Operating Wireless Sensor Nodes without Energy Storage: Experimental Results with Transient Computing

Faisal Ahmed,Yar Muhammad,Tauseef Ahmed,Yannick Le Moullec,Paul Annus

doi:10.3390/electronics5040089

Faisal Ahmed, Yar Muhammad + Show 3 more

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https://doi.org/10.3390/electronics5040089

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Abstract

Energy harvesting is increasingly used for powering wireless sensor network nodes. Recently, it has been suggested to combine it with the concept of transient computing whereby the wireless sensor nodes operate without energy storage capabilities. This new combined approach brings benefits, for instance ultra-low power nodes and reduced maintenance, but also raises new challenges, foremost dealing with nodes that may be left without power for various time periods. Although transient computing has been demonstrated on microcontrollers, reports on experiments with wireless sensor nodes are still scarce in the literature. In this paper, we describe our experiments with solar, thermal, and RF energy harvesting sources that are used to power sensor nodes (including wireless ones) without energy storage, but with transient computing capabilities. The results show that the selected solar and thermal energy sources can operate both the wired and wireless nodes without energy storage, whereas in our specific implementation, the developed RF energy source can only be used for the selected nodes without wireless connectivity.

Highlights

Advances in semiconductor technology has given birth to low-power, miniaturized computing units (microcontrollers, DSPs,FPGAs), and radio modules. Such circuits are commonly used for implementing the nodes in wireless sensor networks (WSN) and, more generally, in the internet of things (IoT)
Before evaluating the practical feasibility of energy harvesting (EH) combined with transient computing (TC), we briefly review the fundamentals of the three selected EH sources and related analytical models
Our practical experimental results show that EH combined with TC in WSN nodes is feasible

Summary

Introduction

Advances in semiconductor technology has given birth to low-power, miniaturized computing units (microcontrollers, DSPs, (nano)-FPGAs), and radio modules. Such circuits are commonly used for implementing the nodes in wireless sensor networks (WSN) and, more generally, in the internet of things (IoT). Many research efforts strive at designing (A) architectural solutions that effectively reduce energy consumption in the processing and communication modules, and (B) energy harvesting (EH) solutions that can complement, or even replace, the energy storage units of the nodes for, e.g., autonomous systems, leading to the concept of transient computing (TC) discussed later on. For some applications, it is sometimes not possible to include a battery or super-capacitor in the nodes due to stringent physical constraints or for maintenance reasons (for example, it may be impossible to access a node integrated in a physical structure and replace its energy storage unit if the battery fails or once its maximum number of charge/discharge cycles have been reached, in the case of e.g., intensive and/or very-long term applications) [1].

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