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EP-4739905-A2 - FLEXIBLE OPERATION AND RECIPROCATING NEAR-ISOTHERMAL GAS COMPRESSOR/EXPANDER FOR WIND ENERGY STORAGE

EP4739905A2EP 4739905 A2EP4739905 A2EP 4739905A2EP-4739905-A2

Abstract

A system for flexible operation for wind energy storage, and a related method, the system including a wind turbine having a rotor disposed thereon, a rotor shaft extending from the rotor and rotatable therewith, an electrical generator disposed in communication with the rotor shaft, a power generation/regeneration system, which may include a fluid power system, is disposed in communication with the rotor shaft, where rotation of the rotor shaft rotates the electrical generator to produce generator power (P g ), where, when the fluid power system is in a power generation mode, aerodynamic rotation of the rotor shaft produces fluid power (P f ) at the fluid power system, at least a portion of which is stored as energy in an energy storage, and where, when the fluid power system is in a power regeneration mode, energy is released from the energy storage and converted by the fluid power system to fluid power (P f ) that can be combined with aerodynamic rotor power to drive the electrical generator.

Inventors

  • LOTH, ERIC

Assignees

  • University Of Virginia Patent Foundation

Dates

Publication Date
20260513
Application Date
20240703

Claims (20)

  1. WHAT IS CLAIMED: 1. A system for flexible wind turbine operation for wind energy storage, comprising: a wind turbine having a rotor disposed thereon; a rotor shaft extending from the rotor and rotatable therewith; an electrical generator disposed in communication with the rotor shaft; a power generation/regeneration fluid power system, whose shaft is disposed along the rotor shaft or with a constant gear ratio relative to the rotor shaft; wherein aerodynamic rotation of the rotor shaft rotates the electrical generator to produce generator power (P g ); wherein, when the fluid power system is in a power generation mode, aerodynamic rotation of the rotor shaft produces fluid power (Pf) at the fluid power system, at least a portion of which is stored as energy in an energy storage; and wherein, when the fluid power system is in a power regeneration mode, energy is released from the energy storage and converted by the fluid power system to fluid power (Pf) that rotates the rotor shaft within the electrical generator.
  2. 2. The system of claim 1, wherein: - when the fluid power system is not operating, the electrical generator has a maximum power rating (P g,rated ), which can be achieved for wind speeds between a rated wind speed (U rated ) and a cut-out wind speed (U cut-out ) with a rated rotor speed (ω r,rated ); - when the fluid power system is in the power generation mode, the rotor power (P r ) produced by the aerodynamic rotation of the rotor is the sum of the generator power (Pg) combined with the fluid power (Pf), and - when the fluid power system is in the power regeneration mode, the generator power (Pg) is the sum of the rotor power (Pr) produced by the aerodynamic rotation of the rotor combined with the regenerated fluid power (Pf).
  3. 3. The system of claim 2, wherein: - the fluid power system has a maximum power rating (Pf,rated); - the generator power (P g ) can flexibly operate anywhere in the range from 0% and 100% of the maximum generator power rating (Pg,rated); - the fluid power (Pf) can flexibly operate anywhere in the range from 0% and 100% of the maximum fluid power rating (P f,rated ).
  4. 4. The system of claim 3, wherein: - proportions of rotor power (P r ), fluid power (P f ), and generator power (P g ) can be adjusted based on available wind energy, grid demand (including generator curtailment), and available storage capacity for flexible operation; - a rotor blade pitch can be controlled to achieve the desired rotor power (P r ); - the fluid power (P f ) can vary with shaft speed and by deactivating individual compressor/expanders.
  5. 5. The system of claim 3, wherein: - the rotor speed (ωr) is limited to the rated rotor speed (ωr,rated) even if the rotor power exceeds the maximum generator power rating (P g,rated ); - a rotor thrust (T) is limited to a rated rotor thrust (Trated) even if the rotor power exceeds the maximum generator power rating (P g,rated ).
  6. 6. The system of claim 3, wherein the fluid power system is composed only of a pneumatic compressor/expander system with no intermediary hydraulic system.
  7. 7. The system of claim 1, further comprising a tower having an interior volume and one or more tower side casings disposed on an exterior of the tower, wherein components of the wind turbine that are typically enclosed within the tower are disposed in and/or extend through one or more of the tower side casings, and wherein this allows the energy storage and/or an interstage settling chamber is disposed in at least part of the internal volume of the tower.
  8. 8. The system of claim 1, wherein - the fluid power generation/regeneration system for energy storage may be augmented or replaced with a gravitational potential energy storage system; - the fluid power generation/regeneration system for energy storage may be augmented or replaced with a rotational kinetic energy storage system comprising a flywheel disposed in the wind turbine tower or as part of a base of the wind turbine - the fluid power generation system may be augmented or replaced, a system to produce hydrogen via hydrolysis, and/or a desalination system to produce freshwater from saltwater;
  9. 9. The system of claim 4, wherein: - the power generation/regeneration system is a fluid power system comprising an air compressor/expander; - wherein the fluid power system shaft is directly connected to the rotor shaft such that fluid power system shaft and the rotor shaft rotate at the same speed, or the fluid power system shaft is connected to the rotor shaft by a geared mechanism such that the fluid power system shaft and the rotor rotate at different speeds but with a fixed speed ratio; - wherein the electrical generator is directly connected to the rotor shaft such that electrical generator and the rotor shaft rotate at the same speed, or the electrical generator is connected to the rotor shaft or to the fluid power system shaft by a geared mechanism such that the electrical generator and the rotor shaft or fluid power system shaft, respectively, rotate at different speeds; -wherein the air compressor/expander and any associated gearing mechanisms are disposed in a nacelle, and/or within a front frame, and/or adjacent to a generator and/or within a nosecone and/or within a tower;
  10. 10. The system of claim 9, wherein an air duct inlet located on the exterior of the nacelle or the nose cone extracts ambient air from a wind stream directed at the wind turbine, and is configured to direct the entrained air over the pistons for convective heat transfer and then to exhaust air to the nacelle exterior and/or to direct the entrained air to be used as intake ambient air for piston compression operation and then to exhaust the outlet ambient air from a piston expansion operation to the nacelle exterior.
  11. 11. The system of claim 9, wherein: - at least one stage of the compressor/expander comprises one or a plurality of pistons coupled to a crankshaft whereby rotation of the crankshaft drives the piston or pistons in a reciprocating manner - at least one piston comprises at least one storage valve for directing air compressed within the piston to the energy storage for compressed air energy generation and for receiving air from energy storage to be expanded during energy regeneration; - at least one piston comprises at least one ambient valve for drawing air into the piston from an ambient environment; - each cylinder comprises a cylinder casing, a piston head disposed movably in the cylinder, and a cylinder volume within the cylinder that varies upon movement of the piston head; and - the compressor/expander cylinders may include single-acting or double-acting pistons.
  12. 12. The system of claim 11, wherein the cylinder volume contains a liquid volume, a gas volume, and porous heat transfer surfaces.
  13. 13. The system of claim 12, wherein the porous heat transfer surfaces are disposed at an upper region of the cylinder volume adjacent to the storage and ambient valves, the porous heat transfer surfaces being configured to allow the gas and liquid to pass therethrough during compression and expansion of the cylinder volume upon movement of the piston head and to provide convective heat transfer between the gas, liquid, and casing of the cylinder, and the ambient environment.
  14. 14. The system of claim 12, wherein the porous heat transfer surfaces are horizontal, vertical, or angled porous layers, or other porous geometries and comprise one or more of the following: - fixed heat transfer elements secured immovably within the cylinder volume; - fixed heat transfer support system secured immovably within the cylinder volume to allow high thermal conductivity between the heat transfer elements and the cylinder casing; - movable heat transfer elements that expand and compress within the cylinder volume during movement of the piston head by way of bellows, spring coils, and/or axial cables; and - heat transfer elements formed of wire mesh, perforated plates, honeycomb structures, bio-inspired mesh, or stackable mating plates; - one or a plurality of nozzles disposed in the cylinder volume configured to spray liquid into the gas volume to provided cooling.
  15. 15. The system of claim 12, further comprising an emergency pressure relief valve for releasing compressed air from the piston on demand.
  16. 16. The method of claim 12, further comprising a liquid jacket disposed on the casing of the cylinder of the piston configured to provide convective heat transfer between the casing and the ambient environment.
  17. 17. The system of claim 12, further comprising a drainage valve to remove some or all heat transfer liquid after each cycle or after a change in operation.
  18. 18. The system of claim 12, further comprising a liquid supply and valve to add some or all heat transfer liquid after each cycle or after a change in operation.
  19. 19. The system of claim 12, wherein the cylinder head is coned, curved, or slanted and the valves are located at a topmost portion of the cylinder head to help reduce dead volume.
  20. 20. The system of claim 9, wherein one or more of compressor/expander cylinder casings is disposed within the turbine tower or is part of the tower shell to provide structural support for elevated air pressure and a thermally conductive casing.

Description

FLEXIBLE OPERATION AND RECIPROCATING NEAR-ISOTHERMAL GAS COMPRESSOR/EXPANDER FOR WIND ENERGY STORAGE CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is related to and claims the benefit of U.S. Provisional Patent Application Numbers 63/512,226 and 63/647,957 filed July 06, 2023 and May 15, 2024, respectively. This application is also related to International Patent Application Number PCT/US2022/044620, filed on September 23, 2022, which claims priority to United States Provisional Patent Application Numbers 63/248,124 and 63/305,734, filed on September 24, 2021 and February 02, 2022, respectively. All of the cited applications are herein incorporated by reference in their entirety. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] This disclosure was made with government support under DE-AR0000667 awarded by the U.S. Department of Energy, and 2324460 awarded by the National Science Foundation. The government has certain rights in the disclosure. TECHNICAL FIELD [0003] The disclosure generally relates to wind energy technologies and, more particularly, to a flexible operation for wind energy storage, including super-rated operation which allows a rotor to generate excess power beyond that of an electrical generator for a large variety of operational conditions, and to a means of compressed air energy storage, including a reciprocating piston-based near-isothermal air compressor/expander which employs piston-based coupling for pneumatic power take-off and/or regeneration. This turbine operation with energy storage can be highly flexible to accommodate variations in wind resources and energy demand. The tower may be used as an internal storage chamber for pressurized fluid and a tower side casing or multiple tower side casings can be added along with a modified rotor operation to address rotor-tower interference limits. The energy storage can later be regenerated to provide electrical energy. In addition, the power take-off can be converted to other forms of energy including electrolysis to generate hydrogen, to perform water desalination, potential energy by raising/lowering large masses, and rotational kinetic energy to drive a fly wheel. [0004] To facilitate wind energy storage, also disclosed herein is a reciprocating piston-based near-isothermal air compressor/expander which employs piston-based coupling for pneumatic power take-off and/or regeneration. To provide high round-trip efficiency for the fluid power energy storage, the compression and expansion processes are made nearly isothermal by using low rotation speeds and heat exchanger networks combined with a Liquid Layer And Mesh with Mechanical Piston (LLAMMP) approach. Also provided herein are new geometries for a compressible/flexible heat exchanger and/or a spray-based heat exchanger design with the mechanical piston approach. BACKGROUND [0005] Wind turbines provide intermittent power and thus may benefit from an integration with energy storage systems. Locally integrating energy storage at the site of wind energy generation can level the resulting energy generation. This reduction in intermittency can provide more value to the grid. Integrated onsite energy storage for wind turbines can capture power that might have been curtailed due to low grid demand as well as excess power beyond the rated electrical power, which would otherwise be lost without energy storage. Capturing curtailed and/or excess power at the wind turbine/farm without increasing the size of the electrical generator can increase the capacity factor of a wind turbine/farm which can reduce relative transmission costs. For example, increasing the wind farm capacity factor by 20% reduces the size/cost of the needed transmission lines by 20% relative to the average energy delivered. This benefit can be especially pronounced when the cost of energy transmission lines is high (due to long distances or complex siting, as in offshore or mountainous locations), when upgrading line capacity for new generation is problematic (due to permitting, safety, and impact issues), and when transmission lines are environmentally/socially invasive. The ability to integrate energy storage and the ability to capture curtailed and/or excess energy are facilitated with the present disclosure which provides flexible operation for wind turbines to store energy. This may allow the net electrical energy delivered to be increased relative to that of a conventional wind turbine while keeping approximately the same size rotor, tower, generator, and transmission lines. This curtailed and/or excess power can be translated to fluid power, or can be used for electrolysis to generate hydrogen, or can be used for water desalination, or be used to raise/lower large masses to store gravitational potential energy, or can be used to drive a fly wheel (within the tower or at the base of the turbine) to store rotational kinetic energy. [0006] Where fluid power is utilized, the ener