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 Savanius rotor theorie |
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| This project was undertaken to improve the efficiency of vertical axis wind turbines with the expectation that the inherently simple vertical axis turbines could be manufactured at low cost, leading to their widespread use. The research proposal noted that small units could be manufactured for distributed generation of electricity in residential and commercial locations. The units would be grid connected to take advantage of net metering and would provide pollution free generation of electricity using a renewable resource at a cost competitive with power supplied by the grid. The researcher estimates that a moderate sized residential unit would generate 2700 kWh per year and that the low cost of the unit would allow a simple payback of investment from energy savings in three years. If 100,000 of these small wind turbines were installed in California they would eliminate the annual generation and release of nearly 10 tons of oxides of nitrogen and over 13 tons of carbon monoxide gas. These calculations are based on California’s 2007 air emission standards for natural gas burning distributed generation. Displacing older generators would result in greater environmental benefits. The simplest vertical axis wind turbine is called the Savonius wind turbine. Operation of the Savonius wind turbine is based on the difference of the drag of its semi-spherical vanes, depending on whether the wind is striking the convex or the concave part of the vane. The advantage of this type of wind turbine is that it is self-starting and relatively independent of the wind direction. It is simple to design and has relatively low construction cost. However it has low efficiency. The approach taken by this project was to improve the efficiency of the vertical axis (Savoniustype) wind turbine by modifying the blades. The blade shape was iteratively designed using Computational Fluid Dynamics software embedded within a torque maximization program using the Trans Finite Interpolation method, (see appendix A). A scale model vertical axis wind turbine featuring the optimized blade design was constructed and tested in the Boeing/CSULB low speed wind tunnel. Wind tunnel tests confirmed a 40% increase in peak power coefficients over prior art. |
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