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Abstract The objective of this work is to propose an experimental apparatus setup for a small-scale three-bladed, horizontal-axis Ocean Current Turbine (OCT). This OCT model is under investigation using the University of New Orleans (UNO) towing tank to establish an electromechanical power takeoff system to produce sustainable renewable energy. The system is currently in the design phase. This paper describes the experimental apparatus design by considering sizing elements, bill of materials, schematics, and performance simulation for the expected system. The implementation of an actual experimental small-scale turbine complements the analytical and numerical investigations on turbine design characteristics achieved by ongoing research at UNO based on conformal mapping methods along with Blade Element Momentum Theory (BEM) for generated power prediction. The towing tank experimental approach is used to verify performance of the turbine. 

Abstract Conformal mapping techniques have been used in many applications in the two-dimensional environments of engineering and physics, especially in the two-dimensional incompressible flow field that was introduced by Prandtl and Tietjens. These methods show reasonable results in the case of comprehensive analysis of the local coefficients of complex airfoils. The mathematical form of conformal mapping always locally preserves angles of the complex functions but it may change the length of the complex model. This research is based on the design of turbine blades as hydrofoils divided into different individual hydrofoils with decreasing thickness from root to tip. The geometric shapes of these hydrofoils come from the original FX77W121 airfoil shape and from interpolating between the FX77W121, FX77W153, and FX77W258 airfoil shapes. The last three digits of this airfoil family approximate the thickness ratio times 1000 (FX77153 => 15.3 % thickness ratio). Of the different airfoil shapes specified for the optimal rotor, there are 23 unique shapes.[15, 16, 17, 18, 19, 20, 21, 22, 24, 25, 28] This study describes the advantage of using at least one complex variable technique of transformation conformal mapping in two dimensions. Conformal mapping techniques are used to form a database for sectional lift and drag coefficients based on turbine blade design to be used in Blade Element Momentum (BEM) theory to predict the performance of a three bladed single rotor horizontal axis ocean current turbine (1.6-meter diameter) by considering the characteristics of the sea-water. In addition, by considering the fact that in the real ocean, the underwater ocean current turbines encounter different velocities, the maximum brake power will be investigated for different incoming current velocities. The conformal mapping technique is used to calculate the local lift coefficients of different hydrofoils with respect to different angles of attack: −180 ≤ AOA ≤ +180. These results will be compared to those from other methods obtained recently by our research group. This method considers the potential flow analysis module that follows a higher-order panel method based on the geometric properties of each hydrofoil cross section. The velocity and pressure fields are obtained directly by the applications of Bernoulli’s principle, then the lift coefficients are calculated from the results of the integration of the pressure field along the hydrofoil surface for any angle of attack. Ultimately, the results of this research will be used for further investigation of the design and construction of a small-scale experimental ocean current turbine to be tested in the towing tank at the University of New Orleans. 

In this work, we propose a control framework for farms consisting of ocean current turbines (OCT). The ocean current turbine systems used in this farm are tethered to the ground of the ocean, and their depth can be adjusted online based on the maximum ocean current power available. To maximize the average power generated by the farm, the ocean current turbine wake interactions must be taken into account, and also each turbine in the farm should achieve these changes in the position reference with minimum control energy. Considering additional limitations such as keeping the tethering cables away from each other and avoiding collisions between the turbines, an advanced optimization framework is developed to achieve the maximum power generation in a specified region. Tracking of the reference trajectories by the ocean current turbine systems is achieved by model predictive control (MPC). A case study is presented to highlight the significant estimated improvement in the average energy generated by the farm using the proposed framework and control methodology. 

Increased global renewable power demands and the high energy density of ocean currents have motivated the development of ocean current turbines (OCTs). These compliantly mooring systems will maintain desired near-surface operating depths using variable buoyancy, lifting surface, sub-sea winches, and/or surface buoys. This paper presents a complete numerical simulation of a 700 kW variable buoyancy controlled OCT that includes detailed turbine system, inflow, actuator (i.e., generator and variable buoyancy), sensor, and fault models. Simulation predictions of OCT performance are made for normal, hurricane, and fault scenarios. Results suggest this OCT can operate between depths of 38 m to 329 m for all homogeneous flow speeds between 1.0-2.5 m/s. Fault scenarios show that rotor braking results in a rapid vertical OCT system assent and that blade pitch faults create power fluctuations apparent in the frequency domain. Finally, simulated OCT operations in measured ocean currents (i.e., normal and hurricane conditions) quantify power statistics and system behavior typical and extreme conditions.