing with gas absorption in hydraulic liquids associated with the very large piston-less accumulators which might be used in pulp mills by means of allowing gravimetric separation of gas rich liquid by means of laminar flows through long vertical tubes. This requires very large physical structures, and despite the great cost, is only marginally effective.
- PCT Application No. PCT/US2010/035795 proposes a solution comprised of inserting into the compression columns structures with umbrella like "caps" to catch gas bubbles.
- the required structure is complex, and it efficacy is not proven.
- United States Patent Application Serial No. 12/813,781, and PCT Application No. PCT/CA2008/002178 discloses the use of two devices the first of an isolation piston shuttle (with appropriate commutation valves) where a solid metal piston separates the liquid and the gas (in a device resembling a hydraulic intensifier).
- the first does not directly relate to a liquid piston compressor, but does relate to "piston-less" accumulators.
- the second is of the use of low absorption liquids like compressor fluid EXXCOLUB, or of the use a floating layer of "light oil impervious to gas" floating on top of the hydraulic fluid.
- the phenomenon of cavitation consists in the disruption of continuity in the liquid where there is considerable local reduction of pressure.
- the formation of bubbles within liquids begins even in the presence of positive pressures that are equal to or close to the pressure of saturated vapour of the fluid at the given temperature.
- the mechanism of cavitation can be described as follows: Any liquid will contain either gaseous or vaporous bubbles, which serve as the cavitation nuclei. When the pressure is reduced to a certain level, bubbles become the repository of vapour or of dissolved eases. The immediate result of this condition is that the bubbles increase rapidly in size.
- cavitation is believed that reduction in volumetric stability in most liquids is associated with the contents of various admixtures, such as solid unwetted particles and gas-vapour bubbles, particularly those on a submicroscopic level, which serve as cavitation nuclei.
- a critical aspect of the cavitation wear process is surface destruction and material displacement caused by high relative motions between a surface and the exposed fluid. As a result of such motions, the local pressure of the fluid is reduced ...When the pressure returns to normal (which is higher than the vapour pressure of the fluid), implosions occur causing the cavity or vapour bubbles to collapse. This collapse of bubbles generates shock waves that produce high impact forces on adjacent metal surfaces and cause work hardening, fatigue and cavitation pits.
- cavitation is the name given to a mechanism in which vapour bubbles (or cavities) in a fluid grow and collapse due to local pressure fluctuations.”
- the use of a two liquid buffered process employs one liquid for the liquid piston and a second liquid for the operation for the hydraulic pump 12.
- the first liquid may be, for example, ethylene glycol/water/inhibitor based coolant for the compression of reactive gases since this liquid does not freeze or boil easily, and is also non-flammable and therefore does not produce an explosive mixture in combination with air).
- the second liquid may be, for example, hydraulic oil.
- the two liquids are separated by an isolator piston (of solid material), such that the liquid piston liquid never passes through components likely to produce cavitation.
- a two liquid system employing a buffer is shown in Figure 16.
- Such an apparatus is preferably configured so that the heavier liquid is always "under” the lighter liquid. As such, even if the two liquids leak past their seals, their basic order is maintained.
- the "compression liquid” 203 is used for heat exchange it passes down through pipe 205 which rises behind the isolation cylinder 204 and through 206 an external high pressure shell and tube heat exchanger 207 on its way from the compression/expansion chamber 21 1.
- the buffer piston chamber liquid 203 is the same as liquid 210 and it is this liquid which passes through the internal heat exchange mesh inside the compression/expansion chamber.
- Liquid 201 is the lighter (less dense) hydraulic oil which actually flows in and out of the conventional hydraulic pumps motors and valves. It has no contact with the gas, and is buffered by solid piston 202.
- FIG. 17 A two liquid system without a buffer is shown in Figure 17.
- This system employs a primary liquid that is a dense and non-reactive liquid like DuPont KRYTOX vacuum pump fluids, Dupont KRYTOX NRT series oils, or halo-carbon oils with density approximately 1.9 gm/cc.
- the buffer liquid is a liquid with extremely low gas solubility such as ionic liquid GEMIM][BTA], [BMIM][BTA], or [BMMIM][BTA] for example, having a density of approximately 1.5 gm/cc. Since the buffer liquid floats on the primary liquid and since only the primary liquid will pass through the pump (or out of the
- the buffer cap will remain floating. Furthermore, since the ionic liquid has a low viscosity, it will easily pass through internal heat exchange structures within the liquid piston compression/expansion chamber.
- FIG. 18 A system that employs a solid piston to isolate the first and second ports 14, 16 of the hydraulic pump is shown in Figure 18.
- This embodiment is very similar to the buffered "two liquid" system shown in Figure 16.
- the two isolation pistons are replaced by a single structure that accepts the first and second pump ports 14, 16 of a conventional hydraulic pump/motor (for example an axial piston variable displacement over the center pump/motor like the Linde HPW280) and connects pump ports 14, 16 to the central two annular chambers of a structure resembling a hydraulic intensifier.
- the purpose of this is two fold: first, to isolate the hydraulic liquid passing through the motor pump from the liquid acting as the liquid piston, and second, to nullify any "offset pressure" or charge pressure.
- Many hydraulic components require charge pressure. If a hydraulic motor or pump requires charge pressure, then pressure at the pump ports 14, 16 cannot drop below the charge pressure. Since the pressures in a
- a cluster of parallel intensifier structures may be connected in parallel each with a volume smaller than the compression/expansion chamber volume, but which in aggregate exceed the compression/expansion chamber volume. If for example 4 intensifier structures were used, each with an intensification ratio of 1, then each could be chosen to have a volume slightly greater than one quarter (1/4) of the
- the direction of motion of the solid pistons may be alternated, so that the acceleration of pistons produces reduced total forces and moments on the mechanical structure and supports.
- a real intensification ratio may be incorporated in the intensifier so that higher pressure hydraulics can be used with lower pressure gases, or vice- versa (e. g. 5 : 1 intensification for 5000 PSI oil to compress/expand 1000 PSI gas).
- VFD variable frequency drive
- both more extreme filtering against harmonics and feedback control recognizing the slow acceleration required for a synchronous motor are employed to "start" the generator.
- the excitation current typically has to be applied as an AC waveform of a frequency between 40 and 240 Hz in order to use the exciter windings as "a transformer” as the generator is started from an angular speed of zero.
- the exciter stator winding as the primary of a transformer, and the exciter rotor winding as the secondary which receives the transformed current and rectifies it before that current flows into the main rotor windings of the generator being used as a motor.
- the rotor is thus transformed into the equivalent of a multi-pole permanent magnet whose rotational torque is generated by the application of a rotating magnetic field to the stator coils of the generator. Since the magnetic fields and stator current intensities are still high even when then rotor is static or starting, the fields generated by the "VFD" may be applied only as widely separated single half phase pulses as the motor starts to turn. If they are conventionally and continuously applied, the generator (acting as a synchronous motor) may fail to start to turn or else oscillate in a more or less locked position.
- the post-IGBT filtering should be both high in inductance and tuned, so that wave forms tend to be smooth.
- Use of phase controlled rectifiers or IGBT's in the diode bridge can be used to achieve further smoothing.
- the output tuning can be highly peaked
- the gas pressure differential may be initially used in an "expander" mode to generate starting torque on the over the center" pump shaft to help start turning the generator shaft as the generator comes up to speed as a motor.
- FIG. 9 is a graph showing variation of power output/input of a generator/motor over time. As each stroke completes, the power drops - restarting at its peak value as the flow reverses and a new stroke commences.
- An inverse cycle describes the storage of energy in the compression cycle. The cycling of power in compression is equally important to regulate; the regulation mechanisms are the same, but used in the inverse.
- Figure 10 is a graph showing variation of angular speed of rotation and variation of power output/input of the generator/motor over time. Since the magnetism within the rotor of generator/motor 10 can be controlled by using the exciter current, it is possible to regulate the rate at which power goes in and out. Modulation of the exciter current peaks as the rotational speed hits its minimum, and dips as the rotational speed hits its maximum. This enables smoothing the power variations within the stroke and cycle.
- Figure 11 is a graph showing modulation of exciter current of the generator/motor with the variation of angular speed over time for smoothing the power output/input variations.
- the modulation of this exciter current (or the modulation of a higher frequency carrier (40-200Hz) which describes the exciter current) provides significant regulation of the power output as shown schematically in Figure 12, which is a graph showing the resultant variation of power output/input of the generator/motor over time as a result of variation of exciter current.
- variable rotational frequency requires the use of devices similar to VFD's to allow for efficient connection to main or grid power. This is because the rotational speed must vary somewhat from the synchronized motor speeds dictated by grid frequency (typically 50 or 60 Hz)).
- the electronic components which perform this function allow for isolated rectification of incoming three-phase power, re-synthesis by means of filtering the output waveforms coming from PWM IGBT's into three-phase output power at a different frequency, and the careful switching of that power so it can be delivered from the mains to the prime mover (or in the opposite direction coming from the generator toward the mains with a frequency re-synthesis when power is electrically generated).
- such circuits are employed to achieve Variable Frequency Drive when the motor/generator 10 is being used as a motor, and the reuse of the same circuit elements to serve as an inverter which re-samples the power produced when the motor/generator 10 is being used as a generator (generating at frequencies which must differ from the mains since angular speed variations are necessary to smooth the power output).
- the VFD elements produce electrical output for delivery to electrical mains or grid which is matched in both frequency and phase to the power on the grid.
- "Bleed" resistors are attached to the three stator windings as the generator is switched between motor and generator function.
- a separate contactor may be used to disconnect the bleed so that the efficiency loss is limited during continuous operation.
- the bleed resistors ensure there is an "escape" path for residual energy, since the generator/motor 10 will typically be continuously turning regardless of the mode system 5 is in.
- the contactors are all open, it is also necessary that the exciter current be minimized to avoid excess transients.
- This co-ordination of exciter current, pump volume, pump direction, gas valves, liquid levels, and 1GBT modes is all managed by the control subsystem 7.
- the gate leads of the IGBT's are typically connected to a local
- microcomputer programmed to implement the appropriate starting/stopping, and running PWM strategies, and are controlled and sequenced by the control subsystem 7.
- UPS Uninterruptable Power Supplies
- Figure 20 is a schematic diagram of a rectification stage for the
- the rectifiers shown in Figure 20 are in fact Silicon Controlled Rectifiers or SCR's. These allow very good control of the charging, but in most applications simple solid state diodes will suffice.
- Figure 21 is a schematic diagram of an alternative rectification stage for the uninterruptible power supply of Figure 19.
- the circuit in Figure 21 is more practical for higher power levels allowing for a controlled charging of a capacitor, which stores the DC and provides the conventional stiffness of the DC bus in the original known designs.
- Figure 22 is a schematic diagram of voltage rectification, smoothing and inverting stages of a variation on the uninterruptible power supply of Figure 19.
- the appropriate filtering is provided so that the charging circuit produces smooth DC at the capacitor (the capacitor being the defining nodal centre of the DC bus).
- Figure 23 is a schematic diagram of the output stage of the uninterruptible power supply of Figure 19, and provides the resynthesized AC waveform using the technique of Pulse- Width Modulation (PWM). This is shown schematically in Figure 24, which isolates one of the sets of IGBTs.
- PWM Pulse- Width Modulation
- a stiffened DC bus is used as the primary means of interconnection between a variety of loads (like a multiplicity of high horsepower AC motors) and both the AC Mains and electrical storage system and backup generators.
- excitation is controlled in combination with the natural switching characteristics of diode bridges to allow for generally more seamless transitions between backup and primary power sources in the case of a momentary dropout or brownout of the primary power source.
- Such control can be had via control of the exciter voltage and current applied to the excitation coils of a synchronous AC generator.
- VFD Variable Frequency Drive
- multiple secondary power sources and a primary power source are connected in parallel to a DC bus, as shown in Figure 25.
- This bus is "stiffer" than the DC bus within a normal VFD or UPS because it has multiple possible sources of DC voltage. It may further be stiffened by the addition of supercapacitors, as suggested in EPRI, Sandia, NETL materials like Energy Storage for Distributed Energy Resources and Other Electric Power Systems (2003).
- the DC bus may be stiffened further by connecting batteries as secondary power sources.
- AVR Automatic Voltage Regulation
- the traditional AVR is in fact removed, and replaced by a computer controlled exciter current (by means of a digital to analog, or D/A, converter attached to the control computer, or an Analog output module attached to a PLC.
- the excitation current on the generator within the apparatus is held at a level which produces a rectified output "just below” the voltage level produced by rectifying the mains. Since the shaft of the apparatus is always turning and it requires only the release of gas pressure via the solenoid valves, and the movement of the "swash plate" within the over the center pump to release that power to the shaft of the generator, the gentle control of the excitation current provides a smooth means of transitioning between several large high power sources sharing the "stiff DC bus".
- the generators feeding a "stiff DC bus" do not need to be synchronized with each other.
- flywheels, or other energy storage retrieval devices like system 5 described above and alternatives thereof which produce their AC output through spinning generators or alternators may be held at standby simply by holding their excitation voltage at a level just low enough that ordinary variations in the "stiff DC bus" do not traverse the peak rectified voltage level from that particular AC source.
- Priority loads can be maintained for as long as is necessary (perhaps indefinitely if the load is operating theatre power, or the cooling pump on a nuclear reactor). Non priority loads can be browned out or sequenced out smoothly since the inverted AC power that drives them is individually controlled by IGBT output blocks.
- Such semiconductor output blocks have almost no cost (in comparison to, for example, a fully implemented VFD) and would offer at the very least soft starting of motors/loads at all times.
- these IGBT blocks are useful since the algorithm for the PWM module control can be modified to allow for some "droop" in the DC bus.
- Figure 28 illustrates the basic voltage switching mechanism.
- Figure 30 illustrates centralized control for the overall power management.
- the variation in the PWM strategy (from conventional) required to overcome droop can be simply expressed in the concept that the nominal set voltage of the "stiff DC bus" is set higher than would ordinarily be required so that the pulse widths and density of pulses required to achieve ordinary operation are shorter and lower than ordinary.
- the pulse widths and densities then "degrade" to normal. This requires a choice of slightly higher voltage IGBT' s but the cost premium should not be significant.
- the "stiff DC bus" structure also may require the physical running of high voltage DC cables throughout factories or facilities utilizing this process or this type of apparatus.
- the generator/motor subsystem may comprise a generator that is a separate component from the motor.
- the shaft to which the hydraulic pump 12 is coupled would also be coupled to two components: a motor and a generator.
- the motor could be selected and/or tuned to the requirements of receiving power externally and driving the hydraulic pump, and the generator could separately be selected and/or tuned to the requirements of being driven by the hydraulic pump and generating electricity.
- the generator may be oversized, such that if for example it is desired to generate lOOkW, a generator is selected that is capable of generating a multiple of the desired power. While the cost of the system infrastructure would likely increase, operational efficiencies would be gained because the heat loss in a larger generator operating within a very efficient range would be less than the heat loss in a smaller generator perhaps operating outside of its most efficient range.
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Abstract
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Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
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EP11764997.0A EP2556263B1 (en) | 2010-04-09 | 2011-04-11 | System for energy storage and retrieval |
CN201180025715.7A CN103221694B (en) | 2010-04-09 | 2011-04-11 | For the system and method for stored energy and recovery |
DK11764997.0T DK2556263T3 (en) | 2010-04-09 | 2011-04-11 | ENERGY STORAGE AND RECOVERY SYSTEM |
CA2795645A CA2795645C (en) | 2010-04-09 | 2011-04-11 | System and method for energy storage and retrieval |
JP2013502968A JP5756849B2 (en) | 2010-04-09 | 2011-04-11 | System and method for storing and extracting energy |
ES11764997.0T ES2616562T3 (en) | 2010-04-09 | 2011-04-11 | System for storage and energy recovery |
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EP (2) | EP2556263B1 (en) |
JP (2) | JP5756849B2 (en) |
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CN103244353A (en) * | 2012-02-09 | 2013-08-14 | 韩金福 | Method for obtaining compressed air through wind power to generate power |
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GB2527228B (en) | 2013-03-11 | 2017-01-04 | Trane Int Inc | Controls and operation of variable frequency drives |
US9353451B2 (en) * | 2013-04-19 | 2016-05-31 | Fuel and Emissions Controls, LLC | Hydrolysis system and method for a vehicle engine |
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- 2011-04-11 CA CA2795645A patent/CA2795645C/en not_active Expired - Fee Related
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Also Published As
Publication number | Publication date |
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DK2556263T3 (en) | 2017-02-06 |
JP2013530661A (en) | 2013-07-25 |
CA2795645C (en) | 2014-04-08 |
JP2015180183A (en) | 2015-10-08 |
US20110247323A1 (en) | 2011-10-13 |
ES2616562T3 (en) | 2017-06-13 |
CA2846309A1 (en) | 2011-10-13 |
EP2556263A1 (en) | 2013-02-13 |
CN103221694B (en) | 2015-07-29 |
US20140190155A1 (en) | 2014-07-10 |
EP3147518A1 (en) | 2017-03-29 |
EP2556263A4 (en) | 2015-08-05 |
US8667788B2 (en) | 2014-03-11 |
EP2556263B1 (en) | 2016-10-19 |
CN103221694A (en) | 2013-07-24 |
JP6129892B2 (en) | 2017-05-17 |
JP5756849B2 (en) | 2015-07-29 |
CA2795645A1 (en) | 2011-10-13 |
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