Organic Rankine Cycle/Thermal Tower: Lower Cruise Ship Reverse Osmosis Costs

Abstract

A novel combination of an Organic Rankine Cycle (ORC) and a hydration-dehydration Thermal Tower (TT) provides a potential source of pressurized water for a reverse osmosis (RO), desalination plant for a cruise ship. An analysis of the combined ORC-TT has been applied to a Wärtsilä 12V46F 14.4 MW diesel to provide an additional 560 kW shaft power and a source of evaporated seawater of 0.824 cubic meters per hour (0.229 kg/s). The water is available at 7 bar pressure at the bottom of a 70m Thermal Tower. The system features two separate ORC bottoming cycle turbines. The system uses a thermal heat exchange fluid to remove heat from the charge air cooler for the compressed air engine inlet, as well as the engine cooling liquid. Another exhaust-to-liquid cooler is used to remove energy from the exhaust downstream of the turbocharger. The heated fluid then passes through a high temperature ORC unit and a low temperature ORC unit. The high temperature ORC can generate up to 409 kW and the low temperature unit 155 kW. The remaining energy in the heat transfer fluid is used via a 70-meter hydration – dehydration Thermal Tower to heat seawater to evaporate water. The combined system offers additional shaft power while providing a source of desalinated water to reduce the load on reverse osmosis water purification systems.