Influence of seawater temperature on thermal efficiency of an integrated electric power generation and water desalination plant

Abstract

This paper is an attempt to demonstrate the effect of sea water temperature on the overall efficiency of electric power generation combined with a water desalination plant. The plant under consideration is composed of two thermally and mechanically coupled loops: a steam power plant loop to produce electricity and a reverse osmosis loop including pressure exchange system to provide drinkable water from seawater. The reverse osmosis loop including pressure exchange system is known to be the state of the art desalination technology for obtaining fresh water. The waste pressure from reverse osmosis is transferred to the low pressure concentrate in a pressure exchange system to save a considerable amount of energy. It is shown in the body of paper that the sea water inlet temperature has a direct impact on the overall efficiency of the system. This is fundamentally accomplished by the rejected heat of Rankine cycle in a condenser. As a result, this paper shows that the overall efficiency of the combined plant is found to be highest when sea water temperature at the condenser exit is elevated to around 30 degrees C.