Optimization design and exergy analysis of organic rankine cycle in ocean thermal energy conversion

Abstract Performance analytical function and exergy efficiency of organic rankine cycle (ORC) in ocean thermal energy conversion (OTEC) are derived and optimized in this paper. Firstly, the state function corresponding to every point in ORC and depending strongly on the temperature of the evaporator and condenser is successfully achieved, where the suitable working fluids include, but not limited to, ammonia, r134a, etc. And then the system net power output function is achieved based on the characteristics of the ORC, which is mainly decided by the warm seawater temperature, warm seawater mass flow rate, evaporator temperature, condenser temperature, etc. After that, a further optimization is carried out to maximize the net power output of ORC. Results show that ammonia is a good choice for ORC utilized in OTEC from net power output viewpoint. In addition, thermal efficiency and exergy efficiency at maximum net power output are also given as reference. Finally, the preliminary design criteria of ORC in OTEC illustrates that the design of the ORC in a certain scale should choose its corresponding reasonable heat exchanger since it is a choke point for the larger maximum net power output.

[1]  A. Bejan,et al.  On the Thermodynamic Optimization of Power Plants With Heat Transfer and Fluid Flow Irreversibilities , 1998 .

[2]  Chih Wu,et al.  Power optimization of a finite-time Rankine heat engine , 1989 .

[3]  Haruo Uehara,et al.  Performance Analysis of an OTEC Plant and a Desalination Plant Using an Integrated Hybrid Cycle , 1996 .

[4]  Sang Soo Kim,et al.  An analytical formula for the estimation of a rankine‐cycle heat engine efficiency at maximum power , 1991 .

[5]  S. G. Penoncello,et al.  Ashrae Thermodynamic Properties of Refrigerants , 1987 .

[6]  Shao Yingjuan,et al.  A biomass-fired micro-scale CHP system with organic Rankine cycle (ORC) – Thermodynamic modelling studies , 2011 .

[7]  Haruo Uehara,et al.  Conceptual design of ocean thermal energy conversion (OTEC) power plants in the Philippines , 1988 .

[8]  F. Curzon,et al.  Efficiency of a Carnot engine at maximum power output , 1975 .

[9]  Abdul Khaliq.  Finite-time heat-transfer analysis and generalized power-optimization of an endoreversible Rankine heat-engine , 2004 .

[10]  Y. Ikegami,et al.  OPTIMIZATION OF A CLOSED-CYCLE OTEC SYSTEM , 1990 .

[11]  Yasuyuki Ikegami,et al.  Direct Method to Maximize Net Power Output of Rankine Cycle in Low-Grade Thermal Energy Conversion , 2010 .

[12]  P. Nag,et al.  Exergy analysis of the Kalina cycle , 1998 .

[13]  Guo Tao,et al.  Performance comparison and parametric optimization of subcritical Organic Rankine Cycle (ORC) and transcritical power cycle system for low-temperature geothermal power generation , 2011 .

[14]  Emilie Sauret,et al.  Candidate radial-inflow turbines and high-density working fluids for geothermal power systems , 2011 .

[15]  Changxu Wu.  Specific power optimization of closed-cycle OTEC plants , 1990 .

[16]  Yiping Dai,et al.  Exergy analyses and parametric optimizations for different cogeneration power plants in cement industry , 2009 .

[17]  Zhen Lu,et al.  Performance analysis and optimization of organic Rankine cycle (ORC) for waste heat recovery , 2007 .

[18]  C. Gault.  THE PHYSIOLOGY OF THE ATRIO-VENTRICULAR CONNECTION IN THE TURTLE: III. The Influence of the Vagi and of the Sympathetic Nerves on its Rhythm-Forming Power , 1917 .

[19]  Lourdes García-Rodríguez,et al.  Analysis and optimization of the low-temperature solar organic Rankine cycle (ORC) , 2010 .