6.4 Attenuator and Terminator Systems
3 min read•august 7, 2024
Wave energy converters come in various shapes and sizes. Attenuators and terminators are two key types that harness ocean power differently. Let's dive into how these devices work and what makes them unique.
Attenuators, like the Pelamis, are long snake-like machines that ride waves. Terminators, such as , face waves head-on. Both convert wave motion into electricity, but their designs and challenges differ significantly.
Attenuator Devices
Pelamis Wave Energy Converter
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Top images from around the web for Pelamis Wave Energy Converter
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- Pelamis is a well-known device that consists of multiple cylindrical sections connected by hinged joints
- Operates in water depths greater than 50 meters and is typically installed 2-10 km offshore
- Sections move relative to each other as waves pass along the length of the device
- Power takeoff systems at the joints convert the motion into electricity
Multi-body System Dynamics
- Attenuators like Pelamis are multi-body systems composed of several interconnected floating bodies
- Wave-induced forces cause adjacent sections to move relative to each other at the hinged joints
- Relative rotational motion between sections is essential for power capture
- Control systems are used to optimize the motion and maximize energy absorption
Pitch and Heave Motions
- Attenuators extract energy from both pitch (rotational) and heave (vertical) motions of the waves
- occurs as the wave propagates along the length of the device, causing adjacent sections to rotate relative to each other
- is the vertical up and down movement of the sections as waves pass
- Combined pitch and heave motions are converted into electricity by hydraulic rams or other power takeoff mechanisms
Energy Absorption Efficiency
- Attenuators are designed to absorb as much wave energy as possible along their length
- Longer attenuators can absorb more energy, but there is a trade-off with cost and complexity
- Efficiency depends on factors such as device length, wave conditions, and control strategies
- Optimal power absorption occurs when the device is tuned to resonate with the incoming waves (i.e., when the device's natural frequency matches the wave frequency)
Terminator Devices
Salter's Duck
- Salter's Duck is a device named after its inventor, Stephen Salter
- Consists of a cam-shaped floating body that rotates about a horizontal axis perpendicular to the wave direction
- Wave action causes the duck to nod, and this motion is used to drive an electrical generator
- Originally designed to be deployed in arrays, with each duck connected to a common spine
Directional Dependency
- Terminator devices are highly directional, meaning they are most effective when aligned perpendicular to the incoming wave direction
- Salter's Duck must face the oncoming waves to capture energy efficiently
- can be a disadvantage in locations with variable wave directions
- Some designs incorporate mechanisms to allow the device to rotate and face the prevailing wave direction
Survivability Challenges
- Terminator devices like Salter's Duck are exposed to the full force of oncoming waves, which can pose
- Extreme wave conditions, such as during storms, can cause structural damage or failure
- Designing for survivability often involves compromises in efficiency and cost
- Strategies to improve survivability include using robust materials, incorporating breakwater structures, and designing for submergence during extreme events
Power Conversion
Hydraulic Power Take-Off Systems
- Many wave energy converters, including attenuators and terminators, use hydraulic systems for power conversion
- Motion of the device (e.g., relative motion between sections or nodding of a duck) drives hydraulic rams or pumps
- Pressurized hydraulic fluid is used to drive a hydraulic motor, which in turn drives an electrical generator
- Advantages of hydraulic power conversion include high force density, energy storage capability, and smooth power output
- Challenges include efficiency losses, maintenance requirements, and the need for effective sealing to prevent fluid leaks
Key Terms to Review (26)
Attenuator: An attenuator is a device designed to reduce the amplitude of a wave, often used in wave energy systems to optimize performance and minimize the impact of excessive energy fluctuations. By dampening the energy of incoming waves, attenuators help maintain a steady output while protecting the system from damage due to extreme conditions. This is crucial for enhancing the efficiency and longevity of wave energy converters.
Buoyancy: Buoyancy is the upward force exerted by a fluid on an object that is partially or fully submerged in it. This force is essential in understanding how different wave energy converters operate, particularly in relation to their ability to float and harness energy from ocean waves. A solid grasp of buoyancy helps in designing efficient devices that can maintain stability and optimize energy capture from water movement.
Capacity Factor: The capacity factor is a measure of how effectively an energy generation system produces electricity compared to its maximum potential output over a specific period. It reflects the actual energy output relative to the maximum possible output if the system operated at full capacity continuously, which is essential for understanding the efficiency and reliability of energy systems, especially in the context of renewable sources like ocean energy.
Current velocity: Current velocity refers to the speed and direction of water movement in a specific location, which is crucial for understanding the energy available from tides and waves. This measurement directly influences the efficiency of energy conversion systems, such as those that harness wave and tidal power, and helps determine the best sites for installation. An accurate assessment of current velocity is essential for optimizing device performance and maximizing energy extraction.
Directional Dependency: Directional dependency refers to the relationship between the orientation of wave energy and the efficiency or effectiveness of energy capture systems, especially in the context of wave energy converters. It highlights how certain systems may perform better or worse depending on the direction from which waves approach, influencing design and placement considerations for optimal energy harvesting.
Dr. Ian F. D. Smith: Dr. Ian F. D. Smith is a prominent researcher and expert in the field of wave energy technology, known for his contributions to the design and analysis of attenuator and terminator systems. His work focuses on the efficient harnessing of wave energy through innovative engineering solutions, significantly influencing the development and optimization of energy conversion systems in marine environments.
Dr. J. A. T. de Boer: Dr. J. A. T. de Boer is a notable figure in the field of renewable energy engineering, specifically known for his work in the development of wave energy converters and ocean energy systems. His research contributions and innovations have significantly influenced the design and implementation of attenuator and terminator systems, which are critical for harnessing energy from ocean waves effectively.
Energy absorption efficiency: Energy absorption efficiency refers to the ability of a device or system to convert incoming wave energy into usable mechanical or electrical energy. This concept is crucial in the design and performance evaluation of devices that harness ocean wave energy, such as attenuator and terminator systems, which are specifically engineered to optimize the capture of wave energy.
Energy Conversion: Energy conversion refers to the process of changing energy from one form to another, enabling its utilization for various applications. This is crucial in harnessing energy from natural resources, particularly in ocean energy systems, where kinetic and potential energy from waves and tides are transformed into mechanical and then electrical energy. Understanding energy conversion is essential for optimizing performance and efficiency in different ocean energy technologies.
Energy Yield: Energy yield refers to the amount of usable energy produced by a system, particularly in relation to renewable energy technologies. This concept is essential for evaluating the efficiency and effectiveness of various energy generation methods, as it directly influences the feasibility and economic viability of deploying such technologies in real-world applications.
Feed-in Tariff: A feed-in tariff is a policy mechanism designed to encourage the development of renewable energy sources by guaranteeing fixed payments for energy produced from renewable resources over a specified period. This financial incentive helps to reduce investment risks for developers and promotes the integration of clean energy technologies into the power grid, fostering innovation and sustainability in the energy sector.
Heave Motion: Heave motion refers to the vertical movement of a floating body, such as a wave energy converter, in response to the changing surface elevation of ocean waves. This motion is crucial for energy capture, as it directly impacts the performance and efficiency of devices designed to harness wave energy, particularly in attenuator and terminator systems.
Hydraulic system: A hydraulic system is a technology that uses pressurized fluid to transmit power and control movements in various applications. It operates based on the principles of fluid mechanics, allowing for efficient energy transfer and mechanical motion. In renewable energy contexts, hydraulic systems play a crucial role in converting kinetic energy from water movement into usable power, making them essential for devices like turbines and wave energy converters.
Hydrodynamics: Hydrodynamics is the study of fluids in motion, particularly focusing on the forces and interactions that occur when water flows. This field is crucial for understanding how ocean energy systems harness wave and tidal movements, which are influenced by factors like flow velocity, pressure distribution, and fluid behavior around structures.
Mooring Design: Mooring design refers to the process of creating secure anchoring systems for floating structures like wave energy converters or attenuators, ensuring their stability and functionality in marine environments. It involves careful consideration of environmental conditions, structural integrity, and operational requirements to effectively anchor these systems to the seabed while allowing for necessary movements caused by waves and currents.
Multi-body system dynamics: Multi-body system dynamics refers to the study of the motion and interaction of interconnected rigid or flexible bodies under the influence of forces and constraints. This concept is crucial in analyzing how different components of a system, like those found in wave energy converters, interact and respond to dynamic environmental conditions such as waves and currents.
Pelamis Wave Energy Converter: The Pelamis Wave Energy Converter is a type of wave energy device designed to convert the kinetic and potential energy of ocean waves into electrical power. This innovative technology has played a pivotal role in the development of ocean energy technologies, demonstrating effective energy extraction and providing insights into the efficiency and viability of wave energy as a renewable resource.
Pitch motion: Pitch motion refers to the rotational movement of a floating structure around a horizontal axis, which is typically oriented from side to side. In the context of energy systems, especially those that harness wave energy, pitch motion plays a crucial role in the efficiency and effectiveness of energy conversion. Understanding pitch motion helps in optimizing the design of devices that respond to changing wave conditions, ensuring they can capture maximum energy while maintaining stability.
Power Take-Off: Power take-off refers to the mechanism that converts the kinetic energy of waves or tides into usable mechanical energy for electricity generation or other applications. This system is crucial for harnessing renewable energy from ocean resources, allowing for efficient energy conversion and integration into power grids. The design and effectiveness of power take-off systems significantly influence the overall performance of wave and tidal energy devices, especially in terms of energy extraction and operational reliability.
Renewable Energy Standards: Renewable energy standards are regulations that require a certain percentage of energy production to come from renewable sources, such as wind, solar, and tidal energy. These standards are designed to promote the use of clean energy, reduce greenhouse gas emissions, and encourage investment in renewable technologies. By setting clear goals for renewable energy adoption, these standards influence the development and implementation of various energy conversion systems, including tidal range energy and wave energy converters.
Salter's Duck: Salter's Duck is a type of wave energy converter designed as an oscillating water column system, which captures the energy generated by waves to produce electricity. This innovative device utilizes the up-and-down movement of ocean waves to drive air through turbines, generating renewable energy. Its unique design enhances the efficiency of energy capture in varying wave conditions, making it an important development in the field of wave energy technology.
Structural Integrity: Structural integrity refers to the ability of a structure to withstand its intended load without experiencing failure, deformation, or collapse. This concept is crucial in ensuring that energy devices can operate safely and efficiently under various environmental conditions, making it vital in the design and analysis of wave energy converters and mooring systems.
Survivability challenges: Survivability challenges refer to the difficulties faced by energy systems, particularly those harnessing tidal and wave energy, in withstanding harsh marine environments while maintaining operational efficiency and reliability. These challenges include the impact of extreme weather, corrosion from saltwater, biofouling, and mechanical stresses from waves and currents. Addressing these issues is crucial for the long-term success and feasibility of energy conversion devices.
Terminator: In the context of wave energy systems, a terminator is a type of device designed to capture the energy from ocean waves by converting their kinetic energy into usable power. Terminators are typically deployed perpendicular to the direction of wave propagation and can vary in design, often utilizing buoyancy changes or oscillating water columns to harness energy effectively. They play a crucial role in optimizing energy extraction from ocean waves, complementing other devices like attenuators.
Wave height: Wave height is the vertical distance between the crest (the highest point) of a wave and the trough (the lowest point). This measurement is crucial for understanding wave dynamics, energy potential, and the design of systems that harness wave energy. It influences how waves propagate, interact with structures, and contribute to the overall energy available in oceanic systems.
Wave Propagation: Wave propagation refers to the movement of waves through a medium, which can be water, air, or even solid materials. This concept is crucial in understanding how energy travels across different environments and how it interacts with various structures, such as attenuator and terminator systems that capture wave energy. Effective wave propagation analysis helps in optimizing energy extraction and ensuring that these systems perform efficiently under varying conditions.