Optimum pitch angle of downwind Thai sail windmill for maximum annual energy production

摘要

The traditional Thai sail windmill (TSW) has been a workable machine for centuries and is used mainly to pump waterfor agriculture, but it suffers from low operating efficiency in the order of 10%. For a wind turbine, pitch angle and windstatistics are significant parameters which affect efficiency and annual energy production (AEP). The optimum pitch angledepends on the local wind statistics. The pitch angle of the TSW is typically designed using rules of thumb,, which have beencarried on from one generation to the next. Therefore, the optimum design features have not been systematically confirmed. Theobjective of the current study is to investigate the optimum pitch angle of a TSW by a systematic experiment in order to obtainthe maximum AEP. The test model was built similarly to a TSW but scaled down 8 times and the rotor orientation was changedto downstream (DTSW model) to catch the wind more easily. The experiment was performed by the tow testing method. TheWeibull function was used for the AEP estimation in the Nakhon Ratchasima Province of Thailand as a case study. The resultsshowed that the optimum pitch angles of the 4-blade and 6-blade DTSW models were 5 and 10 degrees and the maximumefficiencies were 17% and 25% and produced AEPs of 20.4 kW-hr and 37.3 kW-hr, respectively.