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Effect of Closing the Blade Tip on Downwind Thai Sail Windmill

Teerawat Klabklay, Wikanda Sridech


Thai sail windmill has been a traditional wind turbine of Thailand, which is a type of horizontal axis wind turbine and now used for pumping the seawater into the salt farms widely in the Samut- Songkhram province for the sea salt production. Currently, the efficiency of the conventional Thai sail windmill is typically quite low that is only approximately 10 percent. Actually, the efficiency of wind turbines depends on many parameters such as blade shape, pitch angle, solidity, wind speed, tip loss, etc. However, this study focused on the tip loss reduction by using technique of closing the blade tip in order to be a guideline for enhancing efficiency. The objective of this study was to investigate the effect of employing technique of closing the blade tip on the efficiency of Thai sail windmill in the fashion of downwind rotor. For experiments, the small scale of 4-blade and 6-blade rotor in the pattern of downwind Thai sail windmill was built and used as a prototype to experiment by using the tow testing method. As a result, the use of technique of closing the blade tip could help the 4-blade rotor increase maximum efficiency from 17 percent into 22 percent at the tip speed ratio of 2.2 and help the 6-blade rotor increase maximum efficiency from 25 percent into 35 percent at the tip speed ratio of 2.0.


Thai sail windmill; Wind turbine efficiency; Downwind rotor; Closing the blade tip

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DOI: 10.14416/


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