Abstract
More than a decade of research in the field of thermal, motion, vibration and electromagnetic radiation energy harvesting has yielded increasing power output and smaller embodiments. Power management circuits for rectification and DC–DC conversion are becoming able to efficiently convert the power from these energy harvesters. This paper summarizes recent energy harvesting results.
Introduction
The low power consumption of silicon-based electronics has enabled a broad variety of battery-powered handheld, wearable and even implantable devices. All these devices need a compact, low-cost and lightweight energy source, which enables the desired portability and energy
Autonomy. Today batteries represent the dominant energy source for many devices and alike. In spite of the fact that energy density of batteries has increased by a factor of 3 over the past 15 years, in many cases their presence has a large impact, or even dominate, size and operational cost. For this reason alternative solutions to batteries are the subjects of worldwide extended investigations. One possibility is to replace them with energy storage systems featuring larger energy density, e.g., miniaturized fuel cells. A second possibility consists in providing the energy necessary to the device in a wireless mode; this solution, already used for RFID tag, can be extended to more power hungry devices, but it requires dedicated transmission infrastructures. A third possibility is harvesting energy from the ambient by using for example, vibration/ energy, thermal energy, light or RF radiation. For each type of sources, different ambient situation are considered. They correspond to various level of available power, and hence of generated electrical power. Wireless sensor networks are made of large numbers of small, low-cost sensor nodes working in collaboration to collect data and transmit them to a base station via a wireless network. They are finding