Onboard refrigeration is a vital link for fish product quality. This article compares mechanical compression, absorption, and cryogenic systems, analyzing their energy consumption, maintenance footprint, and adaptability to different vessel types.
Competing Technologies
In the fishing naval industry, three technologies dominate the marine refrigeration plant market. Each has advantages and limitations depending on the vessel's operating profile, hold capacity, and cold chain requirements.
- Mechanical compression: The most widespread. Uses screw or piston compressors with refrigerants like R-404A or R-507. Offers high efficiency over a wide temperature range, but requires periodic compressor maintenance and a rigorous leak control system.
- Absorption (ammonia/water): Utilizes waste heat from the main engine or a generator. Ideal for vessels with thermal surplus, reduces onboard electrical consumption. However, its coefficient of performance (COP) is lower and requires larger equipment.
- Cryogenic systems (CO₂ or nitrogen): Use liquefied gases to directly cool holds or freezing tunnels. Compact and fast-response, but operating cost depends on gas price and refill logistics at port.
Energy Consumption and Maintenance Footprint
A comparative study conducted on three South Atlantic trawlers yielded the following average data for a 50 kW refrigeration plant:
| Technology |
Electrical Consumption (kWh/day) |
Annual Maintenance (hours) |
Estimated Lifespan (years) |
| Mechanical compression |
180 |
120 |
12–15 |
| Absorption |
60 |
80 |
10–12 |
| Cryogenic (CO₂) |
40 |
40 |
8–10 |
Absorption stands out for its low electrical consumption, but requires a constant heat source and larger equipment. Cryogenic systems minimize maintenance, but their lifespan is shorter and gas costs can fluctuate.
Real Modernization Cases
Two shipowners from the port of Mar del Plata decided to modernize their refrigeration plants in 2023. The first case involved a 35-meter vessel dedicated to hake fishing. A 20-year-old mechanical compression system was replaced with an absorption plant that uses heat from the auxiliary engine. The result was a 65% reduction in the cold room's electrical consumption and an estimated annual savings of 12,000 liters of diesel.
The second case involved a 55-meter factory vessel processing shrimp onboard. A cryogenic CO₂ system was installed for the quick-freezing tunnels, complemented by mechanical compression for the storage holds. The combination reduced thawing losses by 8% and improved final product quality, according to the shipowner's quality control reports.
Considerations for Shipowners and Superintendents
Choosing a refrigeration system depends not only on energy efficiency. Factors such as available space in the engine room, spare parts availability at ports of call, crew training, and environmental regulations on refrigerants must be evaluated case by case.
For fleets operating in areas with limited port infrastructure, mechanical compression remains the most robust option. In contrast, for vessels with thermal surplus and predictable routes, absorption can offer an attractive return on investment in less than three years. Cryogenic systems are ideal for factory vessels requiring ultra-fast freezing and with access to CO₂ supply at home ports.
Reading for Engineers and Technical Buyers
This analysis is aimed at maintenance engineers, fleet superintendents, and technical buyers who need to evaluate concrete options before an investment. The final decision should be based on real operational data, not catalog promises. At Boatshedfishco we work with shipyards and shipowners to size refrigeration plants that fit each vessel's profile, considering both energy efficiency and operational reliability.