Blueprint: Phase-Change Cold Box for Off-Grid Last-Mile Carriage — Build Specification

DESIGN BLUEPRINT — SIMULATED, NOT MEASURED — NOT BUILT. A build specification derived from the source paper (DOI: 10.5281/zenodo.24108635): a passive cold box with 100 mm expanded polystyrene walls (inner chamber 0.50 m x 0.35 m x 0.30 m, 52.5 litres; external 0.70 m x 0.55 m x 0.50 m), carrying a 15.0 kg payload of pre-cooled cargo in the 2-8 degC band, cooled by 14 kg of sealed paraffin panels melting at 5.0 degC (220 kJ/kg, 16.3 litres). Modelled hold is 61.1 hours at 30 degC ambient, 50.9 hours at 35 degC, and 43.6 hours at 40 degC. Recharge requires removing 3.84 MJ: 13.3 hours in a freezer compartment at 80 W net (overnight), 42.6 hours in a 2 degC refrigerator compartment at 25 W, or 7.9 hours from a 1.5 m2 solar absorption unit at 135.0 W of cooling; a simple night-sky panel cannot recharge it on a warm 22 degC night. Plain ice in the same box holds longer per kilogram but at 0 degC, below the cargo band. Includes the EPS cutting list, panel construction and fill, lid seal, bill of materials, assembly sequence, loading and recharge procedures, operating envelope, tolerances, failure modes and maintenance. Sole author: William Alexander Aldred (ORCID 0009-0000-1215-577X). CC BY 4.0.