Analysis of the high-efficiency EP-OTEC cycle using R152a

Abstract

Ocean thermal energy conversion (OTEC) cycles utilize renewable, eco-friendly heat sources. However, their low system efficiency diminishes their advantages and impedes commercialization opportunities. In this study, a liquid vapor ejector and a motive pump are used to enhance the efficiency of the OTEC system through a modified version called the ejector pump OTEC (EP-OTEC) cycle. By applying a liquid vapor ejector, lower turbine outlet pressure may result than in the basic OTEC cycle. Additionally, the motive pump increases the motive pressure, thereby strongly affecting the performance of the liquid vapor ejector. The heat source temperature, mass fraction of the motive flow, and motive pressure are varied to analyze the performance characteristics of the EP-OTEC cycle. Firstly, the higher heat source temperature yields greater turbine power for a given mass flow rate in an evaporator. Moreover, results show that the net power of the EP-OTEC cycle is clearly larger than that of the basic OTEC cycle, proving its superiority. The optimized EP-OTEC cycle using R152a yields a system efficiency of 4.0%, which is 38% higher than that of the basic OTEC cycle. (C) 2016 Elsevier Ltd. All rights reserved.