Vertical axis wind turbine

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MECH 4010 Design Project

Vertical Axis Wind Turbine

Group 2 Jon DeCoste Denise McKay Brian Robinson Shaun Whitehead Stephen Wright

Supervisors Dr. Murat Koksal Dr. Larry Hughes Client Department of Mechanical Engineering Dalhousie University December 5, 2005

With the recent surge in fossil fuels prices, demands for cleaner energy sources, and governmentfunding incentives, wind turbines have become a viable technology for power generation. Currently, horizontal axis wind turbines (HAWT) dominate the wind energy market due to their large size and high power generation characteristics. However, vertical axis wind turbines (VAWT) are capable of producing a lot of power, and offer many advantages. The mechanical power generation equipmentcan be located at ground level, which makes for easy maintenance. Also, VAWT are omni-directional, meaning they do not need to be pointed in the direction of the wind to produce power. Finally, there is potential for large power generation with VAWT because their size can be increased greatly. However, there are also downfalls to the VAWT. Firstly, boundary layer affects from the groundinfluence the air stream incident on the VAWT, which in some cases leads to inconsistent wind patterns. Secondly, VAWT are not self-starting; currently, an outside power source is required to start turbine rotation until a certain rotational speed is reached.

The main objective of this project is to design and build a self-starting vertical axis wind turbine. This report outlinesthe first term efforts in the design of our full-scale VAWT, which is to be built early in the second term.

The self-starting issues surrounding VAWT will be tackled by the use of alternative blade profiles and pitching mechanisms. A model that carries out turbine theory calculations was created to aid in the design of the full-scale turbine. The model inputs include NACA 0012 airfoillift and drag coefficients, angles of attack and relative wind speeds as determined from a MATLAB program, and user inputs such as wind speed, tip speed ratio, overall blade and turbine dimensions, and power required. The model outputs forces and torques produced over a wide range of TSR. The model also uses various angles of attack to determine performance results when pitching isused. Analysis results indicated that passive pitching is an affecting way to boost the turbines ability to selfstart. However, the NACA 0012 profile was unable to achieve self-starting status, as it


does not have large lift coefficients at low Reynolds numbers. It was concluded that a profile with large lift at low speeds used along with passive pitching could achieveselfstarting status. As a result, three blade profiles will be tested and compared over the holiday break in the wind tunnel facility at Dalhousie University. Results from prototype testing in the wind tunnel will reveal the blade profile that offers the best performance for self-starting.

The full-scale VAWT will be approximately 10ft tall, with a blade height of 5ft, and a diameter of 8ft.Three blades will be CNC machined from aluminum stock. The full-scale model will be built early next term to allow for adequate testing time.

To date the group has received $1000 from Richard Rachals, $600 from our Client, the Mechanical Engineering Department, and $864 left over from the previous year wind turbine design project. The primary expense of this project is the costsassociated with CNC machining the three aluminum blades. Other expenses include bearings, a generation unit, and materials. To cut down on costs, equipment from previous year design projects will be used where applicable.


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