Review—power sources for the internet of things

Wireless sensor networks have become integral to enabling numerous applications for the Internet of Things, such as environmental sensing or healthcare monitoring. Powering these networks has been the focus of significant research efforts due to the need for reliable and continuous operation of the sensing nodes. In this review, we outline the progress made in the sensing nodes with a particular focus on their power demands. These requirements are used as a framework for surveying the theoretical limits and developments for various power sources, including energy storage, power distribution, and power scavenging techniques. Finally, we conclude by identifying that harvesting techniques are largely insufficient for powering IoT nodes due to limited power densities or inconsistencies as to when power is harvested; accordingly, direct wiring and storage sources such as batteries are the most promising approaches for IoT applications.