KR20160068037A

KR20160068037A - Reservoir in underground for the storage of highly pressured fluid and CAES system using the same

Info

Publication number: KR20160068037A
Application number: KR1020140172805A
Authority: KR
Inventors: 류동우; 박도현; 박정욱; 오태민; 이항복; 박의섭
Original assignee: 한국지질자원연구원
Priority date: 2014-12-04
Filing date: 2014-12-04
Publication date: 2016-06-15

Abstract

The present invention relates to a high-pressure fluid reservoir for storing a high-pressure gas in a deep part of an underground. A high-pressure fluid reservoir according to the present invention comprises: a tank main body embedded in a cavern formed by digging a ground downward to store a high-pressure fluid, the reservoir main body being formed of a hermetically sealed material and containing therein a high- A back fill layer formed by curing the back fill material to be filled between the main body and the inner wall of the cavern, a plug for closing the covane, and a back fill layer between the inner wall of the rock bed and the back fill layer And a grouting layer interposed between the inner wall of the rock bed and the back fill layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an underground high-pressure fluid storage tank having a back fill layer having enhanced compressive strength and a CAES system using the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy storage system, and more particularly, to a compressed air energy storage (CAES) system that compresses and stores air at a high pressure and supplies compressed air to a power source, To a structure of a high pressure gas reservoir formed in the ground.

In the case of base power generation such as thermal power or nuclear power generation, a certain amount of electric energy is generated when the power is once generated, and this amount can not be controlled. Therefore, there is a problem that power generation does not solve all of the electric power demand at the electricity consumption peak time during the daytime. On the other hand, during the late night hours, a considerable amount of the developed electric power should be discarded because the generation exceeds the demand. In order to overcome this difference in power generation and usage, it is necessary to store the idle electricity at midnight and compensate for insufficient power supply during the peak time of the week.

As a means of energy storage, CAES and secondary batteries are emerging as the key words of national energy strategy. Currently, CAES is expected to be used for large-capacity energy storage, and secondary batteries for small and medium-capacity energy storage. CAES compresses and stores air at high pressure using electricity generated by renewable generation means such as thermal power generation or nuclear power generation, or by means of renewable generation means such as wind power generation, and then compresses the compressed air to power generation means such as turbines and pistons And then converted into electricity and supplied.

Energy storage has a high correlation with the quality of electricity supply besides the disparity of electricity demand and supply. For example, wind power generation can not produce high quality electricity because the wind time or wind intensity is not constant. In addition, when suddenly large amounts of electricity are produced suddenly through wind power generation, problems such as the disturbance of the frequency of the power system are caused. In terms of solving these problems, energy storage is becoming an important concept.

In other words, CAES has a strategic meaning in future energy supply policy as it functions to increase elasticity of energy supply in connection with base power generation and renewable energy generation.

The CAES power plants currently in operation are the Huntorf power plant in Germany and McIntosh power plant in the United States, which utilize underground rock salt dissolved caves as a compressed air storage space. However, in order to overcome limitations of the intellectual conditions, the CAES storage tank is expected to develop in the direction of underground construction.

One of the most important points in the commercialization of CAES is that it guarantees the maximum economical efficiency in order to ensure the safety of the underground compressed air storage tank. Therefore, it is necessary to develop the shape of the underground storage tank to secure the safety and economical efficiency in the structural aspect of the underground compressed air storage tank.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-pressure fluid storage tank having improved stability by increasing compressive strength of a back fill layer and a CAES system using the same.

According to an aspect of the present invention, there is provided a high-pressure fluid reservoir, which is embedded in a cavern formed by digging a ground downward to store a high-pressure fluid, includes a hermetically sealed material, A tank body formed; A back fill layer formed by curing a back fill material filled between the tank main body and the inner wall of the cabin; A plug for closing the covane; And a grouting layer interposed between the inner wall of the rock and the back fill layer by curing the grouting liquid injected between the inner wall and the back fill layer by applying pressure to the back fill layer after the back fill layer is cured, And the like.

According to the present invention, there is further provided a grouting solution injection pipe interposed between an inner wall of the rock bed and a back fill layer for injecting the grouting solution, wherein a plurality of discharge holes are formed. The grouting solution injection pipe may further include a discharge pipe installed between the inner wall of the rock bed and the back fill layer so that the grouting solution discharged from the grouting solution injection pipe can be discharged to the outside of the cavern.

In particular, the grouting solution injection pipes may be arranged in the vertical direction so that a plurality of the grouting solution injection pipes are arranged along the inner wall of the cabin, or may be spirally arranged from the top to the bottom along the inner wall surface of the cabin.

Meanwhile, the energy for compressing air in the CAES system according to the present invention can be linked to a conventional power generation source such as thermal power generation, but can also be connected to a power generation source such as wind power generation or solar power generation.

Also, in the CAES system according to an embodiment of the present invention, the compression of air may be performed by using a turbine for generating a multi-stage compressor, but may also be performed by using a piston system such as a large-scale ship engine.

The high pressure fluid reservoir according to the present invention introduces a compressive force to the backing layer by injecting the grouting solution at a high pressure between the backing layer and the inner wall of the rock to introduce the prestress into the backing layer to improve the stability of the backing layer have.

1 is a sectional view for explaining basic elements of a high-pressure fluid reservoir according to the present invention.
FIG. 2 is a view for explaining a tank body and a reinforcement portion in the high-pressure fluid reservoir shown in FIG. 1. FIG.
3 is a schematic longitudinal sectional view of a high-pressure fluid reservoir with a grouting solution injection tube installed according to an embodiment of the present invention.
4 is a cross-sectional view taken along line aa of FIG. 3;
Fig. 5 is a schematic cross-sectional view for explaining a state in which the grouting liquid is injected between the rock and back filler layers and a pressure acting on the high-pressure fluid reservoir;
6 is a view for explaining the shear force acting on the upper portion of the high-pressure fluid reservoir.
7 is a vertical cross-sectional view of a high-pressure fluid reservoir with an intensifier in an embodiment of the present invention.
Fig. 8 is a cross-sectional view of the upper portion of the plug in Fig. 7 for explaining the arrangement of the strength reinforcement in Fig. 7;
FIG. 9 is a perspective view of key features of a high-pressure fluid reservoir according to an embodiment of the present invention.
Fig. 10 is a cross-sectional view taken along the line aa in Fig. 9 and the line bb in Fig.
FIG. 11 is a perspective view of key features of a high-pressure fluid reservoir according to another embodiment shown in FIG. 9; FIG.
12 is a cross-sectional view of the tank body for explaining the pressure action inside the tank body.
13 is a view for explaining the initial stress state of the underground rock mass.
Figs. 14 and 15 are graphs showing the results of measuring the initial stresses of the rocks through hydraulic fracturing by selecting 710 test zones for 140 individual boreholes at a depth of 15 to 310 m in 45 regions of Korea.
16 is a cross-sectional view of a high-pressure fluid reservoir according to the present invention showing the interaction between air pressure and the initial stress of the rock mass.
17 and 18 are graphs showing the relationship between the maximum lateral pressure coefficient K _H and the average lateral pressure coefficient K _avg , which are the ratio of the horizontal stress to the vertical stress, FIG.

The present invention relates to a high pressure fluid reservoir and a CAES system using the same.

In the present invention, the term 'high-pressure fluid' refers to compressed air at a pressure of at least 50 bar for CAES operation. However, it does not exclude any kind of fluid that can be compressed by applying pressure such as natural gas, It is not limited to more than 50 bar, but extends to a concept that includes high pressure to such an extent that safety considerations are required even if the pressure is less than 50 bar. Accordingly, the high-pressure fluid reservoir according to the present invention can be used as a fluid reservoir for various purposes such as an air compression reservoir for CAES power generation, as well as a gas reservoir for storing energy fuel.

Hereinafter, a high-pressure fluid reservoir according to the present invention and a CAES system having the same will be described in detail with reference to the accompanying drawings. In the following description with reference to the drawings, the same or corresponding elements are denoted by the same reference numerals, and a duplicate description thereof will be omitted.

FIG. 1 is a cross-sectional view for explaining basic elements of a high-pressure fluid reservoir according to the present invention, and FIG. 2 is a view for explaining a tank main body and a reinforcement part in the high-pressure fluid reservoir shown in FIG.

1 and 2, a high-pressure fluid reservoir 100 according to an embodiment of the present invention includes a tank body 10, a stiffener 30, a back fill layer 50, and a plug 90.

The tank body 10 forms a closed internal space portion 14 to provide a space in which compressed air is stored. The tank body 10 is disposed in the vertical direction, preferably in the vertical direction, and buried in the caverns c formed on the rock g of the basement part. The role of the tank body 10 is to maintain the airtightness of the compressed air. Therefore, the tank body 10 is made of a sealing material such as steel, rubber, and plastic, which can prevent leakage. In this embodiment, the tank body 10 is made of steel having a thickness of 4 to 10 mm. Since the strength of the steel itself does not withstand the pressure of the compressed air, the thickness of the steel need not be set to the above range. Furthermore, the tank body can also be formed of a soft material such as rubber.

In this embodiment, the tank body 10 is made up of a plurality of segments, consisting of a lower segment 11, a plurality of torso segments 12, and an upper segment 13. The lower segment 11 forms a lower end of the tank body 10 and is formed in a bowl shape whose upper surface is opened. The trunk segment 12 forms a trunk portion of the tank body 10, and is formed in a ring shape in which both the upper surface and the lower surface are opened. The body segments 12 consist of a plurality of body segments 12, which are sequentially stacked on the lower segment 11. The upper segment 13 forms the upper end of the tank body 10 and is laminated onto the body segment 12. The upper segment 13 is in the form of an inverted lower segment 11, that is, a bowl in which the lower surface is open. When the lower segment 11, the plurality of torso segments 12 and the upper segments 13 are laminated and joined together using welding or the like, a sealed space portion 14 in which a high- .

On the other hand, backfill material is filled between the tank main body 10 and the inner wall of the cavan (c) to form the back fill layer 50. The back fill layer 50 acts to transfer the pressure of the high pressure gas to the rock mass g. In order to transmit the pressure, the space between the tank body 10 and the inner wall must be completely filled with the backfill material. If there is an empty space, the backfill layer 50 and the tank body 10 may be damaged because the pressure is not transferred to the rock mass and concentrated at that portion. Therefore, it is most important that the backfill layer 50 is completely filled with the backfill without any void. In this embodiment, the back fill layer 50 is formed to a thickness of about 30 to 100 cm. Concrete is widely used for backfill, but various kinds of grout materials such as cement milk and mortar can be used. That is, any hydraulic material that can be cured by reacting with water can be used as a backfill material. However, in selecting the backfill material, it is desirable to select a material that can be formed with a low porosity of the backfill layer after curing in consideration of stability and airtightness. Particularly, when the porosity is large, groundwater can easily flow into the tank body 10 from the rock mass, which is not preferable.

The stiffener 30 is embedded in the back fill layer 50. Backfill materials are mainly composed of cement. Cement is strong in compressive stress but very weak in tensile stress. Therefore, in order to reinforce the tensile force of the backsheet layer 50, it is preferable to contain reinforcing materials 30 such as reinforcing bars and wire meshes. The reinforcing bars 31 and 32 used in the present embodiment are arranged in a lattice shape in the horizontal and vertical directions and are arranged to enclose the tank body 10. [ The reinforcing material 30 is disposed in the longitudinal direction (the longitudinal direction of the storage tank) and in the transverse direction (the circumferential direction of the storage tank), respectively, to reinforce the tensile strength. However, the stiffener may be omitted depending on the condition of the rock and the pressure condition of the fluid stored in the tank body 10. [ Reference numerals 70, 71, and 72, which are not shown in FIG. 2, are connecting members for supporting the reinforcing member 30.

On the other hand, when there is a possibility of rockfall or ground collapse in the process of rock excavation, the inner wall of the rock mass g may form a supplementary layer 40 by spraying a quick-hard material such as shotcrete. A separation membrane 60 may be formed between the tank body 10 and the backsheet layer 50. The separation membrane 60 prevents the tank body 10 from being coupled to the backing layer 50 so as to attenuate the shearing force on the friction surface where the tank body 10 contacts the backing layer 50. It is not preferable that the tank body 10 and the backing layer 50 should be in close contact with each other without a space therebetween. That is, when pressure is applied to the tank main body 10 by the compressed air, a shearing force is generated at the contact surface between the tank main body 10 and the back fill layer 50 to cause physical damage to the tank main body 10. However, If the backing layer 10 and the backing layer 50 are not bonded to each other and are separated from each other, the pressure is dispersed and the shearing force can be attenuated. In this embodiment, the separation membrane 60 is formed by applying a fluid material such as bitumen or grease to the outer wall of the tank body 10 or by using a film or sheet of material not bonded to the cement, As shown in Fig.

A waterproof membrane 81 is formed between the separation membrane 60 and the backing layer 50 or on the inner surface of the tank body 10 to prevent corrosion of the tank body 10 due to the inflow of groundwater. The waterproof film 81 can be formed by applying a waterproofing agent or attaching a waterproof sheet. In order to prevent corrosion of the tank body 10, a corrosion inhibitor may be applied to at least one of the inner circumferential surface and the outer circumferential surface of the tank body 10 in addition to the waterproof film 81 to form the rust preventive film 82.

In addition, the temperature of the fluid stored in the tank body 10 is increased during the compression process. In order to prevent the temperature of the fluid from dropping due to heat exchange with the surroundings, at least one of the inner circumferential surface and the outer circumferential surface of the tank body 10 (83) can be formed. The heat insulating film 83 is also formed by attaching or applying a heat insulating material.

The supplementary layer 40, the separation membrane 60, the waterproof membrane 81, the rust preventive membrane 82, the heat insulation membrane 83 and the like are not essential and can be selectively applied according to all conditions.

A pedestal 20 is provided at the bottom of the cabin c to keep the tank body 10 away from the bottom surface of the cabin c. A plug 90 is provided at an upper portion of the tank main body 10 to close the upper side of the tank main body 10. A pipe (p) for air inflow and outflow is inserted into the tank main body (10), and this pipe (p) is connected to an air compression facility and a power generation facility provided on the ground.

On the other hand, a plug 90 is formed by closing the upper portion of the cov- er c with a filling material such as concrete poured therein. More specifically, the plug 90 includes a body 91 formed on the upper portion of the tank body 10, an annular reinforcing member 91 extending from the upper side of the body 91 along the inner wall surface of the covane c, (92). The body portion 91 and the reinforcing portion 92 are integrally formed by a filler such as concrete. The main reason for forming the annular reinforcing portion 92 in this embodiment is to secure safety against longitudinal stress in terms of stability of the fluid reservoir. That is, the reinforcing portion 92 is for suppressing the displacement in the longitudinal direction (height direction) of the fluid reservoir. The reinforcing portion 92 may also perform a secondary function of protecting the inner wall on the caban c. Particularly, if the shock layer is not formed by spraying a shock to the cavity of the cavan (c), the action of protecting the cavity of the reinforcing portion 92 is enhanced. The inner space defined by the reinforcing portion 92 may be filled with water. A reinforcing member 93 is embedded in the body portion 91 of the plug 90 to increase the tensile strength of the plug. The plug 90 may be formed separately from the back fill layer 50, but is preferably formed integrally from the back-filling layer. The pipe (p) connected to the tank body (10) is connected to the electricity generation facility and the compression facility of the land via the plug (90).

The basic structure of the high-pressure fluid reservoir 100 according to the present invention has been described with reference to FIGS. 1 and 2. In order to increase the stability of the high-pressure fluid reservoir, the following three structures I will explain.

The first structure is to increase the strength against the internal pressure of the high pressure gas, and the second structure is to increase the shear strength of the ground above the high pressure fluid reservoir. And the third structure is to improve the stability and economical efficiency of the fluid reservoir by changing the thickness of the backsheet layer 50.

First, the first structure will be described.

The first structure we developed is to increase the strength of the gas against internal pressure. 3 is a longitudinal sectional view showing a state in which a grouting solution injection tube is installed to reinforce the strength against the internal pressure of the gas, and Fig. 4 is a cross-sectional view taken along the line a-a in Fig.

3 and 4, in the high-pressure fluid reservoir 100 according to the present invention, the grout solution injection pipe 85 is brought into close contact with the inner wall of the caban c before filling the concrete to form the back fill layer 50, . A plurality of grouting solution injection pipes 85 are arranged along the circumferential direction of the cave (c) as shown in Fig. The grouting solution injection pipe 85 is mainly made of a steel material, and a plurality of discharge holes 86 are formed over the entire pipe, so that the grouting solution can be discharged to the outside.

The backing layer 50 is formed by filling and curing the concrete after the grouting solution injection pipe 85 is installed and then the grouting solution is sandwiched between the rock mass g and the backing layer 50 through the grouting solution injection pipe 85, . Since the back fill layer 50 is in close contact with the rock mass (g, inner wall of the cavern), the grouting liquid must be pumped to a high pressure in order to inject the grouting liquid therebetween. In addition, when injecting the grouting solution, the inside of the tank body 10 should be filled with air at a predetermined pressure or higher.

As described above, when the grouting solution is injected at a high pressure between the back ply layer 50 and the rock mass g, two effects occur. The first effect is incidental, so that if there is an empty space between the back ply layer 50 and the rock mass g in the back ply layer formation process, this space can be completely filled. The second effect is important. When the grouting solution is injected at a high pressure, the rock mass g and the back fill layer 50 are respectively subjected to compressive stress in the radial direction of the cavern c, and the grouting solution is cured in this state, When the grouting layer 89 is formed thin, the back fill layer 50 is kept in a compressed state. That is, since the back ply layer 50 is pre-stressed, the back ply layer 50 has an increased compressive strength and an effect of applying a reaction force P _{r in a} direction opposite to the inner pressure P _{i of the} gas Lt; / RTI >

Although only the grouting solution injection tube 85 is shown in FIG. 5 for convenience of explanation, it is preferable that discharge tubes (not shown) composed of a multi-tube tube are arranged alternately so that the grouting solution can be discharged. The grouting solution injected between the rock g and the back fill layer 50 is intended to use cement milk mixed with cement and admixture. However, various materials having a certain level of compressive strength can be used.

Although a plurality of grouting solution injection pipes 85 are vertically disposed in the drawing, the grouting solution injection pipes 85 may be spirally arranged along the inner surface of the rock mass g .

The second structure adopted in the present invention is to improve the shear strength of the upper ground of the high-pressure fluid storage tank. Will be described with reference to Figs. 6 to 8. Fig. FIG. 6 is a view for explaining the shear force acting on the upper portion of the high-pressure fluid reservoir, FIG. 7 is a vertical cross-sectional view of the high-pressure fluid reservoir, and FIG. 8 is a cross-sectional view of the upper portion of the plug. Referring to the drawing, the gas pressure inside the tank body 10 acts upward and is applied to the ground above the plug 90. A shearing force T for causing the region X directly acting on the pressure and the peripheral region Y thereof to slide along the boundary line B (shear fracture surface) acts on the ground above the plug 90 . If the shear strength of the rock is less than the shear force, shear failure may occur along the shear failure plane (B). 3, the shear failure surface B may be formed in a direction perpendicular to the outer periphery of the plug 90 when it is conservatively determined.

When the shear failure occurs, the pressure of the upward gas acts only by the weight of the upper part of the plug. Therefore, in order to strengthen the shear strength of the rock, the present invention has developed a structure in which the X region and the Y region are integrated with each other in anticipation of the shear failure plane.

That is, as shown in FIG. 7, which is a vertical cross-sectional view of the high-pressure fluid storage tank 100, an intensifying stiffener 80 such as a rock bolt or an anchor is installed from the inner circumferential surface of the cabin c toward the ground. Also, as shown in Fig. 8 (cross-sectional view), a plurality of strength reinforcement members 80 are provided along the circumferential direction of the cov- ening c. The strength stiffener is to be inserted deeper than the expected shear failure surface (B) from the inner circumferential surface of the cabin, that is, both the X and Y regions are inserted. Therefore, if the shear failure surface is sloped, the strength stiffener to be inserted above should be longer than the bottom.

After inserting the strength reinforcement 80, a tensile force is applied by pulling the strength reinforcement to apply a compressive force in a direction to bring the rock in the X region and the rock in the Y region in close contact with each other. The X region and the Y region are integrated by the strength reinforcement 80. [ Mechanically, it is a result of improving the shear strength of the rock by applying a compressive force corresponding to the shear force. In order to maximize the compressive force, it is preferable to insert the strength reinforcement 80 in a direction perpendicular to the shear force, that is, in a direction perpendicular to the shear failure plane.

As described above, when the strength reinforcement 80 is provided on the rock on the upper portion of the plug 90, the shear strength of the rock is increased, and the risk of shear failure due to the pressure of the high-pressure gas can be reduced.

The third structure adopted in the present invention will be described with reference to FIGS. 9 to 11, with reference to the thickness variation of the back fill layer 50. FIG.

1 and 2 show that the thickness of the back fill layer is constant in order to explain the basic structure and action of the high pressure fluid reservoir. However, a key feature of the present invention is that the thickness of the back fill layer gradually increases .

FIG. 9 and FIG. 11 illustrate key features of the high-pressure fluid reservoir 100 according to the present invention. In FIGS. 9 and 11, two structures for increasing the thickness of the back fill layer in the present invention as compared with that in the upper and lower portions are shown. In other words, the structure shown in FIG. 9 has a structure in which the upper and lower portions of the cave (c) are vertically excavated to have a constant diameter, but the tank body 10 is inclined downward. In the second structure shown in FIG. 11, the tank body 10 is formed with a constant upper and lower diameter, but the cavan c is formed narrower toward the lower side. In both structures, the thickness of the backsheet layer 50 is thicker than that of the upper portion.

9, the tank main body 10 employed in the present invention has a substantially dome shape in its top and bottom portions, and a substantially cylindrical shape in its body portion. The cylindrical portion has the same area But has a shape in which the cross-sectional area gradually increases from the upper portion to the lower portion. Assuming that the tank main body 10 has a circular section, the diameter of the lower portion of the tank main body 10 is formed larger than the diameter of the upper portion, Is formed with a slope of? With respect to the vertical direction. Since the tank main body 10 is formed so as to be wider as it goes down, the thickness of the back fill layer 50 is inverted by the slope of? And gradually becomes thicker than the lower portion.

FIG. 10 is a cross-sectional view taken along the line a-a in FIG. 9 and the line b-b in cross section taken along the line b-b in FIG. 9. The difference in diameter between the tank body 10 and the back fill layer 50 can be observed.

On the other hand, referring to FIG. 11, contrary to the case of FIG. 9, the tank main body 10 is made constant without a difference in diameter between the upper and lower portions, and the cave c is excavated in a funnel shape. Therefore, when the tank body 10 is buried in the cavern c and the backfill material is filled between the tank body 10 and the inner wall of the cavern c, the lower portion of the cavern c is thicker . As in the case of FIG. 9, the thickness variation of the back fill layer 50 can have a constant rate of change with a slope of?.

As described above, the reason why the thickness of the back fill layer 50 is made thicker than that of the lower back layer 50 is that the two purposes of enhancing the safety of the high-pressure fluid reservoir and securing the volume of the internal space of the tank, This is because we have to. Will be described in detail with reference to the drawings.

12 is a cross-sectional view of the tank main body for explaining the pressure action of the air contained in the tank main body. 12, the air pressure in the cylindrical tank body 10 can be divided into a compressive force acting in the radial direction of the tank body and a tensile force acting in the tangential direction on the cylindrical outer circumferential surface. The compressive force gradually increases along the radial direction from the point where the pressure is applied (the outer peripheral surface of the tank body), and the tensile force tends to be the largest point at which the pressure is applied and gradually decreases along the radial direction. As in the present invention, the reservoir buried in the underground portion has a very high strength of surrounding rocks, and the concrete forming the backsheet layer 50 has a very high compressive strength, so that the risk of compression force of the high- . An important issue is the tensile strength of the backsheet layer 50. As described above, since the concrete has a large compressive strength, but tensile strength is relatively weak, cracks can be formed in the back fill layer 50 by the tensile force acting on the back layer 50. As shown in Fig. 12, the formation of a slight crack f1 along the thickness direction of the back fill layer 50 (the radial direction of the tank body) does not affect the stability, 50, the concrete part D is completely removed from the back fill layer 50, which is dangerous. If a part of the back ply layer 50 is dropped, the pressure of the gas can not be transmitted to the rock mass g at that portion, so that the back ply layer and the tank main body can be broken in a chain. Accordingly, the most important factor in designing the high-pressure fluid reservoir according to the present invention is to set the thickness of the backing layer. The thickness of the backing layer should be made sufficiently thick according to the magnitude of the tensile force acting on the backing layer so that the crack does not penetrate through the backing layer thickness.

Up to now, only the inner pressure conditions acting from the gas inside the tank body have been described. The second consideration in designing the thickness of the back fill layer is the outer pressure condition. If the high-pressure fluid reservoir is installed on the ground, all the external pressure conditions are constant at the atmospheric pressure. However, if the high pressure fluid reservoir is installed on the ground, as in the present invention, the external pressure condition varies depending on the depth. Therefore, it is necessary to consider the interaction between the external pressure and the internal pressure.

13 is a view for explaining the initial stress state of the underground rock mass. 13, the initial stress of the underground rock is calculated from the normal stress (S _V ) in the vertical direction, the smallest minimum horizontal stress (S _h ) in the horizontal direction acting on the four sides, and the minimum horizontal stress S _h ) and the maximum horizontal stress (S _H ) acting at a 90 ° angle.

In the graphs of FIGS. 14 and 15, 710 test sections were selected from 140 individual boreholes at a depth of 15 to 310 m in 45 regions of Korea, and the initial stresses of the rocks were measured by hydraulic fracturing.

14 and 15, the maximum horizontal stress (S _H ) and the minimum horizontal stress (S _h ) are 0.90 to 21.13 MPa and 0.65 to 11.51 MPa, respectively. As the depth increases, the horizontal stress of the rock increases. The vertical stress corresponds to the weight at the upper part of the measuring point, so the deeper the depth, the greater the stress.

A subject of interest in the present invention is a change in horizontal stress. 16 is a cross-sectional view of a high-pressure fluid reservoir according to the present invention. Referring to FIG. 16, the maximum horizontal stress (S _H ) and the minimum horizontal stress (S _h ) are shown in the rock mass. Internal pressure (Pi) of the gas is constant, because it is all the same tension (σ _θ) to be applied to each point of the back pilcheung 50. Neglecting the external stress conditions. However, the initial stress in rock mass against tensile stress is different between maximum horizontal stress (S _H ) and minimum horizontal stress (S _h ). Back pilcheung applied to the top of cracks in the 50 back-pilcheung tension (σ _θ) is the resultant force is greater than the back-pilcheung tensile strength and physical properties of the external stress. That is, if cracks occur in the backsheet layer 50, it will be the point A where the minimum horizontal stress acts, not the point B in the drawing which is influenced by the maximum horizontal stress. Since the tensile strength of the back fill layer is the same at all points, the smallest area (A point) of external stress is broken first. More specifically, working in tension (σ _θ) to be cross-going concrete, based on the line indicated by A, and, in response to a pulling force to the rock stress acts to the line indicated by A does not happen, The stress that prevents A point from spreading is the minimum horizontal stress (S _h ) with the smallest force in the horizontal direction. Conversely, the stress in the rock that causes the line marked B to not open is the maximum horizontal stress (S _H ). Therefore, breakage of backfill layer can be predicted at point A where the minimum horizontal stress (S _h ) affects.

Therefore, when designing the backfill layer 50 concrete thickness, the minimum horizontal stress along the depth of the underground and the magnitude of the tensile force of the high-pressure gas should be considered together. And, as explained earlier, the horizontal stress increases with deeper depth. Therefore, the thickness of the concrete should be thicker as it is closer to the surface, and it may become thinner as the depth is deeper.

However, in the case where the tank body is buried in the vertical direction by excavating the ground in a vertical direction, it is general to design the structure in which the cave is drilled to the same diameter from the upper part to the lower part and the tank body is formed into a cylindrical shape having the same diameter. And the thickness of the concrete is designed based on the region where the horizontal stress is weakest, that is, near the surface. That is, considering the stability, the thickness of the backsheet layer is set based on the point closest to the surface, and the thickness of the backsheet layer is uniformly formed to the bottom.

However, in the present invention, unlike the conventional design practice, a method of improving economical efficiency by changing the thickness of the back fill layer and increasing the storage volume of the gas with stability is selected. That is, as the depth increases, the horizontal stress increases. Therefore, even if the thickness of the back layer is reduced, the stability can be ensured. Therefore, by increasing the thickness of the back layer, the storage volume of the gas is increased. It is possible to increase the volume at which the gas can be stored in the entire space for forming the high-pressure fluid reservoir as much as possible, thereby increasing the efficiency of space use and improving the economical efficiency in terms of cost.

It is preferable that the thickness of the back fill layer 50 is changed at a constant slope. For example, the rate of change of the thickness of the backsheet layer can be determined based on the rate of change according to the depth of the minimum horizontal stress.

On the other hand, the standard of the thickness variation of the back fill layer may be based on the lateral pressure coefficient K.

The lateral pressure coefficient (K) is the ratio of the horizontal stress to the normal stress. For example, define the maximum lateral pressure coefficient K _H = S _H / S _V for the maximum horizontal stress and the minimum lateral pressure coefficient K _h = S _h / S _V for the minimum horizontal stress. Alternatively, the average lateral pressure coefficient K _avg = (K _H + K _h ) / 2 may be expressed by combining K _H and K _h . 17 and 18 are graphs showing the relationship between the maximum lateral pressure (K _H ) and the average lateral pressure (K), which are the ratio of the horizontal stress to the vertical stress, _avg ) distribution. The mean lateral pressure coefficient (K _avg ) ranges from about 0.52 to 4.91 and the maximum lateral pressure coefficient (K _H ) ranges from 0.83 to 5.63. As the depth increases, the rate of change of the vertical stress and the horizontal stress becomes almost constant, and the value of the lateral pressure coefficient converges. However, there are areas where an excessive horizontal stress field is formed in which the horizontal stress is relatively large with a lateral pressure coefficient of 2.5 or more even at a depth of 100 m from the surface or a depth of 200 m depending on the region. In another embodiment of the present invention, the rate of change of thickness of the back fill layer can be set in conjunction with the rate of change of the lateral pressure coefficient according to the depth.

As described above, in the present invention, the thickness of the backsheet layer is reduced as the depth of the backsheet is deeper, thereby ensuring stability and maximizing the volume at which the gas can be stored, thereby improving stability and economy.

In addition, according to the present invention, there is an advantage that the shear strength of the rock is improved by providing an intensifying member such as an anchor or a rock bolt to the rock over the plug.

Further, in the present invention, grouting solution is injected between the back fill layer and the rock at a high pressure to give a prestress to the back layer, thereby further improving the strength of the back layer.

Meanwhile, the power generation system according to the present invention is connected to the pipe (p) of the high-pressure fluid storage tank 100 and the ground power generation system. The CAES power generation system may be a turbine power generation system or a cylinder-motor power generation system. In the turbine power generation system, a plurality of compressors, a heat exchanger, an inflator and a turbine are provided to compress air in multiple stages in a compressor, store it in a high-pressure fluid storage tank 100, and supply compressed air to the turbine . In the cylinder-motor system, an engine shaft connected to a motor is driven to drive a plurality of cylinders to compress air and store the compressed air in a high-pressure fluid storage tank 100. The compressed air is then supplied to the cylinder again, to be. In addition, the high-pressure fluid storage tank may be used to improve power generation efficiency by being connected to a combined thermal power generation system that combines a turbine system and thermal power. In the present invention, as an energy source for compressing air, it is preferable to use electricity generated from a renewable energy source such as wind power.

As described above, according to the present invention, it is possible to increase the utilization of CAES by providing a practical technique for installing a high-pressure fluid reservoir having a diameter of several meters or more and a height of several tens of meters or more in the deep part of the underground, . Furthermore, the present invention is expected to promote the commercialization of CAES as a part of future energy policy by suggesting a method for constructing a high-pressure fluid reservoir economically.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation and that those skilled in the art will recognize that various modifications and equivalent arrangements may be made therein. It will be possible. Accordingly, the true scope of protection of the present invention should be determined only by the appended claims.

100 ... high pressure fluid reservoir, 10 ... tank body, 11 ... lower segment
12 ... trunk segment, 13 ... upper segment, 14 ... space
20 ... pedestal, 30 ... stiffener, 31,32 ... reinforced
40 ... Complementary layer, 50 ... Backfill layer, 60 ... Membrane
70, 71, 72 ... connecting member, 80 ... strength stiffener
81 ... waterproof film, 82 ... rustproof film, 83 ... insulating film,
85 ... injection tube, 86 ... exhaust hole, 89 ... grouting layer
90 ... plug, 91 ... body portion, 92 ... reinforced portion
g ... ground, c ... cavern, p ... pipe, f1, f2 ... crack

Claims

A tank main body formed of a hermetically sealed material and having an accommodating portion in which a high-pressure fluid is stored, the tank main body being embedded in a cabin formed by digging the ground downward to store high-pressure fluid;
A back fill layer formed by curing a back fill material filled between the tank main body and the inner wall of the cabin;
A plug for closing the covane; And
And a grouting layer interposed between the inner wall of the rock and the back fill layer by applying pressure to the back fill layer so as to apply a compressive force to the back fill layer to harden the grouting liquid injected between the inner wall and the back fill layer, Pressure fluid reservoir.

The method according to claim 1,
Further comprising a grouting solution injection pipe interposed between the inner wall of the rock bed and the back fill layer so as to inject the grouting solution and has a plurality of discharge holes formed therein.

3. The method of claim 2,
Further comprising a discharge pipe installed between the inner wall of the rock plate and the back fill layer so that the grouting liquid discharged from the grouting liquid injection pipe can be discharged to the outside of the cavern.

3. The method of claim 2,
And a plurality of grouting solution injection pipes are disposed along the inner wall of the cabin.

3. The method of claim 2,
Wherein the grouting solution injection tube is formed in a spiral shape and is installed along the inner wall surface of the cabin.

The method according to claim 1,
Further comprising a reinforcing portion formed in an annular shape along the inner wall surface of the cabin on the upper side of the plug and coupled to the inner wall surface of the cabin.

The method according to claim 6,
Wherein the reinforcing portion and the plug are integrally formed by filling the filler together.

The method according to claim 1,
Wherein the tank body is formed by stacking a plurality of segments.

9. The method of claim 8,
Wherein the segment forming the tank body comprises:
A lower segment having an upper surface opened to form a lower end portion of the tank main body, a ring-shaped body segment sequentially stacked on the lower segment, and an upper end portion of the tank main body stacked on the body segment, And an upper segment that is open.

A CAES system comprising a power generation system in which the high pressure fluid reservoir is compressed at high pressure and the compressed air is used in the high pressure fluid reservoir,
Wherein the high-pressure fluid reservoir is the high-pressure fluid reservoir according to any one of claims 1 to 9.

11. The method of claim 10,
And a new and renewable energy is used as an energy source for compressing air in the high-pressure fluid reservoir.