The Defence Advanced Research Projects Agency and a team of researchers from MBARI lead by Andy Hamilton are working together on project ‘power buoy’ that will supply electricity for oceanographic instruments in Monterey Bay. The basis of the project is to harness wave power and divert it for electricity generation. After nine months of intensive research, Hamilton devised a buoy measuring 2.5m across, hanging in the water it is a massive metal plate 3m wide and 5.5m long. Throughout the team was faced with many challenges working with erratic ocean waves and a complex hydraulic system, these are discussed after the break.
The motion wave occurring at sea surface makes the buoy move with its waves, so the plate hanging down solved the purpose of keeping it relatively stable. There is a large hydraulic cylinder with a piston inside, which is pushed by the motion of the waves. When this happens, the hydraulic fluid is forced through a hydraulic motor and that in turn generates electricity.
While working on the project, several challenges were faced by the team. The first was one was converting vertical motion of waves into rotary motion for powering the generator. After several trials, the team finally ended designing their own system that used an off the shelf hydraulic motor that would move the hydraulic fluid for rotating the shaft. This system worked with a 95 percent efficiency rate.
The next challenge was to make the piston return to its starting point after the wave had passed. To deal with this, the team developed and incorporated a pneumatic spring, which is a chamber filled with nitrogen gas and is mounted at one end of the piston. Eventually through as they progressed they added fluid reservoirs, rebuilding the system several times.
By the end of 2011, the power buoy deployed at Monterey Bay was able to generate 400 watts of power. Next in line, the team aspires to generate a steady current of 24 volts by 2012 and the eventual challenge is to extend the scope of the power buoy project to include a underwater charging station for undersea robots.