The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Dohyun Park - One of the best experts on this subject based on the ideXlab platform.
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Analysis on heat transfer and heat loss characteristics of Rock Cavern thermal energy storage
Engineering Geology, 2014Co-Authors: Jung-wook Park, Byung Hee Choi, Dohyun Park, Dong-woo Ryu, Eui-seob ParkAbstract:Abstract The present study is aimed at demonstrating the feasibility of the Rock Cavern, compared with the above-ground tank, for the storage of large-scale high-temperature thermal energy by quantitatively evaluating the heat transfer inside the storage tank and the heat loss characteristics of the surrounding environment. As a conceptual model, we consider a thermal energy storage (TES) system coupled with an adiabatic compressed air energy storage plant (A-CAES), which utilizes loosely packed bed of Rocks as heat storage medium and stores heat of up to 685 °C. The specifications of the TES model, such as the mass flow rate of the heat transfer material and the storage volume, were determined through the analysis of the heat transfer in the packed bed, using a quasi-one-dimensional two-phase numerical model developed in this study. In this procedure, the inlet and outlet fluid temperatures and the thermal energy rates to be stored or extracted were examined over 200 consecutive daily cycles to ensure the TES met the requirements for the power generation of the A-CAES plant. Then, with the determined specifications of the TES, a comparative study on the heat loss characteristics of the Rock Cavern-type TES and above-ground-type TES systems was performed by simulating the operations on a daily basis for a period of 10 years using a three-dimensional numerical model. The comparison results indicated that the amount of cumulative heat loss in the Rock Cavern-type TES system over the operation period was far smaller than that in the above-ground-type TES system because of the surrounding Rock heating and the consequent reduction in the thermal gradient between the surrounding Rock and the storage medium. In terms of long-term operation, the rate of heat loss from the Rock Cavern-type TES system exhibited less-sensitive and less-dependent behaviors with respect to the insulator performance than that of the above-ground-type TES system.
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Heat transfer and mechanical stability analyses to determine the aspect ratio of Rock Caverns for thermal energy storage
Solar Energy, 2014Co-Authors: Dohyun Park, Eui-seob Park, Choon SunwooAbstract:Abstract Thermal stratification in solar thermal storages is used to improve the efficiency of solar heating systems because a high degree of thermal stratification in the storages increases the thermal performance of the systems. It has been demonstrated that better thermal stratification can be achieved by increasing the aspect ratio (height-to-width ratio) of the heat storage containers. However, a high-aspect-ratio design may lead to mechanical (structural) instability of the storage space because of its tall, narrow shape. Therefore, heat storage containers should be designed to provide good thermal performance, while considering the mechanical stability of the storage space. This is an important issue in the design of thermal energy storage (TES) spaces, particularly the underground Rock Caverns used for TES, because the stability of Rock Caverns depends largely on geomechanical factors, such as Rock properties and in-situ stresses. To address this issue, we present a numerical approach for determining the aspect ratio of underground TES Caverns that considers both thermal performance and mechanical stability. This approach is based on a thermal performance evaluation in terms of thermal stratification using heat transfer analysis and a mechanical stability assessment that calculates the factor of safety using finite element analysis combined with a shear strength reduction (SSR) method. The applicability of our approach is demonstrated in the preliminary design of a silo-shaped Rock Cavern used to store hot water for district heating. The results of the numerical analyses under various design conditions are presented and discussed in detail, and we propose an aspect ratio for the Rock Cavern.
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Numerical Analysis-Based Shape Design of Underground Rock Caverns for Thermal Energy Storage
Rock Mechanics and Rock Engineering, 2013Co-Authors: Dohyun Park, Dong-woo Ryu, Byung Hee ChoiAbstract:The efficiency of thermal energy storage (TES) using water can be improved by storing the water in a thermally stratified form. Previous studies on the thermal performance of heat storage tanks, undertaken by Lavan and Thompson (1977), Cotter and Charles (1993), Matrawy et al. (1996), Ismail et al. (1997), Eames and Norton (1998), and Bouhdjar and Harhad (2002), have demonstrated that better thermal stratification can be obtained by increasing the aspect ratio (height-to-width ratio) of heat storage containers. However, a high-aspect-ratio storage design may lead to structural instability of the storage space because of its narrow, tall shape. Therefore, heat storage spaces should be designed to provide good thermal performance but should also consider the stability of the storage. This is an important issue in the design of heat storage, particularly for underground TES using Rock Caverns, because the stability of Rock Caverns is greatly influenced by geotechnical factors such as in situ stresses and Rock properties. Therefore, a quantitative stability assessment is required to determine the shape of Rock Caverns used for TES, and to thus ensure the structural stability of the Caverns. This technical note describes a numerical approach for the shape design of a Rock Cavern in which to store hot water for district heating. For reliable evaluation of the stability of the Cavern, the approach employs probabilistic methods that can take into account the variability of input parameters using probability distributions. The arch height of the Cavern roof is determined through a comparison of excavation-induced ground displacements between Caverns with different arch heights.
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A Comparative Study on Heat Loss in Rock Cavern Type and Above-Ground Type Thermal Energy Storages
Journal of Korean Society For Rock Mechanics, 2013Co-Authors: Jung-wook Park, Dohyun Park, Byung Hee Choi, Dong-woo Ryu, Joong-ho Synn, Choon SunwooAbstract:A large-scale high-temperature thermal energy storage(TES) was numerically modeled and the heat loss through storage tank walls was analyzed using a commercial code, FLAC3D. The operations of Rock Cavern type and above-ground type thermal energy storages with identical operating condition were simulated for a period of five consecutive years, in which it was assumed that the dominant heat transfer mechanism would be conduction in massive Rock for the former and convection in the atmosphere for the latter. The variation of storage temperature resulting from periodic charging and discharging of thermal energy was considered in each simulation, and the effect of insulation thickness on the characteristics of heat loss was also examined. A comparison of the simulation results of different storage models presented that the heat loss rate of above-ground type TES was maintained constant over the operation period, while that of Rock Cavern type TES decreased rapidly in the early operation stage and tended to converge towards a certain value. The decrease in heat loss rate of Rock Cavern type TES can be attributed to the reduction in heat flux through storage tank walls followed by increase in surrounding Rock mass temperature. The amount of cumulative heat loss from Rock Cavern type TES over a period of five-year operation was 72.7% of that from above-ground type TES. The heat loss rate of Rock Cavern type obtained in long-period operation showed less sensitive variations to insulation thickness than that of above-ground type TES.
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Probability-based structural design of lined Rock Caverns to resist high internal gas pressure
Engineering Geology, 2013Co-Authors: Dohyun Park, Byung Hee Choi, Hyung-mok Kim, Dong-woo Ryu, Kong-chang HanAbstract:Abstract This paper describes a probability-based structural design approach to underground, lined Rock Caverns for the bulk storage of pressurized gas, such as compressed air, compressed natural gas, or compressed gaseous hydrogen. Our design approach is based on a combination of a point estimate method and a deterministic numerical analysis code. In the present study, we demonstrate the validity of this numerical approach in the design of underground structures by comparing it with a theoretical solution for a lined-tunnel problem. Our design approach is then applied to the preliminary structural design of a lined Rock Cavern for storing compressed natural gas at a high pressure of 15 MPa, where structural support for ensuring gas-tightness and the Cavern's mechanical stability is supplied by both steel and concrete liners. In this application, a probability-based design chart for determining the strength and thickness of the steel liner is presented, and the structural performance of the concrete liner is evaluated in a probabilistic manner.
Yu Zhou - One of the best experts on this subject based on the ideXlab platform.
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Long-term stability of a lined Rock Cavern for compressed air energy storage: thermo-mechanical damage modeling
European Journal of Environmental and Civil Engineering, 2018Co-Authors: Shuwei Zhou, Caichu Xia, Yu ZhouAbstract:The long-term stability of a lined Rock Cavern (LRC) for underground compressed air energy storage is investigated using a thermo-mechanical (TM) damage model. The numerical model is implemented in...
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Numerical simulation for the coupled thermo-mechanical performance of a lined Rock Cavern for underground compressed air energy storage
Journal of Geophysics and Engineering, 2017Co-Authors: Shuwei Zhou, Caichu Xia, Hai-bin Zhao, Song-hua Mei, Yu ZhouAbstract:Compressed air energy storage (CAES) is a technology that uses compressed air to store surplus electricity generated from low power consumption time for use at peak times. This paper presents a thermo-mechanical modeling for the thermodynamic and mechanical responses of a lined Rock Cavern used for CAES. The simulation was accomplished in COMSOL Multiphysics and comparisons of the numerical simulation and some analytical solutions validated the thermo-mechanical modeling. Air pressure and temperatures in the sealing layer and concrete lining exhibited a similar trend of 'up–down–down–up' in one cycle. Significant temperature fluctuation occurred only in the concrete lining and sealing layer, and no strong fluctuation was observed in the host Rock. In the case of steel sealing, principal stresses in the sealing layer were larger than those in the concrete and host Rock. The maximum compressive stresses of the three layers and the displacement on the Cavern surface increased with the increase of cycle number. However, the maximum tensile stresses exhibited the opposite trend. Polymer sealing achieved a relatively larger air temperature and pressure compared with steel and air-tight concrete sealing. For concrete layer thicknesses of 0 and 0.1 m and an initial air pressure of 4.5 MPa, the maximum Rock temperature could reach 135 °C and 123 °C respectively in a 30 day simulation.
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an analytical solution for mechanical responses induced by temperature and air pressure in a lined Rock Cavern for underground compressed air energy storage
Rock Mechanics and Rock Engineering, 2015Co-Authors: Shuwei Zhou, Caichu Xia, Pingyang Zhang, Yu ZhouAbstract:Mechanical responses induced by temperature and air pressure significantly affect the stability and durability of underground compressed air energy storage (CAES) in a lined Rock Cavern. An analytical solution for evaluating such responses is, thus, proposed in this paper. The lined Cavern of interest consists of three layers, namely, a sealing layer, a concrete lining and the host Rock. Governing equations for Cavern temperature and air pressure, which involve heat transfer between the air and surrounding layers, are established first. Then, Laplace transform and superposition principle are applied to obtain the temperature around the lined Cavern and the air pressure during the operational period. Afterwards, a thermo-elastic axisymmetrical model is used to analytically determine the stress and displacement variations induced by temperature and air pressure. The developments of temperature, displacement and stress during a typical operational cycle are discussed on the basis of the proposed approach. The approach is subsequently verified with a coupled compressed air and thermo-mechanical numerical simulation and by a previous study on temperature. Finally, the influence of temperature on total stress and displacement and the impact of the heat transfer coefficient are discussed. This paper shows that the temperature sharply fluctuates only on the sealing layer and the concrete lining. The resulting tensile hoop stresses on the sealing layer and concrete lining are considerably large in comparison with the initial air pressure. Moreover, temperature has a non-negligible effect on the lined Cavern for underground compressed air storage. Meanwhile, temperature has a greater effect on hoop and longitudinal stress than on radial stress and displacement. In addition, the heat transfer coefficient affects the Cavern stress to a higher degree than the displacement.
Eui-seob Park - One of the best experts on this subject based on the ideXlab platform.
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coupled thermal hydrological mechanical behavior of Rock mass surrounding a high temperature thermal energy storage Cavern at shallow depth
International Journal of Rock Mechanics and Mining Sciences, 2016Co-Authors: Jung-wook Park, Eui-seob Park, Dong-woo Ryu, Jonny Rutqvist, Joong-ho SynnAbstract:Abstract We numerically model the thermal-hydrological-mechanical (THM) processes within the Rock mass surrounding a Cavern used for thermal energy storage (TES). We consider a cylindrical Rock Cavern with a height of 50 m and a radius of 10 m storing thermal energy of 350 °C as a conceptual TES model, and simulate its operation for thirty years. At first, the insulator performance are not considered for the purpose of investigating the possible coupled THM behavior of the surrounding Rock mass; then, the effects of an insulator are examined for different insulator thicknesses. The key concerns are hydro-thermal multiphase flow and heat transport in the Rock mass around the thermal storage Cavern, the effect of evaporation of Rock mass, thermal impact on near the ground surface and the mechanical behavior of the surrounding Rock mass. It is shown that the Rock temperature around the Cavern rapidly increases in the early stage and, consequently, evaporation of groundwater occurs, raising the fluid pressure. However, evaporation and multiphase flow does not have a significant effect on the heat transfer and mechanical behavior in spite of the high-temperature (350 °C) heat source. The simulations showed that large-scale heat flow around a Cavern is expected to be conduction-dominated for a reasonable value of Rock mass permeability. Thermal expansion as a result of the heating of the Rock mass from the storage Cavern leads to a ground surface uplift on the order of a few centimeters, and to the development of tensile stress above the storage Cavern, increasing the potentials for shear and tensile failures after a few years of the operation. Finally, the analysis shows that high tangential stress in proximity of the storage Cavern can some shear failure and local damage, although large Rock wall failure could likely be controlled with appropriate insulators and reinforcement.
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Analysis on heat transfer and heat loss characteristics of Rock Cavern thermal energy storage
Engineering Geology, 2014Co-Authors: Jung-wook Park, Byung Hee Choi, Dohyun Park, Dong-woo Ryu, Eui-seob ParkAbstract:Abstract The present study is aimed at demonstrating the feasibility of the Rock Cavern, compared with the above-ground tank, for the storage of large-scale high-temperature thermal energy by quantitatively evaluating the heat transfer inside the storage tank and the heat loss characteristics of the surrounding environment. As a conceptual model, we consider a thermal energy storage (TES) system coupled with an adiabatic compressed air energy storage plant (A-CAES), which utilizes loosely packed bed of Rocks as heat storage medium and stores heat of up to 685 °C. The specifications of the TES model, such as the mass flow rate of the heat transfer material and the storage volume, were determined through the analysis of the heat transfer in the packed bed, using a quasi-one-dimensional two-phase numerical model developed in this study. In this procedure, the inlet and outlet fluid temperatures and the thermal energy rates to be stored or extracted were examined over 200 consecutive daily cycles to ensure the TES met the requirements for the power generation of the A-CAES plant. Then, with the determined specifications of the TES, a comparative study on the heat loss characteristics of the Rock Cavern-type TES and above-ground-type TES systems was performed by simulating the operations on a daily basis for a period of 10 years using a three-dimensional numerical model. The comparison results indicated that the amount of cumulative heat loss in the Rock Cavern-type TES system over the operation period was far smaller than that in the above-ground-type TES system because of the surrounding Rock heating and the consequent reduction in the thermal gradient between the surrounding Rock and the storage medium. In terms of long-term operation, the rate of heat loss from the Rock Cavern-type TES system exhibited less-sensitive and less-dependent behaviors with respect to the insulator performance than that of the above-ground-type TES system.
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Heat transfer and mechanical stability analyses to determine the aspect ratio of Rock Caverns for thermal energy storage
Solar Energy, 2014Co-Authors: Dohyun Park, Eui-seob Park, Choon SunwooAbstract:Abstract Thermal stratification in solar thermal storages is used to improve the efficiency of solar heating systems because a high degree of thermal stratification in the storages increases the thermal performance of the systems. It has been demonstrated that better thermal stratification can be achieved by increasing the aspect ratio (height-to-width ratio) of the heat storage containers. However, a high-aspect-ratio design may lead to mechanical (structural) instability of the storage space because of its tall, narrow shape. Therefore, heat storage containers should be designed to provide good thermal performance, while considering the mechanical stability of the storage space. This is an important issue in the design of thermal energy storage (TES) spaces, particularly the underground Rock Caverns used for TES, because the stability of Rock Caverns depends largely on geomechanical factors, such as Rock properties and in-situ stresses. To address this issue, we present a numerical approach for determining the aspect ratio of underground TES Caverns that considers both thermal performance and mechanical stability. This approach is based on a thermal performance evaluation in terms of thermal stratification using heat transfer analysis and a mechanical stability assessment that calculates the factor of safety using finite element analysis combined with a shear strength reduction (SSR) method. The applicability of our approach is demonstrated in the preliminary design of a silo-shaped Rock Cavern used to store hot water for district heating. The results of the numerical analyses under various design conditions are presented and discussed in detail, and we propose an aspect ratio for the Rock Cavern.
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coupled hydro thermal modeling of ice ring formation around a pilot lng Cavern in Rock
Engineering Geology, 2011Co-Authors: Yong Bok Jung, Eui-seob Park, So-keul Chung, Hoyeoung KimAbstract:Abstract A new method of storing LNG (Liquefied Natural Gas) in a lined, hard Rock Cavern has been developed and verified by the construction and operation of a pilot plant in Korea. Creation of an ice ring is one of the core techniques in LNG storage in a lined Rock Cavern. The ice ring serves not only as a primary barrier against the intrusion of groundwater into an LNG Cavern, but also as a secondary protection in case of leakage of LNG. Dry conditions within an ice ring protect a containment system against cracking due to the freezing of groundwater. Therefore, it is crucial to estimate and control the thickness and location of the ice ring when designing and operating an underground LNG storage Cavern. In order to find suitable numerical scheme that simulates field results, the behavior of the ice ring around the pilot LNG Cavern is investigated by hydro-thermal-coupled analyses. Through coupled analyses composed of three cases (CASE_1: constant thermal properties, CASE_2: temperature-dependent thermal properties, and CASE_3: phase change consideration in addition to CASE_2), the position and thickness of the ice ring, the temperature distributions and the groundwater level around the Cavern are estimated and compared with measured data obtained from the pilot LNG Cavern. The results show that the temperature distribution and groundwater level around the LNG Cavern can be estimated reliably within an error of less than 4 °C and 1.0 m, respectively. The accuracy of numerical modeling is increased when the temperature-dependent properties are taken into account. The effect of phase change during freezing and thawing of groundwater is relatively small due to the dryness inside the ice ring and low porosity of the Rock mass. These results imply that the adopted numerical method can be applied to full-scale underground LNG Caverns for the control of the ice ring.
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Pilot study on the underground lined Rock Cavern for LNG storage
Engineering Geology, 2010Co-Authors: Eui-seob Park, Yong Bok Jung, Dae Hyuk Lee, Won-kyong Song, So-keul ChungAbstract:This paper reports the background information and the initial results obtained from the pilot underground LNG (liquefied natural gas) storage Cavern in Korea, where all natural gas is stored in the condition of liquid phase. Many attempts have been made in the past to store LNG underground in unlined containment, though without success. A new concept for storing LNG in a lined Rock Cavern has been developed to provide a safe and cost-effective solution. It consists of protecting the host Rock against the extremely low temperature and providing a liquid and gas tight liner. One of the most significant problems related to underground storage of cryogenic material is the need to prevent the leakage of liquid and gas from the containment system to the Rock mass caused by tensile failures due to shrinkage of the Rock mass around the Caverns. In order to verify the technical feasibility of this storage concept, a pilot plant was constructed for storing Liquefied Nitrogen and has been in operation since January 2004, though has now been decommissioned. The overall monitored results from the pilot operations confirmed that the construction and operation of underground LNG storage in lined Rock Caverns is technically feasible for a Rock engineering point of view. The results of this study may promote the first ever real scale underground LNG storage system in a Rock Cavern in the world. © 2010.
Byung Hee Choi - One of the best experts on this subject based on the ideXlab platform.
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Analysis on heat transfer and heat loss characteristics of Rock Cavern thermal energy storage
Engineering Geology, 2014Co-Authors: Jung-wook Park, Byung Hee Choi, Dohyun Park, Dong-woo Ryu, Eui-seob ParkAbstract:Abstract The present study is aimed at demonstrating the feasibility of the Rock Cavern, compared with the above-ground tank, for the storage of large-scale high-temperature thermal energy by quantitatively evaluating the heat transfer inside the storage tank and the heat loss characteristics of the surrounding environment. As a conceptual model, we consider a thermal energy storage (TES) system coupled with an adiabatic compressed air energy storage plant (A-CAES), which utilizes loosely packed bed of Rocks as heat storage medium and stores heat of up to 685 °C. The specifications of the TES model, such as the mass flow rate of the heat transfer material and the storage volume, were determined through the analysis of the heat transfer in the packed bed, using a quasi-one-dimensional two-phase numerical model developed in this study. In this procedure, the inlet and outlet fluid temperatures and the thermal energy rates to be stored or extracted were examined over 200 consecutive daily cycles to ensure the TES met the requirements for the power generation of the A-CAES plant. Then, with the determined specifications of the TES, a comparative study on the heat loss characteristics of the Rock Cavern-type TES and above-ground-type TES systems was performed by simulating the operations on a daily basis for a period of 10 years using a three-dimensional numerical model. The comparison results indicated that the amount of cumulative heat loss in the Rock Cavern-type TES system over the operation period was far smaller than that in the above-ground-type TES system because of the surrounding Rock heating and the consequent reduction in the thermal gradient between the surrounding Rock and the storage medium. In terms of long-term operation, the rate of heat loss from the Rock Cavern-type TES system exhibited less-sensitive and less-dependent behaviors with respect to the insulator performance than that of the above-ground-type TES system.
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Numerical Analysis-Based Shape Design of Underground Rock Caverns for Thermal Energy Storage
Rock Mechanics and Rock Engineering, 2013Co-Authors: Dohyun Park, Dong-woo Ryu, Byung Hee ChoiAbstract:The efficiency of thermal energy storage (TES) using water can be improved by storing the water in a thermally stratified form. Previous studies on the thermal performance of heat storage tanks, undertaken by Lavan and Thompson (1977), Cotter and Charles (1993), Matrawy et al. (1996), Ismail et al. (1997), Eames and Norton (1998), and Bouhdjar and Harhad (2002), have demonstrated that better thermal stratification can be obtained by increasing the aspect ratio (height-to-width ratio) of heat storage containers. However, a high-aspect-ratio storage design may lead to structural instability of the storage space because of its narrow, tall shape. Therefore, heat storage spaces should be designed to provide good thermal performance but should also consider the stability of the storage. This is an important issue in the design of heat storage, particularly for underground TES using Rock Caverns, because the stability of Rock Caverns is greatly influenced by geotechnical factors such as in situ stresses and Rock properties. Therefore, a quantitative stability assessment is required to determine the shape of Rock Caverns used for TES, and to thus ensure the structural stability of the Caverns. This technical note describes a numerical approach for the shape design of a Rock Cavern in which to store hot water for district heating. For reliable evaluation of the stability of the Cavern, the approach employs probabilistic methods that can take into account the variability of input parameters using probability distributions. The arch height of the Cavern roof is determined through a comparison of excavation-induced ground displacements between Caverns with different arch heights.
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A Comparative Study on Heat Loss in Rock Cavern Type and Above-Ground Type Thermal Energy Storages
Journal of Korean Society For Rock Mechanics, 2013Co-Authors: Jung-wook Park, Dohyun Park, Byung Hee Choi, Dong-woo Ryu, Joong-ho Synn, Choon SunwooAbstract:A large-scale high-temperature thermal energy storage(TES) was numerically modeled and the heat loss through storage tank walls was analyzed using a commercial code, FLAC3D. The operations of Rock Cavern type and above-ground type thermal energy storages with identical operating condition were simulated for a period of five consecutive years, in which it was assumed that the dominant heat transfer mechanism would be conduction in massive Rock for the former and convection in the atmosphere for the latter. The variation of storage temperature resulting from periodic charging and discharging of thermal energy was considered in each simulation, and the effect of insulation thickness on the characteristics of heat loss was also examined. A comparison of the simulation results of different storage models presented that the heat loss rate of above-ground type TES was maintained constant over the operation period, while that of Rock Cavern type TES decreased rapidly in the early operation stage and tended to converge towards a certain value. The decrease in heat loss rate of Rock Cavern type TES can be attributed to the reduction in heat flux through storage tank walls followed by increase in surrounding Rock mass temperature. The amount of cumulative heat loss from Rock Cavern type TES over a period of five-year operation was 72.7% of that from above-ground type TES. The heat loss rate of Rock Cavern type obtained in long-period operation showed less sensitive variations to insulation thickness than that of above-ground type TES.
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Probability-based structural design of lined Rock Caverns to resist high internal gas pressure
Engineering Geology, 2013Co-Authors: Dohyun Park, Byung Hee Choi, Hyung-mok Kim, Dong-woo Ryu, Kong-chang HanAbstract:Abstract This paper describes a probability-based structural design approach to underground, lined Rock Caverns for the bulk storage of pressurized gas, such as compressed air, compressed natural gas, or compressed gaseous hydrogen. Our design approach is based on a combination of a point estimate method and a deterministic numerical analysis code. In the present study, we demonstrate the validity of this numerical approach in the design of underground structures by comparing it with a theoretical solution for a lined-tunnel problem. Our design approach is then applied to the preliminary structural design of a lined Rock Cavern for storing compressed natural gas at a high pressure of 15 MPa, where structural support for ensuring gas-tightness and the Cavern's mechanical stability is supplied by both steel and concrete liners. In this application, a probability-based design chart for determining the strength and thickness of the steel liner is presented, and the structural performance of the concrete liner is evaluated in a probabilistic manner.
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numerical study on the thermal stratification behavior in underground Rock Cavern for thermal energy storage tes
Journal of Korean Society for Rock Mechanics, 2012Co-Authors: Dohyun Park, Byung Hee Choi, Hyung-mok Kim, Dong-woo Ryu, Choon Sunwoo, Kong-chang HanAbstract:Abstract Using a computational fluid dynamics (CFD) code, FLUENT, the present study investigated the thermal stratification behavior of Lyckebo storage in Sweden, which is the very first large-scale Rock Cavern for underground thermal energy storage. Heat transfer analysis was carried out for numerical cases with different temperatures of the surrounding Rock mass in order to examine the effect of Rock mass heating due to periodic storage and production of thermal energy on thermal stratification and heat loss. The change of thermal stratification with respect to time was quantitatively examined based on an index of the degree of stratification. The results of numerical simulation showed that in the early operational stage where the surrounding Rock mass was less heated, the stratification of stored thermal energy was rapidly degraded over time, but the degradation and heat loss tended to reduce as the surrounding Rock mass was heated during a long period of operation. Key words Cavern thermal energy storage, Thermal stratification, Degree of thermal stratification, Computational fluid dynamics초 록 본 연구에서는 전산유체역학 코드인 FLUENT를 이용하여 열에너지 지하 저장을 위한 최초의 대규모 암반공동인 스웨덴 Lyckebo 저장소의 열성층화 거동을 분석하였다. 열에너지의 반복적인 저장 및 생산으로 인한 주변 암반의 히팅이 열성층화와 열손실에 미치는 영향을 분석하기 위해 암반의 온도조건을 달리하여 열전달 해석을 수행하였으며, 성층화 지수를 토대로 열에너지 저장 후 시간경과에 따른 열성층화의 변화를 정량적으로 분석하였다. 분석결과, 주변 암반이 히팅되지 않은 저장공동의 초기 운영단계에서는 시간경과에 따라 저장된 열에너지의 성층화가 빠르게 저하되는것으로 나타났으며, 저장공동의 운영기간이 늘어남에 따라 주변 암반의 히팅으로 인해 열성층화의 변화 및 열손실이 줄어드는 것을 확인하였다. 핵심어 암반공동 열에너지 저장, 열성층화, 열성층도, 전산유체역학
Caichu Xia - One of the best experts on this subject based on the ideXlab platform.
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Long-term stability of a lined Rock Cavern for compressed air energy storage: thermo-mechanical damage modeling
European Journal of Environmental and Civil Engineering, 2018Co-Authors: Shuwei Zhou, Caichu Xia, Yu ZhouAbstract:The long-term stability of a lined Rock Cavern (LRC) for underground compressed air energy storage is investigated using a thermo-mechanical (TM) damage model. The numerical model is implemented in...
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Numerical simulation for the coupled thermo-mechanical performance of a lined Rock Cavern for underground compressed air energy storage
Journal of Geophysics and Engineering, 2017Co-Authors: Shuwei Zhou, Caichu Xia, Hai-bin Zhao, Song-hua Mei, Yu ZhouAbstract:Compressed air energy storage (CAES) is a technology that uses compressed air to store surplus electricity generated from low power consumption time for use at peak times. This paper presents a thermo-mechanical modeling for the thermodynamic and mechanical responses of a lined Rock Cavern used for CAES. The simulation was accomplished in COMSOL Multiphysics and comparisons of the numerical simulation and some analytical solutions validated the thermo-mechanical modeling. Air pressure and temperatures in the sealing layer and concrete lining exhibited a similar trend of 'up–down–down–up' in one cycle. Significant temperature fluctuation occurred only in the concrete lining and sealing layer, and no strong fluctuation was observed in the host Rock. In the case of steel sealing, principal stresses in the sealing layer were larger than those in the concrete and host Rock. The maximum compressive stresses of the three layers and the displacement on the Cavern surface increased with the increase of cycle number. However, the maximum tensile stresses exhibited the opposite trend. Polymer sealing achieved a relatively larger air temperature and pressure compared with steel and air-tight concrete sealing. For concrete layer thicknesses of 0 and 0.1 m and an initial air pressure of 4.5 MPa, the maximum Rock temperature could reach 135 °C and 123 °C respectively in a 30 day simulation.
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an analytical solution for mechanical responses induced by temperature and air pressure in a lined Rock Cavern for underground compressed air energy storage
Rock Mechanics and Rock Engineering, 2015Co-Authors: Shuwei Zhou, Caichu Xia, Pingyang Zhang, Yu ZhouAbstract:Mechanical responses induced by temperature and air pressure significantly affect the stability and durability of underground compressed air energy storage (CAES) in a lined Rock Cavern. An analytical solution for evaluating such responses is, thus, proposed in this paper. The lined Cavern of interest consists of three layers, namely, a sealing layer, a concrete lining and the host Rock. Governing equations for Cavern temperature and air pressure, which involve heat transfer between the air and surrounding layers, are established first. Then, Laplace transform and superposition principle are applied to obtain the temperature around the lined Cavern and the air pressure during the operational period. Afterwards, a thermo-elastic axisymmetrical model is used to analytically determine the stress and displacement variations induced by temperature and air pressure. The developments of temperature, displacement and stress during a typical operational cycle are discussed on the basis of the proposed approach. The approach is subsequently verified with a coupled compressed air and thermo-mechanical numerical simulation and by a previous study on temperature. Finally, the influence of temperature on total stress and displacement and the impact of the heat transfer coefficient are discussed. This paper shows that the temperature sharply fluctuates only on the sealing layer and the concrete lining. The resulting tensile hoop stresses on the sealing layer and concrete lining are considerably large in comparison with the initial air pressure. Moreover, temperature has a non-negligible effect on the lined Cavern for underground compressed air storage. Meanwhile, temperature has a greater effect on hoop and longitudinal stress than on radial stress and displacement. In addition, the heat transfer coefficient affects the Cavern stress to a higher degree than the displacement.
