Zero Energy IoT Devices in Smart Cities Using RF Energy Harvesting

The invention of batteries made it possible to store electricity for many purposes. One of the purposes is to keep the operations of WSN running without any interruptions. The main drawback of sensor nodes is their limited energy sources. The researcher introduces the energy harvesting (EH) concept for IoT-based WSNs to overcome energy limitations and charge the IoT devices. Many energy harvesting techniques have been introduced, such as solar, thermal, and flow-based ones, but radio frequency (RF)-based EH techniques received great attention from researchers due to their easy availability (from TV, radio, and wireless frequencies). In this paper, we have conducted a real-world experiment on Powercast energy harvesting devices and examined the behavior of sensed data in different scenarios, such as indoor, distance (feet/meters), and directional antennas. In our experiments, we have observed that when a device is removed from the charger, the energy scavenging process degrades and reaches a dead state. To stop a device from entering a dead state, we introduce a mobile charger technique to charge the device and find the optimal place for chargers and sensor devices. During mobile charging, we have also observed that when the directional antennas change their angle, the energy scavenging process degrades. To tackle these problems, we introduced two algorithms for directional and omni-directional antennas that efficiently solve the problem. Furthermore, we have obtained results for these scenarios and show that this technique has a promising output.