Thursday, June 23, 2011

Designed to Start: Developing Successful Vertical Axis Wind Turbines

Small vertical axis wind turbines (VAWT) are very attractive sources of clean wind energy for individual residences, small communities, localized power supplies (such as cell phone towers) and other applications.  A major problem for custom designed and production vertical axis turbines is in starting the rotation process.  This is especially true for low wind conditions .  This blog entry provides a new solution where the designer can develop working designs directly on their personal computer and reduce both the cost of building prototypes and development times.  This results in a less expensive line of products that will be an affordable source of clean energy for a growing client base.

The Design Process
Wind turbines and other devices are efficiently designed using a modern computer aided design (CAD) program such as SolidWorks or Autodesk Inventor.  However, for the engineer to know if the designs work or not, they must be built and tested in a wind tunnel or the physical environment.  This is a time consuming and costly step. 

A faster and cost effective solution is to test the design directly on the computer (ideally the same one where the design was developed).  An aerodynamics analysis software program such as Stallion 3D that can test the turbine designs directly in their digital form (as produced by the CAD program).

The figure below shows a vertical axis wind turbine that was imported into Stallion 3D using the STL format.  This file format is available export option in most three dimensional CAD software tools.

Analyze the Turbine
The next step is to determine whether or not the design will spin under desired wind conditions.  Stallion 3D allows the engineer to enter various wind conditions and angles to test the design.  This is done by simply entering the wind condition in a dialog box as shown in the picture below.

Of course Stallion 3D is not the only software package that can perform an aerodynamics analysis on a CAD file.  However, Stallion 3D works on an ordinary personal computer or laptop that runs Windows XP, Vista or 7.  It also eliminates the time consuming and expensive process of grid generation that is inherent in other computational fluid dynamics (CFD) method.  Since cost and time reduction is the goal of this new design  process, using Stallion 3D with its automatic grid generation tool is the logical choice.  The picture below shows the pressure solution and a crosssection of the computational grid that comprises 150,000 cells.  The grid and solution for this case were obtained in less than two  hours.

Designed to Start
To design a starting machine, the engineer must test the design for various wind velocity conditions (speed and direction).   Stallion 3D computes the flow field, forces and moments for any value of the wind direction.  The picture below shows separated flow on the lower blade at 45 degree wind direction and 15 miles per hour.

The software also computes the aerodynamics moments generated by the wind turbine and compares it to the starting torque of the power generator.  If the aerodynamic moments are greater than the starting torque, then the generator will turn for the specified wind conditions and we will have success.  If not, the engineer can make modifications in the CAD program and repeat the process without the expensive step of metal cutting.  The picture below shows the forces and moment that are computed by Stallion 3D to determine the torque and structural requirements of the wind turbine tower.

Stallion 3D is a 3-dimensional aerodynamics software product developed by Hanley Innovations.  The product is intended as a tool for engineers, designers and students that will allow them to solve problems on their personal computers (without the need for external assistance).  It is a component of their professional toolbox and bag-of-tricks that allow them to be innovation and productive at work and contribute to their professional advancement.

More information about Stallion 3D and other professional aerodynamics software tools can be found at