Synergistic Multi-Source Ambient Radio Frequency and Thermal Energy Harvesting for IoT Applications

Abstract

The Internet of Things (IoT) is a global infrastructure of physical world objects connected to each other via the Internet and capable of collecting/exchanging data to achieve efficient resource management. These billions of devices must be self-powered and low-cost considering the massive global scale of the IoT. Thus, there is a need to develop low-cost harvesters from ambient energy sources to power IoT devices for self-sustainable, reliable, and continuous operation. Achieving this by using ambient energy harvesting technologies is challenging since ambient energy might be unpredictable, intermittent, and sometimes insufficient to power IoT devices. For example, solar energy has limitations such as intermittence (only daytime) and unpredictability (clouds, sandstorms) despite having the highest power density among ambient energy sources and relatively mature technology. Designing a multi-source ambient energy harvester based on continuous and ubiquitous ambient energy sources might alleviate these issues by providing versatility and robustness of power supply. However, combining two or more energy harvesters into one module must be done smartly and synergistically to ensure miniaturization, compactness, and more collected energy. Also, innovative additive manufacturing techniques must be considered to lower the cost of the harvester as well as to ensure their mass manufacturability. This dissertation presents two different kinds of ambient energy harvesters, namely radio frequency (RF) energy harvester (RFEH) and a thermal energy harvester (TEH), which after their individual optimized designs are synergistically integrated into a multi-source energy harvester (MSEH). In the first step, an RFEH is designed for triple-band harvesting (GSM 900, GSM 1800, and 3G) using the antenna-on-package (AoP) concept and fabricated through a combination of 3D and screen printing. TEH, which collects energy from diurnal temperature fluctuations of the ambient environment through a smart combination of a thermoelectric generator (TEG) and a phase change material (PCM), is developed in collaboration with Prof. Strano’s group at MIT, specifically for the desert conditions of Saudi Arabia. Later, TEH and RFEH are combined to realize an MSEH that has minimum intermittence, source-dependence, and location-specific issues. Smart integration of the two harvesters is achieved by designing a dual-function component, a heatsink antenna, that serves as a receiving antenna for the RFEH and a heatsink for the TEH. The heatsink antenna has been optimized for both the antenna radiation performance as well as the heat transfer performance. Field tests have shown that the MSEH can collect 3680 µWh energy per day and the outputs of the TEH and the RFEH have increased 4 and 3 times compared to the independent TEH and RFEH respectively. To validate the utility of the MSEH, a temperature/humidity sensor-based IoT node has been successfully powered through this energy harvesting system. Overall, the sensor’s data can be wirelessly transmitted with time intervals of 3.5 seconds from the harvested power, highlighting the effectiveness of the synergistic design of the MSEH for powering future IoT devices.

Brief Biography

Azamat Bakytbekov received his bachelor's degree from the Electrical Engineering and Electronics Department at Nazarbayev University, Kazakhstan in 2015, and his master's degree from the Electrical Engineering Department at King Abdullah University of Science and Technology in 2017. He is currently a Ph.D. student at KAUST under the supervision of Dr. Atif Shamim. His research interests include antenna, rectifier, and matching network design for energy harvesting applications, multi-source ambient energy harvesting (radio frequency, thermal), 3D printing, and inkjet printing techniques.