Designing and managing sub-milliwatt energy harvesting nodes: Opportunities and challenges

The ultimate goal of low-power distributed embedded systems is to develop devices which are able to operate unattended for years. Micro-energy harvesting systems can scavenge milliwatts from solar, thermal and vibrational sources and are considered as the breakthrough which will revolutionize ultra-low power systems, wireless sensor networks (WSN) and pervasive applications. This paper will demonstrate that muW harvesters are capable to power systems for operation at extremely low power levels. In particular we deal with musolar-scavengers of some mm² which address the small energy budget optimizing the efficiency of energy collection even when tracking the maximum power point (MPP) becomes difficult and burdensome to implement. Simulations and experimental results show the impact of light intensity variations on the activity of the sensor node.