Powering indoor sensing with airflows: a trinity of energy harvesting, synchronous duty-cycling, and sensing

For indoor Wireless Sensor Networks (WSNs), as the conventional energy harvesting (e.g., solar) ceases to work in an indoor environment, the limited lifetime is still a threaten for practical deployment. We report in this demo a self-sustaining indoor sensing system. First of all, given the pervasive operation of heating, ventilation and air conditioning (HVAC) systems indoors, our system harvests energy from airflow introduced by the HVAC systems to power each sensor node. Secondly, as the harvested power is tiny (only of hundreds of μW) such that the exiting sensor products cannot be afforded due to their high energy consumption, we exploit the feature of our harvester to sense the airflow speed in an energy-free manner, which can pay back the environment by enhancing the awareness of the indoor microclimate. We also present two complementary algorithms to synchronize the duty-cycles of the sensor nodes to adapt to the energy harvesting. To our knowledge, this is the first indoor wireless sensing system that encapsulates energy harvesting, network operating, and sensing all together.