Heaving Buoy Point Absorber with Adjustable Reference Mass
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Solution Overview
Problem
The development of commercially viable wave energy converters is hindered by costly sea-bed anchoring, alignment challenges, and performance constraints in deep water, particularly for self-reacting heaving buoy point absorbers and oscillating water columns, which struggle to maintain resonance and phase difference for effective power recovery across varying wave conditions.
Innovation Solution
A wave energy converter featuring a resonant heaving buoy point absorber with a surface-piercing float coupled to an adjustable reference mass, allowing for a varying volume of seawater and air trapped above an enclosed water column, enabling adjustment of the natural oscillation period and phase control through a control mechanism to optimize energy absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a heaving buoy point absorber reacts against the sea-bed via taut moorings or a spar, then the device can convert wave energy effectively, but the anchoring systems become expensive to install and maintain in deep water
Solution Approach 1:
The invention extracts the reaction mass from the sea-bed anchoring system and replaces it with an internal water column contained within the buoy chamber. This eliminates the need for expensive deep-water anchoring systems while maintaining the ability to convert wave energy effectively through the interaction between the heaving buoy and the internal water column.
Solution Approach 2:
The internal water column acts as an intermediary between the heaving buoy and the power take-off system. Instead of reacting against the sea-bed, the buoy reacts against the internal water column, which transmits the force to the power take-off mechanism, thereby avoiding the need for complex deep-water anchoring infrastructure.
2Reliability
If a heaving buoy point absorber uses a fixed natural period, then it can resonate with specific wave conditions, but it responds best only to a narrow band of the total energy distribution
Solution Approach 1:
The invention makes the natural period of the buoy dynamic rather than fixed by allowing the mass of the internal water column to vary. As waves enter and exit the chamber, the water level changes, altering the mass and thus the natural period of the system. This enables the buoy to resonate with a broader range of wave periods and adapt to varying sea conditions, expanding the energy absorption bandwidth.
3Power
If an OWC is included in a heaving spar buoy, then wave energy can be converted, but the oscillations of the heaving spar buoy and the enclosed OWC must be maintained out of phase for effective power recovery
Solution Approach 1:
The invention merges the heaving buoy mechanism and the oscillating water column into a single integrated system rather than treating them as separate components. The buoy chamber itself contains the water column, and the heving motion of the buoy naturally drives the water column oscillation. This integration eliminates the need for separate phase control systems while maintaining effective power recovery.
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 enhances energy absorption efficiency by matching the natural period with prevailing wave frequencies, maintaining phase difference between the heaving buoy and water column, and facilitating cost-effective operation in deep water environments.
Implementation Method 1
a heaving buoy point absorber that reacts against the surface of an enclosed volume of water via a trapped volume of air
Implementation Method 2
maximum energy absorption occurs when the natural oscillation of the water column, with the air trapped above it, is in step with the incoming wave train
Implementation Method 3
A heaving buoy point absorber which oscillates or heaves in a vertical mode
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A wave energy converter (100) is provided which comprises a heaving buoy point absorber (122) having a surface piercing float (120) operably coupled to an adjustable reference mass (125) defining a volume for accommodating sea water therein. The surface piercing float and the adjustable reference mass are configured to move together in response to passing waves. A chamber (105) provided within the surface piercing float is in fluid communication with the sea for trapping a volume of air above an enclosed column of water. The height of the enclosed column of water varies as the point absorber reacts against its surface via an adjustable air-spring. A power take off (140) is configured for being driven by a stream of vented air in communication with the chamber as the heaving buoy point absorber reacts against a trapped volume of air. A control mechanism is configured for tuning one or more operating characteristics of the heaving buoy point absorber.