Harnessing and Converting WavePower in Mild, Moderate, and Extreme           Wave ClimatesPresenter: Michael Raftery, M.E....
Problems• Mild wave slopes do not provide sufficient    acceleration of power take-off components for    existing systems ...
Develop Solutions• Capable of increasing wave slopes and    concentrating wave power•   Capable of eliminating single poin...
Quantify Mild and Moderate Waves• Average annual significant wave heights of  0.75m or less = mild wave climate• Average a...
Wave Tuning Research• A variable-depth, fully-submerged tension leg platform (TLP) was tested in the wave tank facility at...
Wave Tuning “Shoaling” FeatureTLP Shoals10cm Wave overa 20cm BuoyBuoy MotionIncreases withWave Steepness
Mild Wave (H =5.1cm)
5.1cm, 2.21s Wave – 15cm Platform DepthWave Heights:•Before Platform:•5.1cm (2.0 in) •Over Platform:•12.7 cm (5.0 in)•Wave...
Mild Wave ResultsH =0.051m (2.0in)Cg = 1.97 m/s at 1.98m tank depthE = 3.27 J/m^2P = 6.43 W/mShoaled WaveH = 0.127m (5.0in...
Moderate Wave (H = 10.4cm)
10.4cm Wave – 15cm Platform DepthWave Heights:•Before Platform:•10.4 cm (4.1in) •Over Platform:•17.8 cm (7.0 in)•Increase ...
Moderate Wave ResultsH = 0.104m (4.1in)Cg = 1.97 m/s at 1.98m tank depthE = 13.58 J/m^2P = 26.74 W/mShoaled WaveH = 0.178m...
WEHD-Full Scale Design
WEHD – Redundant Systems
Scaling Power Take-Off• Mild Waves 0.51m, 7s = 2.04kW/m• 1.27m Shoaled power = 7.30kW/m• Moderate Waves 1.04m, 7s = 8.47kW...
Energy Storage System• 2 – 10m wide buoys = 20m width• Storage volume, 80 – 300L Accumulators• = 24m3 = 12m3 working volum...
Charge Rate at 35% Efficiency• 20m x 7.30kW/m x .35 = 51kW• 20m x 14.34kW/m x .35 = 100kW• Mild waves charge the energy st...
Discharge Rates• 75kW for 4 hours• 150kW for 2 hours• 300kW for 1 hour• 600kW for 30 minutes• 1.2MW for 15 minutes• 2.4MW ...
Anchor Load Avoidance• Anchor loading can be reduced by lowering the platform near the sea floor
10.4cm Wave – 110cm Platform Depth
10.4cm Wave – 110cm Platform DepthWave Heights:•Before Platform:•10.4 cm (4.1 in) •Over Platform:•10.4 cm (4.1 in)
Northeast Wave Energy Region
44008,66m depth, 54NM offshore
WEHD Benefits for Existing Designs• WEHD platforms can provide    steeper waves to existing    systems such as the    “Pow...
Contact InformationMichael Raftery, M.E.Research EngineerStevens Institute of TechnologyDavidson Marine Laboratory711 Huds...
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Critical Capabilities For Wave Power Conversion In Mild To Moderate Wave Climates 07 Oct 2010

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My Presentation ay the MREC in Cambridge, MA in Nov 2010

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Critical Capabilities For Wave Power Conversion In Mild To Moderate Wave Climates 07 Oct 2010

  1. 1. Harnessing and Converting WavePower in Mild, Moderate, and Extreme Wave ClimatesPresenter: Michael Raftery, M.E.Research EngineerStevens Institute of TechnologyOffice: +1 201 216 8704Testing and Research Funded byThe Office of Naval Research
  2. 2. Problems• Mild wave slopes do not provide sufficient acceleration of power take-off components for existing systems to operate efficiently• Buoyancy and stability related catastrophic failures have occurred during prototype deployments• Power take-off and electricity generation are strongly coupled in existing systems• Storm events result in extreme structural loads all wave climates
  3. 3. Develop Solutions• Capable of increasing wave slopes and concentrating wave power• Capable of eliminating single point, buoyancy and stability related failures• Capable of decoupling power take-off from electricity generation with energy storage• Capable of avoiding extreme anchor loads during storms
  4. 4. Quantify Mild and Moderate Waves• Average annual significant wave heights of 0.75m or less = mild wave climate• Average annual significant wave heights of 0.75-1.5m = moderate wave climate
  5. 5. Wave Tuning Research• A variable-depth, fully-submerged tension leg platform (TLP) was tested in the wave tank facility at Stevens Institute of Technology (Stevens) to quantify the relationships between platform depth, wave period, wave height, mooring stiffness, and the changes in wave form. The test matrix was scaled at 1:10 based on average waves off NJ/NY/NE
  6. 6. Wave Tuning “Shoaling” FeatureTLP Shoals10cm Wave overa 20cm BuoyBuoy MotionIncreases withWave Steepness
  7. 7. Mild Wave (H =5.1cm)
  8. 8. 5.1cm, 2.21s Wave – 15cm Platform DepthWave Heights:•Before Platform:•5.1cm (2.0 in) •Over Platform:•12.7 cm (5.0 in)•Wave Height Increase: 150%
  9. 9. Mild Wave ResultsH =0.051m (2.0in)Cg = 1.97 m/s at 1.98m tank depthE = 3.27 J/m^2P = 6.43 W/mShoaled WaveH = 0.127m (5.0in)Cg = 1.14 m/s at 0.15m platform depthE = 20.25 J/m^2P = 23.07 W/m259% increase in power density
  10. 10. Moderate Wave (H = 10.4cm)
  11. 11. 10.4cm Wave – 15cm Platform DepthWave Heights:•Before Platform:•10.4 cm (4.1in) •Over Platform:•17.8 cm (7.0 in)•Increase in Wave Height: 71%•Note: waves dropped below the wave wire over the platform resulting in an apparent “flat” bottom
  12. 12. Moderate Wave ResultsH = 0.104m (4.1in)Cg = 1.97 m/s at 1.98m tank depthE = 13.58 J/m^2P = 26.74 W/mShoaled WaveH = 0.178m (7.0in)Cg = 1.14 m/s at 0.15m platform depthE = 39.78 J/m^2P = 45.32 W/m69% increase in power density
  13. 13. WEHD-Full Scale Design
  14. 14. WEHD – Redundant Systems
  15. 15. Scaling Power Take-Off• Mild Waves 0.51m, 7s = 2.04kW/m• 1.27m Shoaled power = 7.30kW/m• Moderate Waves 1.04m, 7s = 8.47kW/m• 1.78m Shoaled power = 14.34kW/m• Note: Froude scaling is used as power take-off estimates are based on the wave making resistance of a surface float
  16. 16. Energy Storage System• 2 – 10m wide buoys = 20m width• Storage volume, 80 – 300L Accumulators• = 24m3 = 12m3 working volume• Storage pressure = 3000psi (200 bar)• Adiabatic Storage capacity = 303kWh (1.09GJ)
  17. 17. Charge Rate at 35% Efficiency• 20m x 7.30kW/m x .35 = 51kW• 20m x 14.34kW/m x .35 = 100kW• Mild waves charge the energy storage system in 6 hours• Moderate waves charge the energy storage system in 3 hours
  18. 18. Discharge Rates• 75kW for 4 hours• 150kW for 2 hours• 300kW for 1 hour• 600kW for 30 minutes• 1.2MW for 15 minutes• 2.4MW for 7 minutes 30 seconds• 4.8MW for 3 minutes 45 seconds
  19. 19. Anchor Load Avoidance• Anchor loading can be reduced by lowering the platform near the sea floor
  20. 20. 10.4cm Wave – 110cm Platform Depth
  21. 21. 10.4cm Wave – 110cm Platform DepthWave Heights:•Before Platform:•10.4 cm (4.1 in) •Over Platform:•10.4 cm (4.1 in)
  22. 22. Northeast Wave Energy Region
  23. 23. 44008,66m depth, 54NM offshore
  24. 24. WEHD Benefits for Existing Designs• WEHD platforms can provide steeper waves to existing systems such as the “Powerbuoy” developed by Ocean Power Technologies (OPTT), and the “Pelamis” developed by Pelamis Ltd.• Wave systems can damp waves approaching offshore structures
  25. 25. Contact InformationMichael Raftery, M.E.Research EngineerStevens Institute of TechnologyDavidson Marine Laboratory711 Hudson St.Hoboken, NJ 07030Email: michael.raftery@stevens.eduPhone: 201 216 8704Fax: 201 216 8214

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