Thermodynamic optimization models of gas-hydrate cool storage and cool release processes are established in this paper. The optimal temperature configuration at the sensible heat transfer stage and the optimal gas hydrate phase change rate configuration at the phase change stage in the processes of gas hydrate charging and discharging are obtained by taking entropy generation minimization as optimization objective. The optimal control strategies of the cool storage system are determined. The research results indicate that the optimal operating characteristic of the gas-hydrate cool storage system can be achieved by keeping the phase change rates uniform, which are regulated and controlled according to constant heat transfer rates in the charging and discharging processes of gas hydrate. The analysis method and the results presented in this paper can provide important guidelines for optimal design and operation of gas-hydrate cool storage system. (C) 2009 Elsevier Ltd. All rights reserved.