WO2022271687A2

WO2022271687A2 - System and method for high efficiency, multitiered, pumped electrical energy storage (ptes) utilizing renewable power and co2 working fluid

Info

Publication number: WO2022271687A2
Application number: PCT/US2022/034327
Authority: WO
Inventors: Glen L. Bostick; David L WAIT
Original assignee: Nooter/Eriksen, Inc.
Priority date: 2021-06-21
Filing date: 2022-06-21
Publication date: 2022-12-29
Also published as: WO2022271687A3

Abstract

A system and method for particle based thermal storage and pumped thermal electricity storage (PTES), comprises container for heat absorbing particles, container has first and second inlet and outlet openings; blower; valve connected to first inlet opening, valve connected to the first outlet opening; valve connected with second inlet opening, inlet connected through blower outlet; valve connected with second outlet; air heater connected to blower outlet, outlet connected to valve inlet; heat pump for thermal energy to container contents, heat engine for removing thermal energy from container, heat pump and heat engine can comprise subcritical or supercritical Rankine cycles, heat pump can comprise and economizer and can connect through second valve outlet, heat engine can comprise a turbine and working fluid pump; thermal storage can have multiple storage tanks connected in series.

Description

SYSTEM AND METHOD FOR HIGH EFFICIENCY, MULTITIERED, PUMPED ELECTRICAL ENERGY STORAGE (PTES) UTILIZING RENEWABLE POWER AND C02 WORKING FLUID RELATED APPLICATIONS

[0001] This application claims priority to U.S. provisional application Ser. No. 63/213,140 filed June 21, 2021, the disclosure of which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

BACKGROUND OF THE DISCLOSURE

[0003] Heretofore, Pumped Thermal Electricity Storage (PTES) has been combined with Concentrated Solar Power (CSP) Systems to increase system efficiency. Such known combination systems did not offer significant advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Fig. 1 is a diagrammatic representation of a combined CSP and PTES system where the CSP system has a plurality of reflectors or mirrors that reflects solar energy onto an absorptive tower where a high temperature heat transfer medium, such as molten salt is heated to a relatively high temperature and the molten salt is stored in a high temperature heat storage tank;

[0005] Fig. 2 is a diagrammatic representation of portions of the system of the present disclosure illustrating the heat pump cycle and the heat engine cycle of the present disclosure and illustrating how medium temperature heat energy in a medium temperature storage tank MTS 103 is created by the C02 heat pump; how such medium temperature heat energy is stored in storage tank MTS 103, and how medium temperature energy is removed from the medium temperature tank and is supplied to the power cycle so that a suitable C02 heat engine (e.g., a turbine) can be powered. [0006] Fig. 3 is a flow diagram of an embodiment of an improved pumped thermal energy storage (PTES) and concentrated solar power (CSP) system of the present disclosure illustrating the components of the heat pump cycle on the left side of the diagram, the components of the power cycle on the right side of the diagram, and the components common to both the heat pump cycle and the power cycle in the center of the diagram;

[0007] Fig. 4 is a flow diagram for a system of the present disclosure similar to Fig. 2 except the desirable but not necessary balancer heat exchanger 111 of Fig. 3 has been deleted, where State Points 0_HP through 5_HP for the Heat Pump Cycle and State Points 0_PC through 8_PC for the Power Cycle are shown;

[0008] Fig. 5 is a detailed drawing of the components making up another arrangement for the medium temperature heat storage tank MTS where the preferred heat storage medium is a particulate heat storage material (e.g., sand) that is heated by direct contact with the heated air in a direct contact heat exchanger 103d in which the particulate heat storage material is fluidized;

[0009] Figs. 6 and 7 illustrate other embodiments of the arrangement of Fig. 5 for heating particulate heat storage material; [0010] Table 1 is a list of the components of the system of Fig. 3 showing as an example desirable operating states when the medium temperature heat storage tank MTS 103 is operating in any one of three discussed operating modes, as listed in Table 1;

[0011] Table 2 is a listing of the State Points (0_HP through 5_HP) for the Heat Pump Cycle, as shown in Fig. 4;

[0012] Fig. 8 is a T - S Diagram for the State Points listed in Table 2 for the C02 Heat Pump Cycle, as shown in Fig. 4;

[0013] Table 3 is a listing of the State Points (0_PC through 8_PC) for the Heat Engine Power Cycle points, as shown in Fig. 4; [0014] Fig. 9 is a T - S Diagram for the State Points 0_PC through 8_PC listed in Table 3 for the Heat Engine Power Cycle points, as shown in Fig. 4; [0015] Fig. 10 is another flow diagram of a system of the present disclosure in which the heat storage medium for the medium temperature storage tank MTS is a solid particulate material, such as sand, that is directly heated by a medium temperature heat exchanger 132B located in the lower hopper as the sand flows over said exchanger. The hot solid material is mechanically delivered to the top of the assembly and into hopper 131 A. Valve 131B controls the flow of hot material over the heat exchanger 131C, where the heat is transferred from the hot particles into the working fluid of the power cycle. Valve 131E then controls the flow of now cooled solid particles down into the lower hopper where they are again heated, and the cycle repeated.

[0016] Fig. 11 is a flow diagram of an alternate system similar to that shown in Fig. 10 for a solid particulate heat storage material having a single medium temperature storage tank having an upper heating coil 108 therein for cooling the solid particulate heat storage material by the power cycle, and a lower coil 101 that heats the solid particle by taking heat from the C02 working fluid after it passes through the compressor 109 in the heat pump loop.

[0017] Fig. 12 is a diagrammatic representation of portions of the system of the present disclosure, according to an alternative embodiment, illustrating the heat pump cycle and the heat engine cycle of the present disclosure, and illustrating how medium temperature heat energy in a medium temperature storage tank MTS 103 is created by the C02 heat pump, how such medium temperature heat energy is stored in storage tank MTS 103 and how medium temperature energy is removed from the medium temperature tank and is supplied to the power cycle so that a suitable C02 heat engine (e.g., a turbine) can be powered.

[0018] Figs. 13 and 14 are simplified flow diagrams of further embodiments of the systems of the present disclosure that are similar to the systems represented in Figs. 3 and 4; several of the components of the systems represented in Fig. 13 and Fig. 14 are the same components and are labeled with the same reference numbers.

[0019] Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. DESCRIPTION OF DISCLOSURE

[0020] The broad concept of the present disclosure integrates a CSP power system (or other renewable energy source or even waste heat) with a PTES system so as to transform the intermittent supply of electricity from renewable sources to a dispatchable power source, while relying on a minimal back-up generation using natural gas powered peaking plans or other carbon free alternatives. More particularly, the system of the present disclosure invention relies on storing heat at different temperature ranges, namely, low temperature heat using water/ice as the heat storage medium that is stored in a low temperature storage tank LTS 116 (as shown in Figs. 3 and 4); medium temperature sensible heat that is stored in a bed of natural crushed rock or other suitable thermal storage medium in a medium temperature storage tank MTS 103; and high temperature high heat that is stored in a high temperature storage medium (e.g., a bed of crushed rock, molten salt, or any other suitable sensible/latent heat storage media or the like) within a high temperature storage tank HTS 127. By way of example and not limitation, a high temperature concentrated solar power system CSP supplies molten salt at a high temperature to the high temperature storage tank HTS 127 (See Figs. 1, 3 and 4) when there is adequate solar power available, such as during daylight hours. While it is preferable that the heat for the high temperature storage tank HTS come from the CSP system, it will be understood that the heat can come from another source such as electrical resistance heaters powered by a wind power system or hydroelectric power or from a high temperature heat exchanger (not shown) that uses waste heat from another process. This is shown in Figs. 3 and 4 by the supplemental high temperature heater 128. In addition, the quantity of high temperature heat storage medium (e.g., molten salt) stored in the high temperature tank HTS 127 is sufficient such that heat can be removed from the high temperature tank to power the heat engine (e.g., high temperature/high pressure portion of a steam turbine) that makes up the power cycle. Medium temperature heat can be removed from the medium temperature thermal storage tank MTS 103 and supplied to the power cycle so as to power another portion of a power cycle (e.g., a low temperature/low pressure portion of the steam turbine making up the power cycle) or preferably for heating the working fluid in the power engine loop of the system of this disclosure. The electrical power generated by the power cycle is supplied to a power load. Low temperature heat is removed from the power cycle and is stored in a low temperature storage medium (e.g., water) within a low temperature heat storage tank LTS 116. The present invention makes use of multiple energy storage systems in parallel (i.e., continuous operation) so to provide a highly efficient energy cycle. The heat pump HP and heat engine HE of the system of the present disclosure rely only on transcritical thermal dynamic cycles using C02 as the working fluid. Typical operating pressures for the two power cycles are between about 3.3 MPa and 22 MPa. Operating temperatures are expected to be between about -3°C and about 186° and about 3°C and greater than about 540°C for the heat pump and heat engine power cycle, respectively. Those skilled in the art will appreciate that other working fluids could be used in place of C02 and these other working fluids would have different working conditions as a function of their thermochemical properties. It is understood that alternative fluids could be used in the defined system so long as the intrinsic thermo-physical properties are considered and the overall system performance is suitably considered.

[0021] An important aspect of the system of this disclosure is that the combined CSP and PTES systems run at constant full power to meet a predetermined base load profile for a designed time period. By making the heat capacity of the high temperature storage tank HTS 127 and the intermediate temperature storage tank MTS 103 larger, the longer the system of the present disclosure will make power as the system can store more heat.

[0022] In accord with the present disclosure, a particle bed thermal storage system of the medium temperature thermal storage 103 of the present disclosure comprises a container tank 103, as shown in Figs. 2, 3,

10 and 11 , having a first inlet opening 3 and a second outlet opening 5. A blower 100 is provided to flow atmospheric air through the container 103 entering the container 103 via the first inlet opening 3 and exiting the container 103 via the second outlet opening 5. The container 103 also has a third inlet opening 7 and a fourth outlet/opening 9, as shown in Figs. 3 and

4. As shown in Figs. 3 and 4, the blower 100 has an inlet 11 open to the atmosphere and an outlet 13 in communication with the inlets 3 and 7 of the container or tank 103 via lines L1 and L2, respectively. A first valve or damper 102 is provided in line L1 for controlling the flow of air to inlet 3, and a second damper or valve 104 in line L3 controls the flow of heated air from outlet 5 of the tank MTS 103. A third damper or valve 106 in line L2 controls the flow of air from the blower 100 to the inlet 7 of the MTS tank 103. A fourth damper or valve 107 in line L4 controls the flow of air from outlet 9 of the tank 103. [0023] An air heater (e.g., medium temperature heat exchanger 101 , as shown in Figs. 3 and 4) has its inlet connected by line L1 to the blower 100 and its outlet connected by line L1 to inlet of the valve or damper 102 for heating medium temperature air directed through line L1 from the heat pump cycle to the inlet 3 of tank 103, where it heats a suitable medium temperature heat storage media in tank 103. Heated or partially heated air flowing out of tank 103 via outlet 5 is controlled by valve 104 and is supplied to the inlet of an economizer 105 for heating a low temperature working fluid (e.g., C02) flowing to the low temperature tank LTS 116. Air exiting economizer 105 is discharged to the atmosphere or to the ambient environment. [0024] Heat pump system HP, as shown in Figs. 2 - 4, provides thermal energy to the intermediate heat storage media in tank 103, where the preferred thermal storage media is a bed of particulate material such as sand or the like, or of rocks. A heat engine HE in the power cycle operates on heat or thermal energy removed from the thermal storage media of both the high temperature tank HTS 127 and the medium temperature storage tank 103. The heat pump comprises a supercritical Rankine cycle and the heat engine comprises a supercritical Rankine cycle engine where the working fluid is supercritical C02.

[0025] Referring now to Fig. 3, an embodiment of the present disclosure is illustrated where the components have been grouped into components that pertain to the heat pump cycle (on the left side of left vertical dashed line of Fig. 3), the components that pertain to the power cycle (on the right side of the right vertical line of Fig. 3), and the common or shared components are shown in the middle portion of Fig. 3 between the said vertical dashed lines. The thick or bold-faced lines in Fig. 3 indicate piping or lines that carry air as the working fluid, and the thin lines indicate piping or lines that carry C02 (carbon dioxide) as the working fluid. It will also be appreciated that a different fluid could be used on the heat pump side than is used on the heat engine side.

[0026] As shown in Figs. 3 and 4, it is the medium temperature storage media and tank MTS, as indicated at 103, where the initial heating of the working fluid in the heat engine cycle occurs. The MTS effluent is then directed to recuperator 120 for additional heating. In both the systems of the present disclosure, as shown in Figs. 3 and 4, the working fluid discharged from the expander or turbine 122 of heat engine HE is directed to a low temperature thermal storage tank LTS, as indicated at 116, which contains a suitable low temperature heat storage medium, such as water and ice. [0027] In the heat pump cycle of the embodiment of Fig. 3, C02 is evaporated by the heat storage medium (e.g., water) of the low temperature tank LTS 116 at low pressure using latent heat from the water as it forms ice on the outside of the low temperature heat exchanger 115 within the low temperature tank LTS 116. The C02 from heat exchanger 115 flows out of the low temperature tank 116 through a flow path or conduit such as a pipe to an inlet of superheater 113 and through superheater 113 so that the C02 working fluid is at least somewhat superheated as the C02 fluid flows thorough a flow path and enters a high pressure compressor 109, which is part of the heat pump cycle, where it is further heated using the C02 heat of compression. This superheating of the C02 by the superheater 113 ensures that gaseous, and not liquid, C02 is delivered to the inlet of heat pump compressor 109, and the superheating somewhat lessens the power needed by the compressor 109 to heat the C02 to its desired temperature. The C02 exiting the outlet of the compressor 109 flows through a flow path through one side of a high pressure, medium temperature heat exchanger MTHX 101 where it heats atmospheric air flowing through line L1 from air blower 100 which is delivered to inlet 3 of medium temperature storage tank MTS 103. Upon exiting the heat exchanger MTHX 101, the flow of heated air is controlled by a damper/valve 102 in line L1. MTS 103 holds a supply of medium temperature heat storage medium which is heated by the medium temperature air flowing into tank MTS 103. If the heat storage medium within tank MTS 103, such as a bed of large rocks with air passages therebetween does not unduly restrict the flow of the air through the medium, the heated air entering tank MTS can directly flow through the medium in tank MTS to outlet 5 . However, if the heat storage medium is a particulate heat storage material, such as sand, that fills the medium temperature tank MTS 103, the sand would compact, and it would require a relatively large pressure drop to force the air to flow through the heat storage medium in MTS 103. In order to avoid having such a pressure drop and to be able to use a particulate medium, such as sand, a direct heating approach, as shown in Figs. 5 - 7, can be used. The direct heating of a particulate heat storage medium will be described in detail hereinafter. Such a direct heating approach would utilize a fluidized supply of the particulate heat storage medium (e.g., sand), which is collected in a cyclone tank 103b (as shown in Fig. 5) where the sand particles are metered by a metering valve 103c into a direct contact heat exchanger 103d where the individual particles are directly heated by the hot air in the heat exchanger 103d.

[0028] Between the outlet of heat pump compressor 109 and the medium temperature heat exchanger MTS 101, a so-called balancing circuit, as generally indicated at 15 in Fig. 3, is provided that further heats the C02 working fluid using energy from the heat engine side via a balancing heat exchanger 111 during specific modes of operation. More particularly, a 3- way valve 110 downstream from the outlet of compressor 109 can selectively direct/moderate the C02 working fluid heated by compressor 109 to the medium temperature heat exchanger 101 , which heats the air flowing in line L1 as it is delivered to the medium temperature heat storage than MTS 103. After the C02 working fluid passes through heat exchanger 101 , the working fluid is delivered to superheater 113 via a 3-way valve 112. Depending on the position of valve 112, hot C02 working fluid from heat exchanger 101 and/or from the balancing heat exchanger 111 can be delivered to the heating coil of superheater 113 to superheat the C02 working fluid delivered to the inlet of heat pump compressor 109. The 3-way valve 110 can also be operated to send the heated C02 from the outlet of compressor 109 to the balancer heat exchanger 111 where it is cooled by C02 discharged by the pump 117 in the Power Cycle portion of the system. After passing through the balancing heat exchanger 111 , the C02 working fluid is directed by the 3-way valve 112 to the heating coil of superheater 113 to superheat the C02 working fluid supplied to the inlet of compressor 109. The C02 working fluid exiting superheater 113 is directed to economizer 105 and it flows through a throttle/expansion valve 114 prior to the economizer, which cools the C02 working fluid prior to encountering the economizer. In the economizer, the C02 working fluid is further cooled by the air flowing through the economizer, and the C02 is returned to the low temperature heat exchanger 115 within the low temperature storage tank LTS 116. [0029] On the Power Cycle side of Fig. 3, low temperature C02 working fluid exits low temperature heat exchanger 126 in the low temperature storage tank LTS 116 and is supplied to the inlet of a pump 117, which functions like a boiler feedwater pump in a conventional steam turbine system. Downstream of pump 117 is a 3-way valve 118 which is operable to direct C02 working fluid to a medium temperature heat exchanger 108. Downstream of heat exchanger 108 is another 3-way valve 119. These 3- way valves 118 and 119 meter the flow of the C02 working fluid from the outlet of pump 117 between the balancing heat exchanger 111 or the 108 heat exchanger. With the C02 working fluid from the pump 117 supplied to the balancing heat exchanger 111 or to the medium heat exchanger 108, the C02 working fluid is heated so as to result in supercritical C02 flowing to a recuperator 120 to pick up additional heat from the outlet of expander 122. Downstream from the recuperator 120, the C02 working fluid is heated in a high temperature heat exchanger 121 from a high temperature working fluid circulating through high temperature storage tank 127. The heated supercritical C02 working fluid is supplied to the inlet of expander 122 to drive the expander (turbine) so as to generate electricity, which is supplied to the grid or to a load, but which is not shown in either Figs. 3 or 4. As shown in the lower right portion of Figs. 3 and 4, a high temperature heater 128 supplies high temperature heat to high temperature storage tank HTS 127. This heater 128 can be powered by a renewable energy system (not shown), such as a concentrated solar power system CSP or wind power, that is not dependent upon sunlight so as to maintain the temperature of the high temperature storage medium in tank HTS 127 when the CSP system is inoperable. Those of ordinary skill will also recognize that in addition, the high temperature storage tank HTS 127 can be supplied by other more traditional heat sources, such as wind power, waste heat or direct firing of hydrocarbon fuels.

[0030] As noted, Fig.4 includes State Points 0_HP thru 5_HP for the Heat Pump cycle and State Points 0_PC through 8_PC for the Power Cycle. Table 2 lists the State Points for the Heat Pump Cycle and Fig. 8 is a temperature vs. entropy plot for the C02 Heat Pump Cycle. Likewise, Table 3 lists the State Points for the Power Cycle and Fig. 9 is a temperature vs. entropy plot for the C02 Heat Engine or Power Cycle. From these State Points and from Figs. 8 and 9, one of ordinary skill in the art will be able to determine the mode of operation of the systems of the present disclosure, as shown in Figs. 3 and 4.

[0031] Referring now to Fig. 5, a system of the present disclosure for direct heating of a pulverized or particulate heat storage material, such as sand, is shown and will now be described. The medium temperature tank MTS 103 is shown in dotted lines in Fig. 5. The inlets and outlets 3, 5, 7 and 9 as described in relation to Fig. 3 are shown in Fig. 5. Heated air from damper valve 102 enters a heat exchanger 103a via inlet 3. A fluidized bed of sand or other particulate particles is suspended in heat exchanger 103a and these particles are directly heated by the hot air from inlet 3. A stream of particularized air is conveyed vertically from heat exchanger 103a and is delivered to a cyclone 103b, where the heated particles settle out and the heated air exits from outlet 5 and is directed in line L3 to valve 104 and to economizer 103 and is exhausted to the atmosphere, as shown in Fig. 3. The heated sand particles in cyclone 103b are metered by a metering valve 103c to drop downwardly into a vertical direct contact with heat exchanger 103d. Air from blower 100 is directed into the bottom of the vertical heat exchanger 103d through inlet opening 7 and is heated by the hot sand particles dropping within the vertical heat exchanger. Heated air exits the vertical heat exchanger 103d through outlet 9 and is directed to a heat exchanger 108. The systems of Figs. 6 and 7 are similar to the system shown in Fig. 5 and thus will not be described in detail.

[0032] Referring now to Table 1 , the systems and methods of Figs. 3 - 4 can be operated in three different modes of operation relating to whether: a.) the medium temperature thermal storage tank MTS 103 is charging while the heat engine cycle produces power (e.g., renewable energy is powering the C02 heat pump and the C02 heat engine is producing electricity to satisfy a connected load); b.) the MTS tank 103 is charging while the heat engine cycle is not producing power (e.g., renewable energy is powering the C02 heat pump and no electricity is generated by the heat engine as there is no load to satisfy); and c.) the MTS tank is discharging (e.g., renewable energy is unavailable to power the C02 heat pump and the C02 heat engine is using previously stored energy to generate electricity to satisfy a connected load). Table 1 describes each of the components of the systems of Fig. 3 and their operating conditions in each of these operating modes. From Table 1, one of ordinary skill in the art can determine the operating positions of each component in the system of Fig. 3 for each of the three modes of operation such that a detailed discussion of all of the components is not required. In some embodiments, the systems disclosed herein can both charge and discharge the MTS 103 simultaneously with heat energy being added by the heat pump cycle and heat energy being withdrawn by the power cycle. [0033] Operation state points 0_HP through 5_HP in the heat cycle and operation state points 0_PC through 8_PC are shown in Fig. 4. The values for these operational state points are listed, respectively, in Tables 2 and 3. Fig. 8 is a Temperature vs. Entropy (T vs. S) diagram showing the operation of the heat pump cycle utilizing C02 as the working fluid having the state points of Table 2. Likewise, Fig. 9 is a Temperature vs. Entropy (T vs. S) diagram showing the operation of the power cycle utilizing C02 as the working fluid having the state of Table 3. From these operating state points and T - S curves and from the flow diagrams of Figs. 3 and 4, one of ordinary skill in the operation of the systems of Figs. 3 and 4 would be apparent to one of ordinary skill in the art. [0034] Referring now to Fig. 10, only the components of the shared medium temperature heat exchanger 131 and the components of the shared medium temperature heat exchanger 132 are shown in the middle of Fig. 10 and will be described in detail. Those skilled in the art will appreciate that the components of the Heat Pump Cycle and of the Power Cycle previously discussed in regard to Figs. 1 - 7 have the same construction and function as previously described. As shown in Fig. 10, the upper medium temperature heat exchanger 131 comprises an upper hopper tank 131 A having a coil 131C therein that picks up heat from and thus cools a solid particulate heat storage medium, such as sand or the like, that is fed into the upper hopper 131 A and that moves downwardly within the upper hopper past heating exchanger 131 C for being directly cooled by heat exchanger 131. A working fluid, such as C02, flowing through coil 131C is heated by the sand and flows to recuperator 120, as shown in Fig. 10. The cooled sand flows downwardly within a converging hopper bottom mass flow nozzle 131D and into the upper end of a lower hopper tank 132C. A valve 131E controls the flow of the particulate heat storage material from the upper hopper to the lower hopper. In short, the upper section (i.e., hopper 131) in Fig. 10 is where heat is “removed” from the hot solid material and transferred into the heat engine cycle. In Fig. 10, the particles leaving hopper 131D are cooled by the MTHX PC Coil (131 C) and then flow over the heating coil 132B which is where the heat of compression of the C02 working fluid flowing through compressor 109 from the heat pump loop is captured in the solid material. The hot solids can then reside in the bottom of the assembly (i.e., in the lower mass flow hopper 132C) while at same time, some of the hot particles can be conveyed via conveyors 129 and 130 to the upper hopper 131 A for storage.

[0035] The upper end of the lower hopper 132A diverges outwardly and has the appropriate spreaders S therein so as to distribute the heated material substantially uniformly across the entire cross section of the lower hopper. A coil 132B is in direct thermal contact with the downwardly moving heat storage medium (sand) so as to heat the solid particles by exchanging heat from within the C02 working fluid discharged from the outlet of the heat pump compressor 109 and to supply C02 working fluid to the heating coil of superheater 113 for superheating the C02 working fluid supplied to the inlet of compressor 109. After the heated sand has been heated by the coil 132B, it is discharged from the bottom end of the hopper tank into a horizontal auger conveyor 129 or the like and a vertical bucket conveyor or lift 130 which lifts the now hot sand from the bottom of the lower hopper and discharges the hot sand into the upper end of the upper of the upper hopper for being heated by the coil 131C.

[0036] The system shown in Fig. 11 is similar to the system above- described and shown in Fig. 8, except only a single vertical hopper tank MTHX 133 is provided which has a coil (108) where heat is transferred into the heat engine power cycle and a lower exchanger coil (MTHX 101 ) where heat from the heat pump cycle side of the system is provided for heating the solid material in the hopper tank. The upper coil 108 is supplied with cool C02 working fluid from pump 117 in the Power Cycle which is then heated by the hot solid particles flowing down through the coil 108. The lower coil 101 has a higher temperature C02 working fluid from the heat of compression that flows therethrough, which, in turn, heats the particulate sand particles for energy storage. The sand exiting the bottom of the hopper is returned to the top via auger conveyor 133 and by bucket lift conveyor 135. [0037] The system shown in Fig. 12 is similar to the system above- described and shown in Fig. 2 and operates consistent with the principles disclosed herein with respect to the system above-described and shown in Fig. 3. However, instead of a single medium temperature heat exchanger MTHX 101, this embodiment includes a first medium temperature heat exchanger MTHX 101a (also labeled MTHX-c1) and a second medium temperature heat exchanger MTHX 101b (also labeled MTHX-c2). The use of two medium temperature heat exchangers allows for different flow rates of air through each medium temperature heat exchanger. In the depicted embodiment, the flow rate through the second medium temperature heat exchanger MTHX 101b is higher than that of the first medium temperature heat exchanger MTHX 101a. This prevents the variable heat capacity of the C02 working fluid from restricting the efficiency of the heat pump. A supplemental blower 100a is included to provide for variable (e.g., increased) air flow through the second medium temperature heat exchanger MTHX 101b. [0038] The inclusion of two medium temperature heat exchangers also allows for the use of a working fluid other than C02 without impacting the efficiency of the heat pump.

[0039] The system shown in Fig. 13 is similar to the system described earlier and shown in Fig. 3 and operates consistently with the principles disclosed herein with respect to the system described and shown in Fig. 3 with the additional information that the system shown in Fig. 14 employs an additional heat storage tank.

[0040] The system as shown in Fig. 14 is similar to the system described and shown in Fig. 13 and operates consistently with the principles disclosed herein with respect to the system described earlier and shown in Fig. 3, with the additional information that the system shown in Fig. 14 employs an additional heat storage tank over that of Figure 13.

[0041] The temperature storage tank 202 represented in each of Fig. 13 and Fig. 14 is similar to the temperature storage tank 103 shown in Fig. 3. The temperature storage tank 202 has a first inlet opening 208 that corresponds to the inlet opening 3, and a second outlet opening 210 the corresponds to the outlet opening 5 of Fig. 3. A blower 212 is operable to produce a flow of air from the outlet opening 210 to the inlet opening 208. However, unlike the blower of Fig. 3, the blower 212 of Fig. 13 and Fig. 14 does not communicate with atmospheric air.

[0042] The tank 202 also has a third inlet opening 214 and a fourth outlet opening 216, as shown in Fig. 13 and Fig. 14. A second blower 218 is operable to produce a flow of air from the outlet opening 216 to the inlet opening 214.

[0043] In a similar manner to that represented in Figs. 3 and 4, a medium temperature heat exchanger 220 has an inlet connected to the blower 212 and an outlet connected to the first inlet opening 208 of the temperature storage tank 202. Operation of the blower 212 creates a flow of air from the outlet opening 210 through the heat exchanger 220 and back to the inlet opening 208. The flow of air through the heat exchanger 220 and to the inlet opening 208 passes through the temperature storage tank 202 and heats the temperature storage medium in the tank 202.

[0044] On the power cycle side of the system represented to the right in Figs. 13 and 14, a heat engine or turbine 226 is operated by heat or thermal energy removed from the temperature storage media of both the temperature storage tank 202 and the temperature storage tank 204 of Fig. 13, and the temperature storage tank 202, the temperature storage tank 204 and the temperature storage tank 206 of Fig. 14.

[0045] As represented in Fig. 13 and Fig. 14, and in a similar manner to that of Fig. 3, the middle temperature storage tank 202 is where the initial heating of the working fluid in the heat engine cycle occurs. The working fluid that has been heated by a heat exchanger 222 communicating with the lower-level temperature storage tank 202 is directed to a heat exchanger 224 communicating with the higher temperature storage tank 204 for additional heating. In the case of Figure 13, the heated working fluid is then directed through the expander or turbine 226 of the power cycle. The working fluid discharged from the turbine to 226 is directed to the low temperature storage tank 200 which contains a suitable low temperature storage medium just as the low temperature storage tank 116 of Fig. 3. [0046] In the system of Fig. 14, the working fluid is directed from the higher temperature storage tank 204 to a still higher temperature storage tank 206 before being directed to the turbine 226. As in the system of Fig. 3 and Fig. 13, the working fluid is then discharged from the turbine 226 of the power cycle and is directed to the low temperature storage tank 200. [0047] In the heat pump cycle of the embodiments of Fig. 13 and Fig. 14, just as in the embodiment of Fig. 3, C02 is evaporated by the heat storage medium of the low temperature storage tank 200. The C02 from the heat exchanger 228 of the low temperature storage tank 200 is directed through a conduit to an inlet of a superheater 230. The C02 is at least somewhat super-heated as it flows through the superheater 230 and enters a high- pressure compressor 232 similar to the high-pressure compressor 109 of Fig. 3. The C02 is further heated by the heat of compression produced by the compressor 232. The superheating of the carbon dioxide by the superheater 230 ensures that gaseous, and not liquid carbon dioxide is delivered to the inlet of the compressor 232, just as occurred in the system of Fig. 3. In Figure 13 carbon dioxide exiting the compressor 232 flows through the heat exchanger 220 communicating with the lower-level temperature storage tank 202, where it heats air flowing through the heat exchanger 220 that is delivered to the inlet 208 of the heat storage tank 202. [0048] In the Figure 14 arrangement, the carbon dioxide exiting the compressor 232 flows through the heat exchanger 219 that communicates with the intermediate HTS 204, and thence through the heat exchanger 220 communicating with the lower temperature level storage tank 202 where it heats air flowing through the heat exchanger 220 that is delivered to the inlet 208 of the heat storage tank 202. As explained earlier with reference to Fig. 3, the lower-level temperature heat storage tank 202 holds a supply of heat storage medium that is heated by the air flowing into the tank 202. The C02 working fluid exiting the heat exchanger 220 is then directed through the superheater 230.

[0049] In Figures 13 and 14 the C02 working fluid exiting the superheater 230 is then directed to an expander/turbine 234. From the expander/turbine 234 the C02 working fluid is further cooled, and the C02 is returned to the low temperature heat exchanger 228 in the low temperature storage tank 200.

[0050] In the Power Cycle side of the system represented to the right in Fig. 13 and Fig. 14, the low temperature C02 working fluid exits the low temperature storage tank 200 and is supplied to an inlet pump 240 that functions in a similar manner to the pump 117 of Fig. 3. The pump 240 of Fig. 13 and Fig. 14 functions like a boiler feed water pump associated with the turbine 226. The pump 240 directs C02 working fluid through the heat exchanger 222 communicating with the middle temperature storage tank 202 and then through the heat exchanger 224 communicating with the higher temperature storage tank 204. In Fig. 13, the C02 working fluid from the pump 240 supplied to the heat exchanger 222 associated with the temperature storage tank 202 and the heat exchanger 224 associated with the heat storage tank 204 is heated to result in super critical C02 flowing to the turbine 226 to drive the turbine.

[0051] In the embodiment of the system represented in Fig. 14, the C02 working fluid exiting the heat exchanger 224 associated with the heat storage tank 204 passes through a further heat exchanger 242 associated with the heat storage tank 206 before being supplied to the turbine 226 to drive the turbine. As represented in Fig. 14, a high temperature heater in the form of concentrated solar power CSP supplies heat to a heat exchanger 244 that in turn heats the air working fluid cycled by a blower 246 through the heat storage tank 206. The source of heat that heats the heat exchanger 244 could be powered by another type of renewable energy system other than the concentrated solar power system CSP represented in Fig. 14, such as wind power, geothermal power and photovoltaic power, and by nonrenewable energy systems such as waste heat systems.

[0052] From the above discussion of the systems represented in Fig. 13 and Fig. 14, and the comparison of those systems to that of Fig. 3, one of ordinary skill in the art can determine the operation of each of the components represented in Fig. 13 and Fig. 14 such that a further detailed description of all the components of Figs. 13 and 14 beyond that thus provided is not required.

[0053] It will be appreciated that additional storage volume of medium heat storage material within the medium temperature storage tank 103 for any of the embodiments of Figs. 1 , 2. 8 or 9 can be provided through the use of appropriate equipment such as surge tanks, hoppers, valves and conveyors on the inlets and outlets of the medium temperature storage tank or even between components of the MTS. [0054] In the foregoing description, fluid flow paths, flow channels or conduits have been described among the various components. The air flow paths or conduits such as shown in bold faced lines can, as known in the art, be ducts, pipes or other flow channels connected with the inlets and outlets of components. The flow paths or conduits for C02 or other suitable fluids can be of steel pipe, tube or other like channels. [0055] With all of the embodiments of the present disclosure, those of ordinary skill in the art will appreciate the following points about the system and methods of the present disclosure:

• The use of air as the heat transfer medium for the Medium Temperature Storage (MTS) loop, as shown in bold faced lines in Figs. 2 - 4.

• The ability to use a common MTS fan 100 or blower for both the charging and discharging of the MTS tank 103.

• The ability to continuously operate the power cycle regardless of the state of the MTS loop (i.e., can charge/discharge the MTS tank 103 charge or discharge while operating the Power Cycle).

• The use of a multi - tiered (two or more) heat storage system including a high temperature storage tank HTS 127 that is provided with heat from the high temperature heating source 128, which is preferably CSP or another renewable source, but it will be understood that the high temperature heat can come from other sources including non-renewable sources such as waste heat.

• The use of a Low Temperature Storage LTS 116 that is equipped with parallel coils 115 and 116, as shown in Figs. 3 and 4 that allow for both the Heat Pump cycle and Power cycle to operate simultaneously. · High efficiency for round trip performance.

• The use of low cost, solid material (e.g., rock, gravel, or particulate material, such as sand) for energy storage in the Middle Temperature Storage tank MTS 103.

• Ice/water used for the heat storage medium in the low temperature heat storage tank LTS 116. • The high temperature heat storage medium in the high temperature storage tank HTS 127 can be any suitable medium such as molten salts, sodium, falling particle media, where supplemental heating of a supplemental high temperature heating system 128 can be electric resistance heaters powered by a renewable energy system or by the burning of hydrocarbon fuel, such as in a gas turbine.

• The components of the heat pump loop could be made from low alloy (i.e., lower cost) steels (CS, P22). The power cycle would also incorporate a majority of low cost, low alloy steels but also would be expected to have some 300 series stainless steels with a lower potential need for more exotic alloys such as Inconel when compared to other C02 cycles. Other C02 cycles that are in the same range of overall efficiencies often times require higher operating temperatures and must therefore employ a larger quantity of more costly materials (Inconel 740H, Haynes 230). · The fluidization of the solid heat storage media as shown in various embodiments, in the MTS allows for very intimate and highly efficient heat transfer to and from the heat storage media.

• The use of ambient air as the working fluid in the intermediate temperature loop, as shown by the bold-faced heavy lines in Figs. 2 - 4 allows for the use of low cost equipment (e.g., blower, duct, dampers).

• Conveyance of air is straightforward and easily accepted by Users/Owners.

• Air does not present or create any inherent safety or hazardous condition (i.e., air is not carcinogenic, toxic, or poisonous). · There are no GHG (greenhouse gas) concerns with the working fluid should a “leak” of the air working fluid occur.

• Do not have storage and transportation costs when using air as a working fluid.

• Short of an inlet air filter at the intake to the fan or blower 100, there is no further treatment or conditioning required for the working fluid and no concern of working fluid breaking down into components that may have deleterious effects on the process or create safety hazards.

• Air and solid particles are separated via standard component items (e.g., cyclones) allowing for direct contact exchangers to be used. Direct contact heat transfer liquids would require the use of expensive Liquid/Liquid separation devices such as centrifuges and then only if the separation characteristics of the fluids were favorable for such a separation.

• Other objects, advantages and efficiencies of the system and method of the present disclosure would be in part apparent to those of ordinary skill in the art upon reviewing the instant disclosure.

• The use of an air-mediated heat exchange eliminates half the volume needed for thermal storage compared to systems that require separate tanks, one for storing all of the particles when they are hot and one for when they are cold.

Claims

CLAIMS:

1 . A particle based thermal storage system for use in association with a combined pumped thermal electricity storage (PTES) system, comprising: a container for containing particles having capacity to absorb heat, the container having a first inlet opening and first outlet opening, a second inlet opening and a second outlet opening; a blower having an inlet open to the atmosphere, and an outlet; a first valve having an outlet connected through a first valve flow path to the first inlet opening of the container, and an inlet; a second valve having an inlet connected through a second flow path to be in flow connection with the first outlet opening of the container, and an outlet; a third valve having an outlet connected through a third valve flow path to be in flow connection with the second inlet opening of the container, and an inlet connected through a blower outlet flow path to be in flow connection with the outlet of the blower; a fourth valve having an inlet connected through a fourth valve flow path to be in flow connection with the second outlet opening of the container, and an outlet; an air heater having an inlet connected through a blower flow path to be in flow connection with the outlet of the blower, and an outlet connected through a flow path to the inlet of the first valve; a heat pump associated with the container for providing thermal energy to the contents of the container; and a heat engine associated with the container for removing thermal energy from the contents of the container.

2. The particle bed thermal storage system of claim 1 , wherein the container has contents comprising solid particles.

3. The particle bed thermal storage system of claim 1 , wherein the heat pump comprises a supercritical Rankine cycle.

4. The particle based thermal storage system of claim 1 , wherein the heat engine comprises a supercritical Rankine cycle.

5. The particle bed thermal storage system of claim 1 , wherein the heat pump comprises a subcritical Rankine cycle.

6. The particle based thermal storage system of claim 1 , wherein the heat engine comprises a subcritical Rankine cycle.

7. The particle based thermal storage system of claim 1 , wherein the heat pump comprises an air cooler having an inlet connected through an air cooler flow path to be in flow connection with the outlet of the second valve, and an outlet open to the ambient environment.

8. The particle based thermal storage system of claim 1 , wherein the heat engine comprises an economizer having an inlet connected through a flow path to be in flow connection with the outlet of the second valve, and an outlet open to the ambient environment.

9. A thermal storage system comprising: a pump, the pump being configured for communicating with a source of working fluid and supplying a flow of the working fluid from the source of working fluid on operation of the pump; a first temperature storage tank, the first temperature storage tank being configured for containing a first temperature storage medium at a first temperature and communicating with the flow of working fluid from the pump and for heating the flow of working fluid to a first temperature; a second temperature storage tank, the second temperature storage tank being configured for containing a second temperature storage medium at a second temperature and communicating with the flow of working fluid at the first temperature and for heating the flow of working fluid at the first temperature to a second temperature; a heat engine, the heat engine being configured for communicating with the flow of working fluid at the second temperature with the flow of working fluid at the second temperature capable of operating the heat engine; and the first temperature storage tank, the second temperature storage tank and the heat engine being connected in series communication.

10. The thermal storage system of claim 9, further comprising: a blower, the blower being configured for communicating with a source of air and supplying a flow of air from the source of air on operation of the blower; a heat exchanger, the heat exchanger being configured for communicating with the flow of air from the blower and heating the flow of air; and the first temperature storage tank being configured for communicating with the heated flow of air with the heated flow of air passing through the first temperature storage medium and heating the first temperature storage medium.

11 . The thermal storage system of claim 9, further comprising: the first temperature storage medium being particles of a temperature storage medium; and the second temperature storage medium being particles of a temperature storage medium.

12. The thermal storage system of claim 9, further comprising: a third temperature storage tank, the third temperature storage tank being configured for containing a third temperature storage medium at a third temperature and being configured for communicating in series communication with the first temperature storage tank, the second temperature storage tank and the heat engine.

13. The thermal storage system of claim 12, further comprising: the first temperature being a higher temperature than the third temperature; and the second temperature being a higher temperature than the first temperature.

14. The thermal storage system of claim 13, further comprising: the third temperature storage tank being connected in series communication with the heat engine.

15. The thermal energy storage system of claim 9, further comprising: the heat engine being a turbine engine.

16. The thermal energy storage system of claim 9, further comprising: the source of working fluid is a low temperature storage tank capable of storing working fluid at a low temperature; the first temperature is a higher temperature than the low temperature; and the second temperature is a higher temperature than the first temperature.

17. The thermal energy storage system of claim 9, further comprising: the working fluid is carbon dioxide.

18. The thermal energy storage system of claim 9, further comprising: a third temperature storage tank, the third temperature storage tank being configured for containing a third temperature storage medium at a third temperature and communicating with the working fluid at the second temperature and for heating the working fluid at the second temperature to a third temperature; the heat engine being configured for communicating with the flow of working fluid at the third temperature with the flow of working fluid at the third temperature capable of operating the heat engine; and the first temperature storage tank, the second temperature storage tank, the third temperature storage tank and the heat engine being configured for communicating in series communication.

19. The thermal energy storage system of claim 18, further comprising: the third temperature storage tank connected in operative communication with a concentrated solar power system that is capable of heating the third temperature storage medium to the third temperature.

20. A thermal storage system comprising: a temperature storage tank; a particulate thermal storage medium in the temperature storage tank; a first inlet opening in the temperature storage tank; a first outlet opening in the temperature storage tank; a blower, the blower being configured for communicating with a source of air, the blower being configured for supplying a flow of air from the source of air on operation of the blower; a heat exchanger, the heat exchanger being configured for communicating with the flow of air from the blower and heating the flow of air producing a heated flow of air; the first inlet opening in the temperature storage tank being configured for communicating with the heated flow of air with the heated flow of air passing through the first inlet opening, through the particulate thermal storage medium and through the first outlet opening and capable of heating the particulate thermal storage medium; and a heat engine operatively connected to the temperature storage tank for removing thermal energy from the bed of particulate thermal storage medium.

21 . The thermal storage system of claim 20, further comprising: the source of air comprising atmospheric air.

22. The thermal storage system of claim 20, further comprising: a pump, the pump being configured for communicating with a source of working fluid and for supplying a flow of the working fluid from the source of working fluid to be capable of operating the pump; the temperature storage tank capable of being a first temperature storage tank; the particulate thermal storage medium comprising a first particulate thermal storage medium capable of being at a first temperature, the first temperature storage tank being configured for communicating with the flow of working fluid from the pump and heating the flow of working fluid to a first temperature; a second temperature storage tank, the second temperature storage tank being configured for containing a second particulate thermal storage medium at a second temperature and for communicating with the flow of working fluid at the first temperature and heating the flow of working fluid at the first temperature to a second temperature; a heat engine, the heat engine being configured for communicating with the flow of working fluid at the second temperature with the flow of working fluid at the second temperature capable of operating the heat engine.

23. The thermal storage system of claim 21 , further comprising: a third temperature storage tank, the third temperature storage tank being configured for containing a third particulate thermal storage medium at a third temperature, the third temperature storage tank being connected in series communication with the first temperature storage tank, the second temperature storage tank and the heat engine.

24. The thermal storage system of claim 23, further comprising: the third temperature storage tank being connected with a concentrated solar power system capable of heating the third bed of temperature storage medium to the third temperature.

25. A method of storing thermal energy comprising: directing a first flow of air through a first heat exchanger and producing a first flow of heated air; directing the first flow of heated air through a thermal energy storage medium contained in a first tank and heating the thermal energy storage medium to a first temperature; directing a second flow of air through the thermal energy storage medium and producing a second flow of heated air; directing the second flow of heated air through a second heat exchanger; directing a flow of working fluid through the second heat exchanger; producing a flow of heated working fluid; and directing the flow of heated working fluid through a heat engine and thereby operating the heat engine.

26. The method of claim 25, further comprising: the air comprising atmospheric air.

27. The method of claim 25, further comprising: the thermal energy storage medium comprising particulate thermal energy storage medium.

28. The method of claim 25, further comprising: the working fluid comprising carbon dioxide.

29. The method of claim 25, further comprising: the heat engine comprising a turbine.

30. The method of claim 25, further comprising: directing a third flow of air through a thermal energy storage medium contained in a second tank and producing a third flow of heated air; directing the third flow of heated air through a third heat exchanger; directing the flow of heated working fluid through the third heat exchanger and then directing the flow of heated working fluid through the heat engine thereby operating the heat engine.

31 . The method of claim 30, further comprising: heating a fourth heat exchanger by energy from a concentrated solar power system; directing a fourth flow of air through the fourth heat exchanger and producing a fourth flow of heated air; and directing the fourth flow of heated air through the thermal energy storage medium contained in the second tank and heating the thermal energy storage medium contained in the second tank.

32. The method of claim 31 , further comprising: the thermal energy storage medium contained in the second tank comprising particulate thermal energy storage medium.

33. The method of claim 31 , further comprising: the thermal energy storage medium contained in the second tank being at a higher temperature than the thermal energy storage medium contained in the first tank.