Assessment of Seasonal Cold Storage and Intake Sizing for Seawater District Cooling

Integrating seasonal cold storage into seawater district cooling can extend the use of natural cold resources across seasons and change the annual cooling supply mix by compensating for temperature-dependent limitations of direct seawater cooling. In this study, an 8760 h simulation evaluates hybrid cooling scenarios using a measured annual cooling-load profile from an operating district cooling branch supplying chilled water, totaling approximately 171 GWh. The system prioritizes direct seawater cooling, followed by discharge from a prescribed initial cold-energy inventory and turbo-chiller backup. Under the same intake conditions, approximately 42 GWh of initial storage reduces the chiller’s annual cooling share from 22.9% to 2.2%. For CS_0.198, with approximately 33.8 GWh of initial storage, a +2 °C source-temperature shift advances the 10% storage discharge cutoff from about day 274 to day 196. Increasing the prescribed daily heat-loss coefficient from 0.03% to 0.15% advances it to about day 239. Hourly pumping profiles and annual electricity comparisons show why this reduction in refrigeration duty does not ensure a comparable electricity reduction. For an annual electricity ratio R ≤ 1.5 relative to the constant-temperature benchmark, the selected storage capacity falls from 42.1 to 16.5 GWh as the intake diameter increases from 1.25 to 1.40 m. These results support joint assessment of storage availability, intake pumping and storage capacity in the preliminary design of hybrid seawater district cooling systems.