Abstract
The use of vertical-axis turbines is raising interest in the field of hydropower production from rivers or water channels, where suitable mass flows are available, without the need of high water jumps or large construction sites. Although many optimization studies on vertical-axis turbines have been carried out for wind applications, lesser examples exist in the technical literature regarding hydrokinetic turbines. In the latter case, the best trade-off between power output and low structural stress is more dependent on the fluid dynamic loadings rather than the inertial loadings, due to the higher fluid density and lower rotation speed. The present work shows the results of an industrial study case application, in which the design of a traditional three-blade Darrieus rotor has been adapted for operating in water flows via hydrokinetic technology. Some specific design rules will be discussed, showing the different concepts adopted for the machine layout in order to achieve the best efficiency and performance. Multiple geometrical parameters of the rotor configuration were involved during the analysis: the number of rotor blades, i.e. two or three blades, the rotor’s shape, i.e. traditional H-shape or unconventional L-shape, and the use of power augmentation systems. The analysis of the numerical results was focused on the following output targets: maximum power coefficient, optimal tip speed ratio (TSR), rotor thrust, blade normal force and the upstream and downstream flow field influence. The outcome of the study shows how the best configuration differs from the common solutions for wind application. Moreover, a high power enhancement can be achieved while guaranteeing a good compromise in terms of structural loads.
Highlights
Traditional hydroelectric power plants exploit the potential energy accumulated by water that has been previously collected inside a storage reservoir
The present work shows the results of an industrial study case application, in which the design of a traditional three-blade Darrieus rotor has been adapted for operating in water flows via hydrokinetic technology
It is worth noting that the 2B-L case shows a much abrupt worsening of the efficiency for tip speed ratio (TSR) lower than the optimal value, justifying the choice of testing the performance of blades equipped with Gurney Flaps (GFs) for the 2B-H case only
Summary
Traditional hydroelectric power plants exploit the potential energy accumulated by water that has been previously collected inside a storage reservoir. The energy harvesting depends on available flow rate and the altitude of the water head This solution requires large investment costs, a suitable area for the plant site and a lot of construction work. The increasing need of alternative energy sources has led to the expansion of hydroelectric power generation to non-conventional sites, such as small natural streams, canals or artificial water networks [2]. For such applications, the technology required for harvesting the energy content is based on hydrokinetic energy conversion systems, which require flow velocities typically higher than 1 m/s. The experience learned in the field of wind turbines is progressively being transferred in order to develop machines capable of working in water flows, as well as marine currents and tides
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
