The Hanna MultiDrive

U.S. Patent 8,745,981       


  "Ocean Powered Take-off for Multiple Rotary Drives"

 The simple sketch above, illustrates the patented Hanna direct drive power-take-off (PTO). The illustration is an artist's rendering that shows how the wave energy converter might be utilized in a surface buoy application.  The rendering is not an accurate representation of how the proprietary buoy would look.  The actual buoy is a single point, slack-moored platform that remains relatively static while the internal drive float moves up and down, spinning multiple generators.  The buoy can also be deployed as a subsurface wave energy converter (U.S. patent application 62/606,589).  To obtain details on the subsurface buoy, write to John Hanna at the address below. 

  In the surface buoy configuration, called the Hanna MultiDrive, a Main Shaft will rise and fall with the sinusoidal motion of passing waves.  The Main Shaft is attached to a Float which is contained inside an enclosure that has openings below and above the water surface.  Thus, the enclosure is a typical Oscillating Water/Air Column system.  However, the surface buoy design is but one application of this versatile device.  Near or on shore PTO's can be built into a jetty or placed on the sea bed as monolithic, pre-cast concrete breakwaters.  The PTO can be integrated into the design of off shore oil rigs and floating wind and wave harvesting structures.

  The reciprocating Main Shaft is a linear rack gear that drives a rotary pinion.  By a proprietary arrangement of gears that are serially engaged, the bi-directional linear movement is directly converted into a unidirectional rotary force.  This rotational, one-way force efficiently drives multiple generators and/or pumps in one continuous direction.  

   Any developer or electric utility provider that wants to maximize power output and lower O&M costs, would benefit by using the MultiDrive system.  It uses 100% of the wave cycle.  With a favorable wave climate, the direct-drive PTO will turn a plurality of permanent magnet generators continuously, in only one direction.  The generators will produce a smooth and sustained power output!  The design directly couples one or two back-to-back unidirectional flywheels to spin multiple generators.  The flywheel's mass and angular momentum provides high rotational speeds.  Up to eight air-cored generators will develop 150 Kw.  The air-core design eliminates magnetic drag on the flywheel's forward momentum.

  The Hanna PTO design is less complicated with greater energy capture than devices using expensive roller screw or variable winch drives.  Variable winch designs rely on a spring mechanism that is tethered to the sea floor.  Spring systems experience high wear and shock-loading.  Long term survivability is poor due to dynamic metal fatigue imposed by cyclic loading on the mechanism.

  An alternative to using multiple generators would be to eliminate the smaller generators altogether and utilize the flywheel as a stand-alone, radial-flux generator.  Powerful magnets will be embedded in the flywheel's outer periphery.  The generator's 'stator' windings are made up of multiple'C'-shaped, air-cored copper coils which shroud the spinning magnets to produce utility-scale power for the grid.  The generator's annular design is a specialized low-speed topology which has been developed specifically for wave energy converters.  The design virtually eliminates the large unwanted magnetic attraction forces that exist in conventional iron-core generators.  

  The highly adaptive MultiDrive system can double its energy harvesting capabilities if used in conjunction with the Hanna Mono-radial Turbine.  The added turbine(s) could provide power to the grid or be used as a back up power source to charge batteries and other onboard energy needs.  A buoy farm or shore-based power plant that leverages these combined technologies would have the greatest level of reliability and survivability of any other wave energy conversion system currently in the world market.


  The videos shown above demonstrates how the rise and fall of ocean waves are converted into a rotational force.  In the full-size, utility-grade device, the flywheel will turn freely under its own momentum between irregular wave sets.  The flywheel's spinning mass will provide a sustained wave-to-wire efficiency over a wide range of sea conditions.

  Contact WETGEN if you would like to learn more about this transformative wave energy technology.  To read the Hanna MultiDrive patent, click HERE.  There you can view computer generated videos of the device in action.  The animated graphics show how the Hanna MultiDrive converts ocean waves into clean, renewable energy.  A simple, cost-efficient system.