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.

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.

Modeling of a Semisubmersible Floating Offshore Wind Platform in Severe Waves

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Irene Rivera-Arreba ◽  
Niek Bruinsma ◽  
Erin E. Bachynski ◽  
Axelle Viré ◽  
Bo T. Paulsen ◽  
...  
Keyword(s):  
Experimental Data ◽  
Potential Flow ◽  
Stokes Equations ◽  
Second Order ◽  
Offshore Wind ◽  
Computationally Efficient ◽  
Viscous Effects ◽  
Floating Platform ◽  
Global Dynamic ◽  
Offshore Industry

Floating offshore wind platforms may be subjected to severe sea states, which include both steep and long waves. The hydrodynamic models used in the offshore industry are typically based on potential-flow theory and/or Morison’s equation. These methods are computationally efficient and can be applied in global dynamic analysis considering wind loads and mooring system dynamics. However, they may not capture important nonlinearities in extreme situations. The present work compares a fully nonlinear numerical wave tank (NWT), based on the viscous Navier–Stokes equations, and a second-order potential-flow model for such situations. A comparison of the NWT performance with the experimental data is first completed for a moored vertical floating cylinder. The OC5-semisubmersible floating platform is then modeled numerically both in this nonlinear NWT and using a second-order potential-flow based solver. To test both models, they are subjected to nonsteep waves and the response in heave and pitch is compared with the experimental data. More extreme conditions are examined with both models. Their comparison shows that if the structure is excited at its heave natural frequency, the dependence of the response in heave on the wave height and the viscous effects cannot be captured by the adjusted potential-flow based model. However, closer to the inertia dominated region, the two models yield similar responses in pitch and heave.

scholarly journals Affects of the Cold Water Pipe Depth in Ocean Thermal Energy Converter Plants with respect to Power Generation Efficiency

2015 ◽  
Vol 2 ◽  
pp. 50-66 ◽  
Author(s):  
Helia Danielle Giordani ◽  
Matheus Lages ◽  
Miguel Medina ◽  
Jade Tan-Holmes
Keyword(s):  
Power Generation ◽  
Surface Water ◽  
Thermal Energy ◽  
Power Efficiency ◽  
Cold Water ◽  
Mechanical Energy ◽  
Heat Engine ◽  
Water Pipe ◽  
Generation Efficiency ◽  
Ocean Thermal Energy

The Ocean provides an extensive renewable energy source. It is the exploitation of the thermal gradient between the warmed surface water and the deep cold water. A heat engine was developed to use the surface water as a heat source and the deep water as a cold source in order to convert thermal energy into mechanical energy and generate electricity. This process is called Ocean Thermal Energy Conversion (OTEC). This paper presents the three different types of OTEC power plants: closed-cycle, open-cycle and hybrid-cycle, showing real and conceptual examples of each. All three systems are analyzed in terms of gross power, net power, efficiency and size. Furthermore, the depth of the cold water pipe is discussed and related to the net power generation of the OTEC plant. The power generation efficiency of the plant increases as the gross power production increases. This is due to the depth of the cold water pipe and amount of power used by the cold water pipe pump.

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.

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.

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