Optimising the Frozen Flow: Buffer Design for the Dispatch Area in Automated Cold Storage Warehouses

Abstract

Automated cold storage warehouses increasingly rely on automation to manage growing throughput demands, labour complexities, and sustainability requirements. However, the design of outbound buffer areas remains underexplored relative to long-term storage and retrieval processes. Fixed buffer lanes, commonly used to stage pallets ahead of truck pickup, create a structural mismatch with the stochastic nature of truck arrivals. When trucks are delayed, buffer lanes fill up, disrupting outbound flow and forcing manual exception handling. Shuttle-based storage and retrieval systems (SBS/RS) are identified in the literature as a promising alternative, given their fast-retrieval, small-footprint, and flexible release characteristics. Their application to outbound dispatch buffering, particularly in a cold-storage context and grounded in real operational data, remains largely unexplored. This research investigates how a shuttle-based dispatch buffer can be designed and controlled to minimise crane congestion and outbound delays in an automated cold-storage warehouse, using NewCold's Piacenza facility as a case study. The research combines a literature review and expert consultation with a system analysis and a discrete-event simulation model, built in Simio, validated against real operational data from the existing Piacenza warehouse. Three scenarios are compared: a validated baseline reflecting the current traditional bufferlane layout, a shuttle-based buffer design where picked pallets return to the highbay before staging, and a variant where picked pallets are routed directly into the shuttle buffer. The results show that a shuttle-based dispatch buffer's core mechanism, decoupling pallet retrieval from truck-arrival timing, substantially reduces the outbound system's dependence on truck-arrival forecasting accuracy. Routing picked pallets directly into the buffer further reduces the total crane workload required per pallet, creating an opportunity to operate with a smaller crane fleet for comparable outbound performance. This benefit does not come without cost: a smaller crane fleet operates closer to its capacity limit, and an under-resourced buffer configuration is shown to destabilise the system rather than absorb demand, confirming that such a design must be deliberately dimensioned rather than assumed to work at any scale. For the wider automated cold-storage warehouse industry, the findings demonstrate that a shuttle-based dispatch buffer's primary value lies in decoupling outbound operations from arrival uncertainty and reallocating pressure away from cranes, rather than in a proportional reduction in total truck dwell time, an important distinction for operators evaluating similar designs on throughput metrics alone. Academically, this research addresses a gap in the shuttle-based storage and retrieval system literature by applying this technology to an outbound dispatch-buffering role, validated against real operational data, and identifies crane capacity as an external coordination dependency not previously characterised in studies treating the shuttle system as self-contained.