8.1 Hydraulic Power Take-Off Systems

Hydraulic power take-off systems are crucial for converting wave and tidal energy into usable power. These systems use fluid pressure to drive actuators, motors, and other components, efficiently capturing and transmitting the energy from marine sources.

Designing effective hydraulic systems involves careful component selection, circuit layout, and efficiency optimization. From cylinders and accumulators to valves and seals, each element plays a vital role in harnessing ocean energy and delivering reliable power output.

Hydraulic Components

Actuators and Storage

Top images from around the web for Actuators and Storage

• 

  Hydraulic Cylinders - SolidsWiki View original

  Is this image relevant?

• 

  Hydraulic Actuators - SolidsWiki View original

  Is this image relevant?

• 

  MS - Design and performance analysis of wave linear generator with parallel mechanism View original

  Is this image relevant?

• 

  Hydraulic Cylinders - SolidsWiki View original

  Is this image relevant?

• 

  Hydraulic Actuators - SolidsWiki View original

  Is this image relevant?

1 of 3

Top images from around the web for Actuators and Storage

• 

  Hydraulic Cylinders - SolidsWiki View original

  Is this image relevant?

• 

  Hydraulic Actuators - SolidsWiki View original

  Is this image relevant?

• 

  MS - Design and performance analysis of wave linear generator with parallel mechanism View original

  Is this image relevant?

• 

  Hydraulic Cylinders - SolidsWiki View original

  Is this image relevant?

• 

  Hydraulic Actuators - SolidsWiki View original

  Is this image relevant?

1 of 3

• Hydraulic cylinders convert hydraulic energy into linear mechanical motion
  • Consist of a piston moving inside a sealed cylinder
  • Commonly used for linear actuation in wave energy converters (heave, surge, or sway motions)
• Hydraulic motors convert hydraulic energy into rotary mechanical motion
  • Utilize fluid flow and pressure to drive a shaft or gear
  • Applicable for rotary power take-off in tidal turbines or oscillating water column devices
• Accumulators store and release hydraulic energy
  • Act as energy buffers to smooth out power fluctuations
  • Types include bladder, piston, and diaphragm accumulators
  • Essential for managing variable power input from waves or tides
• Hydraulic fluids transmit power and lubricate components
  • Common fluids include mineral oils, water-based fluids, and synthetic oils
  • Fluid properties (viscosity, compressibility, thermal stability) impact system performance

Control and Sealing

• Pressure relief valves protect the system from excessive pressure
  • Open when pressure exceeds a set threshold to release fluid and prevent damage
  • Critical safety components in high-pressure hydraulic systems
• Check valves allow fluid flow in one direction and prevent backflow
  • Maintain proper fluid direction and prevent reverse flow
  • Used in hydraulic circuits to control flow paths and isolate components
• Sealing systems prevent fluid leakage and maintain pressure
  • Include static seals (O-rings, gaskets) and dynamic seals (rod seals, piston seals)
  • Proper sealing is crucial for efficient operation and environmental protection

Hydraulic Control Elements

Valves for Pressure and Flow Control

• Pressure relief valves safeguard the system from overpressure
  • Automatically open to release fluid when pressure exceeds a preset limit
  • Protect components from damage due to excessive pressure spikes
• Check valves ensure unidirectional fluid flow
  • Allow fluid to flow in one direction while blocking reverse flow
  • Maintain proper fluid circulation and prevent backflow in hydraulic circuits
• Directional control valves route fluid flow to different parts of the system
  • Control the direction of fluid flow to actuators (cylinders or motors)
  • Types include spool valves, poppet valves, and rotary valves
• Flow control valves regulate the rate of fluid flow
  • Adjust flow rate to control the speed of actuators or motors
  • Needle valves, flow dividers, and pressure compensated flow control valves are common types

Sealing and Leakage Prevention

• Sealing systems are critical for maintaining system pressure and preventing fluid leakage
  • Static seals (O-rings, gaskets) seal stationary components and joints
  • Dynamic seals (rod seals, piston seals) seal moving components
• Proper seal material selection depends on fluid compatibility, temperature, and pressure
  • Common seal materials include elastomers (nitrile, Viton), plastics (PTFE), and metals
• Regular seal inspection and replacement are necessary to prevent leakage and maintain efficiency
  • Leakage can lead to reduced performance, contamination, and environmental issues

System Design Considerations

Hydraulic Circuit Design

• Hydraulic circuit design involves selecting and arranging components to achieve desired functionality
  • Considers factors such as power requirements, control strategies, and safety features
  • Includes sizing and selecting pumps, actuators, valves, and accumulators
• Proper component sizing and selection are critical for optimal performance
  • Oversizing components leads to inefficiency and higher costs
  • Undersizing components results in inadequate performance and potential failure
• Hydraulic circuit simulation and modeling tools assist in design optimization
  • Predict system behavior, identify bottlenecks, and optimize component selection
  • Examples include Simulink, Amesim, and Hopsan

Efficiency and Loss Reduction

• Hydraulic systems are subject to various efficiency losses
  • Fluid friction losses in pipes, hoses, and fittings
  • Leakage losses through seals and valve clearances
  • Compressibility losses due to fluid compression under pressure
  • Mechanical losses in pumps, motors, and bearings
• Minimizing efficiency losses is crucial for optimal power take-off performance
  • Proper component sizing and selection to match system requirements
  • Use of high-efficiency components (pumps, motors) with reduced internal leakage
  • Optimal hydraulic circuit design to minimize pressure drops and flow restrictions
  • Regular maintenance to address leakage, contamination, and component wear
• Heat generation and management are important considerations
  • Efficiency losses manifest as heat in the hydraulic fluid
  • Adequate cooling systems (heat exchangers, cooling circuits) are necessary to maintain optimal fluid temperature
  • Proper fluid selection with good thermal stability and heat transfer properties