Performance Evaluation Concept for Ocean Thermal Energy Conversion toward Standardization and Intelligent Design

Abstract

Ocean thermal energy conversion (OTEC) uses a very simple process to convert the thermal energy stored mainly in tropical oceans into electricity. In designs, operations, and evaluations, we need to consider the unique characteristics of OTEC to achieve the best performance or lower the electricity cost of projects. The concept and design constraints of OTEC power generation differ from those of conventional thermal power plants due to the utilization of a low temperature difference. This research theoretically recognizes the unique characteristics of the energy conversion system and summarizes the appropriate performance evaluation methods for OTEC based on finite-time thermodynamics and the equilibrium condition of the heat source. In addition, it presents the concept of normalization of thermal efficiency for OTEC and exergy efficiency based on the available thermal energy in the ocean defined as the transferable thermal energy from the ocean and the equilibrium condition as the dead state for exergy. The differences between conventional thermal efficiency and the effectiveness of the evaluation methods are visualized using the various reference design data, and it is ascertained that there is no clear relation between the conventional thermal efficiency and exergy efficiency, whereas the normalized thermal efficiency is definitely proportional to the exergy efficiency. Moreover, the exergy efficiency shows the effectiveness of the staging Rankine, Kalina, and Uehara cycles. Therefore, the normalized thermal efficiency and the exergy efficiency are important to analyze the heat and mass balance as well as improvement of the system.

Ocean Thermal Energy Conversion: Technological Readiness and Indonesia Progress

“…The result shows the multistage open cycle will be the highest exergy efficiency. Yasunaga et al (2021) shows the relationship between thermal efficiency and the work of heat engines in OTEC and propose to use the exergy efficiency for performance evaluation in OTEC by comparing the thermal efficiency and exergy efficiency in various designs of OTEC. Ikegami and Bejan (1998) theoretically expressed the relationship between the net power and thermal efficiency and exergy efficiency in OTEC.…”

Four-Objective Optimization for an Irreversible Porous Medium Cycle with Linear Variation in Working Fluid’s Specific Heat

“…Finite time thermodynamics (FTT) [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ] has been made significant progress in the research of thermal cycles and processes, including optimal configurations [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ] and optimal performances [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. The FTT studies of internal combustion engine cycles mostly focus on the following factors [ 33 ]: the effects of different loss models such as heat transfer loss (HTL) [ 34 ], friction loss (FL) [ 35 ] and internal irreversibility loss (IIL) [ 36 ] on the performances of cycles; the effects of power output ( ) and thermal efficiency ( ) [ 37 ], efficient power ( ) [ 38 ], ecological function ( ) [ 39 ], power density ( ) [ 40 ] and other ob...…”

Optimizing Power and Thermal Efficiency of an Irreversible Variable-Temperature Heat Reservoir Lenoir Cycle

“…According to the nature of the cycle, the researched heat engine (HEG) cycles include steady flow cycles [32][33][34][35][36][37] and reciprocating cycles [38][39][40][41][42][43][44][45][46][47][48]. For the steady flow HEG cycle, considering the temperature change of the heat reservoir (HR) can make the cycle closer to the actual working state of the HEG, therefore, some scholars have studied the steady flow cycles with variable temperature HR [49][50][51][52][53].…”