A sensor node driven by air flow

The growth of the IoT infrastructure requires the development of new devices able to harvest energy from the environment to power Wireless Sensor Network (WSN) nodes. Among the available sources (light, mechanical vibrations, temperature differences...), air flow can represent a good choice in many cases: we consider not only a natural wind, but also air flow in building pipelines or air flow around a moving vehicle (trains, trucks, cars...). Usually, an energy harvester EH device for IoT applications has centimeter-size dimensions: this constraint hinders the use of blade rotors, since the efficiency goes down at this scale. In this contribution, we present an EH device, called FLEHAP (Fluttering Energy Harvester for Autonomous Powering), which is based on an aeroelastic effect named fluttering. Via an electromagnetic coupling, the FLEHAP device can produce several mW in an air flow of 5 m/s. However, to efficiently transform the mechanical energy in electrical energy, a specialized electronics is needed. In particular, since the brake effect associated with the electromagnetic coupling strongly interacts with the fluttering dynamics, for the sake of the overall system efficiency, it is necessary to control the power drain from the coils. In our paper, we will describe our approach, based on an AC-DC switching converter, supervised by a low-power microcontroller circuit. The latter will be also able to collect data from sensors and send them through a dedicated wireless link.