GOAL
The goal of this project is to utilize additive manufacturing to adjust a series of parameters of scaled down vertical axis wind turbines’ blades, in order to identify an optimal design.
WHY
Although, horizontal axis wind turbines (HAWTs) have proven to be ultimately more reliable, vertical axis wind turbines (VAWTs) do have benefits [1]. They perform better in turbulent winds, they are quieter, they take up less space and are easier to maintain. Therefore, with continued research and design adjustments, it is possible that vertical wind turbines could play an increasing role in generating clean energy. The more clean energy, the better!
PLANS
For this experiment, each tested turbine will consist of three total blades and each of which will have a NACA 0018 airfoil profile. The height-to-diameter will also be kept the same throughout all of the designs. PLA is the first choice of material to print all of the blades with because it has a relatively high ultimate strength and durability [2]. It is a common thermoplastic to 3D print with, which will aid with choosing the proper printer settings. When compared to ABS, PLA is less likely to warp while cooling, which will benefit the accuracy of the twist angle.
A single constant vertical axis will be fitted with an attachment hub, to which each of the different variations of blades will be mounted on.
Center hub designed for blade attachment at changing locations [3]
This hub will be machined out of aluminum and mounted to a generator from which the efficiency of each turbine will be determined. The individually printed blades can then be attached to the hub at a variety of angles. Initial experimental plans include alternating the the twist angle, the turbine solidity and the print density between to be determined high and low levels. This will sum up to be 8 variations that are expressed in the following design matrix,
Proposed Design Matrix
The twist angle of a VAWT is depicted below,
Twist area of a VAWT [1]
The solidity of a turbine is the ratio of a its blade area to its swept area.
As of right now this hub only allows for a single point of attachment, which would mean each blade would only have a single strut. This design is uncommon for a Darrieus style VAWT, especially one with a twist angle [4]. For this reason, before designing and printing all of the iterations of blades, a set of test blades will be printed. They will be printed with PLA, have a twist angle of 120 degrees, the low level solidity and low print density. The intention of this initial test observe how the highest risk design performs and make any necessary adjustments before printing all 8 sets of three blades. Ultimately, this should lead to better final results.
REFERENCES
[1] Z. Wang, Y. Wang, and M. Zhuang, “Improvement of the aerodynamic performance of vertical axis wind turbines with leading-edge serrations and helical blades using CFD and Taguchi method,” Energy Conversion and Management, vol. 177, pp. 107–121, 2018.
[2] T. Letcher and M. Waytashek, “Material Property Testing of 3D-Printed Specimen in PLA on an Entry-Level 3D Printer,” Volume 2A: Advanced Manufacturing, 2014.
[3] K. Dressler, “Hub_v02,” Lab 6.2 – Wind Turbine Hub, 2019.
[4] L. Battisti, A. Brighenti, E. Benini, and M. R. Castelli, “Analysis of Different Blade Architectures on small VAWT Performance,” Journal of Physics: Conference Series, vol. 753, p. 062009, 2016.