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Construction and Testing of an Electric Generator for Wind or Human Power

Abstract One of the most important engineering challenges nowadays is the developing and implementation of renewable energy systems that are practical, cost effective, and bring benefits to the society as well as to the environment. In general, wind generators operate satisfactorily at certain wind speeds which are rarely present in some geographic locations, and at other than the rated speed, they have poor performance. A permanent magnet three-phase alternating current (AC) generator was built in this project and it allows modifying its design and experimenting with several operating and control strategies at different speeds and load configurations. The performance of the generator was determined while charging deep-cycle batteries, and promising results were obtained. The generator is intended to be powered by wind or human power. For the human power application, a cyclist generates electricity by riding a regular mountain bicycle whose transmission was connected to the shaft of the generator. The bike becomes a stationary exercise machine because the rear wheel is lifted so that it does not have contact with the ground. Therefore, part of the energy burned during bicycling is stored in batteries instead of wasting it as it commonly happens with stationary bikes. The output of the three-phase AC generator was connected to a rectifier to obtain direct current (DC) voltage to charge the batteries. The main purpose of this paper is to present the experimental results obtained with this generator constructed as part of an undergraduate research project by a Mechanical Engineering student. Future work includes characterizing other configurations of the stator and designing a control system algorithm to optimize energy conversion not only to charge deep-cycle batteries but also to power loads connected to the batteries in a simultaneous or alternating way. Additional results are going to be obtained through experimental research to design, model, and optimize this relatively low-power electric generator propelled by wind or human power. The generator is developed for these specific applications taking into account the power limitations of such energy sources but considering as a very important task to harvest this energy for long time periods to benefit our society as well as the environment.

1. Introduction

Wind generators could be good electricity providers when moved by other means as long as there is enough power to rotate them in the neighborhood of their rated speed and to sustain the torque required to continuously operate them under those conditions for a long time. Human power could be used to propel these generators; but, the maximum power a person is able to generate for several minutes while exercising is in the order of 80-120 W at the optimal rate of about 60 rpm, which depends on the athletic ability and training of the individual1. Power losses in the mechanical transmission between the crankset of the bike and the generator need to be minimized by avoiding rubbing parts and using some sort of lubrication on moving parts. A few people taking turns to pedal a bike could store useful energy to power lights and preferably other energy efficient devices. In most well-off electrified cities and urban communities, because of needed exercise activities for individuals, there are homes, hotels, schools, and gyms with bikes

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Vasquez, H., & Gomez, C. (2009, June), Electric Generator For Wind Or Human Power Paper presented at 2009 Annual Conference & Exposition, Austin, Texas. 10.18260/1-2--5426