Hydraulic energy accumulator

Abstract

Example energy storage systems ( 20, 20′, 20 ″) comprises a fluid circuit ( 22, 22′, 22 ″) and an electrical unit ( 24, 24′, 24 ″) configured to operate as a motor in a first phase of operation and to operate as a generator in a second phase of operation. The fluid circuit ( 22, 22′, 22 ″) comprises a first fluid container ( 30, 30′, 30 ″) situated so content of the first fluid container experiences a first pressure level; a tank ( 32, 32′, 32 ″) having its content at a second pressure level (the second pressure level being less than the first pressure level): and, a first hydraulic motor/pump unit ( 34, 134, 34 ″) connected to communicate a first working fluid between the tank and the first fluid container. In the first phase of operation electricity is supplied to the first hydraulic/motor unit ( 34, 134, 34 ″) whereby the first hydraulic/motor unit transmits the first working fluid from the tank into the first fluid container ( 30, 30′, 30 ″). In the second phase of operation pressurized first working fluid in the first fluid container ( 30, 30′, 30 ″) is transmitted from the first fluid container through the first hydraulic/motor unit 34, 134, 34 ″) to the tank ( 32, 32′, 32 ″), thereby causing the electrical unit ( 24, 24′, 24 ″) to generate electricity.

1 . An energy storage system comprising:
 a fluid circuit comprising:
 a first fluid container situated so content of the first fluid container experiences a first pressure level; 
 a tank configured so that content of the tank is at a second pressure level, the second pressure level being less than the first pressure level; 
 a first hydraulic motor/pump unit connected to communicate a first working fluid between the tank and the first fluid container; 
   an electrical unit configured to operate as a motor in a first phase of operation and to operate as a generator in a second phase of operation, wherein in the first phase of operation electricity is supplied to the first hydraulic/motor unit whereby the first hydraulic/motor unit transmits the first working fluid from the tank into the first fluid container, and wherein in the second phase of operation pressurized first working fluid in the first fluid container is transmitted from the first fluid container through the first hydraulic/motor unit to the tank thereby causing the electrical unit to generate electricity.   
     
     
         2 . The apparatus of  claim 1 , wherein the first hydraulic motor/pump unit is connected between the tank and the first fluid container; wherein the first pressure level is vacuum; and wherein the first fluid container is submerged whereby the first pressure level is hydrostatic pressure. 
     
     
         3 . The apparatus of  claim 2 , wherein the first fluid container comprises a first flexible bladder. 
     
     
         4 . The apparatus of  claim 2 , wherein the fluid circuit and the electrical unit are situated below the reference pressure level. 
     
     
         5 . The apparatus of  claim 2 , further comprising a ballast configured to prevent at least a portion of the system from floating. 
     
     
         6 . The apparatus of  claim 3 , further comprising:
 a second fluid container situated so that content of the second fluid container is at a second container pressure level, the second container pressure level being less than the first pressure level;   a second hydraulic motor/pump unit;   a third hydraulic motor/pump unit;   wherein the second hydraulic motor/pump unit is operatively connected to the electrical unit and fluidically connected between the second fluid container and the third hydraulic motor/pump unit, wherein the third hydraulic motor/pump unit is fluidically connected between the second hydraulic motor/pump unit and the first fluid container; and wherein the second hydraulic motor/pump unit and the third hydraulic motor/pump unit are configured during the first phase of operation to operate as pumps to transmit fluid from the second fluid container to the first fluid container, and during the second phase of operation to operate as motors as fluid from the first fluid container is transmitted to the second fluid container;   wherein the electrical unit is configured during the first phase of operation to operate as the motor for the second hydraulic motor/pump unit and during the second phase of operation to operate as a generator driven by the second hydraulic motor/pump unit.   
     
     
         7 . The apparatus of  claim 1 , further comprising:
 a second fluid container, the first hydraulic motor/pump unit being fluidically connected between the tank and the second fluid container for communicating a second working fluid between the tank and the second fluid container;   wherein the first working fluid comprises compressed gas;   wherein the first fluid container is submerged in a liquid, the first fluid container having a fluid container first internal region in communication with the liquid and a fluid container second internal region in communication with the compressed gas;   wherein the first hydraulic motor/pump unit is configured during the first phase of operation to operate as a pump to transmit the second working fluid from the second fluid container to the tank and thereby drive the first working fluid from the tank to the fluid container first internal region and during the second phase of operation to operate as a motor as the second working fluid is driven by the first working fluid from the tank to the second fluid container;   wherein the electrical unit is configured during the first phase of operation to operate as the motor for the first hydraulic motor/pump unit and during the second phase of operation to operate as a generator driven by the first hydraulic motor/pump unit.   
     
     
         8 . The apparatus of  claim 1 , further comprising:
 an electrical power source;   a cable network configured during the first phase of operation to convey electricity from the electrical power source to the electrical unit to operate the electrical unit during the first phase of operation and configured during the second phase of operation to transmit electricity generated by the electrical unit to the electrical power source.   
     
     
         9 . The apparatus of  claim 8 , wherein the electrical power source is a power grid, a storage cell, or a renewable power source. 
     
     
         10 . The apparatus of  claim 8 , further comprising a transformer connected on the cable network between the electrical power source and the electrical unit. 
     
     
         11 . A method of operating an energy storage system, the method comprising:
 situating a first fluid container so content of the first fluid container experiences a first pressure level;   situating a tank so that content of the tank is at a second pressure level, the second pressure level being less than the first pressure level;   providing an electrical unit configured to operate as a motor in a first phase of operation and to operate as a generator in a second phase of operation;   communicating a first working fluid between the tank and the first fluid container in a first direction during the first phase of operation and in a second direction during the second phase of operation,   in the first phase of operation supplying electricity to the first hydraulic/motor unit whereby the first hydraulic/motor unit transmits the first working fluid from the tank into the first fluid container;   in the second phase of operation transmitting pressurized first working fluid in the first fluid container from the first fluid container through the first hydraulic/motor unit to the tank thereby causing the electrical unit to generate electricity.   
     
     
         12 . The method of  claim 11 , further comprising connecting the first hydraulic motor/pump unit between the tank and the first fluid container; situating the first fluid container below a reference pressure level; and submerging the first fluid container whereby the first pressure level is hydrostatic pressure. 
     
     
         13 . The method of  claim 12 , further comprising using a first flexible bladder as the first fluid container. 
     
     
         14 . The method of  claim 12 , further comprising situating the fluid circuit and the electrical unit below the reference pressure level. 
     
     
         15 . The method of  claim 12 , further comprising using a ballast to prevent at least a portion of the system from floating. 
     
     
         16 . The method of  claim 13 , further comprising:
 situating a second fluid container situated so that content of the second fluid container is at a second container pressure level, the second container pressure level being less than the first pressure level;   providing a second hydraulic motor/pump unit and a third hydraulic motor/pump unit, the second hydraulic motor/pump unit being operatively connected to the electrical unit and fluidically connected between the second flexible bladder and the third hydraulic motor/pump unit, wherein the third hydraulic motor/pump unit is fluidically connected between the second hydraulic motor/pump unit and the first flexible bladder;   during the first phase of operation operating the second hydraulic motor/pump unit and the third hydraulic motor/pump unit as pumps to transmit fluid from the second flexible bladder to the first flexible bladder,   during the second phase of operation operating the second hydraulic motor/pump unit and the third hydraulic motor/pump unit as motors as fluid from the first flexible bladder is transmitted to the second flexible bladder;   during the first phase of operation operate the electrical unit as the motor for the second hydraulic motor/pump unit; and   during the second phase of operation operating the electrical unit as a generator driven by the second hydraulic motor/pump unit.   
     
     
         17 . The method of  claim 11 , further comprising:
 providing a second fluid container with the first hydraulic motor/pump unit being fluidically connected between the tank and the second fluid container for communicating a second working fluid between the tank and the second fluid container;   providing the first working fluid as comprising compressed gas;   submerging the first fluid container in a liquid and providing in the first fluid container a fluid container first internal region in communication with the liquid and a fluid container second internal region in communication with the compressed gas;   during the first phase of operation operating the first hydraulic motor/pump unit as a pump to transmit the second working fluid from the second fluid container to the tank and thereby drive the first working fluid from the tank to the fluid container first internal region;   during the second phase of operation operating the hydraulic motor/pump unit as a motor as the second working fluid is driven by the first working fluid from the tank to the second fluid container;   during the first phase of operation operating the electrical unit as the motor for the first hydraulic motor/pump unit; and   during the second phase of operation operating the hydraulic motor/pump unit as a generator driven by the first hydraulic motor/pump unit.