Research Article A Coupled Thermo-Hydro-Mechanical Model of Jointed Hard Rock for Compressed Air Energy Storage Xiaoying Zhuang, 1,2 Runqiu Huang, 2 Chao Liang, 3 and Timon Rabczuk 4,5 1 National Key Laboratory of Disaster Reduction and Protection, Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China 2 State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu, China 3 Department of Geophysics, School of Earth Sciences, Stanford University, USA 4 Institute of Structural Mechanics, Bauhaus-Universit¨ at Weimar, Weimar, Germany 5 School of Civil, Environmental and Architectural Engineering, Korea University, Republic of Korea Correspondence should be addressed to Xiaoying Zhuang; xiaoyingzhuang@tongji.edu.cn and Timon Rabczuk; timon.rabczuk@uni-weimar.de Received 8 September 2013; Accepted 7 November 2013; Published 19 January 2014 Academic Editor: Goangseup Zi Copyright © 2014 Xiaoying Zhuang et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Renewable energy resources such as wind and solar are intermittent, which causes instability when being connected to utility grid of electricity. Compressed air energy storage (CAES) provides an economic and technical viable solution to this problem by utilizing subsurface rock cavern to store the electricity generated by renewable energy in the form of compressed air. Tough CAES has been used for over three decades, it is only restricted to salt rock or aquifers for air tightness reason. In this paper, the technical feasibility of utilizing hard rock for CAES is investigated by using a coupled thermo-hydro-mechanical (THM) modelling of nonisothermal gas fow. Governing equations are derived from the rules of energy balance, mass balance, and static equilibrium. Cyclic volumetric mass source and heat source models are applied to simulate the gas injection and production. Evaluation is carried out for intact rock and rock with discrete crack, respectively. In both cases, the heat and pressure losses using air mass control and supplementary air injection are compared. 1. Introduction Renewable energy such as wind, solar, tidal, and wave only produces electricity intermittently and with low power and energy density, thus, nondispatchable and difcult to use at large scales as the modern society requires [1]. Tat is why many renewable energy technologies are lacking the econo- mies of scale, which reduces their competitiveness and delays the transition to a low carbon economy. Terefore, economic solutions to bulk energy storage are urgently needed in order for renewable energy to take a signifcant share in the total energy mix. A critical issue for renewable energy to be integrated into grids with satisfactory stability is appropriate energy storage to defer electricity demand from peak to of peak times. Most energy storage systems are expensive, either in terms of Capex and Opex or in terms of energy losses incurred in storing and retrieving the energy. For exam- ple, batteries are costly, fy wheels are suitable for short- duration storage only. Te CAES, besides pumped-hydro, is the only conceivable technology able to provide the very large scale energy storage deliverability above 100 MW in single unit sizes while free from adverse environmental efects of pumped-hydro. Hence, CAES has recently received lots of attention [2, 3] and it has been recently proposed that large- scale solar-CAES and wind-CAES deployment can enable renewable energy to compete against coal-fred electricity generation [4, 5]. In CAES, a source energy is stored in the form of highly pressurized air in underground rock cav- erns and the compressed air is released through turbines to generate electricity when needed [6] as shown in Figure 1. Underground rock caverns are the mostly chosen type of reservoirs in the CAES which provide initial ground stress against air pressure, strengths to withstand cyclic loadings, Hindawi Publishing Corporation Mathematical Problems in Engineering Volume 2014, Article ID 179169, 11 pages http://dx.doi.org/10.1155/2014/179169