Design and preliminary testing of a novel concept low depth hydropower device

This paper introduces a new type of kinetic hydropower generator, ideally suited to relatively small shallow rivers and channels. The design utilizes rectangular hydroplanes (`sails') moving around the device. The device extracts energy from a flow of water using an elongated vertical axis turbine, where a series of sails are mounted between two belts at the top and bottom of the device, rotating in the horizontal plane. The concept would be ideally suited to relatively shallow rivers and channels, because it can be designed to fill more of the channel's cross-sectional area than the circular rotor of a standard marine turbine or array of turbines. As a hydrokinetic device it would not require extensive civil works, unlike head turbine installations. The initial analysis undertaken to assess its potential for power generation is presented. This analysis comprises both experimental testing of a physical model and the related hydrodynamic computational modeling. The physical testing produced reliable, meaningful coefficient of power results. The trend of these results match that predicted by the theoretical model, however, the physical prototype yielded a much lower coefficient of performance, even after subtracting the (high) mechanical losses. This must be in large part due to the fluid losses in the device not considered in theoretical model, in particular the ratio of swept area to shrouded area (where the sails rotate at the ends of the device, shielded from the flow). Even though no electrical power was ever generated during testing, the concept has been shown to be capable of producing useful electrical power: a maximum coefficient of power for the prototype was observed to be at approximately 0.25, negating mechanical losses. The coefficient of thrust for the device showed a constant value of coefficient of thrust of 1.75, however these results may be unreliable due to a low strain sampling rate. Increasing the swept area to shroud ratio would yield further performance increases, though it is not known what maximum performance could be reached. Further research in this area would be beneficial, as the concept can not realistically be compared to other turbines without first determining the optimal swept area to width ratio, and therefore the maximum performance of the concept.