Everything You Wanted to Know About Secure Energy Harvesting Techniques for IoT Devices: A Review

In recent years, the rapid growth in urbanization and smart cities is being empowered by efficient and intelligent solutions in areas such as transportation, governance, and smart banking. These applications feature large-scale Internet of Things (IoT) deployment of wirelessly connected smart embedded devices with sensors and actuators. Providing adequate energy to power these large number of IoT devices remains a crucial challenge. In this regard, energy harvesting (EH) emerges as a promising approach that converts ambient energy into usable electrical energy, allowing IoT devices to function autonomously and sustainably, thereby reducing maintenance efforts while enhancing the overall system reliability. Although EH systems offer significant advantages, they are also vulnerable to various threats and attacks that underscores the need of designing secure and reliable EH solutions. In this paper, we comprehensively review the state-of-the-art EH techniques and associated security aspects. We discuss current research on energy management techniques, optimization algorithms, and the challenges involved in energy-efficient routing within IoT. Next, we analyze the existing EH methods in two directions – energy extraction and energy storage. In terms of energy extraction from renewable sources, we review the Maximum Power Point Tracking (MPPT) algorithms used in IoT devices. Then, we explore the energy storage capabilities of sensor nodes, which are crucial for consistent operation. Furthermore, we discuss the security and reliability mechanisms within IoT EH frameworks identifying the threats and countermeasures. We conclude the survey discussing the future research directions and listing a few open problems.