Cold Water Pipe Connection for Floating OTEC Heave Motion
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Solution Overview
Problem
Ocean Thermal Energy Conversion (OTEC) power plants face low overall efficiency, high parasitic loads, and high construction and operating costs due to the limited temperature difference between warm and cold ocean waters, as well as environmental concerns related to nutrient-rich cold water discharge.
Innovation Solution
A floating, multi-stage heat engine system with a structurally integrated cold and warm water intake and discharge system, utilizing a continuous offset staved cold water pipe and a hybrid cascading multi-stage heat exchange design to minimize pressure drops and enhance energy transfer, while discharging water at appropriate depths to reduce environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a long cold water intake pipe is used to reach deep ocean water, then cold water supply is achieved, but construction costs and structural complexity increase
Solution Approach 1:
The cold water intake pipe is divided into multiple sections that can be assembled in stages. The pipe structure is segmented into upper, middle, and lower portions with different structural characteristics, allowing each section to be optimized independently and simplifying construction and installation processes.
Solution Approach 2:
The pipe transitions from a purely vertical structure to a curved path that extends horizontally before descending vertically. This dimensional change allows the pipe to reach deep water while reducing the height requirement and improving structural stability against wave-induced movements.
2Ease of manufacture
If the floating platform is kept minimal to reduce costs, then construction costs decrease, but the platform becomes more susceptible to wave-induced heave motion
Solution Approach 1:
Ballast tanks are incorporated into the platform structure to provide counterweight and stabilize the platform against wave-induced heave motion. The ballast system compensates for the minimal platform size, maintaining stability without requiring a larger or more complex structure.
Solution Approach 2:
The platform utilizes flexible membrane structures and thin-walled components that can adapt to wave motions while maintaining structural integrity. This flexibility allows the minimal platform to respond to environmental forces without requiring heavy reinforcement.
3Ease of manufacture
If a simple pipe connection is used between floating platform and cold water pipe, then ease of installation improves, but the connection cannot accommodate platform heave motion
Solution Approach 1:
The connection system incorporates dynamic elements including spherical bearings and universal joints that allow the rigid pipe to connect to the moving platform. These dynamic components accommodate heave, pitch, and roll motions while maintaining a secure, leak-free connection.
Solution Approach 2:
The connection geometry and orientation are designed to change with platform motion parameters. The spherical bearing radius and joint configurations are specifically calculated to maintain proper alignment and sealing under varying motion conditions.
4Loss of energy
If large heat exchange surface areas are used to maximize heat transfer, then energy transfer efficiency improves, but parasitic load increases
Solution Approach 1:
The heat exchange surfaces are distributed throughout the water column at different depths and locations rather than concentrated in one area. This local distribution optimizes heat transfer at each depth zone while reducing the total pumping power required to move water through a centralized exchange system.
Solution Approach 2:
Heat exchange occurs across multiple vertical and horizontal dimensions throughout the ocean water column. The system utilizes the three-dimensional space available in the water column, placing heat exchange surfaces at various depths to maximize thermal gradient utilization without requiring excessive surface area in any single location.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution increases overall efficiency, reduces parasitic loads, lowers construction and operating costs, and minimizes environmental impact by optimizing energy transfer and water discharge practices, making OTEC power generation more viable and sustainable.
Implementation Method 1
The cold water pipe is suspended from the floating, minimal heave structure
Implementation Method 2
multi-stage heat exchange system
Implementation Method 3
uses the temperature difference between surface and deep sea tropical waters to drive a heat engine to produce electrical energy
Implementation Method 4
The offset staved pipe design has been shown to reduce the forces acting on the pipe
Data Source
AI summary
An offshore structure for use with an OTEC system includes a submerged spar having a lower portion having a cold water intake. The cold water intake includes a domed terminus in fluid communication with a cold water pipe. A dry machinery space adjacent the cold water intake includes one or more cold water supply pumps and one or more cold water pipe lifting and retention winches having a lifting cable connected to the cold water pipe.