Wave Energy Converter Internal Oscillator Spring Design
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Solution Overview
Problem
Existing wave energy converter (WEC) systems face challenges such as complex and expensive components due to marine growth, corrosion, and viscous damping, which limit energy collection and require impractically long springs to achieve desired natural periods, making it difficult to construct and house these springs within the float.
Innovation Solution
A WEC system incorporating an internal oscillator with a reaction mass and a parallel combination of an elastic spring and a constant force spring, where the constant force spring counterbalances the static weight of the reaction mass, allowing the elastic spring to maintain a reduced static length while providing the necessary dynamic range, thus reducing the physical size and complexity of the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a spring is designed to provide the desired natural period for wave energy conversion, then the energy conversion efficiency is improved, but the spring length becomes impractically long and difficult to house within the float
Solution Approach 1:
The patent applies the counterweight principle by introducing a reaction mass that is suspended from the float by a spring. The reaction mass counterbalances the buoyant force on the float, allowing the spring to be optimized for dynamic wave energy conversion rather than static support. This enables the spring to be much shorter while still providing the desired natural period for energy conversion, as the spring only needs to handle dynamic oscillations rather than the full static weight.
2Productivity
If the float and spar are exposed to water elements to capture wave energy, then the energy collection capability is improved, but the components become subject to marine growth, corrosion, and contamination
Solution Approach 1:
The patent extracts the power take-off device and bearings from the water environment by placing them inside the float. The reaction mass and spring system are contained within the float, allowing mechanical components to operate in a protected, dry environment. Only the float itself remains exposed to water, minimizing the surface area subject to marine growth and corrosion while maintaining wave energy capture capability.
Solution Approach 2:
The patent introduces an air-tight seal as an intermediary between the water environment and the internal mechanical components. This seal allows the float to be exposed to water for energy capture while protecting the internal power take-off device, bearings, and spring-mass system from marine growth, corrosion, and contamination.
3Device complexity
If the spring length is reduced for compact design, then the device complexity and physical size are reduced, but the static weight balance becomes problematic
Solution Approach 1:
The reaction mass serves as a counterweight that balances the buoyant force on the float. By positioning the reaction mass and adjusting its weight, the system achieves static equilibrium without requiring a long spring for support. The spring only needs to provide the necessary stiffness for dynamic oscillation at the desired natural period, enabling a compact design while maintaining proper weight balance.
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
This configuration enables efficient energy conversion by reducing the static length of the elastic spring, allowing for a more compact design that can still capture wave energy effectively, overcoming the limitations of long springs and improving hydrodynamic performance.
Implementation Method 1
an elastic spring and constant force spring which connect the reaction mass to the float
Implementation Method 2
internal oscillator including a reaction mass and a spring system... relative motion between the float and the reaction mass
Data Source
AI summary
A wave energy converter (WEC) system includes a shell containing an internal oscillator comprised of a reaction mass suspended from the shell by an elastic spring in parallel with a constant force spring. The constant force spring provides a relatively constant force (Fc) to counterbalance the static weight of the reaction mass and reduce the extension “static” length of the elastic spring while the elastic spring exerts a force (Fes) on the reaction mass that is proportional to the displacement, x, of the elastic spring. A power take-off (PTO) device, located within the shell, coupled between the shell and the internal oscillator converts their relative motion into electrical energy.