Tidal Turbines Green Energy From Maine

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					                                      A Test-Bed Design Characterization of Tidal Turbine Flows
                                           Patrick Bates                                     Russell Dunn                                       Jacob Folz                                Scott Lessard                                     Eric M. Martin                                                                                                     Richard Peale
                                                                                                                           University of Maine, Department of Mechanical Engineering
                                                      Over the past decade there has been intense development of In-Stream Tidal power generation as a viable sustainable and renewable energy source. Many companies have designed proprietary turbines; little published data exists key aspects of In-Stream
                                                      tidal turbine flows, including basic performance characteristics, wake flow patterns, turbine array interaction effects and surface profile effects. This poster presents the development of a test platform for efficiently characterizing the performance and flow
                                                      patterns of scale model tidal turbine designs. The University of Maine and Maine Maritime Academy created this testing capability as part of a larger effort, which aims to create an internal structure that can achieve the following:

                                                        Develop a rapid design/build/test                                       Create a series of baseline turbine                                          Generate detailed performance                                                                                Provide these resources to the
                                                        sequence for rapid development                                               designs using this rapid                                               and flow field data for this design,                                                                               public and turbine
                                                               of turbine designs                                                     development process                                                      which is publicly available                                                                                  development community

                                                     Figure 1 shows the tidal passage in the Bagaduce narrows, a site being studied by Maine Maritime Academy as a potential tidal energy site. In-            Tidal In-Stream systems would look more like underwater wind farms, using an array of turbines located
Figure 1: Tidal Power Site at Bagaduce Narrows       Stream tidal turbines extract energy from the kinetic energy of a tidal flow, as opposed to the traditional tidal barrage dam, which utilizes a head      along high velocity tidal flow channels, as seen in Figure 2.
                                                     rise created by a dam for the energy source.                                                                                                                                                                                                                                                                                                                                                               Figure 2: Rendering of potential Tidal Turbine Farm

    Design                                                                                                                                                                                                                                                   Procedure
                                                                                 Upper Driveline: (Figure 4) Instrument mounting
    The tidal turbine test bed was engineered to test the performance of                                                                                                                                                                                     Using the designed and fabricated test bed, ran a controlled
    tidal turbine designs in an overhead carriage tow tank. Many different                                                                                                                                                                                     experiment to develop dimensional and non-dimensional
                                                                                   • Upper .500” stainless steel drive shaft                                                                                                                                   performance curves.
    design matrices were used to select the current design.. The final design
                                                                                   • Three supporting, self aligning Rylon linear bearings
    Figure 3 shows the entire test bed assembled contained:                                                                                                                                                                                                  • Created flow through scaled model of a tidal turbine
                                                                                   • Incremental Rotary Encoder coupled to the upper plate shaft
                                                                                   • DC stepper motor to provide rotational resistance                                                                                                                         (Figure 8) in a 100’ long tow tank by attaching test bed to
    The Test Bed Five Sub-Assemblies:
                                                                                   • Two ABS skate wheels reducing friction within motor                                                                                                                       movable carriage (Figure 3)
    • Instrumentation to read torque, rotational velocity, and frontal force                                                                                                                                                                                 • Ran carriage at three controllable speeds and multiple
                                                                                   • Torque measuring reactant force gimble with a S-Type Load Cell
    • Multidirectional support and force measurement capability
                                                                                   • Six-axis dynamometer which suspends driveline with necked slender rods                                                                                                    torsional loads
    • Streamlined extension                                                                                                                                                                                                                                  • Data collected using Data Acquisition System (Figure 7)
                                                                                     and collects drag force data
    • Housing and universal driveline for turbine mounting
                                                                                   • High efficiency steel chain and nylon sprocket for trasmision of rotational
    • Data collection of instrumentation output                                                                                                                                                                                                                                                                                                                                                                                                                     Figure 8: 3D printed OpenProp propeller
                                                                                     motion from lower to upper driveline                                                                                                                                    Results
                                                                                                                                                                                                                                                             Figures 9 -12 show experimental data, equations utilized, and performance curves of the turbine.

                                                                                                                                                                                                                                                             • Collected average steady state angular velocity and average torsional load from Figure 9 to develop dimensional
                                                                                                                                                                                                                                                               performance curves shown in Figure 11
                                                                                                                                                                                                                                                             • Applied equations from Figure 10 to show the precision of the test bed and performance of turbine design
                                                                                                                                                                                                                                                               shown in Figure 12

                                                                                                                                                                                                                                                                                                                Turbine Data - Vo = 1.831 m/s, Total Torque = .178 N m

                                                                                                                                                                                                                                                                                        4                                                                                                         0.2

                                                                                                                                                                                                                                                                                       3.5                                                                                                        0.15
                                                                                                                                                                                                                                                                                                                                                                                                  0.1                                                           Power Coefficient:                              Cp 
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          V 3 A

                                                                                                                                                                                                                                                                                                                                                                                                          Load Cell Output (V)
                                                                                                                                                                                                                                                                  Encoder Output (V)

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                TR 

                                                                                                                                                                                                                                                                                                                                                                                                  -0.05                                                          Tip Speed Ratio:
                                    Figure 4: 3D Computer Model of Driveline                                                                                                                                                                                                           0.5                                                                                                        -0.1

                                                                                                                                                                                                                                                                                        0                                                                                                         -0.15
                                                                                                                                                                                                                                                                                             0              5                   10                    15                 20                  25
                                                                                                                                                                                                                                                                                                                                       Time (s)

                                                                                                                                                                                                                                                                                                                                Encoder (V)   Torque (V)                                 RUN # 022608C2

                                                                                                                                                                                                                                                                                                  Figure 9: Raw data from test run                                                                                                                     Figure 10: Equations used in non-dimensional
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                performance curves
                                                                                                                                                                                                                                                                                       5.00                                                                                                                                                          0.18



                                                                                                                                                                                                                                                                                                                                                                                                                                 Power Coefficient

                                                                                                                                                                                                                                                                   Torque (N m)

                                                                                                                                                                                               Figure 3: Test Bed setup in wave tank                                                   2.50




                                                                                                                                                                                                                                                                                       0.50                                                                                                                                                          0.02

                                                                                                                                                                                                                                                                                       0.00                                                                                                                                                            0
                                                                                                                                                                                                                                                                                           0.00     50.00        100.00     150.00     200.00         250.00   300.00         350.00     400.00          450.00                                             0       0.5          1        1.5               2          2.5         3   3.5
                                                                                                                                                                                                                                                                                                                                                RPM                                                                                                                                       Tip Speed Ratio
                                                                                                                                                                                                                                                                                                                Vo = 1.38 m/s             Vo = .914 m/s                 Vo = 1.831 m/s                                                                                    Vo = 1.38 m/s         Vo = .914 m/s      Vo = 1.83 m/s

                            Figure 5: 3D Computer Model of the Nacelle with a Section View                                                                                                                                                                                                    Figure 11: Dimensional performance                                                                                                                                Figure 12: Non-dimensional performance

Strut: (Figure 6) Hydrodynamic extension
                                                                                                                                                                                                                                                             The dimensional curves (Figure 11) follows a partial power curve for the high end angular velocity of the turbine.
• Solid, welded, streamlined extension for complete lower driveline submersion                                            Figure 6: 3D Computer Model of Struts                                                                                              Further data points at lower rotational speeds would provide a full scale power curve for the turbine. This would
• Two side-by-side hollow aluminum airfoil struts connect Upper Driveline                                                                                                                                                                                    show the optimum rotational velocity for the turbine to run at its highest power efficiency. In the non-dimensional
  System to Lower Driveline System                                                                                                                                                                                                                           performance curve (Figure 12), the points collapse to a single curve for the middle and higher flow velocities,
• Top end of struts welded to connector plate for tensioning chain                           Data Acquisition: (Figure 7) Acquire, condition, and store data                                                                                                 indicating that the test apparatus was properly measuring the turbine performance. The lower speed data may have
• Bottom end of strut contoured to OD of Nacelle for hydrodynamic efficiency                                                                                                                                                                                 suffered from the lower measurement forces due to the internal friction in the test bed system, but the number of
• High efficiency chain encapsulated by struts                                               • Instrumentation:                                                                                                                                              data points collected was insufficient to make any concrete conclusions.
• Nylon tube within strut to reduce friction on chain                                            • Angular velocity of shaft – Incremental Rotary Encoder

Nacelle & Lower Driveline: (Figure 5) Hydrodynamic driveline containment
                                                                                                 • Frontal drag force – 100 lbs. S-Type Load Cell                                                                                                            Conclusion
                                                                                                 • Reaction force from resistance torque – 50 lbs. S-Type Load Cell
                                                                                             • Signal Conditioners convert instrumentation output to 0-5 Volts                                                                                               A test bed for the testing of scale model tidal turbines was developed and implemented in the University of Maine
                                                                                                                                                                                        Figure 7: Wiring Diagram of Data Acquisition Assembly
• 3.50” OD, 12” long, internally threaded aluminum pipe                                      • DAQ Unit supplies LabVIEW with conditioned data                                                                                                               tow tank. A sample turbine was tested which successfully demonstrated the test beds measurement capabilities. Data
• UHMW Polyethylene bearing fixture insert                                                   • Interactive program for data readout and storage                                                                                                              was collected over a range of speeds and it was shown that the non-dimensionalized power curves collapsed to a
• Two unsealed stainless steel ball bearings                                                                                                                                                                                                                 single performance curve as expected. This was used to validate the performance of the test bed measurement system.
• Stainless steel .500” shaft with spherical thrust transmitting end and threaded end        Dynamometer: (Figure 3) Support and force measurement                    References
  for turbine mounting
• Threaded UHMW tail cone to maintain converging streamline flow                             •   Six-axis force measurement capability
                                                                                                                                                                      D’Epagnier, Chung, Stanway and Kimball, 2007: An Open sourced Parametric               Acknowledgements
• Nylon sprocket and stainless steel chain for efficient power transmission                                                                                           Propeller Design Tool; MTS/IEEE Oceans 2007 Conference, Vancouver, B.C.
                                                                                             •   Force captured parallel to velocity vector of carriage motion                                                                                               This project was made possible with the contributions by Mick L. Peterson, Meg Smith, Mo Shahinpoor, and the
• Threaded UHMW nose cone to reduce flow separation and support shaft bearing                •   S-Type load cell connected to upper driveline                        Zeh,M.: Development of a Six Axis Dynamometer for Tow Tank Testing;                    Department of Mechanical Engineering. Rich Kimball and students from Maine Maritime Academy were an essential
                                                                                             •   Dynamometer frame bolted to carriage for rigid support               Undergraduate Capstone Project, April 2006 Maine Maritime Academy, Castine             part in designing, fabricating, and testing the test bed. The AMC and Art Pete aided in the fabrication process, along
                                                                                             •   Designed and built by Matt Zeh of MMA (Zeh 2006)                     Me.                                                                                    with Neil Greenberg.

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