Energy storage system

An energy storage system for use with renewable electrical sources. Illustratively, the system includes a pumped glycerol battery (PGB) which is a mechanical system designed to store renewable electricity in a manner that can be readily dispensed back into the national electrical power grid or smaller grid systems on demand. The energy is illustratively stored in three additive forms of potential energy—(1) gravitational, (2) high-pressure gas derived by phase-change, and (3) vacuum draw. The primary working fluid medium (that which propels a turbine-generator to create electricity) is illustratively a dense liquid material that will be physically elevated at its energy storage site. The secondary working medium (that which assists the primary medium by adding more stored energy) is a gas, such as carbon dioxide.

BACKGROUND AND SUMMARY OF THE INVENTION

The present disclosure relates generally to energy storage systems and, more particularly, to such a system including a pumped glycerol battery for storing energy from renewable electricity sources.

The storage of energy from renewable electrical sources may be achieved by various methods using, for example, chemical, gravitational, thermal, electrical, and mechanical devices. One common method for utility scale energy storage is so-called “Pumped Storage Hydropower” (PSH). In this method, water is pumped upward against gravity to a reservoir for storage until electrical energy is needed in the electrical power grid (“The Grid”). Pumped Storage Hydropower is commonly considered the preferred method for longest duration energy delivery at utility scale.

The energy storage system of the present disclosure detailed herein illustratively includes a pumped working fluid battery and, more particularly, a pumped glycerol battery (PGB). The illustrative pumped glycerol battery utilizes glycerol (aka: glycerin or glycerine) as the “working fluid” component. However, the PGB system of the present disclosure is not limited to only glycerol and may work as well or better with other fluids not yet tested or to be specially designed. Given that the illustrative PGB system is economically viable and is also safe for the planet and mankind, this system could function in many ways like pumped storage hydropower but without its limitations of geography, environmental impact, and cost. The PGB system could also be scaled down for smaller individual projects, but it is primarily intended to provide utility scale storage for the surplus electricity provided by renewable electrical sources, such as wind and/or solar generation.

Illustratively, the energy storage system includes a pumped glycerol battery (PGB) which is a mechanical system designed to store renewable electricity in a manner that can be readily dispensed back into the national electrical power grid or smaller grid systems on demand. The energy is illustratively stored in three additive forms of potential energy—(1) gravitational, (2) high-pressure gas derived by phase-change, and (3) vacuum draw. The primary working fluid medium (that which propels a turbine-generator to create electricity) is illustratively a dense liquid material that will be physically elevated at its energy storage site. The secondary working medium (that which assists the primary medium by adding more stored energy) is a gas, such as carbon dioxide.

Various pipes, pumps, valves, and controlling equipment complete the basic energy storage system which is envisioned as efficiently storing low-cost surplus electricity at utility scale but may also prove workable at a smaller scale in more isolated cases. The primary medium selected for use may have properties much like standard hydraulic fluids, but may be further developed in its formulation through continuous product research. In all, it is expected that a utility scale PGB system will provide longer-duration peaking/emergency power that is more cost effective and less risky than Lithium-ion battery farms or other storage systems currently available or under development.

According to an illustrative embodiment of the present disclosure, an energy storage system includes a supply vessel having a first portion receiving a pressurized carbon dioxide, and a second portion receiving a working fluid. A receiving vessel is in fluid communication with the supply vessel. A turbine is positioned intermediate the supply vessel and the receiving vessel, wherein the working fluid passes through the turbine to generate electricity.

According to another illustrative embodiment of the present disclosure, a method of storing energy includes the steps of providing a supply vessel receiving a working fluid, flowing the working fluid through a turbine to generate electricity, using pressurized gas to push the working fluid from the supply vessel to the turbine, and providing a receiving vessel to receive the working fluid after flowing through the turbine.

Additional features and advantages of the present invention will become apparent of those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.

DETAILED DESCRIPTION OF THE DRAWINGS

For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, which are described herein. The embodiments disclosed herein are not intended to be exhaustive or to limit the invention to the precise form disclosed. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings. Therefore, no limitation of the scope of the claimed invention is thereby intended. The present invention includes any alterations and further modifications of the illustrated devices and described methods and further applications of principles in the invention which would normally occur to one skilled in the art to which the invention relates.

With reference initially toFIG.1, an illustrative energy storage system100is shown as including a working fluid battery, more particularly a pumped glycerol battery102. The working fluid (WF) illustratively comprises a liquid, such as glycerol (aka: glycerin or glycerine). However, the energy storage system100of the present disclosure is not limited to only glycerol and may work as well or better with other working fluids not yet tested or to be specially designed. The pumped glycerol battery102is operably coupled to an electrical power grid (commonly referred to as the Grid)104via a conventional or specifically designed turbine106, illustratively a working fluid turbine such as a Francis hydro turbine106′ (FIG.1A). As is known, the turbine106,106′ is operably coupled to a generator108for generating electricity in response to rotation of the vanes or impellers109,109′ of the turbine106,106′. Conventional power lines110electrically couple the generator108to the power grid104.

The pumped glycerol battery102illustratively includes a supply vessel, such as a first sealed vessel or upper storage tank112for storing the working fluid at elevation above a second sealed vessel or lower receiving tank114. The upper storage tank112illustratively includes a first or upper portion112areceiving a pressurized gas, such as pressurized carbon dioxide (CO2) gas, and a second or lower portion112breceiving the working fluid. An electric heater (not shown inFIG.1) is illustratively supported by the upper storage tank112and is in thermal communication with the working fluid in the second portion112b. The electric heater may be internal or external to the tank112and is configured to keep the working fluid at a desired temperature to maintain it in a liquid state. A fluid conduit116illustratively provides for fluid communication between the upper storage tank112and the lower receiving tank114. Illustratively, a working fluid pump118is fluidly coupled to the fluid conduit116and is configured to pull the working fluid from the lower receiving tank114to the upper storage tank112(as represented by arrows120).

The lower receiving tank114is configured to receive the working fluid after the working fluid has expended its gravitational energy through the turbine106to generate electricity. A fluid conduit122illustratively provides for fluid communication between the lower portion112bof the upper storage tank112and the turbine106, wherein the working fluid flows from the upper storage tank112and the turbine106(as represented by arrows124). A fluid conduit126illustratively provides for fluid communication between the turbine106and the lower receiving tank114, wherein the working fluid flows from the turbine106to the lower receiving tank114(as represented by arrows128). A control valve127may be fluidly coupled to the fluid conduit126to control the rate of working fluid flow through the fluid conduit126. When the working fluid flows in a first direction (e.g., from the upper storage tank112to the lower storage tank114), the turbine106illustratively acts as a generator. When the working fluid flows in a second direction opposite the first direction (e.g., from the lower storage tank114to the upper storage tank112), the turbine106illustratively acts as a pump.

While a single turbine106is shown inFIG.1, it should be appreciated that a plurality or array of turbines106may be provided. Such an array of turbines106may be of any number, and arranged in parallel or series. Additionally, in order to be responsive to variations in the Grid104, the turbine106may act as a leakable pump (i.e., change direction of flow without reversing the pump).

The illustrative energy storage system100may include various pumps, valves, sensing units and digital management or control units operably coupled to the first and second sealed vessels112and114. A sealed pressure vessel130may receive a pressurized fluid. Illustratively, the pressure vessel130includes a first or upper portion130areceiving a pressurized gas, such as high pressure carbon dioxide (CO2) gas, and a second or lower portion130breceiving a liquid, such as liquid CO2. Illustratively, the pressurized, liquid carbon dioxide (CO2) is designed to maintain a constant pressure on the working fluid (glycerol) during the energy discharge, so as to maximize toward steady and sufficient electrical output from the turbine-generator components106,108.

Fluid conduits132and134illustratively provide for fluid communication between the pressure vessel130and the upper storage tank112. More particularly, high pressure CO2gas flows from the upper portion112aof the first sealed vessel112to the upper portion130aof the pressure vessel130(as represented by arrows136) via the fluid conduit132. Similarly, high pressure CO2gas flows from the upper portion130aof the pressure vessel130to the upper portion112aof the first sealed vessel112(as represented by arrows138) via the fluid conduit134. A compressor140may be fluidly coupled to the fluid conduit132to compress the CO2gas therein.

Illustratively an electric heater (not shown) may also be provided in thermal communication with the pressure vessel130to change the CO2from a liquid state to a gaseous state on demand. A fluid conduit loop142may be fluidly coupled to the fluid conduit132to provide a heat saving route for the CO2(as represented by arrows144). Illustratively, various pipes and valves, sensing devices, and other control parts may be operably coupled to the pressure vessel130. Various electrical components of the system100may be controlled by a controller150including a processor152. In certain illustrative embodiments, the controller150may be in wireless communication with such electrical components (as represented by arcs154).

During operation of the illustrative energy storage system100, incoming (low-cost) electricity is used to pump the glycerol from the lower receiving tank114to the upper storage tank112to gain gravitational potential energy. Electricity from the electrical power grid104is also used to drive the turbine106and thereby pump working fluid back into the storage tank114via the fluid conduit126. A minimal level of glycerol is to be retained in the lower portion112bof the upper storage tank112in order to prevent the CO2from coursing through the turbine-generator components106,108of the system100. Pumping glycerol back into the lower portion112bof the upper storage tank112will in part push the CO2back into the pressure vessel130via the fluid conduit132as the glycerol level rises (as represented by arrows136), where it is to liquefy and await another cycle of energy discharge. The electrical compressor140is illustratively provided to further compress the CO2and regain its full phase change potential energy at the desired temperature. This compressor also minimizes the amount of CO2that will phase-change to liquid in the upper tank112a.

While other battery systems have been proposed to store excess electrical energy by compressing CO2into a liquid, the pumped glycerol battery (PGB)102of the present disclosure utilizes the physical phase-change of CO2(liquid to gas) for a purpose other than for it to be the working fluid that drives the turbine106and attached generator108. Liquid CO2can be self-regulated as a guarantor of constant pressure upon another liquid working fluid. Expansion of the space for the pressure-providing CO2above the working fluid (glycerol) will instantly drop the CO2's pressure and thusly cause more CO2to change phase from liquid to gas, thus maintaining the desired pressure against the glycerol fluid. Though this action is fast and unassisted, a controlled heater can also activate the change from liquid to gas for additional CO2-pressure on the glycerol when needed. The whole system102is both closed (sealed) and space conserving, as the glycerol is much more energy dense and does not require a large external receiving bag, as found in other systems that must store their expanded CO2working fluid in a flexible low-pressure vessel until recompressed into high-pressure tanks for liquid energy storage.

Referring now toFIG.2, a further illustrative energy storage system200is shown as including a working fluid battery, more particularly includes a pumped glycerol battery (PGB)202. The illustrative energy storage system200includes many similar elements as the energy storage system100detailed above. As such, in the following description similar components are identified with like reference numbers.

The illustrative energy storage system200includes sealed vessels212and214for holding a working fluid (WF), including a supply vessel, illustratively a first or upper storage tank212for storing the working fluid under pressure at elevation, and a second or lower storage tank214at a lower level for receiving the working fluid after the liquid has expended its gravity and gas-pressure-derived energy through the turbine106and the generator108that generates electricity. The working fluid (WF) illustratively comprises a liquid, such as glycerol (aka: glycerin or glycerine). Secondary to these vessels212and214are related pumps, pipes, valves, sensing units, and digital management units.

While a single turbine106is shown inFIG.2, it should be appreciated that a plurality or array of turbines106may be provided. Such an array of turbines106may be of any number, and arranged in parallel or series.

The upper storage tank212illustratively includes a first or upper portion212areceiving a pressurized gas, such as pressurized carbon dioxide (CO2) gas, and a second or lower portion212breceiving the working fluid. Illustratively, the first portion212aand the second portion212bare received within a single sealed storage tank212. However, it should be appreciated that the first portion212aand the second portion212bmay be defined by separate vessels or tanks. Illustratively, the first portion212ais positioned above the second portion212b, and a movable diaphragm216is positioned between the first portion212aand the second portion212b. The diaphragm216may be flexible and move in response to a pressure differential on opposing sides thereof (i.e., different pressures of the pressurized carbon dioxide (CO2) gas in the first portion212a, and the working fluid in the second portion212b). In an illustrative embodiment, the diaphragm216may be formed of a thin membrane formed of a self-lubricated graphene.

An electric heater217is illustratively supported by the upper storage tank212and is in thermal communication with the working fluid in the second portion212b. The electric heater217may be internal or external to the tank212and is configured to keep the working fluid at a desired temperature to maintain it in a liquid state. The electric heater217is illustratively coupled to the electric switch230and may be powered by a battery or a supercapacitor.

A fluid conduit218provides for fluid communication between the second portion212band the turbine106, while a fluid conduit220provides for fluid communication between the turbine106and the storage tank214. A control valve222may be fluidly coupled to the fluid conduit218to control the rate of working fluid flow through the fluid conduit218.

The lower storage tank214is illustratively a sealed tank including a first or upper portion214areceiving a vacuum, a second or lower portion214bto receive the working fluid. The lower portion214bis in fluid communication with the turbine106via the fluid conduit220.

When the working fluid flows in a first direction (e.g., from the upper storage tank212to the lower storage tank214), the turbine106illustratively acts as a generator. When the working fluid flows in a second direction opposite the first direction (e.g., from the lower storage tank214to the upper storage tank212), the turbine106illustratively acts as a pump.

A sealed pressure vessel130illustratively receives CO2gas and, more particularly, supercritical carbon dioxide (SCD), which is designed to maintain a constant pressure on the working fluid (glycerol) in the second portion212bof the storage tank212during energy discharge of the battery202, so as to guarantee sufficient electrical output from the turbine-generator106,108. Illustratively, the vessel130includes a first or upper portion130areceiving the CO2gas, and a second or lower portion130breceiving supercritical CO2liquid. A fluid conduit224fluidly couples the first portion130aof the vessel130to the first portion212aof the storage tank212. A compressor225may be fluidly coupled to the conduit224for removing CO2gas from upper tank212abefore it would phase-change within that tank212a.

Ancillary equipment regarding the pressure tank130may include a compress CO2gas, an internal electric-heater unit, plus pipes and valves, and various control and containment parts. Illustratively, an electric heater226may be in thermal communication with the vessel130to heat the liquid CO2into a CO2gas. A supercapacitor or battery228powers the electric heater226and may be controlled by an electric switch230.

When there is demand for the pumped glycerol battery (PGB)202to provide electricity to the Grid104, the working fluid in the upper vessel212(tank1) is released at the bottom to the turbine-generator106,108and then onward to the receiving vessel214(tank2) below. The force of the working fluid upon the turbine106is made greater by having high-pressure carbon dioxide (CO2) gas above the working fluid in the upper tank212pushing downward against the surface of the fluid. In addition to this, the vacuum stored in the lower tank214(which was created during the charging cycle) draws on the working fluid and thus adds additional energy to propel the turbine106and its attached electrical generator108. As such, the system200provides energy in three different but synchronous manners: (1) CO2pressure from gasified SCD upon the working fluid, (2) the weight of the working fluid itself, and (3) the drawing-down of the working fluid by the vacuum within the receiving tank.

When surplus energy from the Grid104is available, the charging of the pumped glycerol battery (PGB)102is effected by pumping the working fluid from the lower (receiving) tank214(#2) to the upper storage tank212(#1) in order to gain gravitational potential energy from the weight of the fluid. In so doing, the electricity from the Grid104also pushes the gaseous CO2residing above the working fluid within the upper tank212, as the working fluid level rises, back into the CO2storage vessel130where it then converts back to SCD and awaits another energy discharge cycle. A compressor may be added to the system in order to accelerate the compression of the CO2back into its own SCD storage vessel130.

While other battery systems have been proposed to store excess electrical energy by compressing CO2into a supercritical liquid or sCO2state, the pumped glycerol battery (PGB)202of the present disclosure utilizes the physical phase-change of CO2(liquid/sCO2to gas) for a purpose other than for the CO2gas to be the working fluid that drives the turbine106and its attached generator108. In the PGB system202, the liquid-to-gas CO2pair serves as a self-regulating provider of constant pressure applied upon the primary liquid working fluid (glycerol). Because a lowering of the stored glycerol in the upper tank212, as it is used, creates an expansion of the space above for more of the pressure-providing CO2, the CO2's pressure will accordingly drop within the sCO2tank130; and that in turn will cause more of the sCO2to instantly change phase from “liquid” to gas, thereby restoring the desired pressure of the CO2gas against the glycerol fluid residing in the upper tank212(#1). Though this action is naturally fast and unassisted, a controllable electric-heater element imbedded within the “liquid” sCO2inside the sCO2tank130can also be used to force the change from sCO2to CO2gas and thusly create additional CO2-pressure on the glycerol when needed.

The pumped glycerol battery (PGB) system202is comparatively space-conserving, as the glycerol remains very dense after coursing through the turbine-generator106,108and accordingly does not require a large external receiving bag, as found in other systems where their expanded CO2(working-fluid) must be collected and stored in a very large, flexible low-pressure vessel until such gas is recompressed into high-pressure tanks for storage as a liquid. The PGB system202is very energy dense in its design because it employs two different working media that are additive in delivering pressurized working fluid to the turbine-generator106,108. In this, the glycerol itself will store considerable potential energy (gravitational) within the elevated upper storage tank proportional to its volume; while in addition to this, the PGB's “liquid” CO2(sCO2) also stores potential energy densely as a “liquid” that can phase-change into high pressure gas. Together, both the glycerol's own weight and the CO2's high-pressure (pushing down on the glycerol from above) add up to a very high pressure working fluid going into the turbine106, which means a smaller amount of working fluid is needed to generate an equivalent output of electricity.

The above-described energy storage system200, including the illustrative pumped glycerol battery202, has numerous potential advantages. For one, if glycerol proves adequate as the preferred working fluid, then cost savings and availability will be benefits. Glycerol is presently produced in large quantities as a by-product of converting soybeans into biodiesel. Because of this, the market supply of glycerol greatly exceeds the market demand for this substance, which can be readily produced in the United States without any dependence upon foreign supply chains. Likewise, the steel pipes and tanks can all be fabricated within North America, yielding local jobs and enhanced national security. It should be noted that in the closed-loop PGB system, replenishment of the primary working fluid (glycerol) may not be required even after many charge-discharge cycles. However, protection of this medium might require a separating diaphragm to block CO2from dissolving into the medium, or to block organisms than can attack the glycerol molecules.

Another benefit of the illustrative energy storage system200is the lack of risk of fire (as opposed to Lithium batteries) or toxicity from any fugitive leakage of media from the PGB site. Another advantage is the lack of any high-temperature storage (e.g., white hot media) of questionable efficiency and safety. Lastly, a PGB site may be located nearly anywhere, on the Grid or not, and possibly in closed-down coal-fired power plants which already have existing ties to the National Grid. In this latter aspect, the PGB system may accelerate the closing of polluting coal-fired generation units that are being retained solely to guarantee a stable Grid, and it may simultaneously encourage further development of wind and solar farms that will be made more economical due to the PGB's improvement to their off-peak markets.