Coupled Analysis Approach in OTEC System Design

2012 ◽  
Author(s):  
Shan Shi ◽  
John Halkyard ◽  
Nishu Kurup ◽  
Lei Jiang
Keyword(s):  
System Design ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Cold Water ◽  
Large Diameter ◽  
Working Fluid ◽  
Coupled Analysis ◽  
Ammonia Vapor ◽  
Water Pipe ◽  
Floating Platform

Ocean Thermal Energy Conversion (OTEC) technologies based on floating platforms generate electrical energy by utilizing the temperature difference between the deep ocean water and the surface water. One typical offshore floating OTEC system uses the temperature difference to drive a heat engine, utilizing a closed-loop Rankine cycle with a working fluid such as ammonia (NH3). Cold water is pumped through a large flexible pipe from approximately 1000m depth to heat exchangers which condense the ammonia vapor. Warm water from the surface is pumped through heat exchangers to evaporate the liquid ammonia to drive the turbine. An OTEC floating platform could be a semisubmersible, a spar, or other typical offshore hull form with a taut or a catenary mooring system. As opposed to oil and gas production platforms, the OTEC system consists of a large diameter cold water pipe (CWP) which will participate in the global performance of the floating platform. Its unique behavior also includes the contribution of CWP entrained water which behaves differently in lateral and vertical directions due to its open bottom design. The hydrodynamic behavior of the large scale cold water pipe is an important consideration in the system design and analysis. The study presented in this work includes the application of a fully coupled analysis program with an accurate cold water pipe dynamic model in OTEC floating system analysis. The study could be useful for future guidance and reference on OTEC floating platform designs.

Analysis and Design of the Cold-Water Pipe (CWP) for the OTEC System with Application to OTEC-1

1980 ◽  
Vol 17 (03) ◽  
pp. 281-289
Author(s):  
Allan T. Maris ◽  
J. Randolph Paulling
Keyword(s):  
Cold Water ◽  
Large Diameter ◽  
Deep Ocean ◽  
Water Pipe ◽  
Floating Platform ◽  
Pipe System ◽  
Analysis And Design ◽  
Thermal Energy Conversion ◽  
Diameter Pipe ◽  
Ocean Thermal Energy

OTEC--Ocean Thermal Energy Conversion--currently requires a large floating platform and a 1000-metre-long, large-diameter pipe to supply deep ocean cold water. The design of the pipe in this system requires the development and application of analysis procedures to determine the response of the coupled platform pipe system to sea loadings. This paper discusses the development of the analysis procedures and the results of the application of these procedures to several pipe designs which appear feasible for an OTEC-1 MW power plant system.

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.

scholarly journals The Influence of Stack Position and Acoustic Frequency on the Performance of Thermoacoustic Refrigerator with the Standing Wave

2017 ◽  
Vol 38 (4) ◽  
pp. 89-107 ◽  
Author(s):  
Jakub Kajurek ◽  
Artur Rusowicz ◽  
Andrzej Grzebielec
Keyword(s):  
Standing Wave ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Acoustic Power ◽  
Working Fluid ◽  
Parallel Plates ◽  
Acoustic Frequency ◽  
Plate Spacing ◽  
Resonance Frequencies ◽  
Thermoacoustic Refrigerator

Abstract Thermoacoustic refrigerator uses acoustic power to transport heat from a low-temperature source to a high-temperature source. The increasing interest in thermoacoustic technology is caused due to its simplicity, reliability as well as application of environmentally friendly working fluids. A typical thermoacoustic refrigerator consists of a resonator, a stack of parallel plates, two heat exchangers and a source of acoustic wave. The article presents the influence of the stack position in the resonance tube and the acoustic frequency on the performance of thermoacoustic refrigerator with a standing wave driven by a loudspeaker, which is measured in terms of the temperature difference between the stack edges. The results from experiments, conducted for the stack with the plate spacing 0.3 mm and the length 50 mm, acoustic frequencies varying between 100 and 400 Hz and air as a working fluid are consistent with the theory presented in this paper. The experiments confirmed that the temperature difference for the stack with determined plate spacing depends on the acoustic frequency and the stack position. The maximum values were achieved for resonance frequencies and the stack position between the pressure and velocity node.

OTEC Cold Water Pipe Global Dynamic Design for Ship-Shaped Vessels

2013 ◽  
Author(s):  
Sherry Xiang ◽  
Peimin Cao ◽  
Richard Erwin ◽  
Steve Kibbee
Keyword(s):  
Cold Water ◽  
Dynamic Performance ◽  
Dynamic Responses ◽  
Outer Diameter ◽  
Water Pipe ◽  
Floating Platform ◽  
Reinforced Plastics ◽  
Global Dynamic ◽  
Offshore Industry ◽  
Ocean Thermal Energy

Ocean Thermal Energy Conversion (OTEC) technology has been considered as a renewable power generation for the tropical oceans where a thermal gradient from subsea to surface are higher than 20°C since 1980. In 2009, the OTEC technical readiness report has identified that semi-submersible, ship-shaped vessel and spar are most feasible to OTEC application. All three are technically mature and well-established floating facilities and have been widely manufactured and operated in offshore industry all over the world. A pilot OTEC development, led by Lockheed Martin (LM) Industry Team, has configured a semi-submersible floating platform. As an alternative design, SBM is developing OTEC designs based on converted ships. Ship shapes provide good access to facilities for practical operation and maintenance activities. Our study focused on demonstrating the feasibility of constructing and installing a 4 meter outer diameter Cold Water Pipe (CWP) based on conventional land-based manufacture of Fiberglass Reinforced Plastics (FRP) followed by installation with SBM marine equipment. Based on insights gained from this exercise, we will continue to develop the installation methods for larger diameter CWPs. The CWP is a key design challenge for OTEC since it must be strong enough to withstand the forces and motions while being light enough to be installed with available marine equipment. This paper focuses on the cold water pipe global dynamic performance hosted by a converted ship for a 10MW OTEC plantship offshore Hawaii. The offshore Hawaii location was selected for purposes of comparison rather than the existence of any specific prospective projects. The CWP is connected to the vessel via a sealed gimbal device that allows the CWP’s angular motions to be decoupled from the vessel. The fundamental understanding of CWP vibrations is discussed. The CWP global dynamic responses to extreme storms and operational fatigue environments are presented. Vortex Induced Vibration (VIV) and other design issues are discussed. The key global design considerations of CWP for the ship-shaped vessel are identified and summarized.

Simplified Formulation of Coupled System Between Moored Ship and Elastic Pipe for OTEC Plantship

2021 ◽  
Author(s):  
Ryoya Hisamatsu ◽  
Tomoaki Utsunomiya
Keyword(s):  
Numerical Simulation ◽  
Cold Water ◽  
Early Stage ◽  
Large Diameter ◽  
Coupled System ◽  
Equation Of Motion ◽  
Floating Body ◽  
Floating Platform ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Abstract A commercial-scale Ocean Thermal Energy Conversion (OTEC) floating platform will require a large diameter Cold Water Pipe (CWP) to be attached. Several studies have analyzed the dynamic behavior of the coupled system between the floating platform and the CWP. However, the characteristic of the coupled behavior has not yet been fully understood. This study aims to formulate the coupled system of an OTEC floating plant and simplify the formula to clarify the characteristic of the coupled behavior. The formula is suitable for validation of the numerical simulation results and the preliminary design of an OTEC plant. In the first section of this paper, we derive the equation of motion and equilibrium of the direct moored floating body and an elastic pipe hanged off from the floating body. In the second section, we verify the formula for a 100MW OTEC plantship with 800m length and 12m diameter CWP. The Response Amplitude Operator (RAO) is calculated by solving the equation of motion and statistics responses in 3 hours are compared with a numerical simulation by OrcaFlex. As the result of the comparison, we observed that the present formula is applicable in the early stage of the practical design loop.

Analysis of Coupled Hull: Cold Water Pipe Mooring for Offshore Desalination Plant

2007 ◽  
Author(s):  
A. Venkata Subbaiah ◽  
R. Sundaravadivelu ◽  
V. Anantha Subramanian
Keyword(s):  
Cold Water ◽  
Numerical Study ◽  
Scale Model ◽  
Coupled Analysis ◽  
Water Pipe ◽  
Ocean Engineering ◽  
Wave Condition ◽  
Desalination Plant ◽  
Tension Response ◽  
Wave Basin

The design of a 0.25 Million Litres per Day (MLD) low pressure desalination plant in 150m water depth using a Tension Leg Counterweight Platform (TLCP) consisting of a 10m diameter hull, 1m diameter cold water pipe with counterweight and vertical taut mooring has been carried out. A 1:50 scale model of the TLCP is tested in the 30m × 30m × 3m wave basin in Department of Ocean Engineering, IIT Madras. The tensions in mooring lines are measured using load cells. The coupled analysis of the TLCP is studied using the Nonlinear Analysis of Offshore Structures (NAOS) program developed at IIT MADRAS. The measured tension response of mooring line compare well with numerical results. The Surge, Heave, Pitch and Tension response amplitude operators for the TLCP obtained from numerical study are observed to be within the permissible limits for the operational wave condition whereas the TLCP performs satisfactorily for the survival wave condition. The numerical and model studies are carried out for regular waves. The effect of counterweight and pretension on platform motions is studied in this paper.

scholarly journals FLOW FIELD NEAR AN OCEAN THERMAL ENERGY CONVERSION PLANT

1976 ◽  
Vol 1 (15) ◽  
pp. 174 ◽  
Author(s):  
D.M. Sheppard ◽  
G.M. Powell ◽  
I.B. Chou
Keyword(s):  
Low Temperature ◽  
Shear Flow ◽  
Flow Field ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Temperature Difference ◽  
Cold Water ◽  
Water Pipe ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

The flow field in the vicinity of an Ocean Thermal Energy Conversion (OTEC) Plant is extremely complex. The plants will normally be located in an area of relatively high surface currents and the location must also be such that a large temperature difference exists between the lower layers and the surface. Locations that demonstrate this characteristic can in many cases be modeled as a two layer fluid as shown in Figure 1. A number of different designs for the OTEC plants are being considered, but they all have one thing in common, a large vertical cold water pipe. This pipe extends from near the surface to some point in the cold water layer (see Figure 1). In some designs this pipe is as large as 40 m in diameter and 460 m in length. Having such a large object penetrating the interface between the two temperature layers in the presence of a shear flow can significantly alter the character of the interface. The highly turbulent wake downstream from the pipe can drastically effect the mixing across this density interface. A conventional heat engine cycle is used in the plant with the high temperature source being the water in the upper layers and the low temperature reservoir being the water from the lower depths. \ Since the temperature difference is small for this type of plant (20° max.), vast quantities of both high and low temperature water must be used. The intake and discharge for the warm water as well as the cold water discharge will be in the upper layer; the intake for the cold water will be in the lower layer at or near the end of the cold water pipe. The flow problem is thus one of a vertical cylinder in a two layer stratified shear flow with sources and sinks located along the cylinder.

Thermodynamic Effect on Cavitation Performances and Cavitation Instabilities in an Inducer

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Kengo Kikuta ◽  
Yoshiki Yoshida ◽  
Mitsuo Watanabe ◽  
Tomoyuki Hashimoto ◽  
Katsuji Nagaura ◽  
...  
Keyword(s):  
Liquid Nitrogen ◽  
Temperature Difference ◽  
Cavity Length ◽  
Cold Water ◽  
Experimental Results ◽  
Working Fluid ◽  
Blade Passage ◽  
Thermodynamic Effect

Based on the length of the tip cavitation as an indication of cavitation, we focused on the effect of thermodynamics on cavitation performances and cavitation instabilities in an inducer. Comparison of the tip cavity length in liquid nitrogen (76K and 80K) as working fluid with that in cold water (296K) allowed us to estimate the strength of the thermodynamic effect on the cavitations. The degree of thermodynamic effect was found to increase with an increase of the cavity length, particularly when the cavity length extended over the throat of the blade passage. In addition, cavitation instabilities occurred both in liquid nitrogen and in cold water when the cavity length increased. Subsynchronous rotating cavitation appeared both in liquid nitrogen and in cold water. In the experiment using liquid nitrogen, the temperature difference between 76K and 80K affected the range in which the subsynchronous rotating cavitation occurred. In contrast, deep cavitation surge appeared only in cold water at lower cavitation numbers. From these experimental results, it was concluded that when the cavity length extends over the throat, the thermodynamic effect also affects the cavitation instabilities as a “thermal damping” through the unsteady cavitation characteristics.

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