Performance of Multiple Energy Harvesting Elements in a Small-Scale Windmill

Abstract

Wind energy has attracted a lot of attention within the field of energy-harvesting applications because it is a source of a remarkable quantity of energy, particularly when compared to other untapped sources of energies such as solar energy and geothermal energy. Recently, a small-scale windmill containing a piezocomposite electricity generating element (PCGE) driven by a magnetic exciter has been proposed for the possible harvesting of wind energy in urban regions, where the typically observed wind speeds are very low. As an extension of previous work, the characteristics of PCGEs used in a small-scale windmill are investigated in terms of the number of PCGEs. Experiments were performed in cases where one, two, or four PCGEs are attached to the frame of the windmill, with optimization of different gap distances between exciting and secondary magnets carried out to determine the optimal configuration for generating the peak voltage and harvesting the maximum wind energy for the same range of wind speeds. The electricity generating capacity of the device was investigated for each number of PCGEs. In battery-charging tests, the charging time for a 40 mAh battery decreased when the number of PCGE increased. The experimental results show that the prototype can harvest energy in urban regions with low-wind speeds and convert the wasted wind energy into electricity for city use.