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

Highlights

Liquid-vapor ejector and a motive pump were used to enhance the system efficiency of the OTEC, called EP-OTEC.

By applying the liquid-vapor ejector into the OTEC, the turbine outlet pressure becomes lower than that in the basic OTEC.

The system efficiency of EP-OTEC was 4.0%, relatively 38% higher than that of the basic OTEC (2.9%).

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.

Keywords

  • OTEC (Ocean Thermal Energy Conversion) cycle;
  • EP-OTEC cycle;
  • Liquid-vapor ejector;
  • Motive pump

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