Energy Harvesting for Wireless IoT Use Cases: A Generic Feasibility Model and Tradeoff Study

A batteryless Internet of Things (IoT) offers a sustainable alternative to battery-powered IoT devices, which produce billions of dead batteries every year. Devices are instead powered by a small supercapacitor, which is recharged by a renewable energy source. However, since IoT devices are often characterized by intermittent periods of high energy consumption followed by periods of reduced activity, conventional average energy consumption models cannot be used to assess if IoT devices can be powered by energy harvesters. Therefore, this article presents an alternative feasibility evaluation approach that focuses on modeling the worst case periods with peak energy consumption and short idle times, which pose the highest constraints on the capacitor’s behavior. This approach simplifies the characterization of the wireless technology energy consumption as these worst case periods can be determined by a few parameters. The methodology is then applied to combinations of popular IoT technologies (LoRaWAN, BLE Mesh, and 6TiSCH) and energy sources (solar, kinetic, and radio frequency energy) for two common IoT use cases. We show that the proposed parameters can be successfully extracted with power measurements for different network configurations and that the Power Management Unit configuration has a nonnegligible impact on the communication requirements. Finally, we discuss how to apply the model to other technologies and other use cases.

I. Introduction

The Internet of Things (IoT) enables the connection of billions of devices to the Internet and perform sensing, actuating, communication, and localization operations. Due to their relatively low power consumption and because of the desired use cases, these devices are often battery-powered. However, batteries are hazardous, bulky, expensive, sensitive to temperature changes, and last at most a few years, even when rechargeable. Therefore, disposing of billions of dead batteries per year is both economically and ecologically unacceptable [1]. In addition, some use cases require devices to be deployed in remote or hard-to-reach environments, which makes the replacement of batteries expensive and dangerous, if not impossible. Therefore, there has been a significant recent interest in developing batteryless and perpetual IoT devices by using energy harvesting techniques. These devices generally consist of an microcontroller unit (MCU), radio chip, one or more sensors or actuators, power management unit (PMU), and a supercapacitor. The PMU charges the capacitor using an energy source, which can be solar, kinetic, thermal, radio frequency (RF) energy, etc. As the energy source harvests energy from its environment, the type of energy source is highly dependent on this environment.