ENERGY CONSUMPTION FOR PRODUCTION OF SHIPBOARD FRESHWATER

Abstract

ABSTRACTA study was conducted to determine the nature and quantities of energy consumed to produce freshwater on board U.S. Navy ships and to ascertain how that energy consumption might be reduced. Values for energy usage were calculated from available ship heat balances and distilling plant technical manuals. The effects of ship operation on distiller economy were accounted for by factoring in the ship's operational profile, electrical conversion efficiency, boiler efficiency, and auxiliary exhaust steam availability. Results of the analysis showed that freshwater production required approximately 2 percent of all energy consumed aboard ship which equates to a fuel oil cost of 22 million dollars per year for the Fleet. Factors contributing to the high energy consumption of 434 Btu per pound of freshwater were: poor electrical energy conversion and boiler efficiencies, and distiller designs that emphasize weight, volume, and reliability more than fuel economy. Recommended methods for reducing total energy for freshwater production are: reuse of wastewater; reduction of water consumption; investigation of more efficient desalination processes; improvement of electrical conversion and boiler efficiencies; and investigation of actual ship operations and ship's logs to determine more accurately areas of potential water reduction.