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Performance and technology readiness of a freestream turbine in a canal environment

Runge, Stefan 2018. Performance and technology readiness of a freestream turbine in a canal environment. PhD Thesis, Cardiff University.
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In this thesis, the study of performance and technology readiness of a freestream vertical axis twin turbine in a canal environment is reported. Experimental tests of a 1:10 scale model were carried out in the Hydro-Environmental Research Laboratory at Cardiff University. It is shown that a three-bladed, counter-rotating, vertical axis twin-rotor assembly performs best with a low rotor solidity and that channel blockage ratio influences significantly turbine performance and flow backwater effects. Blade manufacturing and surface-finishing was investigated and it is shown that a high quality surface finish of the blades is necessary to achieve the best performance. In a twin-turbine setup, the axis to axis distance between the two rotors is also identified as an important parameter. In order to combine the counter rotating motion of the two rotor shafts to one main shaft, a timing belt drive-train was introduced which drives the power take-off device. In the experiments, a mechanical brake and different generators were used in order to quantify the extracted energy and a comparison to the available hydrokinetic energy was performed. The electrical components needed for operating the turbine at different scales are presented and a control strategy for the maximum power point extraction was investigated. Moreover, the wake recovery downstream of the turbine rotor was investigated in order to predict the interaction between turbines in an array and design parameters such as spacing or direction of rotation accordingly. Three distinct three dimensional wake regions were identified: (i) a near-wake region; (ii) a transition region; and (iii) a far-wake region, where the flow velocity has almost recovered. In order to justify system functionality and performance in a relevant environment as well as up-scalability, a 1:3 scale model of the twin turbine was successfully implemented and tested in a discharge channel of a water treatment plant. This paved the way for a full-scale application: an array of ten full-scale twin turbine prototypes, including all relevant components such as housing, drive-train, gearbox and generator, are successfully installed, deployed and tested in the South Boulder Canal near Denver, Colorado, USA. Finally, the development stages of the twin turbine system were benchmarked by performing the Technology Readiness Level (TRL) assessment procedure. It is shown that the described turbine successfully reaches TRL 7 i.e., “full-scale, similar or prototypical system demonstrated in relevant environment”.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: hydrokinetic; VAT; vertical-axis; micro-hydro; wake; TRL.
Date of First Compliant Deposit: 21 May 2019
Last Modified: 04 Aug 2022 02:09

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