Low power energy harvesting systems: State of the art and future challenges

Recent works on self-charging power technologies mainly focused on the low energy harvesting component, while its integration with the energy storage system was usually not further evaluated or discussed. This was addressed in the present work by providing a comprehensive state-of-the-art review on different types of energy storage used for self-sufficient or self-sustainable power units to meet the power demands of low power devices such as wearable devices, wireless sensor networks, portable electronics, and LED lights within the range of 4.8 mW-13 W. The paper presents the relevant scientific studies and recent developments on incorporating low energy harvesting with energy storage and power management systems. Recent advances on seven types of low energy harvesting technologies or transducers and eight types of micro/small-scale energy storage systems from farads to amps were examined to assess the integrated design's overall efficiency. The study focused on the design, distribution management networks, efficiency, compatibility with other components, costs, and environmental impact of self-sustainable power unit. To effectively assess the most suitable energy storage for the self-charging power unit, assessing its technical characteristics, economical, and environmental impact is discussed. Finally, the review identified the challenges and further research that must be carried out to achieve a more sustainable and stable integrated technology, moving from the proof of concept or laboratory to actual applications.