Ice-Free Fish Preservation at Sea: An Insulated Hold with Phase-Change Panels, Priced in Days of Catch Saved

Small-scale fishers working multi-day trips in warm climates lose a large share of their catch to spoilage where ice is unavailable, unreliable, or expensive. This paper designs an ice-free alternative — a small, well-insulated fish hold cooled only by reusable phase-change material (PCM) panels frozen on shore before departure — and prices it in the unit that matters to a fisher: days of saleable catch. The hold (internal dimensions 1.00 × 0.70 × 0.70 m, 100 mm polyurethane insulation, U = 0.24 W/m²/K) carries 80 kg of PCM panels with a melting point of 0 °C and a latent heat of 240 kJ/kg, charged to −10 °C on shore; there is no active refrigeration at sea. A lumped enthalpy model, with catch loaded at 30 kg per day at a sea temperature of 27 °C into a 32 °C ambient, holds the hold at 0 °C until the panels finish melting at 3.29 days, crosses a 7 °C spoilage temperature threshold at 4.88 days, and, under a Q10 = 3 spoilage model, gives the oldest catch a saleable life of 6.58 days, against 0.45 days for the identical hold without PCM — a gain of 6.13 saleable days. The full system costs $2,610 in capital and $9.00 per trip amortised, or $1.47 per additional saleable day. The design does not beat cheap ice: where ice sells at $0.05/kg, an equivalent ice charge costs $5.00 per trip, less than the PCM system's $9.00, and the PCM capital is never recovered. The break-even ice price is $0.090/kg. The PCM hold is therefore a solution for places where ice is absent or priced above roughly $0.09/kg, not a universal replacement for ice.