Wave-Power Powerbuoy

Powerbuoy at sunset in Monterey Bay

MBARI engineer Andy Hamilton looks out his office window in Moss Landing and points at the waves crashing on the beach below. “Pretty impressive, aren’t they? You’d think there’d be a way to make use of all that energy.”

Since 2009, Hamilton has led a team of engineers trying to do just that. Their goal is not to replace the hulking power plant that overlooks Moss Landing Harbor, but to provide a more generous supply of electricity for oceanographic instruments in Monterey Bay.

Hamilton’s “power buoy” project was initially funded by the Defense Advanced Research Projects Agency (DARPA), which sponsors research into revolutionary new technologies that might one day be used by the U.S. military. The project started with a three-month grant to assess the availability of wave power around the world, and to assess DARPA’s previous attempts to generating electrical power from the waves.

Hamilton’s initial research and calculations showed that DARPA’s previous efforts had been too timid—their small prototype buoys were never able to take advantage of the full energy of the waves. So Hamilton proposed to “go big” (but not as big as commercial wave-power projects).

Because most wave motion occurs at the sea surface, the buoy rises and falls with the waves, but the plate, 30 meters (100 feet) down, remains relatively stationary. Between the surface buoy and the metal plate is a large hydraulic cylinder with a piston inside. As the buoy rises and falls, it pushes and pulls on this piston. This forces hydraulic fluid through a hydraulic motor, which in turn runs an electrical generator.

One of the first challenges the team faced was figuring out the best way to convert the vertical motion of the waves into rotary motion that could power a generator. First they bought a custom-made generator from an outside company, but that turned out to be too inefficient to be useful. Going back to the drawing board, the team designed their own system using an off-the-shelf hydraulic motor similar to those used on earth-moving equipment and on MBARI’s underwater robots. These hydraulic motors use moving hydraulic fluid to drive a rotating shaft with up to 95 percent efficiency.

Another challenge that Hamilton’s team faced was designing a mechanism that would return the piston to its starting point after a wave had passed. Hamilton initially envisioned using a large metal spring for this purpose, but the metal spring turned out to be much too heavy. So the team redesigned the system to incorporate a pneumatic spring—a chamber filled with nitrogen gas, and mounted at one end of the piston. As the piston moves with the waves, it compresses or decompresses the nitrogen gas in the chamber. After the wave passes, the gas in the chamber returns to its original pressure, forcing the piston back to the middle of its stroke.

Power buoy and dolphins

Dolphins swim beside the power buoy as it is towed back to shore. In the background is a huge pod of dolphins that the researchers encountered while recovering the power buoy. Image: Sonia Vargas © 2015 MBARI

wave-power buoy recovery

Experimental wave-power buoy survives winter in Monterey Bay

Feb 4, 2015 - In early January 2015, a team of MBARI engineers, led by Andy Hamilton, set out to sea to recover an experimental buoy that creates electrical energy from ocean waves. This power buoy had been deployed six miles southwest of Moss Landing Harbor for 131 days, while engineers tested the system’s ability to handle storms.

Team

Technology

Solving challenges
Taking the laboratory into the ocean
Environmental Sample Processor (ESP)
In Situ Ultraviolet Spectrophotometer
Midwater Respirometer System
Mobile flow cytometer
Enabling targeted sampling
Automated Video Event Detection
Environmental Sample Processor (ESP)
Gulper autonomous underwater vehicle
Advancing a persistent presence
Aerostat hotspot
Benthic event detectors
Benthic rover
Fault Prognostication
Long-range autonomous underwater vehicle Tethys
MARS hydrophone for passive acoustic monitoring
Monterey Ocean-Bottom Broadband Seismometer
Shark Café camera
Vehicle Persistence
Wave Glider-based communications hotspot
Emerging and current tools
Communications
Aerostat hotspot
Wave Glider-based communications hotspot
Data management
Oceanographic Decision Support System
Spatial Temporal Oceanographic Query System (STOQS) Data
Video Annotation and Reference System
Instruments
Apex profiling floats
Benthic event detectors
Deep particle image velocimetry
Environmental Sample Processor (ESP)
Persistent presence—2G ESP
How does the 2G ESP work?
Arrays on the 2G ESP
Printing probe arrays
Expeditions and deployments
In Situ Ultraviolet Spectrophotometer
Investigations of imaging for midwater autonomous platforms
Lagrangian sediment traps
Midwater Respirometer System
Mobile flow cytometer
SeeStar Imaging System
Shark Café camera
Smart underwater connector
Power
Wave-Power Buoy
Vehicle technology
Benthic Rover
Gulper autonomous underwater vehicle
Imaging autonomous underwater vehicle
Seafloor mapping AUV
Long-range autonomous underwater vehicle Tethys
Mini remotely operated vehicle
ROV Doc Ricketts
ROV Ventana
Video
Automated Video Event Detection
Deep learning
Video Annotation and Reference System
Technology publications
Technology transfer