JPH1092627A - Superconducting electric power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize total energy by compensating the low refrigerating efficiency of a super conducting coil. SOLUTION: A super conducting electric power storage system stores electric energy as the stored energy of a superconducting coil 2 through a power converter 8 and inputs and outputs the stored energy as electric energy. The system is constituted so that the coil 2 can be cooled directly or indirectly by the evaporation latent heat of a liquefied natural gas when the coil 2 is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting power storage system for storing power energy as stored energy in a superconducting coil, and more particularly to a superconducting power storage system for cooling a superconducting coil using a liquefied natural gas vaporization facility.

[0002]

2. Description of the Related Art Recently, a superconducting power storage system (hereinafter abbreviated as SMES) for storing power energy as stored energy in a superconducting coil for the purpose of effectively utilizing surplus power and compensating for power supply to a load during peak power demand. Is planned, and its technical study and production of a demonstration system are underway.

The SMES stores power energy as stored energy in a superconducting coil, converts the stored energy into power energy again by a power converter, and releases the power energy to a power system as needed.

On the other hand, some superconducting coils, which are the core of the system, have already been put to practical use in MRI apparatuses and the like. Since energy conversion is performed, an AC loss occurs inside the coil. For this reason, the amount of heat required for cooling the superconducting coil is larger than that of a coil of a device that mainly generates a DC magnetic field, such as the above-described MRI device.

[0005] Generally, the superconducting coil is cooled by liquid helium because a superconducting material constituting the superconducting coil uses a substance having an extremely low critical temperature such as niobium titanium or niobium tin.

Conventionally, as a system for cooling a superconducting coil with liquid helium, there are a closed-loop refrigeration system using a helium refrigerator or a low-temperature pump, or a system in which a coil is directly immersed in stored liquid helium. In the method of directly immersing the helium, a container for storing liquid helium is required, and it is difficult to apply the method to a large-scale system because the structure becomes complicated.

[0007] The former closed-loop refrigeration system must be equipped with a refrigerator. Liquid nitrogen, which has a suitable boiling temperature and a suitable supply price, is generally used as a high heat source of the refrigeration cycle.

FIG. 5 is a conceptual diagram showing an example of a conventional superconducting coil refrigeration / cooling system. In FIG. 5, reference numeral 21 denotes a cryostat accommodating a superconducting coil 22;
Is a helium refrigerator that circulates liquid helium to the cryostat 21 to cool the superconducting coil 22. The helium refrigerator 23 is connected to a helium compressor 24 and a buffer tank 25 in a liquid helium circulation system.

Helium circulating between the helium refrigerator 23 and the cryostat 21 is stored in a nitrogen storage tank 27.
Heat exchanger 26 that exchanges heat with liquid nitrogen supplied from
Is provided.

[0010] Incidentally, a liquefied natural gas (hereinafter abbreviated as LNG) vaporizer is generally configured as shown in FIG. 6, reference numeral 31 denotes an LNG tanker; 32, an LNG storage tank for storing the LNG liquid transported by the LNG tanker 31; 33, a vaporizer for evaporating the liquid flowing from the LNG storage tank 32 through an LNG pump 34; The vaporizer 33 exchanges heat generated during vaporization by using seawater supplied from a seawater pump 35 as a medium.

Reference numeral 36 denotes an evaporative gas compressor that compresses LNG vaporized in the LNG storage tank 32 and introduces the compressed LNG into the LNG gas outflow system of the vaporizer 33. In such a conventional LNG vaporizer, the liquid transported by the LNG tanker 31 to the base near the supply point is vaporized, but the cold generated at this time is discharged using seawater as a medium, Not only the heat source cannot be used, but also the maintenance of the vaporization equipment has problems such as icing of the vaporizer outside the tube, requiring much labor.

[0012]

As described above, in the conventional superconducting power storage system, the helium refrigeration system used for cooling the superconducting coil has a very low energy efficiency with the current technology, and the energy consumption of the low heat source is low. The energy required for a high heat source is several tens of times or more.

Therefore, for SMES in which a refrigeration load frequently occurs during the operation of the superconducting coil, it is important to determine what energy is required as a high heat source in order to evaluate the overall efficiency of the system.

The present invention has been made in view of the above circumstances, and has as its object to provide a superconducting power storage system capable of compensating for the low refrigeration efficiency of a superconducting coil and achieving effective utilization of total energy. And

[0015]

In order to achieve the above object, the present invention comprises a superconducting power storage system by the following means. According to a first aspect of the present invention, there is provided a superconducting power storage system for storing power energy as stored energy of a superconducting coil through a power converter, and inputting / outputting the stored energy as power energy. The superconducting coil is directly or indirectly cooled by the latent heat of vaporization of the gas.

According to a second aspect of the present invention, there is provided a superconducting power storage system for storing power energy as stored energy of a superconducting coil through a power converter and inputting / outputting the stored energy as power energy. The superconducting coil is incorporated in a facility for natural gas vaporization, and the superconducting coil is directly or indirectly cooled by the latent heat of vaporization of the natural gas by the facility during operation of the superconducting coil.

In the superconducting power storage system according to the first and second aspects of the present invention, the latent heat of vaporization of the LNG is about 890 kJ / kg, and the superconducting coil is directly or indirectly operated by the cold heat. And a power converter that inputs and outputs power energy to and from the superconducting coil, thereby achieving a power storage system with low overall loss.

According to a third aspect of the present invention, there is provided a superconducting power storage system for storing power energy as stored energy of a superconducting coil through a power converter, and for inputting / outputting the stored energy as power energy. The superconducting coil is cooled by liquid helium obtained by operating a helium refrigerator that performs heat exchange using latent heat as a high heat source and helium as a low heat source.

In the superconducting power storage system according to the third aspect of the present invention, the latent heat of vaporization of LNG is used as a high heat source as a cooling means, and a helium refrigerator is operated using helium as a low heat source to supply liquid helium. By inputting and outputting power energy to and from the superconducting coil by the power converter while cooling the superconducting coil, a power storage system with low overall loss can be realized.

According to a fourth aspect of the present invention, there is provided a superconducting power storage system for storing power energy as stored energy in a superconducting coil through a power converter, and for inputting / outputting the stored energy as power energy. Heat exchange is performed using latent heat as a high heat source, and the superconducting coil is cooled using a refrigerant such as helium circulated by operation of a low-temperature pump as an intermediate refrigerant.

In the superconducting power storage system according to the invention, the latent heat of vaporization of LNG is used as a high heat source as a cooling means, and the superconducting coil is forcibly operated by operating a low temperature pump using helium as a low heat source. By inputting and outputting power energy to and from the superconducting coil by the power converter while cooling, a power storage system with low loss can be realized overall.

According to a fifth aspect of the present invention, in the third aspect, the superconducting coil is made of an oxide superconducting material whose critical temperature is higher than the boiling point of liquefied natural gas.

In the superconducting power storage system according to the fifth aspect of the present invention, as the superconducting material used for the superconducting coil, the critical temperature is the boiling point of liquefied natural gas (about 1 point).
When an oxide-based superconducting material higher than 20K) is used, the generation loss of the superconducting coil can be directly removed by the latent heat of vaporization of LNG.

According to a sixth aspect of the present invention, in a superconducting power storage system for storing power energy as stored energy of a superconducting coil through a power converter and inputting / outputting the stored energy as power energy, the operation of the superconducting coil is performed. Sometimes, the heat radiation shield in the cryostat necessary for keeping the superconducting coil cool is cooled directly or indirectly by the latent heat of vaporization of liquefied natural gas.

In the superconducting power storage system according to the present invention, LNG is directly vaporized for cooling a heat radiation shield provided as an element in a cryostat (vacuum insulated container) for keeping a superconducting coil cool. Latent heat can be used, and a power storage system with less loss can be realized overall.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of a superconducting power storage system according to the present invention. FIG.
1 is a superconducting coil 2 for storing electric energy
Is a helium refrigerator that circulates liquid helium to the cryostat 1 to cool the superconducting coil 2. In the helium refrigerator 3, helium circulating between the cryostat 1 and the cryogenic heat of the LNG is cooled. An LNG heat exchanger 4 for exchanging heat is provided. The LNG heat exchanger 4 performs heat exchange with an LNG supply system on the primary side and a liquid helium circulation system on the secondary side.

The primary side of the LNG heat exchanger 4 is LNG
The LNG flowing out of the storage tank 5 is supplied under pressure by an LNG pump 6 and exchanges heat with the liquid helium flowing on the secondary side, and then is added to the LNG compressor 7, where it is vaporized and compressed by the LNG compressor 7. We supply natural gas to the outside.

In the figure, reference numeral 8 denotes a power converter for converting a current flowing from a superconducting coil to a current supply system into AC power. The power converted by the power converter 8 is supplied to a power system (not shown). Has become.

In the superconducting power storage system having such a configuration, when LNG is pressure-fed to the LNG heat exchanger 4 in the helium refrigerator 3 by the LNG pump 6, LNG becomes L
After generating cold heat in the NG heat exchanger 4, the LNG compressor 7
Is supplied to the outside as vaporized natural gas.

In this case, the latent heat of vaporization of LNG is about 890 kj
The superconducting coil 2 is cooled by helium of about 4.5K by performing heat exchange with helium flowing in the helium circulation system by this cold heat.

Therefore, according to the first embodiment,
Since the evaporative cooling of LNG can be effectively used for cooling the superconducting coil, a superconducting power storage system with less loss can be provided.

Next, a second embodiment of the present invention will be described with reference to FIG. 2. The same parts as those in FIG. 1 are denoted by the same reference numerals, and only different points will be described. In the second embodiment, a circulation system for circulating liquid helium by a low-temperature pump 9 between the superconducting coil 2 housed in the cryostat 1 and the LNG storage tank 5 as shown in FIG. LN immersed in LNG liquid inside
The superconducting coil 2 is forcibly cooled by exchanging heat between the cold heat and the liquid helium flowing through the refrigerant circulation system by the G heat exchanger 4.

In this case, in the upper space in the LNG storage tank 5, natural gas which partially evaporates and accumulates LNG liquid by heat exchange is pressurized by the LNG compressor 7 and supplied to the outside.

Therefore, according to the second embodiment,
The liquid helium flowing through the refrigerant circulation system is transferred to the LNG storage tank 5 in the LNG storage tank 5.
Since the liquid is cooled directly by the cold of the NG liquid, the vaporized cold of the LNG can be effectively used for cooling the superconducting coil, and a superconducting power storage system with less loss can be provided. A helium refrigerator is not required as in the embodiment, and the cooling equipment can be simplified.

Next, a third embodiment of the present invention will be described with reference to FIG. 3. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and only different points will be described. In the third embodiment, as shown in FIG. 3, the superconducting coil 2 housed in the cryostat 1 is cooled via the LNG heat exchanger 4 by the LNG liquid pumped from the LNG storage tank 5 by the LNG pump 6. The natural gas vaporized by the cold generated from the LNG heat exchanger 4 is pressurized by the LNG compressor 7 and supplied to the outside.

In this case, the superconducting coil 2 has a critical temperature of 1
It is made of a conductor using an oxide superconducting material of 20K or more, and electrical insulation can be easily configured as an indirect cooling method using heat conduction.

Therefore, according to the third embodiment,
The LNG is vaporized by the LNG compressor 7 and supplied to the outside as natural gas. In the process, the LNG heat exchanger 4 generates cold heat.
It can be used to cool the superconducting coil 2 as a low heat source of 20K. This makes it possible to provide a superconducting power storage system with low loss that can effectively utilize the cooling heat of vaporization of LNG for cooling the superconducting coil and can greatly simplify the cooling equipment.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 4. In FIG. 4, the same parts as those in FIG. 1 are denoted by the same reference numerals, and only different points will be described. In the fourth embodiment, as shown in FIG. 4, a heat radiation shield 1 is provided on an outer peripheral portion of a superconducting coil 2 housed in a cryostat 1.
0, LN near the heat radiation shield 10
G heat exchanger 4 is provided, and LNG pump 6 is supplied from LNG storage tank 5.
Heat exchanger 4 by LNG liquid pumped by LNG
The natural gas vaporized by the cold generated from the LNG heat exchanger 4 is cooled by LN
The compressor is pressurized by the G compressor 7 and supplied to the outside.

Therefore, according to the fourth embodiment,
The LNG is vaporized by the LNG compressor 7 and supplied to the outside as natural gas. In the process, since the LNG heat exchanger 4 generates cold heat, the LNG heat exchanger 4 is used as a low heat source to cool the heat radiation shield 10. Can be provided.

In this case, the cooling system of the heat radiation shield 10 may be combined with any one of the first to third embodiments to cool the superconducting coil.

[0041]

As described above, according to the superconducting power storage system according to the present invention, the following effects can be obtained. A large amount of heat due to an AC loss generated inside the superconducting coil by the operation of alternating current at the time of energy conversion of the superconducting coil used in the SMES can be effectively cooled by utilizing the cold heat discharged from the liquefied natural gas.

Further, the cold generated when LNG is transported as a liquid and then vaporized at a base near the supply point to obtain liquefied natural gas can be effectively used as a heat source. In addition, the maintenance and management of the vaporization equipment involves problems such as icing of the vaporizer outside the tube, which required a lot of labor.However, the maintenance of the vaporization equipment is required by using the cold heat discharged from liquefied natural gas. Labor can be greatly reduced.

By these effects, as a power storage system for the purpose of comprehensive energy saving for maintaining and improving the global environment, the low refrigeration efficiency of the superconducting coil is compensated for by S
MES can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a superconducting power storage system according to the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the superconducting power storage system according to the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of a superconducting power storage system according to the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of the superconducting power storage system according to the present invention.

FIG. 5 is a configuration diagram showing an example of a conventional superconducting power storage system.

FIG. 6 is a configuration diagram showing an example of a conventional LNG vaporizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cryostat 2 ... Superconducting coil 3 ... Helium refrigerator 4 ... LNG heat exchanger 5 ... LNG storage tank 6 ... LNG pump 7 ... LNG compressor 8 ... Power converter 9 ... Low temperature pump 10 ... … Heat radiation shield

Claims (6)

[Claims] 1. A superconducting power storage system for storing power energy as stored energy in a superconducting coil through a power converter and for inputting / outputting the stored energy as power energy, wherein the latent heat of vaporization of liquefied natural gas during operation of the superconducting coil is provided. A superconducting power storage system characterized in that the superconducting coil is directly or indirectly cooled by the cooling device. 2. A superconducting power storage system for storing power energy as stored energy of a superconducting coil through a power converter and for inputting / outputting the stored energy as power energy, wherein the purpose is to vaporize natural gas at a liquefied natural gas base. A superconducting power storage system incorporated in a facility, wherein the superconducting coil is directly or indirectly cooled by latent heat of vaporization of natural gas by the facility during operation of the superconducting coil. 3. A superconducting power storage system for storing power energy as stored energy in a superconducting coil through a power converter and inputting / outputting the stored energy as power energy, wherein a latent heat of vaporization of liquefied natural gas is used as a high heat source. ,
A superconducting power storage system, wherein the superconducting coil is cooled by liquid helium obtained by operating a helium refrigerator that performs heat exchange using helium as a low heat source. 4. A superconducting power storage system for storing power energy as stored energy of a superconducting coil through a power converter and inputting / outputting the stored energy as power energy, wherein a latent heat of vaporization of liquefied natural gas is used as a high heat source. A superconducting power storage system, wherein the superconducting coil is cooled by using a refrigerant such as helium circulating by operation of a low-temperature pump as an intermediate refrigerant in which heat exchange is performed. 5. The superconducting power storage system according to claim 3, wherein the superconducting coil is made of an oxide superconducting material whose critical temperature is higher than the boiling point of liquefied natural gas. 6. A superconducting power storage system for storing power energy as stored energy of a superconducting coil through a power converter and for inputting / outputting the stored energy as power energy, wherein the latent heat of vaporization of liquefied natural gas during operation of the superconducting coil. A superconducting power storage system, wherein the heat radiation shield in a cryostat necessary for keeping the superconducting coil cool is directly or indirectly cooled.