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Scale model testing has formed a vital part of modelling research activities, allowing modelling researchers to validate code and model set ups against experimental data. Generally, scale testing to-date has proceeded at the 1/30th to 1/20th scale which is in line with the size of facilities available for testing such devices. This paper presents a fundamental study into the effects of Reynolds Number and Rotor Solidity when testing HATTs at 1/5th scale, 1/20th scale and 1/30th scale. The paper utilises a mixture of 1/30th scale (0.5 m diameter) experimental data for two, three and four rotor setups, 1/20th scale (0.9m diameters) experimental data for a three-blade rotor setup.

Renewable energy based systems are expected to contribute on the reduction of greenhouse gases and carbon emission, while satisfying global energy demands. In Mexico, the Cozumel Channel located in the Caribbean Sea has been identified as a potential energy source in the region. Preliminary studies have shown that the ocean current is characterized by almost uniform and unidirectional flow velocities of up to 2.0 m/s within its mid-section with water depths > 500 m. Nevertheless, a detailed resource assessment in shallow waters of the Cozumel Channel is required to address sites potentially suitable for the installation of marine energy converters. Field measurements were taken during September 23rd-29th, 2018 to describe the spatial variation of the marine current velocities at various points along the east-side of the Cozumel Channel, at water depths less than 50 m. Flow velocities higher than 1.0 m/s were identified on the northern east of the Cozumel Channel, at a distance >600 m from the shoreline and over the continental shelf with water depths

The durability and reliability of tidal energy systems can be compromised by the harsh environments that the tidal stream turbines need to withstand. These loadings will increase substantially if the turbines are deployed in exposed sites where high magnitude waves will affect the turbine in combination with fast tidal currents. The loadings affecting the turbines can be modelled using various numerical or analytical methods; each of them have their own advantages and disadvantages. To understand the limitations arising with the use of numerical solutions, the outcomes can be verified with practical work. In this paper, a Blade Element Momentum coupled with wave solutions is used to predict the performance of a scaled turbine in a flume and a tow tank. The analytical and experimental work is analysed for combinations of flow speeds of 0.5 and 1.0 m/s, wave heights of 0.2 and 0.4 and wave periods of 1.5 and 1.7 s. It was found that good agreement between the model and the experimental work was observed when comparing the data sets at high flow conditions. However, even if the average values were similar, the model tend to under predict the maximum and minimum values obtained in the experiments. When looking at the results of low flow velocities, the agreement between the average and time series was poorer.

Wave loading on tidal turbines is of key concern for determining blade and drive train design loads and the fatigue life of components. Furthermore, irregular waveforms are likely to add complexity to the loading patterns, and represent more realistic conditions. To investigate this issue, a set of laboratory tests was conducted in a large wave-tow facility at CNR-INSEAN, Rome. A 0.9 m diameter three bladed horizontal axis turbine model was fixed to the tow carriage and tested under tow, regular wave-tow and irregular-wave-tow conditions at a range of turbine rotational velocities. Thrust and torque on the blades and rotor were measured dynamically during testing using strain gauges. The control mode was switched between constant speed and constant torque to understand how this influenced turbine power capture and thrust loading, and assess the potential to use control methods to mitigate loading fluctuations. It was found that average power and thrust values were not affected by the control mode or the addition of regular or irregular waves. However, using torque control resulted in increased thrust fluctuations per wave period of the order of 40% of the mean thrust compared to under speed control. Therefore, the operational mode must be taken into consideration.

If tidal energy extraction is to be maximised then emphasis needs to be placed on the design of the rotor geometry to optimise performance. The work documented in this paper describes the process used in the design and validation of a new blade based on the Wortmann FX63-137 aerofoil. BEMT was used as an initial tool to redesign the blade due to speed in which calculations can be completed. CFD models were produced after to incorporate the hydrodynamics and provide a 3D solution. The performance coefficients for CP and CT were calculated by each of the two computational methods for comparison with the experimental testing. The experimental testing was conducted at the INSEAN tow tank to provide validation for the computational models. The CFD model was found to closely predict the performance coefficients of the turbine at low TSR at and peak power. The BEMT model over predicted both the CP and the CT when compared to the experimental work, however was found to be good as an initial method for redesigning the blade.

The main objective of this paper is to analyse extreme cases of wave-current interactions on tidal stream energy converters. Experiments were undertaken in the INSEAN tow tank facility where carriage speeds of 0.5 and 1m/s were used with and without waves. The waves studied in this testing campaign had wave heights of 0.2 to 0.4m with a 2s wave period in a stationary reference frame. These wave conditions were considered extreme cases considering the use of a turbine with a rotor diameter of 0.5m. The turbine was equipped with a torque transducer, an encoder and a strain gauge to measure both the rotor torque and the forces on a single blade root. The results of the experiments showed that extreme wave-current cases can result in significant variations in power. Investigating the time histories of the blade root loading in wave-current conditions illuminated the importance of the relationships between the wave phase and blade angular position, and the number of blade rotational periods in a wave period. These affected the loading patterns and also the loading range seen by the blade, both of which have important implications for the fatigue life of the blade.

The purpose of this paper is to investigate the current technical and operational supply chain issues surrounding the development of tidal and marine energy production in the UK. The paper outlines the market and growth potential of tidal energy production in the UK before identifying the key supply chain themes surrounding tidal energy production including an analysis of the portability and transferability of current supply chain thinking and development from other renewable energy systems such as wind turbine technology towards the development of tidal energy supply chain systems. The paper closes by identifying the major challenges that the UK supply chain must overcome in order to develop a comprehensive and robust supply chain system.

Load fluctuations caused by the unsteady nature of tidal streams can have severe impacts on turbine components. As seen in the wind industry, turbine blades can become misaligned due to a fault in the pitch mechanism or blade deformations arising over time. These misalignments will represent a loss of power capture and perhaps even premature failure of the components if not detected in time. Computational fluid dynamic (CFD) techniques can be used to predict the performance of a turbine with a misaligned blade. However, these numerical modelling techniques quickly become computationally expensive when modelling realistic, time-varying conditions. Blade Element Momentum Theory (BEMT) offers a quicker and simpler approach, although with several limitations. In this paper BEMT is adapted to predict the performance of a three bladed tidal turbine with one or two blades offset from the optimum pitch setting. This approach is compared with a CFD model to study the effectiveness of both methods to predict power and thrust when a rotor blade has an offset. The simulations were undertaken at three flow speeds (0.9, 1.0 and 1.1 m/s). Both numerical models are compared to experimental data that was obtained at a flume tank in similar flow conditions. The results showed that both BEMT and CFD are able to predict power coefficients when there is a small offset of one rotor blade. However, the predictions were poorer when two blades had two different offsets at the same time.