Cold Water Pipe Connection for Low-Loss OTEC Heat Exchange
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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 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
1Productivity
If traditional OTEC power plants use simple heat exchange systems, then the device complexity is low, but the heat transfer efficiency is insufficient leading to low overall power efficiency
Solution Approach 1:
The heat exchange system is divided into multiple stages (evaporator stages and condenser stages) that process warm and cold water sequentially. This segmentation allows each stage to operate at optimized conditions, improving overall heat transfer efficiency while maintaining manageable system complexity through modular design
Solution Approach 2:
The patent introduces a vertical dimension to the heat exchange system by using stacked evaporator and condenser stages arranged at different elevations. This vertical arrangement enables gravity-assisted water flow between stages, reducing pumping requirements and improving thermal efficiency without proportionally increasing system complexity
2Productivity
If OTEC plants use high fluid velocities to maximize heat transfer, then heat transfer efficiency improves, but parasitic power load increases significantly
Solution Approach 1:
The stacked stage design creates gravity-driven flow paths where water moves between stages using gravitational potential energy differences. This reduces the need for high-velocity forced circulation, lowering pumping power requirements while maintaining adequate heat transfer through optimized residence time in each stage
Solution Approach 2:
The system maintains continuous water flow through the sequential stages using gravity-assisted circulation rather than intermittent high-velocity pumping. This continuous low-velocity flow reduces parasitic power consumption while ensuring sustained heat transfer activity throughout all stages
3Ease of operation
If OTEC plants discharge nutrient-rich cold water at surface level, then the operation is simple, but environmental harm increases due to disruption of marine ecosystems
Solution Approach 1:
The discharge system utilizes the vertical dimension by releasing cold water at multiple depth levels rather than a single surface discharge point. This vertical distribution of discharge locations reduces localized thermal and chemical shock to marine ecosystems while maintaining operational simplicity through the integrated depth-controlled release mechanism
Solution Approach 2:
The discharge operation applies different release characteristics at different depths, with cold water discharged at multiple staged locations rather than uniformly at one point. This localized variation in discharge quality reduces environmental harm by distributing the thermal and chemical impact across different water columns, allowing simpler overall discharge infrastructure
4Quantity of substance
If OTEC plants use long deep water pipes to access cold water reservoirs, then the cold water supply is sufficient, but construction and operating costs increase
Solution Approach 1:
The deep water pipe system is segmented into multiple sections corresponding to different depth stages. This segmentation allows for modular construction and installation, reducing overall construction cost while maintaining sufficient cold water supply capacity through the distributed staged intake system
Solution Approach 2:
The patent transitions from a single long vertical pipe to a stacked multi-stage pipe arrangement at different elevations. This vertical staging reduces the total pipe length required while accessing sufficient cold water volumes from different depth zones, lowering construction costs through reduced material requirements
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 power demand, lowers construction and operating costs, and minimizes environmental footprint by optimizing heat transfer and water management in OTEC power plants.
Implementation Method 1
A hydrostatic head is provided to deliver the cold water from the cold water pipe to the heat exchange system
Implementation Method 2
hybrid cascading heat exchange design to minimize pressure drops and enhance energy transfer
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.