To the reader:
This Introduction provides an overview of my invention: a special marine hydrokinetic turbine that always spins in one continuous direction even when subjected to bi-directional air or tidal flows. The turbine is uncomplicated and straightforward; it's all about moving air in an elegant and creative way to do useful work. The only moving parts are the two rotors. There are one-way bearings sealed within the hubs of each rotor. These are affordable, off-the-shelf bearings. 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.
Engineering studies have been completed at three universities. The first study at Oregon State University (OSU) validated the Hanna design as a self-rectifying turbine using bi-directional air flows. Another study from France's Paris Tech, compared the Hanna Turbine with the Wells and Impulse Turbines using two advanced predictive methodologies: numerical modelling and 2D monodimensional analysis. In this study, the Hanna design showed better efficiency metrics than the Wells and Impulse Turbines. Read the Master's Thesis' Abstract by Théo Delecour below. This is the Abstract only. For permission to read the entire Master's Thesis, please contact John Hanna directly.
The third study was done at the Dubai campus of Heriot-Watt University, one of Scotland's oldest institutions of higher learning. This CFD study also showed favorable performance over existing self-rectifying wave energy turbines in today's global market. Read the Master's Thesis by Joe Ninan Sunil below.
The reader is encouraged to do an assiduous review of existing wave energy turbines such as the pioneering but inefficient Wells Turbine. Your own informed assessment can then be made. Upon carefully reading the following material, you will understand that this design is the most efficient, versatile and adaptive of all existing wave energy turbines. Importantly, the device is not only a wave energy turbine; it can also be used as a bi-directional tidal turbine!
I am an inventor, not a developer. Therefore, to assure the responsible development of this useful and versatile technology, my patent and IP is being offered for acquisition to a qualified developer or manufacturer.
John Clark Hanna
About J. C. Hanna: Click HERE
Hanna Turbine Tech. Report. (Master's Abstract by Théo Delecour )
Master's Dissertation (Master's dissertation by Joe Ninan Sunil)
OVERVIEW: 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 (
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 Falcao with the Instituto Superior Tecnico, Portugal. Currently, Oceantec Energy, S.L. and Tecnalia are testing this design called MARMOK A-5, at the Bimep ocean test site near Armintza, Spain; (2) axial turbines like the Denniss-Hunter Turbine used by the Australian company Wave Swell Energy; (3) the pioneering Wells Turbine. While the Wells Turbine does spin in one direction, it has numerous weaknesses: it stalls easily, has issues with low-speed operation, has a small operating window, and is difficult to self-start under many conditions, and (4) the Hanna Turbine, a unique dual rotor, mixed flow impulse and reaction type turbine that has both axial blades and radial vanes for maximum efficiency. The Master's Thesis from France's Paris Tech (see the report posted above) predicted 70% efficiency for the Hanna Turbine based on numerical simulations and monodimensional (mean-line) analysis. The predicted 70% efficiency figure only takes into consideration the output of the axial blades. Had the study combined both of the turbine's two primary drive components i.e., the radial vanes and the axial blades, the efficiency numbers would be higher.
Despite the shortcomings of the Wells Turbine, wave energy developers such as AWS, Ocean Energy and the former Wavegen have embraced the Wells. 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 up with Siemens to develop an optimized Wells Turbine. The duct on the atmospheric side has a large, bowl-shaped inlet to take advantage of Bernoulli's principle. It is unlikely that continued refinement of the Wells will garner modest improvements in efficiency and operating window. Alternatives to the Wells Turbine are needed to advance OWC technologies into the global market. The Hanna Turbine shows the greatest promise for improving the efficiency of OWC technology.
COMPARING THE WELLS AND HANNA TURBINES
HANNA TURBINE VERSUS WELLS TURBINE
1. Dual rotor Single or dual rotor
2. Low speed operation High speed operation
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) Impulse type turbine
13. Wave OR tidal energy conversion Wave energy conversion ONLY
The Hanna Turbine (HT) is an uncomplicated design. Its two rotors are the only 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/radial turbines that will extract more energy from a bi-directional air flow. 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 pioneering, 30 year old Wells Turbine design. It will be a less expensive, more efficient alternative to shore-based
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 unique to the Hanna Turbine design. The ability to be used as either a wave energy converter or as a tidal energy converter, sets the Hanna Turbine far and above all other OWC turbine designs!
The images below show a fractional-sized bent duct version of the Hanna Turbine. The sketch at the top of the page shows the "inline" version of the turbine.
There are other patented and proprietary Hanna Designs:
1) A mechanical direct-drive wave energy converter for shore-based, surface and subsurface Power Buoys. Click HERE for details.
2) A small deep ocean autonomous buoy for research and data gathering. Click HERE for details.