The Hanna Wave Energy Turbine Generator

US Patent 8,358,026

To the reader:


  This "Forward Looking Statement" provides an overview of my invention: a special marine turbine that always spins in one continuous direction even when subjected to bi-directional air or tidal flows.  The Hanna wave energy turbine is an uncomplicated device.  The only moving parts are the two rotors.  Simplicity of design is an absolute necessity for an ocean-based device to be successful and cost-efficient. My turbine is designed for long-term survivability.  It is robust and will last for decades with minimal maintenance.  No wave energy turbine components are immersed in sea water.  There are one-way bearings sealed within the hubs of each rotor.  These are affordable, off-the-shelf bearings.  They are the same precision, heavy-duty bearings commonly used in tanks and tractors.

  Preliminary engineering studies have been completed at two universities.  The first study validated the design as a self-rectifying turbine using bi-directional air flows.  The second study compared the Wells Turbine with the Hanna Turbine using steady-state air flows.  In this preliminary, undergraduate study, the Hanna design showed better efficiency metrics than the Wells.  Now, a high-level engineering study is currently underway at a prestigious international university.  This advanced engineering research will optimize the Hanna device from its current TRL 2 status to TRL6.


  The reader is encouraged to do a diligent review of existing wave energy turbines such as the pioneering but inefficient Wells Turbine. Your own informed comparison can then be made. Upon carefully reading the following material, you will understand that this design is the most versatile and adaptive of all existing wave energy turbines.  The device is not only a wave energy turbine; it can also be used as a bi-directional tidal turbine!

  To assure the advancement of this useful technology, I am offering to assign full ownership of the patent, including university research data, 3D drawings and test equipment to a research entity, qualified developer or established manufacturer. After the patent has been transferred, I plan to step aside and retire.


  John C. Hanna

1. Problem to be solved

    To improve the effectiveness of wave energy harvesting and double the electrical output of existing wave energy conversion devices, the technology needs a more efficient air turbine: The Hanna Turbine offers a powerful unidirectional turbine designed to operate seamlessly in the bi-directional air flow environment common to all Oscillating Water/Air Column systems.



 Wave Energy Conversion (WEC) is an emerging technology sector that harvests energy from ocean waves. One sub-class of WEC technology uses special turbines to generate electricity. Although there are different turbine designs in development, they all share a common challenge: Oscillating Water Column (OWC) devices convert wave motion into alternating expansion and compression cycles within an enclosed air duct. The air flow inside the duct can be compared to inhaling and exhaling. This reciprocating air movement is used to spin a turbine. The challenge lies in how to spin the turbine continuously in only one direction while the air stream is moving back and forth.

  OWC technologies are the most mature and well studied of all the other wave energy conversion systems. They have been around for over thirty years; no other WEC system has produced as much utility-grade power to the grid. Open water or shore based OWC structures offer an efficient means of conversion: they filter irregular wave patterns which yield a resonant amplitude response. Also, baffles that are built inside the capture chamber help to dampen and slow down the frequency of incident waves, thus allowing the contained water to continue oscillating after a wave passes by. This stored energy results in a more even amplitude for efficient wave to wire conversion.  The reason OWC turbine designs have not made it big in the global market is because they are either too inefficient or too complex and costly to manufacture and maintain.  The Hanna Turbine promises to overcome all of these issues.

  Four types of OWC turbine designs include: (1) Impulse turbines which show promising efficiency coefficients and are relatively inexpensive to manufacture. Research from 2009 (V. Jayashankar, M. Takao, T. Setoguchi, et al.) favors a twin impulse turbine topology.  Another biradial impulse turbine has been described by Luis Gato and Antonio Falcão (U.S. patent 9,371,815 B2) with the Instituto Superior Tecnico, Portugal.  Currently, Oceantec Energy, S.L. and Tecnalia is testing this design called MARMOK A-5, at the Bimep ocean test site near Armintza, Spain; (2) Variable pitch axial turbines like the Denniss-Auld Turbine which rely on complex movable blades to adapt to the reversing flow every cycle; (3) the pioneering Wells Turbine which is an axial flow, reaction-type turbine. While the Wells Turbine does indeed spin in one direction, design issues have been reported by researchers and wave developers: it stalls easily, has a small operating window, and is difficult to self-start under many conditions, and (4) the Hanna Turbine, is a unique dual rotor, mixed flow impulse and reaction type turbine that has both axial airfoil blades and radial vanes for maximum efficiency.  The Hanna configuration combines the best elements of the Wells (reaction) and Falcão (impulse) designs and creates a new, more efficient turbine.

  Despite the shortcomings of the Wells Turbine, wave energy developers such as AWS, Ocean Energy and the former Wavegen have been staying with the Wells to avoid cost and complexity issues associated with the variable pitch turbines as used by Australia's Oceanlinx. As a result, a great deal of technology development has gone into attempting to enhance and improve the operation of the Wells, including a large body of work from Japan and India. The Dresser-Rand corporation has teamed with Siemens to develop a Wells Turbine connected to a large, unwieldy bowl-shaped inlet to take advantage of Bernoulli's principle.  While it is conceivable that continued investment into Wells refinement might garner a modest improvement in efficiency and operating window, alternatives to the Wells Turbine are needed to successfully advance OWC technologies into the global market.  The new Hanna Turbine shows potential for significant cost reductions and efficiency improvements over the pioneering Wells and all other self rectifying designs.



II. Scientific and Technical Approach - The Hanna Turbine

A. Concept and Principle of Operation


  Two sets of back-to-back turbine rotors are connected to a primary drive shaft. A precision one-way clutch mechanism in each rotor hub allows the turbine to transmit torque during the power stroke and freewheel during the coast mode. The complete Hanna Turbine system has both turbine sets, with mirrored blade configurations, connected to the same common shaft. In this ideation, the shaft will always be turning in one direction regardless of airflow direction. One of the two turbine rotors will be in a power stroke while the other is in a coast mode.


   Originally conceived and described by John Hanna in 2009, the Hanna Turbine (HT) shares some attributes with the Wells turbine. Like the Wells, the HT involves a unique airfoil shape. However, unlike the Wells, the HT airfoils are not symmetrical. The shape of the HT airfoils are asymmetrical which provide greater lift than the Wells configuration. The HT blades respond differently depending on the direction of flow in the oscillating air column. When air flow is impinging on the blades' leading edges, the blades are in a power stroke or "drive mode". The blades' aerodynamics are tuned to maximize energy harnessed from the incoming airflow. When the flow reverses and air is now impinging on the trailing edges, the "drive" rotor now switches over to a "coast mode " and the other rotor switches over to be the "drive" rotor. The reverse flow aerodynamics of the blades do not cause either of the dual turbine rotors to reverse direction as would happen on a conventional axial flow turbine. Instead, the blades continue to generate a small amount of torque in the same direction as the power stroke. The rotating mass of the dual rotors' annular (diffuser) rings function as flywheels and therefore, will also contribute to the angular (spinning) momentum of whichever rotor happens to be in the freewheeling mode.



This arrangement offers several benefits compared to Wells Turbines:

HANNA TURBINE                                        VERSUS                                       WELLS TURBINE

1. Dual rotor                                                                                                                    Single or dual rotor

2. Low speed operation                                                                                                   High speed operation
3.Develops more torque at lower speeds                                                                        Requires high speeds at lower torque

4. Asymmetrical airfoils for increased lift                                                                      Symmetrical airfoils for poor lift

5. Low angle of attack for more lift and less stalling                                                     High angle, poor lift and stalls easily

6. Better self-starting                                                                                                      Poor self starting

7. Wider operating range                                                                                                Narrow operating range

8. Less damping (resistance) to air flows                                                                       Greater resistance to air flows

9. More versatile with three configurations                                                                   One configuration

10. Two generators placed in dry environment...                                                          One generator in wet environment

or, two annular, ring-type generators built into rotors

11. Low noise due to diffuser rings and low speed operation                                       Very noisy, blade tip vortices

12. Impulse and Reaction Turbine (Axial and Radial blades in each rotor)                  Reaction type turbine

13. Wave OR tidal energy conversion                                                                          Wave energy conversion ONLY 


B. Applications


  Near and off shore applications could be large power generating OWC buoy farms or wave and wind harvesting platforms. Although offshore wave energy devices can benefit from a more powerful wave energy climate, the major disadvantage to launching a large, deep water point absorber is the cost of bringing the power to shore. Conservative estimates pencil in at $2 million per mile to run an undersea cable to a shore-based sub-station. Therefore, the preferred location for a utility-grade HT would be on-shore jetties or near-shore breakwaters.


  Another practical use would be self-powered navigational buoys (similar to those invented by Yoshio Masuda in Japanese waters). Other useful applications could have the HT built onto the legs of off shore oil platforms or for powering deep water MOB structures (Mobile Offshore Base), floating concrete docks or floating production, storing, and offloading (FPSO) facilities as designed by Float, Inc.



C. Energy extraction efficiency

  The two spinning rotors are the only moving parts in the entire turbine system. Two types of non-moving subsystem elements will be incorporated into the large, utility grade models: (1)Mechanical turbulators will be used to delay flow separation in the boundary layer of the blades. The turbulators enhance lift and reduce aerodynamic stalling without the need for variable pitch blades. (2) Another innovative method to improve the turbine's efficiency is the use of slots along the trailing edges of the hollow turbine blades. The slots (jets) slant high velocity air downwards, serving the same function as aircraft wing flaps used to avoid stalling and raise the lift coefficient of an airfoil at low speeds. The turbulators, hollow blades and trailing edge jets are for full-size turbines only. These subsystem elements are not used in small versions of the HT.


  With an aim toward more efficient mechanical energy conversion and high survivability, the HT will take advantage of robust, light weight plastic and carbon fiber technologies to streamline the manufacturing process for turbine blades and other rotor components. Low friction hydrostatic and polycrystaline diamond (PCD) bearings will be used. The proprietary airfoil design will be refined using computational fluid dynamics software.


  The OWC wave capture chamber is a key component of the Hanna Turbine's power take-off design. A unique shallow water capture chamber will be used for jetty and breakwater installations. Seasonal local wave climates will be studied and natural wave resonances will dictate the chamber's architecture. The capture chamber will be engineered to be an impedance-matched column to attain maximum wave to air energy transfer. Efficient energy extraction over a large bandwidth of wave frequencies will assure that the Hanna Turbine receives optimal pressure and velocity flowrates. To protect the turbine from pressure spikes during extreme weather conditions, relief valves and a damping plate will be used.

D. Three versatile models


  Adaptive and versatile power take-off options offer three unique, job-specific Hanna Turbine models to choose from: #1) The first model (the 'bent duct' model) is configured as described above which drives two external generators only. #2) The second option is an in-line model called the 'Power Induction Turbine'. It is a self-contained, stand alone power plant where the peripheral rings in both rotors have permanent magnets that induce current into surrounding coils (see drawing at bottom of page). This model will not use external generators. This configuration allows the HT to be placed within a straight intake duct that can be orientated either horizontally or vertically. #3) The third option allows the HT to generate power both internally and externally. This hybrid model will provide internal power for grid connectivity and two external generators will be relativistic (Homopolar) dynamos that will produce high amperage power to run seawater reverse osmosis desalination plants or other high energy industrial processes.

E. Conclusion


  In-house proof of concept evaluations have been successfully completed. The Hanna Turbine is an uncomplicated design with only two moving parts. It offers long-term survivability for decades of low maintenance service. The unique dual rotor configuration can drive two generators, effectively doubling electrical output. The HT is essentially two distinct axial turbines that will extract more energy from a given flow direction of the OWC. This is accomplished without the need for complex and expensive variable pitch or counter-rotating blade mechanisms. The HT can be deployed anywhere in the world as long as a suitable wave climate exists. Environmental studies for similar WEC devices now in place, have all resulted in "Findings Of No Significant Impact". No commercial fisheries will be effected.


  The Hanna Turbine was conceived to develop a self-rectifying turbine that overcomes the shortfalls found in the 30 year old Wells Turbine design. It will be a less expensive alternative to shore-based OWC systems built at Islay, Scotland, Mutriku, Spain and Azores, Portugal. The former Scottish company called Wavegen, developed a variant of their Wells-based design. In an attempt to improve efficiency, Wavegen hoped to market a dual rotor, counter-rotating Wells Turbine. Unfortunately, the design's complexity introduced added frictional losses due to the multiple gear sets. This reduced any modest gains in efficiency. It would also be more expensive to manufacture and maintain. Clearly, the evolution of the Wells has run its course.

  The patented Hanna Turbine promises to  exceed the power production and performance metrics of all other turbines in the global market. Three utility-grade turbine models will be offered as complete, grid-ready packages. The civil engineering, permitting and construction will be done by the utility, government agency or developer that has acquired a Hanna Turbine system. Construction plans will use a pre-determined anchor bolt pattern so the Hanna Turbine can simply bolt into place. The client/owner will be purchasing a turnkey, commercial off-the-shelf (COTS) package that includes everything needed to make clean, renewable energy for decades. As envisioned, the WETGEN business model aims to become a leader in the manufactured turbine supply chain rather than as a wave energy developer.


  To underscore the remarkable versatility of the Hanna Turbine, the design can also be easily modified to function as a TIDAL turbine.  The submerged rotors react to the tidal flow so one rotor will be in the "drive" mode whilst the other is in the "freewheel" mode. As the tidal flow reverses, so does the modality of the turbine's rotor set. Regardless if the tide is going in or out, the two generators will produce electricity at all times. This adaptability and versatility is truly a paradigm shift for marine energy. The ability to be used as a wave energy converter or as a tidal energy converter, sets the Hanna design far and above all other marine hydro kinetic technologies!


  Another Hanna innovation has been successfully tested: A small gateway buoy using the novel Hanna Closed-Loop PTO will provide low wattage power for remote, free-floating buoys. The system's design provides a one way flow of high velocity, low pressure air to spin two brushless generators.  The system specifically eliminates the need for a self-rectifying turbine.  A Hanna gateway buoy will provide persistent charging power for battery-powered components.   Multiple applications will serve the commercial and scientific sectors.  It will provide months of maintenance-free, reliable power for oceanographic monitoring, Iridium satellite links or FreeWave radio transceivers. Its fully encapsulated, closed-loop air supply will function with low noise levels. The proprietary air supply mechanism is self contained; there are no intake or exhaust ports to take on water. All generating and power-conditioning components will be sealed to operate within a dry, corrosion-free environment. Click HERE for more details on the small research buoy.


  The images below show a turbine model that was built for proof of concept testing.  The OSU preliminary evaluation was successfully completed on March 7, 2014. This initial test validated the turbine's ability to spin in only one continuous direction while being influenced by a bi-directional air flow.  As of February 2017, hi-level university studies are currently underway to optimize the turbine's airfoils and internal flow characteristics.

  The Hanna Turbine has now achieved independent, third-party validation from Oregon State University.  A video of this preliminary run-up is posted on the YouTube WETGEN channel. To view the video click HERE. An in-house project has been completed for a pneumatic drive to power the small turbine pictured above. Additional information on WETGEN projects can be seen on LinkedIn. To view, simply Google: John Hanna-WETGEN.


  On June 10, 2014, a U.S. Utility patent (8,745,981) was granted for a remarkable new wave energy technology titled "Ocean Powered Take-off for Multiple Rotary Drives". This latest WETGEN device is a low-cost, mechanical direct drive PTO that converts oceanic wave cycles into a mechanical, bi-directional linear force and then channels this reciprocating linear force through a simple, low friction arrangement of gears to drive multiple rotary generators or pumps in one direction only. The direct drive PTO called the Hanna MultiDrive, can generate electricity from 100% of a wave's full cycle. To learn more and read the patent for this new PTO, click HERE. To read the full patent text for the Hanna Turbine with drawings, click here: WETGEN patent.

TORQUE IS THE ANSWER... Doesn't Matter What The Question Is.

Poly Dome
John Hanna, inventor of the Hanna Wave Energy Turbine alongside of a nine foot (three meter) Containment Dome assembly. Four foot diameter, rotational molded, high density polyethylene, Pressure Containment Domes/Turbine Housings.

 LEFTLLEFT: A simple sketch showing the bent duct configuration of the Hanna Turbine.

Notice that the two generators are located outside of the turbine's enclosure,

permitting easy access for routine maintenance in a dry environment.

   RIGHT: A mockup of the "bent duct" model

LEFT: The in-line, self-generating turbine.

Four rows of magnets in both rotors induce current in surrounding

coils attached to the adjacent bulkheads.

RIGHT:  AN OWC structure with the Inline turbine installed.

LEFT: Cutaway of trailing edge jets and collector ports RIGHT: Turbulators, trailing edge jets and collector ports

LEFT: Close up of trailing edge jets   RIGHT: Cross section of the bent duct model

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