Energy storage system

Abstract

To provide an energy storage system capable of efficiently enhancing power generation efficiency by using liquefied air.SOLUTION: An energy storage system 1 includes: a power generator 120 that generates electric power by using evaporation gas of LNG as fuel; an air liquefier 50 that liquefies air; a liquefied air evaporation heat exchanger 90 that evaporates liquefied air flowing in a liquefied air pump discharge line 181 by exchanging heat with water with room temperature; an air warming heat exchanger 100 disposed downstream of the liquefied air evaporation heat exchanger 90 in the liquefied air pump discharge line 181 and warming gaseous air flowing in the liquefied air pump discharge line 181 by exchanging heat with exhaust gas of the power generator 120; and an air expansion turbine 110 disposed downstream of the air warming heat exchanger 100 in the liquefied air pump discharge line 181 and expanding gaseous air flowing in the liquefied air pump discharge line 181 to generate electric power by using rotating force of the turbine.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an energy storage system that stores energy using liquefied air as a medium, and more particularly to an energy storage system capable of efficiently increasing power generation output.

Background Art

[0002] With the spread of renewable energy, the need for energy storage systems has been increasing, and energy storage using liquefied air has been proposed as one of the methods. However, there has been a drawback in that the charging / discharging efficiency is low because the compression power required for liquefying air is extremely large.

[0003] In this regard, Patent Document 1 discloses a technique in which air is cooled stepwise with LNG and liquid hydrogen (LH2) to be liquefied at a low pressure, and the LNG and LH2 for which cold heat has been used are used as fuel for power generation equipment, and liquefied air is supplied to the power generation equipment as an oxidant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the technique of Patent Document 1 is premised on LH2, which is difficult to obtain, the feasibility of the equipment is poor. Even if LH2 is available, the high cost of LH2 is reflected in the equipment operation cost, which may significantly reduce the profitability. In addition, although there is a description that liquefied air is vaporized with water or air before being expanded by an air expansion turbine for power generation, water and air can only reach a temperature of about room temperature, resulting in low power generation efficiency by the expansion turbine.

[0006] The present invention has been made to solve such problems, and an object of the present invention is to provide an energy storage system that can efficiently increase the power generation efficiency by liquefied air in an energy storage system that stores energy using liquefied air as a medium.

Means for Solving the Problems

[0007] (1) The energy storage system according to the present invention includes an LNG storage tank for storing LNG, an LNG pump for boosting and discharging the LNG stored in the LNG storage tank, an LNG discharge line through which the LNG discharged by the LNG pump flows, a power generation device that generates electricity using the evaporation gas of LNG generated in the LNG storage tank as fuel, and / or a power generation device that generates electricity using the evaporation gas of the LNG discharged by the LNG pump as fuel, an air liquefaction device that liquefies air using the cold heat of the LNG discharged by the LNG pump, a liquefied air storage tank for storing the air liquefied by the air liquefaction device, a liquefied air pump for boosting and discharging the liquefied air stored in the liquefied air storage tank, a liquefied air pump discharge line through which the liquefied air discharged by the liquefied air pump flows, a heat exchanger for evaporating the liquefied air flowing through the liquefied air pump discharge line by heat exchange with normal temperature water, an air heating heat exchanger that is disposed downstream of the heat exchanger for evaporating liquefied air in the liquefied air pump discharge line and heats the gaseous air flowing through the liquefied air pump discharge line by heat exchange with the exhaust gas of the power generation device, and an air expansion turbine that is disposed downstream of the air heating heat exchanger in the liquefied air pump discharge line, expands the gaseous air flowing through the liquefied air pump discharge line, and generates electricity by the rotational force of the turbine.

[0008] (2) Further, in the device described in (1) above, the power generation device that generates power using the evaporation gas of the LNG discharged by the LNG pump as fuel is a gas turbine combined cycle power generation device that combines a gas turbine and a steam turbine. The heat exchanger for evaporating the liquefied air evaporates the liquefied air flowing through the liquefied air pump discharge line by heat exchange with seawater supplied to a condenser provided in the gas turbine combined cycle power generation device.

[0009] (3) Further, in the device described in (1) above, an LNG vaporizer connected to the LNG discharge line that evaporates the LNG supplied from the LNG discharge line by heat exchange with seawater, a vaporizer seawater pump that sucks in and discharges seawater, a vaporizer seawater supply line connected to the vaporizer seawater pump and the LNG vaporizer that supplies the seawater discharged by the vaporizer seawater pump to the LNG vaporizer, and a seawater discharge line that discharges seawater from the LNG vaporizer to the sea. The heat exchanger for evaporating the liquefied air evaporates the liquefied air flowing through the liquefied air pump discharge line by heat exchange with the seawater flowing through the seawater discharge line.

Advantages of the Invention

[0010] In the present invention, since the liquefied air is heated and warmed in two stages by the heat exchanger for evaporating the liquefied air and the heat exchanger for warming the air and then supplied to the air expansion turbine, the power generation efficiency by the liquefied air can be efficiently increased.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] [Embodiment 1] First, with reference to FIG. 1, the configuration and functions of Embodiment 1 of the present invention will be described. An energy storage system 1 according to the first embodiment of the present invention includes an LNG storage tank 10, an LNG pump 20, an LNG vaporizer 30, an air liquefaction device 50, a gas turbine power generation device 40, a heat exchanger 60 for air liquefaction, a liquefied air tank 70, a liquefied air pump 80, a heat exchanger 90 for liquefied air evaporation, a heat exchanger 100 for air heating, an air expansion turbine 110, and a gas engine power generation device 120.

[0013] The LNG storage tank 10 is an above-ground PC (Pre-stressed Concrete) storage tank, which has a steel inner tank and an outer tank, and is circumferentially surrounded by a PC wall. The space between the inner tank and the outer tank is filled with particles called perlite to form a nitrogen atmosphere, which exhibits a high heat insulation effect. As a result, the LNG storage tank 10 stores a large amount of LNG at an extremely low temperature (about -160°C) while suppressing heat input from the outside.

[0014] The LNG pump 20 is, for example, a vertical centrifugal submerged pump disposed on the downstream side of the LNG storage tank 10, and the pump body is immersed inside the pot. The LNG pump 20 boosts the pressure of the LNG supplied from the LNG storage tank 10 through the LNG pump inlet line 171 and discharges it.

[0015] The LNG vaporizer 30 is an ORV (Open Rack Vaporizer) type vaporizer. LNG flows from the bottom to the top inside the vertically arranged heat transfer tube group, and seawater flows from the top to the bottom outside. By doing so, the LNG supplied from the LNG pump outlet line 172 is completely vaporized and supplied as vapor gas to the supply gas line 173.

[0016] The air liquefaction device 50 is a refrigerator that uses a general nitrogen refrigerant, and cools the air taken in from the air inlet line 174 to produce liquefied air.

[0017] The heat exchanger 60 for air liquefaction is a general shell & tube type heat exchanger. As will be described later, it supplies the cold heat of LNG to the nitrogen for the refrigerant in the air liquefaction device 50.

[0018] Figure 2 is a schematic diagram showing the details of the air liquefaction device 50 and the relationship between the air liquefaction device 50 and the heat exchanger 60 for air liquefaction. As shown in Figure 2, the air liquefaction device 50 includes a raw material air compressor 51, an adsorber 53, a compressed air cooler 54, and a nitrogen compressor 55. The raw material air compressor 51 is a centrifugal compressor, which compresses the air introduced from the air inlet line 174 and supplies it to the compressed air line 52.

[0019] The adsorber 53 is an adsorption tower filled with a zeolite-based adsorbent, which adsorbs moisture and carbon dioxide from the compressed air flowing through the compressed air line 52. The compressed air cooler 54 is a plate type heat exchanger, which uses the cold heat of liquid nitrogen described later to cool and liquefy the compressed air flowing through the compressed air line 52.

[0020] The nitrogen compressor 55 is a centrifugal compressor, which compresses the nitrogen gas flowing through the nitrogen circulation line 56. The nitrogen expansion valve 57 is a remotely operated globe valve, which rapidly decompresses the nitrogen gas cooled by LNG in the heat exchanger 60 for air liquefaction to generate liquid nitrogen. The generated liquid nitrogen cools the compressed air in the compressed air cooler 54 and evaporates itself.

[0021] Returning to FIG. 1, the liquefied air tank 70 is a vertical cylindrical steel tank that temporarily stores the liquefied air supplied from the liquefied air supply line 175. The liquefied air pump 80 is a centrifugal pump that pressurizes the liquefied air supplied from the liquefied air pump suction line 177 and supplies it to the liquefied air pump discharge line 181.

[0022] The heat exchanger 90 for evaporating liquefied air is an open rack type heat exchanger that uses normal temperature water such as seawater or warm water as a heating medium to heat and evaporate the liquefied air supplied from the liquefied air pump discharge line 181.

[0023] The heat exchanger 100 for heating air is a shell & tube type heat exchanger that uses the exhaust gas of the gas engine power generation device 120 as a heating medium to heat the air after passing through the heat exchanger 90 for evaporating liquefied air.

[0024] The air expansion turbine 110 is a centrifugal expansion turbine that converts the pressure energy into rotational motion of the turbine by decompressing high-pressure air to the equivalent of atmospheric pressure and generates electricity by a generator.

[0025] The gas engine power generation device 120 is a power generation device that uses a reciprocating gas engine, generates electricity using the BOG supplied from the LNG storage tank 10 via the BOG supply line 185 as fuel, and supplies the generated exhaust gas to the exhaust gas discharge line 186.

[0026] Next, the operation of the energy storage system 1 according to the present embodiment will be described. The energy storage system 1 operates the air liquefaction device 50, liquefies air by using the cold heat of LNG, and stores it in the liquefied air tank 70. Thereby, the energy storage system 1 accumulates energy convertible into electric power in the form of liquefied air.

[0027] The energy storage system 1 operates the liquefied air pump 80 to boost the pressure of the cryogenic liquefied air (e.g., -190°C) stored in the liquefied air tank 70 and discharges it as high-pressure liquefied air (e.g., 10 MPaG) into the liquefied air pump discharge line 181.

[0028] The high-pressure liquefied air discharged into the liquefied air pump discharge line 181 is heated and evaporated in the heat exchanger 90 for liquefied air evaporation, becoming high-pressure air (supercritical state) at normal temperature (e.g., 20°C).

[0029] The high-pressure air is heated by the high-temperature (e.g., 350°C) exhaust gas of the gas engine power generation device 120 in the air heating heat exchanger 100, becoming high-pressure air at high temperature (e.g., 200°C).

[0030] The high-temperature high-pressure air generated in the air heating heat exchanger 100 is introduced into the air expansion turbine 110, driving the air expansion turbine 110 with pressure reduction and temperature decrease, and generating electricity.

[0031] The BOG (methane gas) generated in the LNG storage tank 10 flows through the BOG supply line 185 and is supplied to the gas engine power generation device 120, used as fuel for the gas engine power generation device 120, and converted into electricity.

[0032] In the gas engine power generation device 120, methane gas is supplied from the BOG supply line 185, burned with air as an oxidant, the piston movement in the combustion chamber is converted into the rotational movement of the camshaft, and the generator is rotated by the rotational movement of the camshaft to generate electricity.

[0033] The exhaust gas discharged into the exhaust gas discharge line 186 is cooled to normal temperature (e.g., 50°C) by the high-pressure air in the air heating heat exchanger 100. The exhaust gas cooled to normal temperature is dissipated into the atmosphere.

[0034] According to the energy storage system 1 according to this embodiment, since the cold heat of LNG is effectively utilized in the heat exchanger 60 for air liquefaction, the air liquefaction device 50 can be operated in an energy-saving manner.

[0035] Moreover, according to the energy storage system 1 according to this embodiment, since the cold heat of LNG can be effectively utilized for air liquefaction, the cold heat of LNG that has been discarded into the environment can be reduced. For example, an LNG vaporizer using seawater as a heating medium has discarded the cold heat of LNG into the ocean, but since the amount can be reduced, the impact on the ocean can be reduced.

[0036] In addition, according to the energy storage system 1 according to this embodiment, since the high-temperature exhaust gas (for example, 350 ° C) flowing through the exhaust gas discharge line 186 is used as the heat source of the heat exchanger 100 for air heating, sensible heat is given to the high-pressure air that has evaporated in the heat exchanger 90 for liquefied air evaporation and has reached room temperature (for example, 20 ° C), and the temperature can be further increased. As a result, the output of the expansion turbine can be further increased.

[0037] In this embodiment, the type of the heat exchanger including the heat exchanger 60 for air liquefaction is described as a shell & tube type or an open rack type, but it is not limited to this, and the type is appropriately selected within the design range. The same applies to pumps and valves.

[0038] In addition, in this embodiment, it is described that the gas engine power generation device 120 uses air as an oxidant, but the exhaust air of the air expansion turbine 110 may be taken in. Since the temperature of the exhaust air of the air expansion turbine 110 has decreased due to expansion, its density has increased. As a result, more oxygen can be stably supplied to the gas engine power generation device 120 regardless of the season, so the power generation efficiency of the gas engine power generation device 120 can be improved.

[0039] [Embodiment 2] Embodiment 1 had a gas engine power generation device 130 that used the evaporation gas generated in the LNG storage tank 10 as fuel. However, as shown in FIG. 3, the energy storage system 200 of the present embodiment has a gas turbine power generation device 240 that uses the vaporized gas vaporized by the LNG vaporizer 30 as fuel in addition to the gas engine power generation device 130. Hereinafter, with reference to FIG. 3, the configuration and function of the energy storage system 200 according to the present embodiment will be described. Note that components having the same configuration and function as those in FIG. 1 are given the same numbers.

[0040] The gas turbine power generation device 240 includes a boiler 244 that generates steam to be supplied to the steam turbine 246 by the exhaust heat of the gas turbine 242, a condenser 247 that condenses the exhaust steam of the steam turbine 246, and a condensate pump 248 that feeds the condensate condensed by the condenser 247 to the boiler 244.

[0041] The exhaust gas of the gas turbine 242 is supplied to the boiler 244 via the exhaust gas line 243, the steam generated by the boiler 244 is supplied to the steam turbine 246 via the steam line 245, and the condensate condensed by the condenser 247 is supplied to the boiler 244 via the condensate pump 248.

[0042] A large amount of seawater is supplied to the condenser 247 via the seawater supply line 272. This seawater is cooled by the liquefied air evaporation heat exchanger 90 before being supplied to the condenser 247. Then, the steam is condensed in the condenser 247 by the cooled seawater, and thereafter, the seawater is discharged into the ocean. That is, the low-temperature exhaust heat of the gas turbine power generation device 240 is transferred to the seawater and discarded into the ocean.

[0043] Next, the operation of the energy storage system 200 according to the present embodiment will be described. The high-pressure liquefied air discharged into the liquefied air pump discharge line 177 is heated and evaporated in the liquefied air evaporation heat exchanger 90 to become high-pressure air (supercritical state) at room temperature (for example, 20°C).

[0044] The high-pressure air is heated by the high-temperature exhaust gas flowing through the exhaust gas discharge line 186 in the air heating heat exchanger 100 and becomes high-temperature high-pressure air.

[0045] The high-temperature high-pressure air generated in the air heating heat exchanger 100 is introduced into the air expansion turbine 110, drives the air expansion turbine 110 with decompression and temperature reduction, and generates electric power.

[0046] According to the energy storage system 200, since the seawater at the inlet of the condenser 247 of the gas turbine power generation device 240 is cooled by the low-temperature air, the temperature of the seawater introduced into the condenser 247 becomes lower. As a result, the degree of vacuum in the condenser 247 increases, so the efficiency of the steam turbine 246 increases, and the power generation amount by the gas turbine power generation device 240 increases. Also, although it is generally known that the corrosion of metals by seawater progresses faster as the seawater temperature is higher, the corrosion of the heat transfer tubes of the condenser 247 can be suppressed by lowering the temperature of the seawater introduced into the condenser 247.

[0047] Also, according to the energy storage system 200, since the large flow rate of seawater supplied to the condenser 247 is used as the heat source of the liquefied air evaporation heat exchanger 90, the latent heat of evaporation of liquefied air several times larger than the sensible heat can be supplied. Therefore, the flow rate of the liquefied air supplied to the liquefied air evaporation heat exchanger 90 can be increased, and the output of the air expansion turbine 110 can be increased.

[0048] [Embodiment 3] Next, with reference to FIG. 4, the configuration and function of Embodiment 3 will be described. Those having the same configuration and function as in Embodiments 1 and 2 are given the same numbers. The energy storage system 300 according to Embodiment 3 has a seawater pump 310 for vaporizer.

[0049] The seawater pump 310 for vaporizer is a vertical centrifugal pump, pumps up seawater, and discharges it to the seawater discharge line 371 for vaporizer.

[0050] Next, the operation of the energy storage system 300 according to the present embodiment will be described. Descriptions of the operations similar to those in Embodiments 1 and 2 are omitted. The seawater discharged by the seawater pump 310 for the vaporizer is supplied to the LNG vaporizer 30. After heating the LNG, it is discharged into the seawater return line 372 for the vaporizer.

[0051] The seawater discharged into the seawater return line 372 for the vaporizer is supplied to the heat exchanger 90 for evaporating liquefied air, and the liquefied air is evaporated by heat exchange with the liquefied air. The seawater discharged into the seawater return line 372 for the vaporizer has its temperature decreased by several degrees Celsius through heat exchange with the LNG, but its temperature further decreases through heat exchange with the liquefied air and then is returned to the sea.

[0052] According to the energy storage system 300 according to the present embodiment, since the heating source of the heat exchanger 90 for evaporating liquefied air is the seawater used in the LNG vaporizer 30, the evaporation and warming of the liquefied air can be completed within the LNG base. Therefore, the energy storage system 300 according to the present embodiment can achieve the above-described effects even when the LNG base and the power plant equipped with the gas turbine power generation device 240 are far apart.

[0053] Also, according to the energy storage system 300 according to the present embodiment, since the heating source of the heat exchanger 90 for evaporating liquefied air is the seawater after being supplied to the LNG vaporizer 30, the pump dedicated to the heat exchanger 90 for evaporating liquefied air can be reduced.

[0054] In this embodiment, the heat source for the liquefied air evaporator 90 has been described as the seawater used in the LNG vaporizer 30. However, any normal-temperature water including seawater or warm water may be used. For example, the cooling water of the BOG compressor can also be used as the heat source for the liquefied air evaporator 90. In this case, by using the cooling water after the BOG compressor is cooled and its temperature rises, the operating time of the cooling tower can be reduced, so energy conservation can be achieved. Also, by using the surplus low-temperature waste heat within the LNG terminal in the form of steam or warm water, the heat can be effectively utilized.

[0055] Further, in this embodiment, the heat source for the liquefied air evaporator 90 is the seawater after being supplied to the LNG vaporizer 30. However, a dedicated seawater pump and seawater line may be provided. Thereby, since the liquefied air evaporator 90 can be operated independently of the operation of the LNG vaporizer 30, the degrees of freedom in design and operation can be increased.

Industrial Applicability

[0056] The present invention can be used as an energy storage system that can efficiently increase the power generation efficiency by liquefied air in an energy storage system that stores energy using liquefied air as a medium.

Explanation of Signs

[0057] 1, 200, 300 Energy storage system 10 LNG storage tank 20 LNG pump 30 LNG vaporizer 50 Air liquefaction device 51 Raw air compressor 52 Compressed air line 53 Adsorber 54 Compressed air cooler 55 Nitrogen compressor 56 Nitrogen circulation line 57 Nitrogen expansion valve 60 Heat exchanger for air liquefaction 70 Liquefied air tank 80 Liquid air pump 90 Heat exchanger for liquid air evaporation 100 Heat exchanger for air heating 110 Air expansion turbine 120 Gas engine power generation device 171 LNG pump inlet line 172 LNG pump outlet line 173 Gas supply line 174 Air inlet line 175 Liquid air supply line 177 Liquid air pump suction line 181 Liquid air pump discharge line 183 Air discharge line 185 BOG supply line 186 Exhaust gas discharge line 210 Seawater pumping pump 240 Gas turbine power generation device 241 Air supply line 242 Gas turbine 243 Exhaust gas line 244 Boiler 245 Steam line 246 Steam turbine 247 Condenser 248 Condensate pump 271 Seawater pumping line 272 Seawater supply line 273 Seawater discharge line 310 Seawater pump for vaporizer 371 Seawater discharge line for vaporizer 372 Seawater return line for vaporizer

Claims

1. An LNG storage tank for storing LNG; An LNG pump for boosting and discharging the LNG stored in the LNG storage tank; An LNG discharge line through which the LNG discharged by the LNG pump flows; A power generation device that generates electricity using the evaporation gas of the LNG generated in the LNG storage tank as fuel, and / or a power generation device that generates electricity using the evaporation gas of the LNG discharged by the LNG pump as fuel; An air liquefaction device that liquefies air using the cold heat of the LNG discharged by the LNG pump; A liquefied air storage tank for storing the air liquefied by the air liquefaction device; A liquefied air pump for boosting and discharging the liquefied air stored in the liquefied air storage tank; A liquefied air pump discharge line through which the liquefied air discharged by the liquefied air pump flows; A heat exchanger for evaporating liquefied air that causes the liquefied air flowing through the liquefied air pump discharge line to evaporate by heat exchange with normal temperature water; An air heating heat exchanger that is disposed downstream of the liquefied air evaporation heat exchanger in the liquefied air pump discharge line and heats the gaseous air flowing through the liquefied air pump discharge line by heat exchange with the exhaust gas of the power generation device; An air expansion turbine that is disposed downstream of the air heating heat exchanger in the liquefied air pump discharge line, expands the gaseous air flowing through the liquefied air pump discharge line, and generates electricity by the rotational force of the turbine, characterized in that it has an energy storage system.

2. The power generation device, wherein the power generation device that generates electricity using the evaporation gas of the LNG discharged by the LNG pump as fuel is a gas turbine combined cycle power generation device that combines a gas turbine and a steam turbine; The liquefied air evaporation heat exchanger evaporates the liquefied air flowing through the liquefied air pump discharge line by heat exchange with seawater supplied to a condenser provided in the gas turbine combined cycle power generation device, according to claim 1, characterized in that it has an energy storage system.

3. An LNG vaporizer connected to the LNG discharge line and evaporating the LNG supplied from the LNG discharge line by heat exchange with seawater; A vaporizer seawater pump for sucking and discharging seawater; A vaporizer seawater supply line connected to the vaporizer seawater pump and the LNG vaporizer, and supplying the seawater discharged by the vaporizer seawater pump to the LNG vaporizer; A seawater discharge line for discharging seawater into the sea from the LNG vaporizer, and The energy storage system according to claim 1, wherein the heat exchanger for evaporating the liquefied air evaporates the liquefied air flowing through the liquefied air pump discharge line by heat exchange with the seawater flowing through the seawater discharge line.

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