Mini-OTEC Operational Results

1981 ◽  
Vol 103 (3) ◽  
pp. 233-240 ◽  
Author(s):  
W. L. Owens ◽  
L. C. Trimble
Keyword(s):  
Single Point ◽  
Seawater Temperature ◽  
Electrical Power ◽  
Working Fluid ◽  
Mooring System ◽  
Closed Cycle ◽  
Pumping Power ◽  
Thermal Energy Conversion ◽  
Formed Part ◽  
Ocean Thermal Energy

The first at-sea ocean thermal energy conversion (OTEC) power was produced by Mini-OTEC on Aug. 2, 1979. The powerplant was mounted on a barge located approximately 2.2 km off Keahole Point on the Kona Coast of Hawaii. Ammonia was employed as the working fluid in a closed-cycle (Rankine) powerplant, which produced approximately 50 kW of gross electrical power at an average seawater temperature difference of 21°C. Parasitic pumping power requirements for seawater and ammonia resulted in a net electrical power of approximately 15 kW. Cold seawater was drawn from a depth of approximately 670 m through a 0.61 m dia polyethylene pipe, which formed part of a single-point tension leg mooring system. The longest period of continuous operation was 10 days, terminated by the conclusion of the program on Nov. 18, 1979.

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.

OTEC-1 Mooring

1982 ◽  
Vol 19 (03) ◽  
pp. 256-267
Author(s):  
Harold D. Ramsden ◽  
William A. Watts
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Single Point ◽  
Mooring System ◽  
Test Program ◽  
Large Capacity ◽  
Ocean Thermal Energy Conversion ◽  
Engineering Community ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Implementation of the Ocean Thermal Energy Conversion (OTEC-1) Early Ocean Test Program presented the engineering community with some unique challenges. One of the challenges was to provide a mooring system to keep the ship on station at least nine months per year for five years. The resulting design proved to be the most economical. It also became the world's deepest large-capacity single-point moor. This paper discusses the background, requirements and design details of the OTEC-1 Platform mooring system.

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.

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.

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.

The Ocean Thermal Gradient Hydraulic Power Plant and Its Scope

2003 ◽  
Author(s):  
Earl J. Beck
Keyword(s):  
Power Plant ◽  
Thermal Gradient ◽  
Cold Water ◽  
Working Fluid ◽  
Hydraulic Power ◽  
Tropical Oceans ◽  
Thermal Energy Conversion ◽  
Near Shore ◽  
Power Outputs ◽  
Ocean Thermal Energy

Heretofore, the concept of developing power from the tropical oceans, (Ocean Thermal Energy Conversion, or OTEC) has assumed the mooring of large platforms holding the plants in deep water to secure the coldest possible condensing water. As the Ocean Thermal Gradient Hydraulic Power Plant (OTGHPP) does not depend, on the expansion of a working fluid, other than forming a foam of steam bubbles. It does not need extremely cold water as would be dictated by Carnot’s concept of efficiency and the 2nd Law of Thermodynamics. Plants may be based on or near-shore on selected tropical islands, where cool but not extremely cold water may be available at moderate depths. This paper discusses the above possibilities and two possible plant locations, as well as projected power outputs. The location and utilization of large of amounts of power on isolated islands, where cabling of power to major population centers would not be feasible are discussed. Two that come to mind are the reduction of bauxite to produce aluminum and the of current interest is the electrolyzing of water to produce gaseous hydrogen fuel to be used in fuel cells, with oxygen as a by-product.

scholarly journals Dynamic Simulation of System Performance Change by PID Automatic Control of Ocean Thermal Energy Conversion

2020 ◽  
Vol 8 (1) ◽  
pp. 59 ◽  
Author(s):  
Lim Seungtaek ◽  
Lee Hoseang ◽  
Kim Hyeonju
Keyword(s):  
Control System ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Temperature Difference ◽  
Pid Control ◽  
Seawater Temperature ◽  
Ocean Thermal Energy Conversion ◽  
Control Value ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Near infinite seawater thermal energy, which is considered as an alternative to energy shortage, is expected to be available to 98 countries around the world. Currently, a demonstration plant is being built using closed MW class ocean thermal energy conversion (OTEC). In order to stabilize the operation of the OTEC, automation through a PID control is required. To construct the control system, the control logic is constructed, the algorithm is selected, and each control value is derived. In this paper, we established an optimal control system of a closed OTEC, which is to be demonstrated in Kiribati through simulation, to compare the operating characteristics and to build a system that maintains a superheat of 1 °C or more according to seawater temperature changes. The conditions applied to the simulation were the surface seawater temperature of 31 °C and the deep seawater temperature of 5.5 °C, and the changes of turbine output, flow rate, required power, and evaporation pressure of the refrigerant pump were compared as the temperature difference gradually decreased. As a result of comparing the RPM control according to the selected PID control value, it was confirmed that an error rate of 0.01% was shown in the temperature difference condition of 21.5 °C. In addition, the average superheat degree decreased as the temperature difference decreased, and after about 6000 s and a temperature decrease to 24 °C or less, the average superheat degree was maintained while maintaining the superheat degree of 1.7 °C on average.

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.

Improving the OTEC Power Plant Performance by Metal Hydride Energy Systems

1997 ◽  
Vol 119 (2) ◽  
pp. 145-151 ◽  
Author(s):  
M. Gambini
Keyword(s):  
Power Plant ◽  
Metal Hydride ◽  
Performance Optimization ◽  
Energy System ◽  
Point Of View ◽  
Plant Performance ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

A new system to improve the present OTEC (ocean thermal energy conversion) power plant performance is here presented. This is a metal hydride energy system operating as a “temperature upgrading” device which allows an increase of the OTEC plant working fluid temperature at the turbine inlet. The integrated MHTUP (metal hydride temperature upgrading)—OTEC plant has been investigated, taking into account the dynamic operations of MHTUP system and the OTEC pumping power increase due to the water circulation in the MHTUP system. The results show an increase in the OTEC net power of about 20 percent and the technological feasibility of the proposal. The large amounts of metal hydride and of heat transfer surface required by MHTUP system involve a critical situation from an economical point of view. The further analysis, particularly regarding the performance optimization and new plant arrangement of the MHTUP system, have to be developed in order to attain the economical feasibility of the proposal.

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