Techno-economic analysis of seasonal cold thermal energy Storage: Operation scheduling and tank Size-dependent levelized cost of storage

Seasonal cold thermal energy storage (SCTES) preserves winter’s natural cold for summer cooling and can reduce energy use, peak demand, and carbon emissions. Yet its economic viability is highly sensitive to storage sizing, operating strategy, and electricity tariff structures. This study proposes a novel integrated optimization framework that co-optimizes hourly operation and storage capacity while explicitly accounting for time-of-use tariffs with both fixed and energy charges, enabling a consistent lifecycle assessment (CAPEX + OPEX) and comparison of operating strategies. A mixed-integer linear programming (MILP) model minimizes total cost by scheduling hourly charging/discharging and chiller operation. Model inputs and operating profiles are benchmarked against building energy management system (BEMS) data from a Korean research campus to enhance practical realism. Two configurations are evaluated: (i) seasonal storage only and (ii) combined seasonal–diurnal storage for peak shifting. Results show that stored natural cold can be preferentially supplied during summer peak periods, reducing both fixed and energy charges while enabling chiller capacity downsizing, thereby lowering required cooling-equipment capital investment. Importantly, the relationship between economics and storage size is strongly strategy-dependent. Under the seasonal-only configuration, the levelized cost of storage (LCOS) decreases as ice storage capacity increases, whereas investment recovery becomes less favorable with increasing capacity. In contrast, when seasonal storage is integrated with diurnal storage for peak-shifting operation, the LCOS is lower than that of the seasonal-only case at small storage capacities; however, under peak-shift operation it exhibits an opposite dependence on storage size, increasing as the ice storage capacity grows. These findings highlight that operating strategy and tariff-sensitive dispatch, not storage size alone, are critical determinants of SCTES economic feasibility. Overall, the proposed framework provides a tariff-consistent basis for assessing economically favorable SCTES sizing and operation for the investigated campus case under strategy-dependent trade-offs.