Variable Geometry Buoy for Off-Resonance Wave Energy Capture
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Solution Overview
Problem
Current wave energy converters (WECs) operate less efficiently when off-resonance with incoming waves, and existing control methods are based on linear techniques, which limit their ability to capture energy over a wide range of sea states.
Innovation Solution
A wave energy converter buoy with variable geometry, specifically an hourglass shape, that utilizes a nonlinear control design to increase energy capture by varying its steepness angle in response to wave motion, eliminating the need for energy storage and power electronic elements, and producing reactive power through nonlinear interactions with waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If linear control methods are used in wave energy converters, then the device operates efficiently at resonance frequency, but the energy capture efficiency deteriorates when operating off-resonance with varying wave conditions
Solution Approach 1:
The buoy geometry is made dynamically adjustable through variable steepness angle that can be modified in real-time based on wave conditions. This allows the device to adapt its hydrodynamic characteristics to match varying wave frequencies and amplitudes, maintaining resonance conditions across different sea states rather than being fixed at a single resonance frequency
Solution Approach 2:
The invention changes the physical parameter of the buoy's geometric shape (steepness angle) to optimize performance. By adjusting the steepness angle, the device modifies its water plane area and hydrostatic restoring moment characteristics, enabling it to capture energy efficiently across a wide range of wave conditions including off-resonance scenarios
2Power
If the buoy geometry is fixed to achieve resonance at a specific frequency, then maximum energy capture is achieved at that frequency, but the device cannot effectively capture energy from waves with different frequencies
Solution Approach 1:
The buoy transitions from a fixed geometry design to a dynamically adjustable geometry where the steepness angle can be varied. This dynamic adjustment capability allows the device to maintain optimal resonance conditions across multiple frequencies by adapting its shape to match the dominant wave frequency, thereby extending its effective operating frequency range
Solution Approach 2:
The invention employs a composite approach combining fixed structural elements with adjustable geometric components. The buoy consists of a base structure with modifiable steepness angle sections, allowing it to integrate the stability of fixed geometry with the adaptability of variable geometry to capture energy across broader frequency spectra
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 variable geometry buoy design enhances power generation by capitalizing on nonlinear cubic storage effects, achieving increased energy capture and reactive power production, as demonstrated by numerical simulations, particularly in off-resonance conditions.
Implementation Method 1
By exploiting the nonlinear static coupling between an hourglass (HG) buoy geometry and the potentially wideband frequency spectrum of incoming waves, the buoy design can increase power/energy captured
Implementation Method 2
producing reactive power from the wave motion
Data Source
AI summary
A nonlinear control design technique capitalizes on a wave energy converter comprising a shaped buoy having a variable geometry wave energy. For example, the shaped buoy can have an hourglass (HG) geometry having a variable cone or steepness angle. The HG buoy is assumed to operate in the heave motion of the wave. The unique interaction between the HG buoy and the wave creates a nonlinear cubic storage effect that produces actual energy storage or reactive power during operation. A multi-frequency Bretschneider spectrum wave excitation input was simulated for the HG design both with constant and varying steepness angle profiles which demonstrated further increased power generation with changing sea states for the variable design.