Floating OTEC Heat Exchange Layout for Lower Parasitic Load
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Solution Overview
Problem
Ocean Thermal Energy Conversion (OTEC) power plants face low overall efficiency, high construction and operating costs, and environmental concerns due to low thermodynamic efficiency, large parasitic loads, and design challenges related to deep sea water intake and discharge, which limit their commercial viability.
Innovation Solution
A floating OTEC power plant with a multi-stage heat engine and integrated heat exchange compartments, featuring a continuous offset staved cold water pipe and a hybrid cascading multi-stage heat exchange system, reduces parasitic loads and construction costs while minimizing environmental impact through efficient water flow and discharge management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional single-stage heat exchange systems are used in OTEC plants, then the system is simpler to construct, but the thermodynamic efficiency is low and parasitic loads are high
Solution Approach 1:
The heat exchange system is divided into multiple stages (evaporator stages and condenser stages) that operate at different temperature levels. Each stage handles a specific temperature range, allowing the system to more closely match the temperature profile of the ocean water and extract energy more efficiently across the entire temperature differential.
Solution Approach 2:
The patent introduces a vertical dimension to the heat exchange process by stacking multiple heat exchange stages vertically. This multi-stage vertical arrangement allows warm water to flow downward through successive evaporator stages and cold water to flow upward through condenser stages, maximizing heat transfer efficiency while maintaining a compact footprint.
2Loss of energy
If large heat exchange surface areas are used to maximize energy transfer, then thermodynamic efficiency improves, but construction costs and device complexity increase
Solution Approach 1:
The large heat exchange surface area requirement is met by segmenting the system into multiple modular heat exchange stages. Each stage contains heat exchange surfaces, and they are arranged in series to collectively provide the necessary total surface area while maintaining manageable complexity through modular design.
Solution Approach 2:
The heat exchange tubes are nested within the ocean water flow paths, with multiple stages nested vertically. The warm water flow path and cold water flow path are nested in counter-flow configurations, maximizing heat transfer surface area utilization while minimizing the overall structural footprint.
3Loss of energy
If high fluid velocities are used in heat exchangers to maximize heat transfer, then energy transfer efficiency improves, but parasitic power requirements increase
Solution Approach 1:
The system employs dynamic flow distribution across multiple stages, where the flow velocity and distribution can be optimized for each stage based on the local temperature differential. This allows efficient heat transfer at lower velocities by leveraging the cumulative effect of multiple stages rather than requiring high velocity in a single stage.
Solution Approach 2:
The counter-flow arrangement creates periodic temperature gradients along the flow paths, with temperature differences varying systematically from one end of the heat exchanger to the other. This periodic temperature distribution optimizes heat transfer efficiency across the entire system without requiring uniformly high fluid velocities.
4Temperature
If deep sea water intake pipes are extended to reach cold water reservoirs at great depths, then cold water supply is improved, but construction costs and structural complexity increase
Solution Approach 1:
The deep water intake system is segmented into multiple sections or stages, with intermediate support structures or buoyancy elements distributed along the pipe length. This segmentation reduces the complexity of any single pipe section and allows for modular construction and deployment.
Solution Approach 2:
The intake pipes incorporate buoyancy elements or are designed with buoyant characteristics that counteract the weight of the long pipe extending to great depths. This reduces the structural support requirements and simplifies the anchoring and deployment systems needed for deep water intake.
5Loss of energy
If OTEC plants are located in tropical regions with optimal temperature differentials, then thermodynamic efficiency improves, but environmental concerns and operational constraints increase
Solution Approach 1:
The system converts the potentially harmful effect of warm water discharge into a beneficial by utilizing it for secondary purposes such as aquaculture, desalination, or industrial process heating. The cold water discharge is similarly utilized for cooling applications or to create favorable conditions for marine life, transforming what would be environmental liabilities into assets.
Solution Approach 2:
Instead of simply discarding the warm and cold water discharges, the system recovers their thermal energy for useful purposes. The warm water is utilized for applications requiring thermal input, and the cold water is used for cooling needs, thereby recovering energy that would otherwise be wasted and reducing the environmental footprint.
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 enhances overall efficiency, reduces construction and operating costs, and minimizes environmental footprint by optimizing energy transfer and reducing pressure losses, making OTEC power plants more commercially viable and environmentally friendly.
Implementation Method 1
heat exchange surfaces and working fluid passages, wherein the first deck working fluid passages are in communication with a second deck working fluid passages
Implementation Method 2
efficient flow of the warm water or cool water through the multi-stage heat exchanger
Implementation Method 3
the cold sea water and the working fluid in the second deck working fluid passages to cool the working fluid to a liquid
Implementation Method 4
The OTEC process uses the temperature difference between surface and deep sea tropical waters to drive a heat engine to produce electrical energy
Implementation Method 5
the temperature of the surface sea water remains nearly constant... deep ocean water remains a fairly constant 40° F. Thus, the tropical ocean structure offers a large warm water reservoir at the surface and a large cold water reservoir at depth
Data Source
AI summary
An offshore power generation structure comprising a submerged portion having a first deck portion comprising an integral multi-stage evaporator system, a second deck portion comprising an integral multi-stage condensing system, a third deck portion housing power generation equipment, cold water pipe; and a cold water pipe connection.