System and method for energy storage and retrieval

Abstract

Disclosed herein is a system including a generator/motor subsystem configured to interchangeably impart and receive mechanical force; a stiff DC bus; and power conditioning circuitry electrically connected between the generator/motor subsystem and the stiff DC bus, the power conditioning circuitry conditioning electrical power received from the stiff DC bus to control the angular speed of a rotor of the generator/motor subsystem when imparting mechanical force, and also conditioning electrical power generated for provision to the stiff DC bus by the generator/motor subsystem when receiving mechanical force.

What is claimed is: 
     
         1 . A system comprising:
 a generator/motor subsystem configured to interchangeably impart and receive mechanical force;   a stiff DC bus; and   power conditioning circuitry electrically connected between the generator/motor subsystem and the stiff DC bus, the power conditioning circuitry conditioning electrical power received from the stiff DC bus to control the angular speed of a rotor of the generator/motor subsystem when imparting mechanical force, and also conditioning electrical power generated for provision to the stiff DC bus by the generator/motor subsystem when receiving mechanical force.   
     
     
         2 . The system of  claim 1 , wherein the power conditioning circuitry comprises:
 an inverter for converting DC electrical power received from the stiff DC bus into AC power having a controllable frequency and voltage for provision to the generator/motor subsystem; and   a rectifier for converting AC electrical power generated by the generator/motor subsystem into DC electrical power for provision to the stiff DC bus.   
     
     
         3 . The system of  claim 2 , wherein the power conditioning circuitry is electrically connected to the stiff DC bus via a diode. 
     
     
         4 . The system of  claim 2 , wherein the power conditioning circuitry comprises:
 bleed resistors electrically connected to respective stator windings of the generator/motor subsystem.   
     
     
         5 . The system of  claim 4 , wherein the bleed resistors are electrically connected to respective stator windings via respective contactors. 
     
     
         6 . The system of  claim 1 , further comprising:
 an energy storage/retrieval system mechanically coupled to the rotor of the generator/motor subsystem, the energy storage/retrieval system controllable to store energy in response to mechanical force imparted to the energy storage/retrieval system by the rotor, and further controllable to release stored energy via mechanical force imparted to the rotor of the generator/motor subsystem.   
     
     
         7 . The system of  claim 6 , wherein the energy storage/retrieval system comprises:
 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; and   a control subsystem for controlling at least a plurality of gas valves associated with the gas storage subsystem to switch between the storing and releasing,   wherein, during storing, responsive to hydraulic fluid being pumped by the hydraulic pump between the first and second pump ports, gas is caused to be compressed in the gas storage subsystem thereby to store energy, and   wherein, during releasing, responsive to pressure from release of compressed gas from the gas storage subsystem, hydraulic fluid is forced to flow between the first and second pump ports thereby to release energy.   
     
     
         8 . The system of  claim 7 , wherein the gas storage subsystem comprises:
 a high pressure gas chamber for selectively exchanging gas with the first or second compression/expansion vessel responsive to open/closed states of respective gas valves; and   a low pressure gas chamber for selectively exchanging gas with the first or second compression/expansion vessel responsive to open/closed states of respective gas valves.   
     
     
         9 . The system of  claim 1 , further comprising a flywheel associated with the generator/motor subsystem. 
     
     
         10 . The system of  claim 7 , wherein the hydraulic pump is configured to rotate in the same direction whether hydraulic fluid is flowing from the first pump port to the second pump port or from the second pump port to the first pump port. 
     
     
         11 . The system of  claim 1 , wherein the generator/motor subsystem comprises a unitary generator/motor. 
     
     
         12 . The system of  claim 1 , wherein the generator/motor subsystem comprises both a generator and a motor, each of which are mechanically connected to the hydraulic pump. 
     
     
         13 . The system of  claim 1 , wherein the stiff DC bus comprises a supercapacitor. 
     
     
         14 . A system comprising:
 a stiff DC bus receiving electrical power from at least one power source and comprising a supercapacitor;   at least one motor configured to impart mechanical force; and   power conditioning circuitry electrically connected between the at least one motor and the stiff DC bus, the power conditioning circuitry conditioning electrical power received from the stiff DC bus to control the angular speed of a rotor of the generator/motor subsystem when imparting mechanical force.   
     
     
         15 . A system comprising:
 a stiff DC bus;   a primary power source providing electrical power to the stiff DC bus via a respective diode;   at least one motor configured to impart mechanical force; and   power conditioning circuitry electrically connected between the motor and the stiff DC bus, the power conditioning circuitry conditioning electrical power received from the stiff DC bus to control the angular speed of a rotor of the generator/motor subsystem when imparting mechanical force.   
     
     
         16 . The system of  claim 15 , wherein the power conditioning circuitry comprises:
 an inverter for converting DC electrical power received from the stiff DC bus into AC power having a controllable frequency and voltage for provision to the generator/motor subsystem.   
     
     
         17 . The system of  claim 15 , further comprising a first backup power source comprising:
 a generator/motor subsystem configured to interchangeably impart and receive mechanical force;   power conditioning circuitry electrically connected between the generator/motor subsystem and the stiff DC bus via a respective diode, the power conditioning circuitry conditioning electrical power generated for provision to the stiff DC bus by the generator/motor subsystem when receiving mechanical force; and   an energy storage/retrieval system mechanically coupled to the rotor of the generator/motor subsystem, the energy storage/retrieval system controllable to store energy in response to mechanical force imparted to the energy storage/retrieval system by the rotor, and further controllable to release stored energy via mechanical force imparted to the rotor of the generator/motor subsystem.   
     
     
         18 . The system of  claim 17 , wherein the energy storage/retrieval system comprises:
 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; and   a control subsystem for controlling at least a plurality of gas valves associated with the gas storage subsystem to switch between the storing and releasing,   wherein, during storing, responsive to hydraulic fluid being pumped by the hydraulic pump between the first and second pump ports, gas is caused to be compressed in the gas storage subsystem thereby to store energy, and   wherein, during releasing, responsive to pressure from release of compressed gas from the gas storage subsystem, hydraulic fluid is forced to flow between the first and second pump ports thereby to release energy.   
     
     
         19 . The system of  claim 18 , wherein the gas storage subsystem comprises:
 a high pressure gas chamber for selectively exchanging gas with the first or second compression/expansion vessel responsive to open/closed states of respective gas valves; and   a low pressure gas chamber for selectively exchanging gas with the first or second compression/expansion vessel responsive to open/closed states of respective gas valves.   
     
     
         20 . The system of  claim 17 , further comprising a flywheel associated with the generator/motor subsystem. 
     
     
         21 . The system of  claim 18 , wherein the hydraulic pump is configured to rotate in the same direction whether hydraulic fluid is flowing from the first pump port to the second pump port or from the second pump port to the first pump port. 
     
     
         22 . The system of  claim 17 , wherein the generator/motor subsystem comprises a unitary generator/motor. 
     
     
         23 . The system of  claim 17 , wherein the generator/motor subsystem comprises both a generator and a motor, each of which are mechanically connected to the hydraulic pump. 
     
     
         24 . The system of  claim 15 , further comprising at least one secondary backup power source electrically connected to the stiff DC bus via a respective diode. 
     
     
         25 . A system comprising:
 a stiff DC bus;   at least one primary power source providing electrical power to the stiff DC bus via a respective diode;   at least one backup power source, each of the at least one backup power source electrically connected to the stiff DC bus via a respective diode; and   a control subsystem for controlling the output voltage of each of the at least one backup power source such that current from the backup power source is caused to flow onto the stiff DC bus via its respective diode only when the operating voltage of the stiff DC bus drops below an acceptable operating level thereby to smoothly return the stiff DC bus to at least the acceptable operating level.   
     
     
         26 . The system of  claim 25 , wherein at least one of the backup power sources comprises:
 a generator/motor subsystem configured to interchangeably impart and receive mechanical force;   power conditioning circuitry electrically connected between the generator/motor subsystem and the stiff DC bus via its respective diode, the power conditioning circuitry conditioning electrical power generated for provision to the stiff DC bus by the generator/motor subsystem when receiving mechanical force; and   an energy storage/retrieval system mechanically coupled to the rotor of the generator/motor subsystem, the energy storage/retrieval system controllable to store energy in response to mechanical force imparted to the energy storage/retrieval system by the rotor, and further controllable to release stored energy via mechanical force imparted to the rotor of the generator/motor subsystem.   
     
     
         27 . The system of  claim 26 , wherein the energy storage/retrieval system comprises:
 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; and   a control subsystem for controlling at least a plurality of gas valves associated with the gas storage subsystem to switch between the storing and releasing,   wherein, during storing, responsive to hydraulic fluid being pumped by the hydraulic pump between the first and second pump ports, gas is caused to be compressed in the gas storage subsystem thereby to store energy, and   wherein, during releasing, responsive to pressure from release of compressed gas from the gas storage subsystem, hydraulic fluid is forced to flow between the first and second pump ports thereby to release energy.   
     
     
         28 . The system of  claim 27 , wherein the gas storage subsystem comprises:
 a high pressure gas chamber for selectively exchanging gas with the first or second compression/expansion vessel responsive to open/closed states of respective gas valves; and   a low pressure gas chamber for selectively exchanging gas with the first or second compression/expansion vessel responsive to open/closed states of respective gas valves.   
     
     
         29 . The system of  claim 26 , further comprising a flywheel associated with the generator/motor subsystem. 
     
     
         30 . The system of  claim 27 , wherein the hydraulic pump is configured to rotate in the same direction whether hydraulic fluid is flowing from the first pump port to the second pump port or from the second pump port to the first pump port. 
     
     
         31 . The system of  claim 26 , wherein the generator/motor subsystem comprises a unitary generator/motor. 
     
     
         32 . The system of  claim 26 , wherein the generator/motor subsystem comprises both a generator and a motor, each of which are mechanically connected to the hydraulic pump. 
     
     
         33 . The system of  claim 26 , wherein the control subsystem controls the output voltage of the at least one backup power source via its power conditioning circuitry by modifying exciter current applied to its generator/motor subsystem thereby to control balance of power supplied by the primary and at least one backup power source to the stiff DC bus. 
     
     
         34 . The system of  claim 25 , wherein the at least one primary power source is an AC power source providing rectified DC voltage to the stiff DC bus. 
     
     
         35 . The system of  claim 25 , wherein there are at least two backup power sources, at least one of the at least two backup power sources being an AC power source providing rectified DC voltage for the stiff DC bus, and at least one of the at least two backup power sources being a DC power source providing DC voltage for the stiff DC bus. 
     
     
         36 . The system of  claim 35 , wherein the DC power source is a battery.