Performance and dynamic characteristics of a multi stages vertical axis wind turbine

Abstract

Vertical axis wind turbines (VAWTs) are used to convert wind energy to mechanical output or electricity. Vertical axis wind turbines are favorable at buildings as it can receive wind from any direction, have a design that can be integrated simply with building architecture and they have better response in turbulent wind flow which is common in urban areas. Using a calculation code based on the Double Multiple Stream Tube theory, symmetrical straight-bladed NACA0012 wind turbine performance was evaluated. The induction factor for both upwind and downwind zone is determined with the aid of a root-finding algorithm. This numerical analysis highlighted how turbine performance is strongly influenced by the wind speed (Reynolds number) and rotor solidity (turbine radius and blade chord length). Also a dimensional analysis is introduced and is to be considered in such a way to generalize the design for different turbine specifications. One of the qualities provided by dimensional analysis is that geometrically similar turbines will produce the same non-dimensional results. This allows one to make comparison between different sizes wind turbines in terms of power output and other related variables. One of the main problems affecting the turbine performance and dynamics is the torque ripple phenomena. So in this paper a turbine design configuration is introduced in order to decrease the turbine torque fluctuation. This design is carried out by constructing more similar turbine units (stages) on the vertical axis on top of each other with different orientation phase angles. The results showed that using even number of turbine assembly is better than odd number to avoid torque fluctuation and mechanical vibrations acting on the turbine. Also it is preferred to use four turbine stages as the eight stages will have no sensible effect on decreasing the torque fluctuation.

Performance analysis of dual-stage vertical axis hydrokinetic turbine (VAHT) with azimuth variation at open canal hydrokinetic power plant

“…The use of dual-stage configuration is aiming to reduce that problem. The result of its implementation shows that VAHT efficiency increased and lead to lower torque fluctuation [18][19]. Moreover, Baruah, et al get an average result of 27.9% in power coefficient increase by implementing dual-stage configuration in vertical axis wind turbine system and a similar result is expected in VAHT [20].…”

Double-Multiple Streamtube Analysis of a Flexible Vertical Axis Wind Turbine

“…In this study, the performance of various rigid and flexible-bladed VAWTs are estimated using the DMST model [43]. The details of this model are widely available, and have been applied to HAWTs [44], troposkein VAWTs [45] and straight-bladed VAWTs [46]. A short description of the general DMST procedure follows.…”