Resonant Wave Energy Harvesting Pendulum
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Solution Overview
Problem
Existing ocean wave energy harvesting devices face challenges in achieving resonance at low frequencies, such as 0.2 Hz, which requires large mechanical systems with significant static deflections, making them impractical for compact designs.
Innovation Solution
A pendulum constrained to oscillate in a semi-circular path on a low-friction inclined plane, where the length of the pendulum and the angle of the plane are optimized to operate at resonance with ocean wave frequencies, with an electrical source to convert kinetic energy into electrical energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional spring-mass system is designed to resonate at 0.2 Hz, then the resonant frequency matches ocean wave energy, but the device becomes very large with significant static deflection
Solution Approach 1:
The pendulum is constrained to move along an inclined plane rather than in a vertical plane, changing the gravitational component from g to g*sin(θ). This dimensional change in the motion plane allows the same resonant frequency to be achieved with a shorter pendulum length, directly resolving the contradiction between frequency matching and device size.
Solution Approach 2:
By changing the parameter of the inclined plane angle θ, the effective gravitational acceleration is modified from g to g*sin(θ). This parameter change allows tuning of the resonant frequency while maintaining a compact device size, as the resonant frequency formula becomes ω = sqrt(g*sin(θ)/L) rather than ω = sqrt(g/L).
2Length of stationary object
If a pendulum is used to resonate at low frequency, then the device size is reduced, but friction with the support surface increases
Solution Approach 1:
The patent replaces sliding friction with rolling friction by using rollers at the pendulum bob. This substitution dramatically reduces the frictional losses while maintaining the compact inclined plane design, as rolling friction is significantly smaller than sliding friction for the same normal force.
3Reliability
If the pendulum operates on a vertical plane, then the resonant frequency is higher, but the device cannot achieve low-frequency resonance in a compact size
Solution Approach 1:
The pendulum motion is shifted from a vertical plane to an inclined plane, fundamentally changing the gravitational restoring force from mg to mg*sin(θ). This allows the system to achieve low resonant frequencies with short pendulum lengths, as the effective gravity component is reduced by the sine of the inclination angle.
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
Enables efficient energy harvesting at low frequencies in a compact package, allowing for smaller device sizes and reduced friction, suitable for applications like unmanned underwater vehicles.
Implementation Method 1
An electrical production source is mounted to an underside of the inclined plane to convert kinetic energy of the pendulum into electrical energy
Implementation Method 2
The length of the pendulum and the angle of the inclined plane are determined so that the pendulum operates in a resonant state at an ocean wave frequency
Implementation Method 3
A pendulum with a pendulum bob having Teflon rollers to contact an inclined plane with a Teflon surface. The mass of the pendulum bob can be adjusted to optimize the friction force with the optimization generally being the reduction of friction
Data Source
AI summary
An energy harvesting pendulum device is provided to oscillate in a semi-circular path on an inclined plane with a low friction surface in response to wave motion of an ocean surface. An electrical production source is mounted to an underside of the plane to convert kinetic energy of a pendulum bob of the pendulum device into electrical energy. The pendulum device can be enclosed by an enclosure floating on the ocean surface with the pendulum moving bob on the inclined plane within the enclosure. The length of the pendulum and the angle of the inclined plane are determined so that the pendulum operates in a resonant state at the ocean motion frequency. The pendulum bob can include rollers for minimal friction when contacting the inclined plane.