Optimization of a Closed-Cycle OTEC System

1990 ◽  
Vol 112 (4) ◽  
pp. 247-256 ◽  
Author(s):  
Haruo Uehara ◽  
Yasuyuki Ikegami
Keyword(s):  
Heat Exchangers ◽  
Sea Water ◽  
Working Fluid ◽  
Turbine Efficiency ◽  
Thermal Energy Conversion ◽  
Calculation Results ◽  
Change Temperature ◽  
Ocean Thermal Energy ◽  
Powell Method ◽  
Method Of Steepest Descent

Optimization of an Ocean Thermal Energy Conversion (OTEC) system is carried out by the Powell Method (the method of steepest descent). The parameters in the objective function consist of the velocities of cold sea water and warm sea water passing through the heat exchangers, the phase change temperature, and turbine configuration (specific speed, specific diameter, ratio of blade to diameter). Numerical results are shown for a 100-MW OTEC plant with plate-type heat exchangers using ammonia as working fluid, and are compared with calculation results for the case when the turbine efficiency is fixed.

scholarly journals Determine the best location for Ocean Thermal Energy Conversion (OTEC) in Iranian Seas

2016 ◽  
Vol 10 (5) ◽  
pp. 32 ◽  
Author(s):  
Ashrafoalsadat Shekarbaghani
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Caspian Sea ◽  
Power Plants ◽  
Sea Water ◽  
Working Fluid ◽  
The South ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Two-thirds of the earth's surface is covered by oceans. These bodies of water are vast reservoirs of renewable energy.<strong> </strong>Ocean Thermal Energy Conversion technology, known as OTEC, uses the ocean’s natural thermal gradient to generate power. In geographical areas with warm surface water and cold deep water, the temperature difference can be leveraged to drive a steam cycle that turns a turbine and produces power. Warm surface sea water passes through a heat exchanger, vaporizing a low boiling point working fluid to drive a turbine generator, producing electricity. OTEC power plants exploit the difference in temperature between warm surface waters heated by the sun and colder waters found at ocean depths to generate electricity. This process can serve as a base load power generation system that produces a significant amount of renewable, non-polluting power, available 24 hours a day, seven days a week. In this paper investigated the potential of capturing electricity from water thermal energy in Iranian seas (Caspian Sea, Persian Gulf and Oman Sea). According to the investigated parameters of OTEC in case study areas, the most suitable point in Caspian Sea for capturing the heat energy of water is the south part of it which is in the neighborhood of Iran and the most suitable point in the south water of Iran, is the Chahbahar port.

Performance Analysis of an OTEC Plant and a Desalination Plant Using an Integrated Hybrid Cycle

1996 ◽  
Vol 118 (2) ◽  
pp. 115-122 ◽  
Author(s):  
Haruo Uehara ◽  
Akio Miyara ◽  
Yasuyuki Ikegami ◽  
Tsutomu Nakaoka
Keyword(s):  
Performance Analysis ◽  
Heat Exchangers ◽  
Sea Water ◽  
Working Fluid ◽  
Heat Transfer Area ◽  
Total Heat Transfer ◽  
Desalination Plant ◽  
Plate Type ◽  
Method Of Steepest Descent ◽  
Hybrid Cycle

A performance analysis of an OTEC plant using an integrated hybrid cycle (I–H OTEC Cycle) has been conducted. The I–H OTEC cycle is a combination of a closed-cycle OTEC plant and a spray flash desalination plant. In an I–H OTEC cycle, warm sea water evaporates the liquid ammonia in the OTEC evaporator, then enters the flash chamber and evaporates itself. The evaporated steam enters the desalination condenser and is condensed by the cold sea water passed through the OTEC condenser. The optimization of the I–H OTEC cycle is analyzed by the method of steepest descent. The total heat transfer area of heat exchangers per net power is used as an objective function. Numerical results are reported for a 10 MW I–H OTEC cycle with plate-type heat exchangers and ammonia as working fluid. The results are compared with those of a joint hybrid OTEC cycle (J–H OTEC Cycle).

Shell-and-Plate-Type Heat Exchangers for OTEC Plants

1984 ◽  
Vol 106 (3) ◽  
pp. 286-290 ◽  
Author(s):  
H. Uehara ◽  
H. Kusuda ◽  
M. Monde ◽  
T. Nakaoka ◽  
H. Sumitomo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchangers ◽  
Porous Plate ◽  
Working Fluid ◽  
Performance Tests ◽  
Overall Heat Transfer Coefficient ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy ◽  
Plate Type

New titanium, shell-and-plate type heat exchangers for ocean-thermal-energy-conversion (OTEC) plants have been developed which include three different plate types (fluted, impinging, and porous-surface) for the evaporator and two kinds of plates (No. 1 and No. 2) for the condenser. Performance tests with fresh water show that the overall heat transfer coefficient U of the evaporator using the porous plate is the highest among the three plates; it can reach 4000–4500 W/m2K using ammonia as the working fluid and 3500–4000 W/m2K for a Freon, R-22. The U of the condenser using the No. 2 plate is higher than that using the No. 1 plate; it can reach 3800–4500 W/m2K for ammonia and 2000–3500 W/m2K for R-22.

Performance Analysis of 15 kW Closed Cycle Ocean Thermal Energy Conversion System With Different Working Fluids

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Jianying Gong ◽  
Tieyu Gao ◽  
Guojun Li
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Sea Water ◽  
Working Fluid ◽  
Closed Cycle ◽  
Working Fluids ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Stable Operating ◽  
Ocean Thermal Energy

Closed cycle ocean thermal energy conversion (CC-OTEC) is a way to generate electricity by the sea water temperature difference from the upper surface to the different depth. This paper presents the performance of a 15 kW micropower CC-OTEC system under different working fluids. The results show that both butane and isobutane are not proper working fluids for the CC-OTEC system because the inlet stable operating turbine pressure is in a very narrow range. R125, R143a, and R32, especially R125, are suggested to be the transitional working fluids for CC-OTEC system for their better comprehensive system performance. Moreover, it is recommended that propane should be a candidate for the working fluid because of its excellent comprehensive properties and environmental friendliness. However, propane has inflammable and explosive characteristics. As for the natural working fluid ammonia, almost all performance properties are not satisfactory except the higher net output per unit sea water mass flow rate. But ammonia has relative broader range of the stable operating turbine inlet pressure, which has benefits for the practical plant operation.

Thermodynamic Analysis of Ocean Thermal Energy Conversion System With Different Working Fluids

2017 ◽  
Author(s):  
Dashu Li ◽  
Li Zhang ◽  
Xili Duan ◽  
Xiaosuai Tian
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Thermal Efficiency ◽  
Sea Water ◽  
Working Fluid ◽  
Ocean Temperature ◽  
Water Pump ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

A thermodynamic model is developed for ocean thermal energy conversion (OTEC) systems. Considering the narrow temperature range in the evaporator, different refrigerants including R717, R134a and R600 were analyzed and compared under sub-critical state with practical ocean thermal conditions. The results show that larger ocean temperature differences will lead to higher evaporation pressures, and less pumping power requirements for all pumps, i.e., warm sea water pump, cold sea water pump and pumps for the working fluid. The thermal efficiency of different systems and the net power output were found to be closely related to ocean temperature difference, with a positive linear relationship. It was also found that R717 provides the highest thermal efficiency with the least pump power requirement. This working fluid could potentially be used for OTEC system development. This study provides useful insights to the design and equipment selection of OTEC systems.

scholarly journals Thermoelectric Ocean Thermal Energy Conversion

1980 ◽  
Vol 102 (2) ◽  
pp. 119-127 ◽  
Author(s):  
M. S. Bohn ◽  
D. K. Benson ◽  
T. S. Jayadev
Keyword(s):  
Solid State ◽  
Heat Exchangers ◽  
System Performance ◽  
Working Fluid ◽  
Thermoelectric Generators ◽  
Closed Cycle ◽  
Thermal Energy Conversion ◽  
Power Modules ◽  
Ocean Thermal Energy ◽  
High Level

A novel thermoelectric OTEC concept is proposed and compared with the ammonia closed-cycle designs. The thermoelectric OTEC uses no working fluid and therefore requires no pressure vessel, working fluid pumps, or turbogenerator. These components are replaced by power modules which are heat exchangers integrated with thermoelectric generators. The thermoelectric OTEC concept offers several potential advantages including: higher reliability system performance through the use of a high level of redundancy and long-lived, solid-state thermoelectric generators with no moving parts, greater safety for crew and environment by elimination of the pressurized working fluid, and the possibility of comparable system costs, i.e., costs near $2000/kWe (net) in 1980 dollars.

Preliminary Design of a 1-MWe OTEC Test Plant

1982 ◽  
Vol 104 (1) ◽  
pp. 3-8 ◽  
Author(s):  
T. Kajikawa
Keyword(s):  
Cold Water ◽  
Working Fluid ◽  
Test Plant ◽  
Mooring System ◽  
Preliminary Design ◽  
Closed Cycle ◽  
Water Pipe ◽  
Thermal Energy Conversion ◽  
Design Value ◽  
Ocean Thermal Energy

An ocean-based, 1-MWe (gross) test plant has been planned to establish the feasibility of OTEC (ocean thermal energy conversion) power generation in the revised Sunshine Project. The preliminary design of the proposed test plant employs a closed-cycle power system using ammonia as the working fluid on a barge-type platform with a rigid-arm-type, detachable, single-buoy mooring system. Two types each of titanium evaporators and condensers are to be included. The steel, cold-water pipe is suspended from the buoy. The design value of the ocean temperature difference is 20 K. The paper presents an overview of the preliminary design of the test plant and the tests to be conducted.

Experimental Studies on the Seawater Desalination System Based on Ocean Thermal Energy Conversion

2013 ◽  
Vol 448-453 ◽  
pp. 3254-3258
Author(s):  
Feng Yun Chen ◽  
Wei Min Liu ◽  
Liang Zhang
Keyword(s):  
Heat Exchanger ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Sea Water ◽  
Economic Benefits ◽  
Seawater Desalination ◽  
Tube Heat Exchanger ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Seawater desalination system has been established based on the ocean thermal energy conversion in this paper. Through compared finned tube heat exchanger with round tube heat exchanger obtained the fresh water output at different temperature and flow velocity of the warm and cold sea water. In this system the energy of the warm and cold sea water has been fully utilized, and so improved the economic benefits of the ocean thermal energy conversion.

Biofouling Monitors for Noncylindrical OTEC Heat Exchanger Tubes

1982 ◽  
Vol 104 (3) ◽  
pp. 257-261
Author(s):  
T. M. Kuzay ◽  
C. B. Panchal ◽  
A. P. Gavin
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Thermal Energy Conversion ◽  
Shell And Tube ◽  
Ocean Thermal Energy ◽  
Analytical Approaches

Heat-transfer monitors (HTMs) have been used since 1976 to measure the reduction in the seawater heat-transfer coefficient due to buildup of biofouling and corrosion products inside circular tubes of shell-and-tube heat exchangers being developed for ocean thermal energy conversion (OTEC) plants. For OTEC heat exchangers (HXs) with other tube geometries, special, modified HTMs, which we call STMs, are being sought. The analytical approaches and calibration results to date are summarized for STMs of two types: (i) an STM simulating a rectangular seawater passage in a compact, aluminum, plate-fin HX, and (ii) an STM for a helical stainless-steel tube. The development of type 1 has been successful. A software change is needed for type 2.

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