Double Pendulum Wave Energy Harvester Overcomes Cogging Torque
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Solution Overview
Problem
Existing wave energy harvesting systems face challenges such as reduced energy output due to cogging torque and slow rotation speeds in electric generators, as well as exposure to corrosive seawater, which increases maintenance needs.
Innovation Solution
A system comprising a buoyant body with an electric generator and two pivotably connected arms, where the second arm is heavier and shorter than the first arm, allowing it to move chaotically and overcome cogging torque, generating higher rotation speeds and accelerations, and maintaining components out of contact with seawater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a traditional electric generator with cogging torque is used in wave energy harvesting, then the generator structure is simple, but the rotation speed is slow and energy output is reduced
Solution Approach 1:
The patent applies the dynamics principle by implementing a double pendulum mechanism with two arms of different lengths and masses. The first arm (longer, lighter) and second arm (shorter, heavier) create chaotic motion that dynamically overcomes cogging torque, transforming the static generator problem into a dynamic solution that maintains continuous rotation and improves energy output
Solution Approach 2:
The patent applies asymmetry by designing the two arms with deliberately different properties: the first arm has length L1 and weight W1, while the second arm has length L2 and weight W2, where L1 > L2 and W1 < W2. This asymmetric configuration creates the chaotic pendulum motion necessary to overcome cogging torque and generate higher rotation speeds
2Device complexity
If moving parts are exposed to seawater environment, then the system structure is simple, but corrosion increases and maintenance needs increase
Solution Approach 1:
The patent applies the extraction principle by removing the electric generator from the seawater environment and placing it inside a protective buoyant body. Only the buoyant body is exposed to seawater, while the generator and moving parts remain protected inside, significantly reducing corrosion and maintenance needs
Solution Approach 2:
The patent applies this principle through the use of a watertight enclosure (buoyant body) that acts as a protective shell. This shell isolates the generator and mechanical components from the corrosive seawater environment, providing reliable protection against corrosion
3Productivity
If a pivoting arm system is used to overcome cogging torque, then energy output improves, but the arm rotation speed remains slow
Solution Approach 1:
The patent applies dynamics by creating a double pendulum system where the interaction between two arms with different inertial properties generates chaotic motion. This dynamic behavior produces higher rotation speeds and accelerations compared to simple pivoting arms, while still overcoming cogging torque effectively
Solution Approach 2:
The patent applies counterweight principles through the asymmetric mass distribution of the two arms. The heavier second arm (W2 > W1) acts as a counterweight that, combined with the longer first arm (L1 > L2), creates the necessary momentum and acceleration to overcome cogging torque and achieve higher rotation speeds
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 system enhances electric power production efficiency by increasing rotation speeds and accelerations, reducing corrosion and maintenance needs, and effectively converting kinetic energy from sea waves into usable power.
Implementation Method 1
a buoyant body comprising a watertight enclosure
Implementation Method 2
an electric generator including an input shaft adapted to rotate with respect to the buoyant body
Implementation Method 3
a pivot joint rotatably joining the second arm to the first arm
Data Source
AI summary
A system configured for producing electric power from sea waves. The system includes a buoyant body; an electric generator including an input shaft adapted to rotate with respect to the buoyant body; a first arm coupled to the electric generator; a second arm; and a pivot joint rotatably joining the second arm to the arm. The pivot joint is at a distance, along the first arm, from the input shaft. The first arm connects the second arm to the generator. The tandem arms form a double pendulum system powering an autonomous floating sea analysing station.