Optimal design and control of cool thermal energy storage systems for building demand management

Abstract

This thesis presents the investigations on the optimal design and control of cool thermal storage systems for building demand management. The developed strategies include optimal design of active cool thermal energy storage (CTES) for building peak load management, fast power demand response (DR) strategies for buildings involving both active and passive CTES for smart grid applications and optimal design of active CTES for building demand management. These new strategies in different subjects are proposed and validated on a dynamic simulation platform. A simulation-based optimal design method is developed and used to optimize the capacity of CTES. The quantitative analysis on the life-cycle cost saving potentials of active cold storage systems concerning the operational cost, initial investment and the space cost is also proposed. The optimal capacities of active CTES, monthly/annual operational cost savings and corresponding peak demand set-points are obtained from using the marginal decision rule. Results show that small scale storages can offer substantial annual net cost saving. Two fast power DR strategies involving both active and passive cool storages are presented. Certain number of operating chiller(s) is shut down at the beginning of the DR event to achieve a significant and immediate power reduction. In the basic fast DR strategy, only chiller power demand reduction is the control objective while in the improved fast power DR strategy, the building indoor temperature during the DR event is the second control objective to control indoor thermal comfort degradation. The results of case studies show that stepped and significant power reduction can be achieved. The power demand reduction and indoor temperature during the DR event can be also predicted accurately. The life-cycle cost benefit analysis and optimal design of active CTES for building demand management is also proposed. It is assumed that the active CTES is under control of the fast power DR strategy during the DR event. Meanwhile, during the normal days, the active CTES is under control of the storage-priority control to shift peak demand. Based on the different indoor thermal comfort requirements, the optimized capacities of active CTES, the corresponding life-cycle cost saving potentials and the chiller power reduction set-points in the developed fast power DR strategy are then identified. The results show that the optimal capacity of active CTES largely increases with the decrease of the upper limit of indoor temperature set-point.