CO2 refrigeration system design and optimization for LNG driven cruise ships

Abstract

The cruise industry is in the evolution of eco-friendly technologies due to strict environmental regulations. Liquified natural gas (LNG) is an alternative marine fuel. Compared to conventional diesel fuels, LNG offers a reduced environmental impact and can serve as a transition towards zero emission. LNG is stored in onboard cryogenic tanks at low temperatures. Various techniques can be applied to vaporize the LNG fuel before feeding it to the gas engine. The recovery of this vaporization energy with air conditioning as a heat source can enhance system performance. On a cruise ship, heating, cooling, and ventilation (HVAC) require an average 40 % of the ship's total energy demand. The natural refrigerant CO2 is an attractive choice due to its compact units, non-toxic nature, and non-flammability, all being primary concerns on a cruise ship. The energy efficiency can be improved by utilizing LNG cold and reducing the need of indirect loops with CO2 as a refrigerant. This work investigates the LNG cold, waste heat recovery potentials, and CO2 refrigeration system for cruise ships.