A brief review of some energy harvesters including improvements in their power conversion systems: Roadways and road speed bumps

Energy harvesting technologies have attracted interest in recent years given their potential to contribute to energy generation by converting ambient energy into electric energy. However, a great variety of energy harvesting technologies exist, where the energy generation can vary from a few milliwatts to a few watts. This paper aims to provide a brief review of the power magnitudes that some energy harvester technologies can extract at sites such as roadways and road speed bumps. Mechanical motion and thermal energy are two existing environmental power sources at these two sites. The harvesters considered to exploit these sources used transducers that base their operation on piezo-electric vibration, electromagnetic induction, and temperature differentials. In addition, some works related to the improved conversion efficiency of the power conversion circuits in these technologies were also reviewed and analyzed. The results showed that the power magnitudes achieved by the harvesters at the sites under study are sufficient to meet the power demand in devices with low-power electronics such as wireless sensors, data loggers, and data transmitters. In the case of the roadways, the harvesters produced between 0.016 mW to 200 mW. However, the power magnitudes generated in the speed bumps were up to 1.1 kW, considering the large size of the experimental prototypes. The development of these technologies have the potential to extend the lifetime of the energy storage units such as capacitors and primary batteries vital for environmental conservation.