Ocean Thermal Energy Conversion (OTEC): Choosing a Working Fluid

2009 ◽  
Author(s):  
James H. Anderson
Keyword(s):  
Thermal Energy ◽  
Power Plants ◽  
Thermal Power ◽  
Deep Ocean ◽  
Working Fluid ◽  
Closed Cycle ◽  
Working Fluids ◽  
Advantages And Disadvantages ◽  
Open Cycle ◽  
Ocean Thermal Energy

Ocean thermal energy plants are thermal power plants that use warm ocean surface water as a source of heat and cold seawater from the deep ocean as a heat sink. A historical perspective along with the development of the technology will be presented. A short description describing the subtle differences between OTEC and fossil and nuclear plants will be presented. Open cycle OTEC and closed cycle OTEC will be described with a focus on the influence of choice of working fluid on the design of a plant. Various working fluids could be selected for use in closed cycle OTEC plants. A review and comparison of potential working fluids will address the advantages and disadvantages of the individual fluids. Their characteristics along with a comparison to water as a working fluid in open cycle OTEC will be explained.

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.

A New Improved Ocean Thermal Energy Conversion System With Suitable Floating Vessel Design

2009 ◽  
Author(s):  
Nagan Srinivasan
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Power Plants ◽  
Cold Water ◽  
Deep Ocean ◽  
Capital Cost ◽  
Working Fluid ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Demand for energy worldwide is increasing significantly. A need for alternate energy sources has been brought to the attention of scientists and engineers. Ocean Thermal Energy Conversion (OTEC) is one among them which is in the development stage for the past three to four decades. Great amount of energy is available in deep-ocean with temperature difference between in upper surface-layer and in deep-ocean layer with maximum range of say up to 25 degree C in localized offshore locations near of equatorial waters. However, the technology is not in commercial operation due to the need of large capital cost. Advances in heat-exchanger material, cold-water pumps and working-fluid are the areas that research has been done extensively to make OTEC successful system. However none of that improvement in the design made OTEC technology attractive for cost effective commercialization. This paper proposes a new feasible OTEC system for about 100 MW power plants with significant change from the conventional system. The main purpose of the proposed new OTEC system is to reduce the capital cost significantly and make it commercial feasible. New types of floating vessels are proposed to support the new OTEC system to achieve cost efficiency. The floaters are very innovatively designed to support the new OTEC system. The new OTEC system with the corresponding floater significantly reduces the capital-cost of the OTEC system compared to the conventional OTEC system. Both the new OTEC system and the supporting floater system are presented herein.

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.

Bureau of Mines Progress in Developing Open and Closed-Cycle Coal-Burning Gas Turbine Power Plants

1966 ◽  
Vol 88 (4) ◽  
pp. 313-320 ◽  
Author(s):  
J. Smith ◽  
D. C. Strimbeck ◽  
N. H. Coates ◽  
J. P. McGee
Keyword(s):  
Gas Turbine ◽  
Refractory Metal ◽  
Power Plants ◽  
Turbine Blades ◽  
Coal Ash ◽  
Inert Gas ◽  
Working Fluid ◽  
Closed Cycle ◽  
Separation Systems ◽  
Open Cycle

Closed-cycle developments include tests of a turbocompressor with hydrodynamic gas bearings. The working fluid is inert gas, with turbine inlet temperatures to 1600 F. A refractory-metal turbine for tests at 1950 F is described. Open-cycle operations for 1963 hours with turbine blades specially designed to resist erosion by coal ash particles are described. Estimated life of the rotor and stator blading was 20,000 and 5000 hours, respectively. Efforts to increase blade life by reducing the amount of ash entering the turbine through improvements in combustion and ash separation systems are described.

scholarly journals The effect of different organic fluids on performances of binary slag washing water power plants

2017 ◽  
Vol 38 (3) ◽  
pp. 49-62
Author(s):  
Zi-Ao Li ◽  
Yanna Liu ◽  
Peng Dong ◽  
Yingjie Zhang ◽  
Song Xiao
Keyword(s):  
Thermal Energy ◽  
Lower Energy ◽  
Power Plants ◽  
Cycle Performance ◽  
Working Fluid ◽  
Working Fluids ◽  
Water Power ◽  
Energy And Exergy ◽  
Organic Fluids ◽  
Washing Water

AbstractIn this paper, 3 typical organic fluids were selected as working fluids for a sample slag washing water binary power plants. In this system, the working fluids obtain the thermal energy from slag washing water sources. Thus, it plays a significant role on the cycle performance to select the suitable working fluid. Energy and exergy efficiencies of 3 typical organic fluids were calculated. Dry type fluids (i.e., R227ea) showed higher energy and exergy efficiencies. Conversely, wet fluids (i.e., R143a and R290) indicated lower energy and exergy efficiencies, respectively.

Organic Working Fluids for a Combined Power and Cooling Cycle

2005 ◽  
Vol 127 (2) ◽  
pp. 125-130 ◽  
Author(s):  
Sanjay Vijayaraghavan ◽  
D. Y. Goswami
Keyword(s):  
Power Plants ◽  
Thermodynamic Cycle ◽  
Working Fluid ◽  
Water Mixture ◽  
Heat Sources ◽  
Absorption Refrigeration ◽  
Ammonia Water ◽  
Working Fluids ◽  
Fluid Mixtures ◽  
Advantages And Disadvantages

A new thermodynamic cycle has been developed for the simultaneous production of power and cooling from low-temperature heat sources. The proposed cycle combines the Rankine and absorption refrigeration cycles, providing power and cooling as useful outputs. Initial studies were performed with an ammonia-water mixture as the working fluid in the cycle. This work extends the application of the cycle to working fluids consisting of organic fluid mixtures. Organic working fluids have been used successfully in geothermal power plants, as working fluids in Rankine cycles. An advantage of using organic working fluids is that the industry has experience with building turbines for these fluids. A commercially available optimization program has been used to maximize the thermodynamic performance of the cycle. The advantages and disadvantages of using organic fluid mixtures as opposed to an ammonia-water mixture are discussed. It is found that thermodynamic efficiencies achievable with organic fluid mixtures, under optimum conditions, are lower than those obtained with ammonia-water mixtures. Further, the refrigeration temperatures achievable using organic fluid mixtures are higher than those using ammonia-water mixtures.

Ocean Thermal Energy Conversion Primer

2002 ◽  
Vol 36 (4) ◽  
pp. 25-35 ◽  
Author(s):  
L. A. Vega
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Heat Engine ◽  
Bottom Layer ◽  
Working Fluid ◽  
Turbine Generator ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Open Cycle ◽  
Ocean Thermal Energy

The vertical temperature distribution in the open ocean can be simplistically described as consisting of two layers separated by an interface. The upper layer is warmed by the sun and mixed to depths of about 100 m by wave motion. The bottom layer consists of colder water formed at high latitudes. The interface or thermocline is sometimes marked by an abrupt change in temperature but more often the change is gradual. The temperature difference between the upper (warm) and bottom (cold) layers ranges from 10°C to 25°C, with the higher values found in equatorial waters. This implies that there are two enormous reservoirs providing the heat source and the heat sink required for a heat engine. A practical application is found in a system (heat engine) designed to transform the thermal energy into electricity. This is referred to as OTEC for Ocean Thermal Energy Conversion. Several techniques have been proposed to use this ocean thermal resource; however, at present it appears that only the closed cycle (CC-OTEC) and the open cycle (OC-OTEC) schemes have a solid foundation of theoretical as well as experimental work. In the CC-OTEC system, warm surface seawater and cold seawater are used to vaporize and condense a working fluid, such as anhydrous ammonia, which drives a turbine-generator in a closed loop producing electricity. In the OC-OTEC system, seawater is flash-evaporated in a vacuum chamber. The resulting low-pressure steam is used to drive a turbine-generator. Gold seawater is used to condense the steam after it has passed through the turbine. The open-cycle can, therefore, be configured to produce desalinated water as well as electricity.

Organic Working Fluids for a Combined Power and Cooling Cycle

2003 ◽  
Author(s):  
Sanjay Vijayaraghavan ◽  
D. Y. Goswami
Keyword(s):  
Power Plants ◽  
Thermodynamic Cycle ◽  
Working Fluid ◽  
Water Mixture ◽  
Heat Sources ◽  
Absorption Refrigeration ◽  
Ammonia Water ◽  
Working Fluids ◽  
Fluid Mixtures ◽  
Advantages And Disadvantages

A new thermodynamic cycle has been developed for the simultaneous production of power and cooling from low temperature heat sources. The proposed cycle combines the Rankine and absorption refrigeration cycles, providing power and cooling as useful outputs. Initial studies were performed with an ammonia-water mixture as the working fluid in the cycle. This work extends the application of the cycle to working fluids consisting of organic fluid mixtures. Organic working fluids have been used successfully in geothermal power plants, as working fluids in Rankine cycles. An advantage of using organic working fluids is that the industry has experience with building turbines for these fluids. A commercially available optimization program has been used to maximize the thermodynamic performance of the cycle. The advantages and disadvantages of using organic fluid mixtures as opposed to an ammonia-water mixture are discussed. It is found that thermodynamic efficiencies achievable with organic fluid mixtures, under optimum conditions, are lower than those obtained with ammonia-water mixtures. Further, the refrigeration temperatures achievable using organic fluid mixtures are higher than those using ammonia-water mixtures.

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