Energy storage system

Abstract

To provide an energy storage system extremely low in energy loss via a storage and discharge cycle of energy.SOLUTION: An energy storage system 1 of the present invention includes a carbon dioxide gas holder 10 which stores carbon dioxide containing gas, a carbon dioxide gas solidifying device 30 which solidifies carbon dioxide gas by heat exchange between the carbon dioxide containing gas and a refrigerant to generate dry ice, a dry ice melting device 41 which melts the generated dry ice to generate liquefied carbon dioxide, a liquefied carbon dioxide storage tank 50 which stores the liquefied carbon dioxide, a liquefied carbon dioxide booster pump 60 which boosts the liquefied carbon dioxide, a liquefied carbon dioxide heater 70 which heats the boosted liquefied carbon dioxide into a gaseous phase or a supercritical phase, and a carbon dioxide gas expansion turbine 80 which expands the carbon dioxide in the gaseous phase or the supercritical phase so as to recover energy and sends out the carbon dioxide gas at low pressure to the carbon dioxide containing gas holder.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an energy storage system, and more particularly to an energy storage system that uses carbon dioxide as an energy storage medium. [Background technology]

[0002] Energy storage technologies are being developed and popularized to absorb fluctuations in renewable energy. In this regard, Patent Document 1 (JP 2023-514812 A) discloses a technology that includes a casing for storing a working fluid that is in gas phase and in pressure equilibrium with the atmosphere and is different from the atmosphere, and a tank for storing the working fluid in a liquid phase or supercritical phase having a temperature close to its critical temperature (close to the ambient temperature), and that, when charging energy, pressurizes the gas in the casing to the critical temperature and stores it in the tank, and when releasing energy, releases the near-supercritical fluid in the tank to generate mechanical energy to drive a driven machine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special table 2023-514812 publication Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology described in Patent Document 1 requires a large amount of compression power in the process of compressing a gas phase that is in pressure equilibrium with atmospheric pressure to a pressure close to supercritical pressure when storing energy. Although the energy can be recovered when released, the efficiency of the compressor when storing energy is multiplied by the efficiency of the expansion turbine when releasing energy, so energy must be stored and released while allowing a large amount of energy loss relative to the power received by the system.

[0005] The present invention has been made to solve these problems, and aims to provide an energy storage system that stores electrical energy as thermal and pressure energy of a fluid, with extremely little energy loss throughout the energy storage and release cycle. [Means for solving the problem]

[0006] (1) The energy storage system according to the present invention comprises: a carbon dioxide-containing gas holder configured to store a carbon dioxide-containing gas; a carbon dioxide gas solidification device that solidifies the carbon dioxide gas by heat exchange between the carbon dioxide-containing gas stored in the carbon dioxide-containing gas holder and a refrigerant having a boiling point lower than the solidification temperature of carbon dioxide in the carbon dioxide-containing gas, thereby producing dry ice; a dry ice melting device that melts the dry ice generated by the carbon dioxide solidification device through heat exchange with a fluid having a temperature higher than the melting point of the dry ice to generate liquefied carbon dioxide; A liquefied carbon dioxide storage tank for storing the liquefied carbon dioxide produced by the dry ice melting device; a liquefied carbon dioxide pump that pressurizes the liquefied carbon dioxide stored in the liquefied carbon dioxide storage tank; a liquefied carbon dioxide heater for heating the liquefied carbon dioxide pressurized by the liquefied carbon dioxide pump through heat exchange with a heat medium to convert the liquefied carbon dioxide into a gas phase or a supercritical phase; and a carbon dioxide expansion turbine that expands the carbon dioxide that has been converted into a gaseous or supercritical phase by the liquefied carbon dioxide heater to recover energy and delivers the low-pressure carbon dioxide gas to the carbon dioxide-containing gas holder.

[0007] (2) In addition, in the above (1), a carbon dioxide-containing gas cooler is provided to cool the carbon dioxide-containing gas supplied from the carbon dioxide-containing gas holder to the carbon dioxide gas solidification device, The heat obtained from the carbon dioxide-containing gas in the carbon dioxide-containing gas cooler is supplied to the dry ice melting device.

[0008] (3) In addition, in the above (1) or (2), a liquefied carbon dioxide storage pressurizing pump that pressurizes the liquefied carbon dioxide generated in the dry ice melting device and supplies it to the liquefied carbon dioxide storage tank; and a liquefied carbon dioxide storage tank pressurization evaporator that increases the internal pressure of the liquefied carbon dioxide storage tank by heating the liquefied carbon dioxide stored in the liquefied carbon dioxide storage tank.

[0009] (4) In addition, in the device described in any one of (1) to (3) above, the carbon dioxide-containing gas supplied to the carbon dioxide gas solidification device includes surplus gas that is not solidified in the carbon dioxide gas solidification device, The carbon dioxide solidification device is characterized by having an excess gas circulation line for circulating excess gas that has not been solidified in the carbon dioxide solidification device from the carbon dioxide gas solidification device to its inlet.

[0010] (5) Furthermore, in any of the above (1) to (4), the present invention is characterized in that it has a heat storage tank that accumulates the heat of the carbon dioxide-containing gas supplied from the carbon dioxide-containing gas holder to the carbon dioxide gas solidification device and the heat obtained in the liquefied carbon dioxide heater, and cancels out the heat.

[0011] (6) In addition, in the device described in any one of (1) to (5) above, the refrigerant having a temperature lower than the solidification temperature of carbon dioxide is liquefied natural gas.

[0012] (7) In addition, in the device described in any one of (1) to (6) above, the heat source of the heat medium used in the liquefied carbon dioxide heater is waste heat from the plant. [Effects of the Invention]

[0013] According to the present invention, an energy storage system can be realized in which energy loss throughout the energy storage / release cycle is extremely small. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing an energy storage system according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a schematic diagram showing an energy storage system according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a schematic diagram showing an energy storage system according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a schematic diagram showing an energy storage system according to a fourth embodiment of the present invention. [Figure 5] FIG. 10 is a schematic diagram showing an energy storage system according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Embodiment 1] First, the configuration and functions of the first embodiment of the present invention will be described with reference to FIG. The energy storage system 1 according to the first embodiment of the present invention includes a carbon dioxide gas holder 10, a carbon dioxide gas blower 20, a carbon dioxide gas solidification device 30, a dry ice melting device 41, a liquefied carbon dioxide storage tank 50, a liquefied carbon dioxide boost pump 60, a liquefied carbon dioxide heater 70, and a carbon dioxide gas expansion turbine 80.

[0016] The carbon dioxide gas holder 10 is a large metal container that stores carbon dioxide gas. The carbon dioxide gas blower 20 is a centrifugal blower that sucks in the carbon dioxide gas stored in the carbon dioxide gas holder 10 through the carbon dioxide gas blower inlet line 171, increases the pressure to the required pressure for the downstream, and discharges it to the carbon dioxide gas blower outlet line 172.

[0017] The carbon dioxide gas solidification device 30 solidifies carbon dioxide gas stored in a carbon dioxide-containing gas holder by heat exchange with LNG, which has a boiling point lower than the solidification temperature of carbon dioxide in the carbon dioxide-containing gas, to produce dry ice. The carbon dioxide gas solidification device 30 is specifically configured by a scraped surface heat exchanger, and solidifies the carbon dioxide gas supplied from the carbon dioxide gas blower outlet line 172 using the cold energy of LNG, then scrapes it off and discharges it to the dry ice discharge line 175. LNG is supplied from the refrigerant inlet line 173, and is discharged from the refrigerant outlet line 174 after the cold energy has been utilized.

[0018] The dry ice melting device 41 melts the dry ice produced by the carbon dioxide solidification device 30 through heat exchange with a fluid whose temperature is higher than the melting point of the dry ice to produce liquefied carbon dioxide, and is equipped with a dry ice melting tank 40 that stores and melts the dry ice, and a heat medium supply means 42 that supplies a heat medium to the dry ice stored in the dry ice melting tank 40. The dry ice melting tank 40 is a metal container that uses the heat of a melting heat medium supplied from the outside by a heat medium supply means 42 to melt the dry ice supplied from the dry ice discharge line 175 and discharge it to the liquefied carbon dioxide discharge line 181. The heat transfer medium supplying means 42 supplies the melting heat transfer medium to the dry ice melting tank 40 through the melting heat transfer medium inlet line 178 and discharges the melting heat transfer medium that has used its heat through the melting heat transfer medium outlet line 179 .

[0019] The liquefied carbon dioxide storage tank 50 stores the liquefied carbon dioxide produced by the dry ice melting device 41 and consists of a metal container. It temporarily stores the liquefied carbon dioxide supplied from the liquefied carbon dioxide discharge line 181 and discharges it to the liquefied carbon dioxide boost pump inlet line 182.

[0020] The liquefied carbon dioxide boost pump 60 is a centrifugal pump that pressurizes the liquefied carbon dioxide stored in the liquefied carbon dioxide storage tank 50, and pressurizes the liquefied carbon dioxide supplied from the liquefied carbon dioxide boost pump inlet line 182 and delivers it to the liquefied carbon dioxide boost pump outlet line 183.

[0021] The liquefied carbon dioxide heater 70 is a shell-and-tube type heat exchanger that uses the heat of an evaporative heat medium supplied from outside to heat the liquefied carbon dioxide supplied from a liquefied carbon dioxide booster pump outlet line 183 by heat exchange with the heat medium, converting it to a gas phase or supercritical phase, and discharges it to a carbon dioxide gas expansion turbine inlet line 184. The evaporative heat medium is supplied from an evaporative heat medium inlet line 185, and after its heat has been used, is discharged to an evaporative heat medium outlet line 186.

[0022] The carbon dioxide gas expansion turbine 80 is a centrifugal turbine that recovers energy by expanding the gaseous or supercritical carbon dioxide supplied from the carbon dioxide gas expansion turbine inlet line 184, converting it into turbine rotational energy to generate electricity, and then discharges the low-pressure carbon dioxide gas to the carbon dioxide gas expansion turbine outlet line 187.

[0023] Next, the operation of the energy storage system 1 according to this embodiment will be described. <When storing energy> For example, when the amount of power generated by solar power generation exceeds the demand for power consumption during the daytime, creating a demand for storing power, the energy storage system 1 stores energy in the form of liquefied carbon dioxide. Specifically, carbon dioxide gas stored in the renewable energy carbon dioxide gas holder 10 at a slight pressure (for example, 10 kPaG) is pressurized to a low pressure (for example, 20 kPaG) by the carbon dioxide gas blower 20 and supplied to the carbon dioxide gas solidification device 30.

[0024] The carbon dioxide gas supplied to the carbon dioxide gas solidification device 30 is cooled by the LNG and precipitates as dry ice on the surface of a heat transfer tube (not shown). The precipitated dry ice is scraped off by a mechanical mechanism (not shown), drops, and is discharged to the dry ice discharge line 175. The temperature of the dry ice is low, for example, at -79°C or below.

[0025] The dry ice discharged to the dry ice dispensing line 175 is discharged to the dry ice melting tank 40 by alternately opening and closing the first dry ice dispensing valve 176 and the second dry ice dispensing valve 177 .

[0026] The dry ice discharged to the dry ice melting tank 40 is melted by being heated to, for example, −50° C. by a melting heat transfer medium. The liquefied carbon dioxide produced by the melting of the dry ice is supplied to the liquefied carbon dioxide storage tank 50 via the liquefied carbon dioxide discharge line 181 and is temporarily stored therein.

[0027] <When releasing energy> For example, when the amount of power generated by sunlight decreases due to rainy weather or the like and the demand for power consumption exceeds the supply of power, the energy storage system 1 generates power by using liquefied carbon dioxide. Specifically, the liquefied carbon dioxide stored in the liquefied carbon dioxide storage tank 50 is pressurized by the liquefied carbon dioxide booster pump 60 to a high pressure (for example, 10 MPaG).

[0028] The high-pressure liquefied carbon dioxide is evaporated in the liquefied carbon dioxide heater 70 by an evaporation heat medium (for example, silicone oil) that uses, for example, factory waste heat, and is heated to, for example, 100° C. This causes the carbon dioxide to enter a supercritical state.

[0029] The carbon dioxide in a supercritical state generates electricity by driving a turbine in the carbon dioxide gas expansion turbine 80. In this way, the energy storage system 1 generates electricity using the stored liquefied carbon dioxide.

[0030] The carbon dioxide gas that has driven the carbon dioxide gas expansion turbine 80 is supplied to the carbon dioxide gas holder 10 and temporarily stored there until the time when energy storage is to be performed again.

[0031] According to the energy storage system 1 of this embodiment, carbon dioxide gas can be solidified and liquefied with low power by utilizing the cold energy of LNG during energy storage, and therefore energy can be stored efficiently.

[0032] Furthermore, with the energy storage system 1 according to this embodiment, the cold energy of LNG can be effectively utilized to solidify carbon dioxide gas, thereby reducing the amount of cold energy of LNG that has been dumped into the environment up until now. For example, an LNG vaporizer that uses seawater as a heating medium dumps the cold energy of LNG into the ocean, but this amount can be reduced, thereby reducing the impact on the ocean.

[0033] Furthermore, according to the energy storage system 1 of this embodiment, the carbon dioxide gas solidification device 30 solidifies the carbon dioxide, thereby rapidly reducing the volume of the gas, and thereby allowing the carbon dioxide gas to be drawn in from upstream, thereby reducing the power required for the carbon dioxide gas blower 20.

[0034] Although this embodiment does not refer to the handling of LNG using cold energy in the carbon dioxide gas solidification device 30, it may be used to cool the carbon dioxide gas flowing through the carbon dioxide gas blower outlet line 172. By sufficiently cooling the carbon dioxide before entering the carbon dioxide gas solidification device 30 to near the solidification temperature, the proportion of the time used for solidification out of the residence time in the carbon dioxide gas solidification device 30 can be increased, and the efficiency of solidifying the carbon dioxide gas in the carbon dioxide gas solidification device 30 can be improved.

[0035] In addition, in this embodiment, carbon dioxide has been described as an energy storage medium, but in order to adjust the solidification temperature, melting temperature, evaporation temperature, and critical temperature of carbon dioxide, a mixed fluid of carbon dioxide and other substances can be used as an energy storage medium.

[0036] Furthermore, in this embodiment, the types of heat transfer medium and refrigerant, and the types of pumps, valves, heat exchangers, and containers are specified, but the types can be selected appropriately within the scope of the design.

[0037] [Embodiment 2] Next, the configuration and functions of the second embodiment will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first embodiment. In the energy storage system 200 according to the second embodiment, the dry ice melting device 41 has a carbon dioxide gas cooler 210 and a melting heat medium circulation pump 220.

[0038] The carbon dioxide gas cooler 210 is a shell-and-tube type heat exchanger, and cools the carbon dioxide gas supplied to the carbon dioxide gas blower 20 using the heat medium used for heat exchange with the dry ice in the dry ice melting tank 40.

[0039] The melting heat medium circulation pump 220 is a centrifugal pump, which circulates the melting heat medium between the carbon dioxide gas cooler 210 and the dry ice melting tank 40 .

[0040] Next, the operation of the energy storage system 200 according to this embodiment will be described. The explanation of the same functions as those in the first embodiment will be omitted. The melting heat medium circulated in the heat medium return line 271 and the heat medium supply line 272 by the melting heat medium circulation pump 220 supplies the heat of melting the dry ice in the dry ice melting tank 40 and is itself cooled to a temperature close to that of liquefied carbon dioxide (e.g., -50°C).

[0041] The melting heat transfer medium cooled in the dry ice melting tank 40 is supplied to the carbon dioxide gas cooler 210, where it cools the room temperature carbon dioxide gas and is heated to a temperature close to that of the carbon dioxide gas.Then, it is supplied to the dry ice melting tank 40 again.

[0042] According to the energy storage system 200 of this embodiment, the carbon dioxide gas is cooled in the carbon dioxide gas cooler 210 using the molten heat transfer medium cooled in the dry ice melting tank 40, so that the thermal energy within the system can be used efficiently.

[0043] Furthermore, according to the energy storage system 200 of this embodiment, the carbon dioxide gas supplied to the carbon dioxide gas blower 20 can be cooled, and therefore the efficiency of the carbon dioxide gas blower 20 can be improved.

[0044] [Embodiment 3] Next, the configuration and functions of the third embodiment will be described with reference to FIG. Components having the same configurations and functions as those in the first and second embodiments are given the same numbers. The energy storage system 300 according to the third embodiment includes a liquefied carbon dioxide storage pressurization pump 310 and a liquefied carbon dioxide storage tank pressurization evaporator 320.

[0045] The liquefied carbon dioxide storage pressurizing pump 310 is a centrifugal pump, which pressurizes the liquefied carbon dioxide flowing through the liquefied carbon dioxide discharge line 181 and discharges it into the liquefied carbon dioxide storage tank 50.

[0046] The liquefied carbon dioxide storage tank pressurization evaporator 320 is an air-fin type heat exchanger that evaporates the liquefied carbon dioxide stored in the liquefied carbon dioxide storage tank 50 by heat exchange with the atmosphere, and pressurizes the liquefied carbon dioxide storage tank 50 by the volume expansion of the carbon dioxide.

[0047] Next, the operation of the energy storage system 300 according to this embodiment will be described. Explanation of the same functions as those in the first and second embodiments will be omitted. The liquefied carbon dioxide supplied from the liquefied carbon dioxide storage tank pressurized evaporator inlet line 371 evaporates in the liquefied carbon dioxide storage tank pressurized evaporator 320, increasing its volume, and the pressure in the liquefied carbon dioxide storage tank 50 rises toward the equilibrium state at temperature (for example, 5.7 MPaG at a temperature of 20°C).

[0048] The liquefied carbon dioxide storage pressurizing pump 310 pressurizes the low-temperature, low-pressure (for example, −50° C., 0.6 MPaG) liquefied carbon dioxide supplied from the dry ice melting tank 40 and supplies it to the liquefied carbon dioxide storage tank 50 .

[0049] According to the energy storage system 300 of this embodiment, the liquefied carbon dioxide storage tank 50 can be brought into an equilibrium state in terms of air temperature, and therefore it is possible to store liquefied carbon dioxide at a higher temperature and pressure than in the dry ice melting tank 40. As a result, when releasing energy, it is possible to reduce the power of the liquefied carbon dioxide booster pump 60 and also reduce the heat load on the liquefied carbon dioxide heater 70. Therefore, it is possible to store energy more efficiently.

[0050] In this embodiment, the liquefied carbon dioxide storage tank 50 is described as being pressurized by the liquefied carbon dioxide storage tank pressurization evaporator 320, but the liquefied carbon dioxide storage tank 50 itself may be exposed to the atmosphere without being provided with any insulation material.

[0051] [Embodiment 4] Next, the configuration and functions of the fourth embodiment will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first to third embodiments. The energy storage system 400 according to the fourth embodiment includes a surplus gas circulation line 471 and a surplus gas circulation flow rate adjustment valve 472.

[0052] The surplus gas circulation line 471 is a pipe connected to the carbon dioxide gas solidification device 30 and the carbon dioxide gas blower inlet line 171, and circulates surplus gas (e.g., nitrogen gas) that has not solidified in the carbon dioxide gas solidification device 30 to the carbon dioxide gas blower inlet line 171.

[0053] The surplus gas circulation flow rate adjustment valve 472 is a remote-controlled globe valve, and adjusts the flow rate of the surplus gas flowing through the surplus gas circulation line 471 .

[0054] Next, the operation of the energy storage system 400 according to this embodiment will be described. The explanation of the same functions as those in the first to third embodiments will be omitted. Nitrogen gas that is not solidified in the carbon dioxide gas solidification device 30 is supplied to the surplus gas circulation line 471 by the initial make-up or by replenishment as needed.

[0055] In the carbon dioxide gas solidification device 30, the partial pressure of carbon dioxide is reduced by mixing nitrogen gas, and therefore the solidification temperature of carbon dioxide is reduced. For example, the solidification temperature of carbon dioxide is approximately -79°C when the partial pressure is atmospheric pressure, but it drops further as the partial pressure decreases. In other words, the solidification temperature of carbon dioxide can be changed by adjusting the partial pressure of carbon dioxide.

[0056] On the other hand, when considering methane as an example of the composition of LNG, which is a refrigerant, its critical temperature is approximately -83°C and its critical pressure is approximately 4.6 MPaG. As the pressure of a high-pressure LNG line at a typical LNG terminal is approximately 5 MPaG, this exceeds the critical pressure, and it is thought that as it is heated, it will release the latent heat of vaporization near the critical temperature.

[0057] The solidification of carbon dioxide requires latent heat several times greater than sensible heat. However, the refrigerant LNG also releases a large amount of latent heat of vaporization near the solidification temperature of carbon dioxide. This heat exchange between latent heats allows a larger amount of carbon dioxide to solidify with a smaller LNG flow rate.

[0058] Nitrogen gas that has not been solidified in the carbon dioxide gas solidification device 30 is supplied again to the carbon dioxide blower 20 via the surplus gas circulation line 471 and circulates within the system.

[0059] According to the energy storage system 400 of this embodiment, the latent heat of solidification of carbon dioxide can be efficiently exchanged with the latent heat of vaporization of LNG, which is the refrigerant, in the carbon dioxide gas solidification device 30, so that more carbon dioxide can be solidified with less refrigerant. As a result, the scale of the device can be easily expanded.

[0060] [Embodiment 5] Next, the configuration and functions of the fifth embodiment will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first to fourth embodiments. The energy storage system 500 according to the fifth embodiment includes a carbon dioxide gas blower outlet cooler 510, a heat storage tank 520, a carbon dioxide gas cooling refrigerant circulation pump 530, and a liquefied carbon dioxide evaporation heat medium circulation pump 540.

[0061] The carbon dioxide gas blower outlet cooler 510 is a shell-and-tube type heat exchanger that uses the cold heat of the refrigerant supplied from the carbon dioxide gas blower outlet refrigerant line 571 to cool the carbon dioxide gas flowing through the carbon dioxide gas blower outlet line 172.

[0062] The heat storage tank 520 is a metal container and contains particles of a metal compound as a heat storage material. The heat storage tank 520 stores the heat of the carbon dioxide-containing gas supplied from the carbon dioxide-containing gas holder 10 to the carbon dioxide gas solidification device 30 and the heat obtained in the liquefied carbon dioxide heater 70, and cancels out the heat. Specifically, the heat storage tank 520 stores the heat of the refrigerant supplied from the carbon dioxide gas blower outlet refrigerant return line 572 and supplies it to the heat medium supplied from the liquefied carbon dioxide evaporated refrigerant return line 574 .

[0063] The carbon dioxide gas cooling refrigerant circulation pump 530 is a centrifugal pump that pressurizes and discharges the refrigerant flowing through the carbon dioxide gas blower outlet refrigerant flow line 571. The liquefied carbon dioxide evaporation heat medium circulation pump 540 is a centrifugal pump that pressurizes and discharges the heat medium flowing through the liquefied carbon dioxide evaporation heat medium flow line 573.

[0064] Next, the operation of the energy storage system 500 according to this embodiment will be described. Explanation of the same functions as those in the first to fourth embodiments will be omitted.

[0065] <When storing energy> The carbon dioxide gas flowing through the carbon dioxide gas blower outlet line 172 has a higher temperature than the blower inlet due to the pressure increase caused by the carbon dioxide gas blower 20. In the carbon dioxide gas blower outlet cooler 510, this gas is cooled by a refrigerant (e.g., silicone oil), and the refrigerant is heated and returned to the heat storage tank 520. As a result, the relatively high temperature heat transported by the refrigerant is accumulated in the heat storage tank 520.

[0066] <When releasing energy> The low-temperature (for example, −50° C.) liquefied carbon dioxide flowing through the liquefied carbon dioxide heater 70 is heated by the heat transported by the heat medium from the heat storage tank 520 and evaporates.

[0067] According to the energy storage system 500 of this embodiment, when storing energy, the heat of the carbon dioxide gas at the outlet of the carbon dioxide gas blower 20 is stored in the heat storage tank 520, and when releasing energy, the heat stored in the heat storage tank 520 can be used to evaporate the liquefied carbon dioxide, so that heat can be used efficiently within the system and energy can be stored efficiently.

[0068] In this embodiment, it has been explained that the liquefied carbon dioxide is evaporated using only the heat stored in the heat storage tank 520, but it is also possible to use it as a supplement to other heat such as factory waste heat. [Industrial Applicability]

[0069] The present invention can be used as an energy storage system that stores electrical energy as thermal and pressure energy of a fluid, with extremely little energy loss through the energy storage and release cycle. [Explanation of symbols]

[0070] 1 Energy storage system (embodiment 1) 10 Carbon dioxide gas holder 20 Carbon dioxide gas blower 30 Carbon dioxide gas solidification device 40 Dry ice melting tank 41 Dry Ice Melting Device 42 Heat medium supply means 50 Liquefied carbon dioxide storage tank 60 Liquefied carbon dioxide booster pump 70 Liquefied carbon dioxide heater 80 Carbon dioxide gas expansion turbine 171 Carbon dioxide gas blower inlet line 172 Carbon dioxide gas blower outlet line 173 Refrigerant inlet line 174 Refrigerant outlet line 175 Dry ice delivery line 176 First dry ice dispensing valve 177 Second dry ice dispensing valve 178 Melting heat transfer medium inlet line 179 Melting heat transfer medium outlet line 181 Liquefied carbon dioxide discharge line 182 Liquefied carbon dioxide booster pump inlet line 183 Liquefied carbon dioxide booster pump outlet line 184 Carbon dioxide gas expansion turbine inlet line 185 Evaporation heat medium inlet line 186 Evaporation heat transfer medium outlet line 187 Carbon dioxide gas expansion turbine outlet line 200 Energy Storage System (Embodiment 2) 210 Carbon dioxide gas cooler 220 Melting heat transfer medium circulation pump 271 Heat medium return line 272 Heat Transfer Medium Supply Line 300 Energy Storage System (Embodiment 3) 310 Liquefied carbon dioxide storage pressure pump 320 Liquefied carbon dioxide storage tank pressurized evaporator 371 Liquefied carbon dioxide storage tank pressurized evaporator inlet line 372 Liquefied carbon dioxide storage tank pressurized evaporator outlet line 373 Flow Control Valve 400 Energy Storage System (Embodiment 4) 471 Surplus gas circulation line 472 Surplus gas circulation flow control valve 500 Energy storage system (embodiment 5) 510 Carbon dioxide gas blower outlet cooler 520 Heat storage tank 530 Carbon dioxide gas cooling refrigerant circulation pump 540 Liquefied carbon dioxide evaporative heat transfer medium circulation pump 571 Carbon dioxide gas blower outlet refrigerant line 572 Carbon dioxide gas blower outlet refrigerant return line 573 Liquid carbon dioxide evaporation heat transfer line 574 Liquid carbon dioxide evaporation heat medium return line

Claims

1. a carbon dioxide-containing gas holder configured to store a carbon dioxide-containing gas; a carbon dioxide gas solidification device that solidifies the carbon dioxide gas by heat exchange between the carbon dioxide-containing gas stored in the carbon dioxide-containing gas holder and a refrigerant having a boiling point lower than the solidification temperature of carbon dioxide in the carbon dioxide-containing gas, thereby producing dry ice; a dry ice melting device that melts the dry ice generated by the carbon dioxide solidification device through heat exchange with a fluid having a temperature higher than the melting point of the dry ice to generate liquefied carbon dioxide; A liquefied carbon dioxide storage tank for storing the liquefied carbon dioxide produced by the dry ice melting device; a liquefied carbon dioxide pump that pressurizes the liquefied carbon dioxide stored in the liquefied carbon dioxide storage tank; a liquefied carbon dioxide heater for heating the liquefied carbon dioxide pressurized by the liquefied carbon dioxide pump through heat exchange with a heat medium to convert it into a gas phase or a supercritical phase; and a carbon dioxide expansion turbine that expands the carbon dioxide that has been converted into a gas phase or supercritical phase by the liquefied carbon dioxide heater to recover energy and sends the low-pressure carbon dioxide gas to the carbon dioxide-containing gas holder.

2. a carbon dioxide-containing gas cooler that cools the carbon dioxide-containing gas supplied from the carbon dioxide-containing gas holder to the carbon dioxide gas solidification device; 2. The energy storage system according to claim 1, wherein heat obtained from the carbon dioxide-containing gas in the carbon dioxide-containing gas cooler is supplied to the dry ice melting device.

3. a liquefied carbon dioxide storage pressurizing pump that pressurizes the liquefied carbon dioxide produced in the dry ice melting device and supplies the pressurized liquefied carbon dioxide to the liquefied carbon dioxide storage tank; The energy storage system according to claim 1, further comprising: a liquefied carbon dioxide storage tank pressurization evaporator that increases the internal pressure of the liquefied carbon dioxide storage tank by heating the liquefied carbon dioxide stored in the liquefied carbon dioxide storage tank.

4. The carbon dioxide-containing gas supplied to the carbon dioxide gas solidification device includes surplus gas that is not solidified in the carbon dioxide gas solidification device, 2. The energy storage system according to claim 1, further comprising an excess gas circulation line for circulating excess gas that has not been solidified in the carbon dioxide solidification device from the carbon dioxide gas solidification device to its inlet.

5. 2. The energy storage system according to claim 1, further comprising a heat storage tank for storing the heat of the carbon dioxide-containing gas supplied from the carbon dioxide-containing gas holder to the carbon dioxide gas solidification device and the heat obtained in the liquefied carbon dioxide heater, thereby canceling out each other.

6. 6. The energy storage system according to claim 1, wherein the refrigerant having a temperature lower than the solidification temperature of carbon dioxide is liquefied natural gas.

7. 6. The energy storage system according to claim 1, wherein the heat source of the heat medium used in the liquefied carbon dioxide heater is waste heat from a plant.

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