Nonlinear Buoy Geometry for Wave Energy Capture
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Solution Overview
Problem
Conventional wave energy converters (WECs) are limited in their ability to capture energy across the full range of sea states due to linear dynamic models and resonance frequency constraints, leading to inefficiencies when operating off-resonance, and require reactive power and energy storage systems to enhance energy capture.
Innovation Solution
A nonlinear wave energy converter featuring a shaped buoy with a geometric design that produces reactive power through nonlinear coupling between the buoy and wave interaction, eliminating the need for reactive power and energy storage, and incorporating sub/super harmonics to increase energy capture, with optimal limit cycles designed using Hamiltonian surface-shaping power flow control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional linear dynamic models and resonance frequency operation are used, then the WEC operates efficiently at resonance, but it operates much less efficiently when off-resonance with impacting waves
Solution Approach 1:
The patent applies dynamics by making the WEC system adjustable and adaptable through nonlinear control strategies. The control system dynamically adjusts the buoy's motion characteristics to match varying wave conditions, transitioning from fixed resonance operation to adaptive nonlinear operation that maintains efficiency across different sea states and frequencies.
Solution Approach 2:
The patent changes the operational parameters from linear resonance-based control to nonlinear control that incorporates multiple harmonics. By modifying the control approach to account for nonlinear effects and use shaped buoy geometry, the system expands its effective operating range beyond the narrow resonance band to capture energy across the full wave frequency spectrum.
2Productivity
If simple on/off or resonant frequency operation is used, then the device structure is simple, but the WEC generates power over only a small band of the full wave frequency spectrum
Solution Approach 1:
The shaped buoy design provides self-service by inherently producing reactive power through its nonlinear geometry. The buoy's curved outward shape from the vertical axis automatically generates the necessary reactive power components during wave interaction, eliminating the need for external energy storage systems or complex reactive power management infrastructure.
Solution Approach 2:
The patent utilizes mechanical vibration principles by incorporating sub and super harmonics into the buoy's motion. The nonlinear control strategy excites the buoy at multiple frequency components simultaneously, allowing the device to resonate with and capture energy from waves across a broader frequency spectrum through enhanced vibrational coupling.
3Productivity
If reactive power and energy storage systems are added to enhance energy capture, then the energy capture is improved, but the device complexity and cost increase
Solution Approach 1:
The shaped buoy design provides self-service by inherently producing reactive power through its nonlinear geometry. The buoy's curved outward shape from the vertical axis automatically generates the necessary reactive power components during wave interaction, eliminating the need for external energy storage systems or complex reactive power management infrastructure.
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 nonlinear buoy design enhances energy harvesting by increasing capture width, draft, and speed, achieving efficient energy capture across various sea states without reactive power or energy storage requirements, and inherently incorporates wave height and buoy motion measurements.
Implementation Method 1
a shaped buoy that provides nonlinear hydrostatic control of a wave energy converter
Implementation Method 2
Extracting power from ocean waves
Data Source
AI summary
Increased energy harvesting is realized using a nonlinear buoy geometry for reactive power generation. By exploiting the nonlinear dynamic coupling between the buoy geometry and the potential wideband frequency spectrum of incoming waves in the controller/buoy design, increased power can be captured in comparison to conventional wave energy converter designs. In particular, the reactive power and energy storage system requirements are inherently embedded in the nonlinear buoy geometry, therefore requiring only simple rate-feedback control.