Since I began to work on the Flap-turbine I end up doing power calculation about HAWT again and again. Even though this is relatively easy calculation, doing it many times boring and time consuming. I could write a small Perl program to do it, but it would only serve my purpose. I am sure there are many people doing these calculations. For this reason I developed following flash program for power calculation for HAWT.
Notice that program has two slider components, one to change the wind speed and the other to change the radius. When the wind speed increased by the first slider, you will notice that the swept are covered by wind turbine blades changes toward red color. This is to indicate that stresses in the system is increasing. Notice also that efficiency of turbine also decreases substantially with increased wind speed. This is because blades are adjusted by changing the pitch angle so that they expose less area to the wind. This area decrease reduces stresses imposed by high wind on the blades.
The program display three power. The first power is the power available in the wind for given wind speed and radius. The second power is the Betz Power. This is the maximum power can be extracted from the wind if there were no losses or inefficiencies in the system. Please note that it is very difficult to get the Betz power from any turbine. The last power which is labeled as Real Power is the power you can get from the turbine with the efficiency displayed in the screen. This kind turbines will have 0 efficiency for wind speeds above 25 m/s, meaning that turbine reached it is cut of speed and turned of to prevent damage to turbine.
The efficiency is calculated based on typical efficient turbine and you can NOT change efficieny. If you want to do that go to Change Efficiency
This animation will help you to find power generated by HAWT for giwen radius and wind speed. By draggin sliders you can change the radius and the wind speed.
Here is the calculation of different power per square meter and per square feet for given wind speed. You can change wind speed by dragging the slider. You can also change efficiency as long as it is smaller than 59.3.