Sumber tenaga boleh diperbaharui memberikan pengeluaran kuasa yang mampan pada masa hadapan. Tenaga hidro merupakan salah satu daripada pilihan optimum pengekstrakan tenaga boleh diperbaharui. Kebarangkalian, keteraturan, dan kebolehpercayaan menjadikan tenaga hidro pilihan yang paling menarik bagi penghasilan tenaga. Tenaga hidrokinetik berasal daripada aliran sungai, arus pasang surut dan saluran air yang lain. Berbanding tenaga hidro konvensional, pembinaan empangan atau takungan tidak diperlukan kerana sifatnya mengekstrak tenaga melalui gerakan air. Turbin hidrokinetik dibahagikan kepada dua kategori utama: turbin paksi mendatar dan turbin paksi menegak. Untuk projek ini, perhatian diberikan kepada turbin hidrokinetik paksi menegak (VAHT) atas sebab keketaraan penyelidikan atas turbin paksi mendatar dan kekurangan bagi turbin paksi menegak. VAHT dikelaskan mengikut susunan yang berbeza: Darrieus sangkar tupai, H-Darrieus, Darrieus melengkung, Gorlov dan Savonius. Bagi projek ini, turbin H-Darrieus menjadi tumpuan siasatan atas sebab penggunaan bilah berbentuk aerofoil, memudahkan pengiraan kuasa. Demi membuat model matematik, teori-teori baru mengenai VAHT telah dipelajari. Sesetengah model komputasi diperkenalkan, namun tidak akan diguna pakai dalam siasatan ini. Beberapa kajian dahulu yang berkaitan dengan projek ini disorotkan. Seterusnya, kaedah reka bentuk disediakan bagi memudahkan proses pemodelan matematik. Data aerofoil diekstrak daripada sebuah kajian dahulu (aerofoil s1210, NACA-0015). Model matematik yang diperlukan bagi pengiraan prestasi turbin dirumuskan dan ditunjukkan dalam langkah-langkah. Parameter permulaan turut disenaraikan. Kemudian, perincian pengubahsuaian parameter permulaan, kajian mendalam terhadap nisbah kelajuan hujung dan kekukuhan turbin, serta penyiasatan fizik penghidupan sendiri digariskan. Pada hujungnya, semua data yang diperoleh dipaparkan dan dilukis mengikut keperluan projek. Mula-mulanya, rajah baseline bagi konfigurasi satu-bilah diperkenalkan yang menjadi dasar bagi perbandingan keputusan. Seterusnya, rajah bagi konfigurasi turbin dua-bilah dan tiga-bilah dihasilkan dan dibandingkan dengan keputusan satu-bilah. Satu penyiasatan mendalam bagi nisbah kelajuan hujung dan kekukuhan turbin mendedahkan bahawa faktor-faktor ini menjejaskan turbin secara serupa dalam hasilnya tetapi berbeza dalam proses. Satu wawasan ringkas dibuat terhadap fizik dan isu penghidupan sendiri turbin dan cadangan untuk memperbaiki penghidupan sendiri turbin diberikan. Projek ini disimpulkan dengan meringkaskan perkara-perkara yang disebutkan, pembuatan kesimpulan berdasarkan pemerhatian dan inferens, dan juga cadangan bagi memperbaiki projek semasa, serta idea baharu bagi projek lanjutan yang boleh dilaksanakan pada masa hadapan.
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Renewable energy sources provide a sustainable power production for the future. Hydropower is one of the optimum choices for renewable energy extraction. Predictability, regularity and reliability make hydropower the most attractive choices for energy production. Hydrokinetic energy is harnessed from flowing streams, tidal currents and other water channels. Compared to conventional hydropower, construction of a dam or reservoir is not required due to its nature of extracting energy via water motion. Hydrokinetic turbines can be divided into two main categories: horizontal axis turbines and vertical axis turbines. For this project, attention is given to vertical axis hydrokinetic turbines (VAHTs), due to the prominence in research of horizontal axis turbines and lack thereof for vertical axis ones. VAHTs are further classified according to their different arrangements: squirrel-cage Darrieus, H-Darrieus, Curved Darrieus, Gorlov and Savonius. In this project, the H-Darrieus turbine is chosen as the model to be investigated due to its utilization of airfoil-shaped blades, thus easing the calculation of forces. For the sake of creating a mathematical model, new theories related to VAHTs are learned. Some computational models are introduced briefly, but they are not used in this investigation. Also, some previous studies which are related to the project are highlighted. Next, design methodology is prepared to aid the mathematical modelling process. The airfoil data is extracted from a previous study (s1210, NACA-0015 airfoil). The mathematical model required to compute turbine performance is formulated and shown in steps. The initial parameters are also listed. Then, details regarding the modification of initial parameters, the in-depth study of tip speed ratio and turbine solidity, and the investigation of self-starting physics are outlined. In the end, all data acquired are displayed and plotted according to the requirements of the project. First, a baseline plot of one-blade configuration is introduced to provide a basis for comparing results. Then, plots of two-blade and three-blade turbines are made and compared to the one-blade turbine results. An in-depth look into the tip speed ratio and turbine solidity reveals that they affect the turbine similarly in outcomes but differs a little in the process. A brief insight into the self-starting physics and issues of VAHT is provided and suggestions on improving the self-starting of turbines are given. The project is then concluded with the summarization of previously covered stuff, the drawing of conclusions based on the observations and inferences, as well as suggestions provided to improve the current project and ideas for new advanced projects that can be taken in the future.
Numerical investigation on the aerodynamics of vertical axis hydrokinetic turbines with semi-empirical data / Foong Xipeng