小型發電機之振動發電

Abstract

隨著京都議定書的生效與歌本哈根會議的舉行，不僅工廠的生產需要節約能源，我們日常生活也必須朝著節能的目標努力，因此，本論文的目的在探討並設計製作小型振動發電機構。藉由研發出小型輕便的可攜式發電器，引用源源不絕的周遭能源，例如人體行走、橋樑振動、或者車輛行駛間產生的振動能量，經由發電器將機械能轉換成電能，整流及升壓並儲存之後，將可以取代電池而具有多用途的實用性。振動源以模擬人體行走或手臂擺動為目標，利用伺服馬達當振動源，模擬人體行走或車輛行駛時產生的振動能量，使固定在伺服馬達連接擺臂上的小型發電器發電。 除了電磁式振動搖擺發電機構外，本論文也設計出數種壓電發電裝置，包括機翼式、懸臂樑式及中心對稱式，藉由機械能轉換成電能裝置的設計，以達成能源使用的目的。利用壓電彎片的應變獲得發電的效果，期望在配戴行走時，藉由手部的擺動來帶動發電裝置中壓電片的應變，將所得的電量經由整流電路轉換成直流後，直接對電池充電或先對電容充電，再利用電容來對充電電池充電。為了降低發電裝置的共振頻率，除了在壓電彎片上放置一質量塊，以降低共振頻率外，另於壓電彎片與基座之間，加入已知彈簧係數之彈簧與已知質量大小之印刷電路板，來達到彈性基座的效果，進而降低壓電彎片的共振頻率，使其更接近周圍環境的振動頻率而有最大發電量的效果。最終期望能在人體所能產生的振動頻率下，獲得最大的發電量，達成實用的目的。

In view of Kyoto Agreement and Copenhagen Accord that has become effective recently, not only plant production has to save energy, daily energy saving is also the direction we have to strive. It is desired to develop miniature portable generators that employ ambient energy, such as vibration energy from walking people, oscillating bridges, and traversing vehicles, and transform the vibration energy into electric energy. After rectification and voltage elevation, the electric energy will be able to replace batteries in a variety of occasions. This study aims to design and fabricate appropriate mechanisms for vibration generators. First, the appropriate mechanisms for electromagnetic vibration generators are studied. The energy-generation apparatus is installed in the hand and shakes due to walking or swing our arms. A swing arm attached to a servo motor is considered a vibration source to simulate the above situation. The electrical power is generated and charged into capacitors via a full-bridge rectifier circuit. Moreover, different designs of piezoelectric generator, like airfoil type, symmetry type, and cantilever type are studied too. Vibration energy is transformed into the electric energy for storage by piezoelectric benders. A point mass is attached to the piezoelectric bender to lower resonant frequency and approach the frequency range that human movement produces. Additionally, the effect of elastic base is studied. To install the elastic base, this study uses a spring with prescribed stiffness and a board with given mass between the piezoelectric bender and the base, which can make the resonant frequency of piezoelectric benders close to the lower frequency of ambient vibration. Analytical derivation is carried out to obtain optimal mass and stiffness. For adjusting the resonant frequency of piezoelectric benders to be close to that of ambient vibration, the experiments of power generation using different elastic bases are implemented to obtain the optimal design of elastic bases. Accordingly, more electric power can be generated by piezoelectric generators using an elastic base with optimal mass and stiffness.