초록 ▼

최종 목표
〇 열에너지 및 압축공기에너지의 지하암반저장 핵심기술 개발
- 최고 400°C, 고효율 열에너지 지하암반저장모델 설계기술 개발
- 100 MW급 압축공기에너지 지하저장 플랜트 건설 · 운용 지침 개발

개발내용 및 결과
〇 열에너지 저장효율 최적화를 위한 저장공동 형상 설계기술 개발
〇 열저장공동 레이아웃에 설계기술 개발
〇 암반저장시스템 개념모델 설계 및 가이드라인 제시
〇 단열복합체 재료 및 저장매질 적합성 평가
〇 암반의 열적 · 역학적 물성 시험장

최종 목표
〇 열에너지 및 압축공기에너지의 지하암반저장 핵심기술 개발
- 최고 400°C, 고효율 열에너지 지하암반저장모델 설계기술 개발
- 100 MW급 압축공기에너지 지하저장 플랜트 건설 · 운용 지침 개발

개발내용 및 결과
〇 열에너지 저장효율 최적화를 위한 저장공동 형상 설계기술 개발
〇 열저장공동 레이아웃에 설계기술 개발
〇 암반저장시스템 개념모델 설계 및 가이드라인 제시
〇 단열복합체 재료 및 저장매질 적합성 평가
〇 암반의 열적 · 역학적 물성 시험장비 구축 및 평가
〇 암반의 균열 및 손상거동 평가 및 손상 계측기법 개발
〇 저장공동의 균열 및 손상거동 평가를 위한 T-H-M 연계 수치코드 (FRACOD) 개발 및 검증
〇 암반의 장기강도 특성 평가 시험 및 장기안정성 해석
〇 현지암반조건 및 저장조건에 따른 주변 암반 T-H-M 연계거동 및 환경영향권 분석
〇 발파굴착 동하중에 의한 저장공동 주변암반의 손상대 평가
〇 열에너지 저장공동의 발파/지진에 대한 동적 안정성 평가
〇 지하암반 내 압축공기 에너지저장(CAES) 파일럿 플랜트를 이용한 운용기슬 실증실험
〇 CAES 파일럿플랜트 운용 실험을 통한 암반거동 계측 및 분석, 고압대응 내조시스템의 성능평가
〇 에너지저장용 복공식 암반공동(LRC) 활용기술 개발

기대효과
〇 태양열에너지, 산업폐열의 대용량 저장을 통한 에너지 이용효율 증대(지상탱크 저장방식 대비 30% 효율 향상 기대)
〇 Zero Carbon, Energy Building 보급에 기여
〇 2020년 장주기 및 대형 에너지저장 세계시장 점유율 30% 달성

적용분야
〇 AA-CAES 연계형 CTES
〇 CAES 발전(풍력, 원자력, 화력 등 기저전력 저장)
〇 태양열, 산업폐열, 원자로열 연계형 CTES

(출처 : 보고서 요약서 3p)

Abstract ▼

IV. Results of the Work
To develop layout design technology for underground TES caverns, we numerically investigated the mechanical stability and thermal performance of rock caverns by varying the separation distance between multiple caverns. The investigation results showed that as the separatio

IV. Results of the Work
To develop layout design technology for underground TES caverns, we numerically investigated the mechanical stability and thermal performance of rock caverns by varying the separation distance between multiple caverns. The investigation results showed that as the separation distance decreased, cavern stability decreased, whereas thermal performance improved. This numerical result suggests that the spacing of TES caverns should be designed by considering both mechanical stability and thermal performance. Based on these contrasting behaviors, we proposed a design approach for determining the separation distance of TES rock caverns. We also proposed two types of conceptual TES rock cavern models that can be used for district heating and AA-CAES based on the results obtained from the past three-year research.

Two-dimensional heat transfer analysis was performed on an insulation system for high-temperature thermal energy storage using the numerical model with time- and temperature-dependent properties, and the optimum design for insulation system was proposed based on the simulation results. The effect of the operation cycle with periodic heat charging and discharging on heat transfer in surrounding rock mass was examined and the risk regarding to the possible failure of the insulation system was discussed.

Uniaxial compressive strength test and Brazilian test on Hwangdeung granite and Danyang limestone at high-temperature ranging from 20°C to 250°C were conducted to examine the mechanical properties of rocks. The Young's modulus and Poisson's ratio were measured under temperature ≤ 100°C, and remained independent on temperature level. The fracture toughness and tensile strength of Hwangdeung granite decreased dearly with increasing temperature, when the temperature was greater than 150°C. There were no systemic relations between temperature and mechanical properties of Danyang limestone, which may be due to the heterogeneous and anisotropic characteristics of the rock specimens and the consequent large deviations of the experimental data.

Through the AE (acoustic emission) measurement on thermal cracking experiments for rock core and block samples, the critical thermal cracking temperatures were estimated to be 69 °C and 49 °C for the granite and limestone considered in this study, respectively. From the repeated heating and cooling thermal experiments, thermal Kaiser effect was observed. In sonic velocities and CT analysis performed before and after the thermal cracking experiments, the damage of the rocks due to heating was confirmed. The PFC numerical analysis considering the individual thermal properties of each minerals showed the temperature distribution and characteristics of thermal cracking similar to the experiments.

It is necessary to develop standard Mode II fracture toughness test and corresponding subcritical crack growth test for the evaluation of long-term stability of UTES cavern because shearing is dominant in the rock mass surrounding thermal energy storage system. There is no standard Mode II fracture toughness test method and some suggested methods had a disadvantage in specimen preparation and application of confining pressure. To overcome these defects, we developed SCC (Short Core in Compression) test by numerical methods. SCC test method has advantages in specimen preparation and application of confining pressure because of rock core and simple notch configuration.

We have been involved in the international collaboration project for the development of a numerical code to simulate rock mass failure problem, namely FRACOD, since 2012. The current status of the project and the improvements of FRACOD were summarized in the present study. Also, the thermal crack and damage behavior of concrete lining and rock mass regarding to underground TES was examined using FRACOD. With insulator performance for thermal energy storage cavern considered, few thermal cracks were observed in the lining and rock mass, and the heat loss to the surrounding rock mass was remarkably reduced.

The operation of high-temperature underground TES system for a period of 30 years was simulated using TOUGH2-FLAC3D simulator. In the simulation, the heat and fluid flow and mechanical stability of TES cavern and surrounding rock mass were analyzed. The effects of influencing factors such as ground water condition, hydraulic properties, storage temperature, depth of cavern and insulator performance on heat transfer and near surface temperature were examined. The numerical results showed that water saturation degree and permeability of rock mass were key factors that dominated the heat and fluid flow in rock mass. The environmental changes and heat loss characteristics of underground thermal energy storage at shallow depth were also investigated with an axisymmetric models of a cylindrical heat storage cavern and plane models in a vertical cross section through a tunnel-shaped heat storage cavern. The mechanisms of conductive heat transfer and convective heat transfer (natural convection and advection of ground water), and the contributions of the respective mechanisms to the environmental impacts and heat loss characteristics of underground TES were evaluated. The results showed that no significant environmental effects or excessive heat loss were to be expected as a result of convective heat transfer with ground water flow. The heat transfer will be dominated by heat conduction and the instdation performance, but the effect of very permeable faults deserves further studies.

The characteristics of heat diffusion in rock around an underground heat storage cavern are analyzed with considering temperature-dependency of thermal properties of rock. We analyzed heat diffusion patterns according to thermal conductivities, specific heats and heat storage boundary conditions. These results can supplement the simplified analysis using constant thermal properties by considering the influence range of temperature-dependency of thermal properties.

To verify the explosion modeling method for blast-damaged zone (BDZ) around underground cavern, a series of small-scale test blasts was conducted using the concept of wave trap. According to the test results, the input parameters to the numerical model (LS-DYNA) were corrected. On the other hand, a laboratory experiment that simulates the explosion of explosive in blasthole was conducted using a rectangular rock plate with a center hole, inside which a specially designed wedge system is inserted. The wedge system is designed to expand horizontally and thus exerts forces against the wall of the hole when hit by a drop hammer. The test results were compared with PFC3D models. This experiment is useful because it can give us the approximate magnitude of the source blow, and thus make it easy to verify the result of the modeling.

The dynamic response of a storage cavern was investigated in order to assess the input parameters for the numerical analysis of stability of the cavern under dynamic loading condition. Most important parameters were elastic modulus, damping ratio, calculation time step, boundary condition, etc. Some guidelines were suggested to prepare the input parameters.

Energy balance equation for LRC (lined rock cavern) storage cavern was developed, and storage efficiency was calculated using the equation with the input of estimated pressure and temperature. The influence of various LRC conditions such as thermal insulation, operational model, and injection temperature were evaluated using the developed technique. The analysis model for evaluating interaction between the pressure and temperature within LRC system and surrounding system components was developed using COMSOL Multiphysics code as well. The pillar stability and storage efficiency of LRC were estimated, and the effects of pillar thickness and operational methods of synchronized and asynchronized manner was investigated.

The stability analysis of LRS (lined rock shaft), which was supposed to be located in Jeju island, was carried out. The analysis is based on a shear strength reduction method, and its results showed the safety factors of 1.07-2.15 in each case of geologic conditions, which means that the overburden of LRS may be structurally stable. However, it should be noted that these results have the limitation that the shear deformation of the rock, especially only adjacent to the LRS, was analyzed based on a plastic theory. Thus, the additional structural concerns of individual system component such as a plug, steel liner and back-filled concrete should be further inspected with consideration of the properties of the materials and interface as well as an operation schedule. The separator between steel liner and back-filled concrete may result in a reduction of interfacial shear resistance between these two different materials, so that we conducted a preliminary mechanical test of the separator in advance to a scaled model test where its function can be evaluated in a more quantitative manner.

The technical trend of CAES (compressed air energy storage) system and storage method was analyzed. The global trend of the system is the concept of fuel-free CAES. The fuel-free CAES as a next generation CAES has two types; adiabatic and isothermal CAES. For more competitive CAES in price and efficiency perspective, the storage methods with constant pressure have been suggested. Therefore, for the occupation of predominance and technical competitiveness in ESS market, the equipments for these next generation CAES and the new concept storage method should be developed.

(출처 : SUMMARY 10p)

목차 Contents

• 표지 ... 1
• 제 출 문 ... 2
• 최종보고서 요약서 ... 3
• 요 약 문 ... 4
• SUMMARY ... 9
• CONTENTS ... 15
• 목차 ... 17
• 제1장 연구개발과제의 개요 ... 19
• 제1절 연구개발의 목적 및 필요성 ... 19
• 1. 연구개발의 목적 ... 19
• 2. 연구개발의 필요성 ... 19
• 제2절 연구개발 범위 ... 20
• 제2장 국내외 기술개발 현황 ... 23
• 제1절 열에너지 저장 기술 ... 23
• 1. 개요 ... 23
• 2. 열에너지 저장 방법 ... 24
• 제2절 열에너지 저장 시스템의 종류와 특징 ... 27
• 제3절 국내외 시장현황 분석 ... 30
• 1. 태양열에너지 현황 ... 30
• 2. 산업폐열 현황 ... 39
• 제4절 특허조사를 통한 국내외 기술현황 분석 ... 62
• 1. 개요 ... 62
• 2. 단열구조 및 단열재 ... 63
• 3. 열저장 매질 및 열교환 방식 ... 71
• 4. 특허조사 요약 ... 77
• 제3장 연구개발수행 내용 및 결과 ... 79
• 제1절 열저장공동 레이아웃에 대한 모델 설계 ... 79
• 1. 대규모 열에너지 지하저장을 위한 암반공동의 다중배치에 대한 역학 안정 및 열전달 해석 ... 79
• 2. 고온 열저장을 위한 단열구조의 수치해석적 성능 분석 및 설계 제원 도출 ... 96
• 3. 열수 저장 및 AA-CAES를 위한 지하 암반공동 개념모델 제안 ... 107
• 제2절 암반/단열복합체의 열적·역학적 물성 평가 및 열균열/손상거동 예측기술 개발 ... 112
• 1. 열환경 하에서의 암반의 역학적 특성 시험 ... 112
• 2. 코어 및 모델시료를 이용한 열균열 평가 및 계측 ... 121
• 3. 암반 장기강도특성평가 시험 및 장기안정성 해석 ... 149
• 4. 고온 열저장을 위한 단열복합체의 열균열 및 손상거동 특성평가 ... 182
• 5. 저장공동의 장기간 균열/손상거동 평가를 위한 수치코드(FRACOD) 개발 및 검증 ... 188
• 제3절 수치해석적 예측기법을 이용한 열-수리 환경변화 대응기술 개발 ... 196
• 1. 현지암반조건 및 저장조건에 따른 T-H-M 연계거동 및 환경 영향권 분석 ... 196
• 2. 암반 내 지하수 유동에 의한 열흐름 및 저장공동 열손실 특성 분석 ... 215
• 3. 암석열물성의 온도의존성을 고려한 열전파양상 및 영향영역 해석 ... 222
• 제4절 저장공동 동적 안정성 평가 ... 229
• 1. 폭원모델링 기법 검증을 위한 충격/발파하중의 가중실험 및 동적계측 ... 229
• 2. 저장공동 주변 발파손상대의 수치해석적 평가기법 개발 ... 242
• 3. 열저장 다중공동의 발파/지진에 대한 동적 안정성 평가 ... 251
• 제5절 에너지저장용 LRC(복공식 암반공동) 활용기술 개발 ... 266
• 1. 에너지 지하저장을 위한 LRC 운영 중 저장효율 분석 ... 266
• 2. LRC/LRS의 안정성 검토 및 인터페이스 영향에 대한 실험 평가 ... 307
• 3. 차세대 CAES 및 저장방식(정압저장)에 대한 기술동향 분석 ... 315
• 제4장 목표달성도 및 관련분야에의 기여도 ... 321
• 제1절 목표달성도 ... 321
• 1. 최종 연구목표의 달성도 ... 321
• 2. 당해연도 목표의 달성도 ... 322
• 3. 연구수행 내용 요약(1~3차년도) ... 323
• 제2절 관련분야에의 기여도 ... 363
• 1. 기술적 측면 ... 363
• 2. 경제·산업적 측면 ... 363
• 3. 정책적 측면 ... 363
• 제5장 연구개발결과의 활용계획 ... 365
• 제6장 연구개발과정에서 수집한 해외과학기술 정보 ... 367
• 제1절 기술 개발 ... 367
• 제2절 특허 ... 379
• 제3절 논문 ... 390
• 제7장 참고문헌 ... 397
• 끝페이지 ... 405