Di Mauro, Alessio

Dragoni, Nicola

Fafoutis, Xenofon

Madsen, Jan

Vuckovic, Dusan

Energy Harvesting comprises a promising solution to one of the key problems faced by battery-powered Wireless Sensor Networks, namely the limited nature of the energy supply (finite battery capacity). By harvesting energy from the surrounding environment, the sensors can have a continuous lifetime without any needs for battery recharge or replacement. However, energy harvesting introduces a change to the fundamental principles based on which WSNs are designed and realized. In this poster we sketch some of the key research challenges as well as our ongoing work in designing and realizing Wireless Sensor Networks with energy harvesting capability

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 20, 2017Energy-Harvesting Wireless Sensor NetworksFafoutis, Xenofon; Vuckovic, Dusan; Di Mauro, Alessio; Dragoni, Nicola; Madsen, JanPublished in:9th European Conference on Wireless Sensor Networks, EWSN 2012Publication date:2012Link back to DTU OrbitCitation (APA):Fafoutis, X., Vuckovic, D., Di Mauro, A., Dragoni, N., & Madsen, J. (2012). Energy-Harvesting Wireless SensorNetworks. In 9th European Conference on Wireless Sensor Networks, EWSN 2012: Poster and DemoProceedings (pp. 84-85)Poster Abstract: Energy-Harvesting Wireless SensorNetworksXenofon Fafoutis∗, Dusan Vuckovic†, Alessio Di Mauro∗, Nicola Dragoni∗, and Jan Madsen∗∗DTU Informatics, Technical University of Denmark, Denmark, {xefa,adma,ndra,jan}@imm.dtu.dk†DELTA, Denmark, duv@delta.dkAbstract—Energy Harvesting comprises a promising solutionto one of the key problems faced by battery-powered WirelessSensor Networks, namely the limited nature of the energysupply (finite battery capacity). By harvesting energy from thesurrounding environment, the sensors can have a continuouslifetime without any needs for battery recharge or replacement.However, energy harvesting introduces a change to the fundamen-tal principles based on which WSNs are designed and realized.In this poster we sketch some of the key research challenges aswell as our ongoing work in designing and realizing WirelessSensor Networks with energy harvesting capability.I. INTRODUCTIONWireless Sensor Networks (WSNs) are systems of multiplesmall and inexpensive embedded devices that can sense,measure and gather information from the environment they aredeployed. Examples of application range from environmentalmonitoring and control to healthcare monitoring and trafficcontrol, to name only a few. WSNs are typically required torun for long periods of time, often several years, only poweredby batteries. This makes energy-awareness a particular impor-tant issue when designing WSNs. Indeed, one of the majorlimitation of battery-powered nodes is finite battery capacity[1], which means nodes operate for a finite duration, only aslong as the battery lasts. Finite node lifetime implies finitelifetime of the WSN applications or additional cost and com-plexity to regularly change batteries. Indeed, batteries cannoteasily be replaced, since typically WSNs consist of hundredsto thousands of sensors and may be deployed in unreachableplaces, such as mountains or underground. To make mattersworse, depleted batteries constitute environmental problems.Energy Harvesting Wireless Sensor Networks (EH-WSNs)can provide a solution to the energy problem by harvestingenergy that already exists in the surrounding environment.Energy harvesting refers to harnessing energy from the envi-ronment and converting it to electrical energy. If the harvestedenergy source is large and continuously (or periodically) avail-able, a sensor node can be powered perpetually. In this way,energy is essentially infinite; however, not always available.Energy harvesting introduces a change to the fundamentalprinciples based on which protocols for WSNs are designed.Instead of focusing on energy efficient protocols that aim tomaximize sensors lifetime, the main design objective in EH-WSNs is to maximize the performance of the network giventhe rate of energy that is available to be harvested from theenvironment. In other words, the surplus of harvested energycan be used to improve the performance of the network.Another important element that differentiates EH-WSNsfrom classical WSNs is that in EH-WSNs some sensor nodescan be more capable than others. This is due to the non-uniformly distribution of ambient energy. As an example,consider a solar-based EH-WSN where some nodes are cov-ered by shadows while others are under direct sun light. Insuch environment, the more capable nodes can be used forperforming the energy consuming tasks, on behalf of theincapable nodes that need to sleep and recharge.Example: WSNs Powered by Vibration. Vibration en-ergy harvesting is the process by which otherwise wastedvibration (such as from a piece of industrial machinery)is harvested and converted to useful electrical energy toperpetually power wireless sensor nodes. One of the mostprevailing applications for WSNs is to monitor the healthand status of essential industrial machinery assets withinlight and heavy industrial manufacturing environments. Asan example of health monitoring application, a WSN canbe used for monitoring vibrations of a rotating machineand by analyzing the frequency domain of vibrations it ispossible to determine when the machine is going to failand schedule the maintenance in time, before malfunctionof the machine. The fact that the WSN is being poweredby the same vibration its measuring allows the system tocontinuously monitor the operation of the machine withoutthe risk of the node running out of power.In this poster we sketch some of the key research challengesas well as our ongoing work in designing and realizingWireless Sensor Networks with energy harvesting capability.II. CHALLENGE: ENERGY HARVESTINGPotential sources of energy harvesting are all around us.Light, radio signals propagating through the air, wind, differentkinds of vibration and movement, heat flow, just to mentiononly a few. With new materials and new ways of transformingenergy, efficiency of harvesting has risen to the level that canbe used for powering WSNs. Nevertheless, harvesting sourcesare not powerful enough yet to allow continuous operation ofsensor nodes powered by energy harvesting. Therefore carefulplanning is needed in every stage of design.First stage of design is finding a way of converting ambientenergy to electrical energy. Our group will focus on harvestinglight and vibration energy through use of small scale solar cellsfor light harvesting and macro fiber composites for capturingvibration energy. The main challenge at this stage is efficientharvesting of available energy and storing the produced chargein a way so it could be used when needed. This task is nottrivial due to the fact that, in order to harvest the most energyfrom the source, the load on the circuit producing energyneeds to be matched through appropriate circuitry and theload is always application specific making it even harder toimplement.Second stage is to manage the energy stored in the mostefficient way. This block is in charge of selecting when andhow the energy is distributed throughout the system beingpowered by it. Furthermore this block needs to minimizethe leakage from the storage and have the smallest possiblequiescent current.Third stage is the application that is run on the node. Forbattery powered systems the main challenge lies in prolongingof the battery life, but with energy harvesting the designeris aware hat the energy storage will be replenished, thereforeother approaches can be utilized, such as using the power whenharvesting and keeping dormant when no energy is harvested.Changing the duty cycle of operation depending on energylevels is also one of the options.The fact that energy harvesting is application specific andall parts in the design are much interconnected makes thiskind of systems a big challenge to design in a robust wayguaranteeing a very long, maintenance free operation.III. CHALLENGE: NETWORKINGCommunication has always been a major issue in WSNsdue to the amount of energy it requires and the numerousperformance benchmarks that depend on it, such as the delayand the delivery rate of measurements. Energy harvestingprovides the wireless sensor nodes with an energy supplythat varies over time and space. Communication protocolssupporting the sensor network need to be adaptable; so thatwhenever there is an excess of energy, it is used to improvethe performance of the system and whenever there is ashortage of energy, the sensors downgrade their performance,and thus their energy consumption, to an operation state thatis sustainable by the available energy. In other words, thegoal of the system is to operate at the maximum sustainableperformance. Furthermore, communication protocols need tohave certain additional qualities. First, they need to provideflexibility so that the network load is distributed to the nodesthat have access to more environmental energy at any giventime. Secondly, they need to support applications that havedifferent performance requirements. For example, there arealarming applications that require low delays and monitoringapplications that require a consistent data set. Last but notleast, cross-layer optimization is important so that the energyis consumed in the most efficient way.All these qualities constitute important considerations fordesigning communication protocols for EH-WSNs. In par-ticular, MAC protocols need to efficiently support individualduty cycles to allow each node to effectively adapt its energyconsumption to sustainable levels. Hence, the “traditional”approach where nodes have coordinated and synchronizedduty cycles is insufficient. Individual duty cycles can alsosupport distributed autonomous load balancing. If each nodeis able to freely choose its own duty cycle based on itsenergy capabilities, the node with more access to energywill be awake more frequently and eventually perform moreenergy consuming tasks. Moreover, routing protocols needto select the path that best fits the energy conditions of thenetwork as well as the requirements of the application. Forinstance, the paths that minimize the end-to-end delay mightbe the best candidates for a delay-sensitive application. Lastly,opportunistic routing schemes can be used to decrease thesleeping delay caused by the duty cycles. Instead of waitingfor a node to wake up, a node may transmit to the node thatwakes up first out of a set of nodes that meet certain criteria.IV. CHALLENGE: SECURITYSecurity is an extremely important issue for sensor net-works, due to the various kind of data, in many cases sen-sitive, gathered by the network. The introduction of energyscavenging capabilities completely redefines how security inWSNs can be approached. For instance, energy independentattacks (e.g. node replication) become much more effectivesince the average lifespan of a node is greatly increased. Onthe other hand, power related attacks (e.g. energy depletion)can be neutralized by the fact that a node can reacquireenergy over time. Furthermore, the potential of having moreenergy available could make possible to use better securitytools such as sturdier encryption algorithms, longer keys andcomputationally heavier hash functions, just to name a few.Another class of approaches are the ones similar to whatproposed in [2], where the amount of “strength” used in theactive security scheme is function of the available harvestedenergy.For these reasons, we aim to systematically analyze andclassify attacks in EH-WSNs, so that distinctive characteristicscan be pointed out and possible new attacks identified. As afirst result, a taxonomy of attacks for EH-WSNs has been de-termined, with focus on how scavenging capabilities affect thenetwork and which new and specific attacks can be depicted.This classification represents the basis for specifically tailoredsecurity solutions.V. CONCLUSIONEnergy harvesting is introducing some changes to the funda-mental principles based on which Wireless Sensor Networksare designed and realized. In this poster we have sketchedsome of the key research challenges as well as our ongoingwork in designing and realizing Wireless Sensor Networkswith energy harvesting capability.REFERENCES[1] S. Sudevalayam and P. Kulkarni, “Energy harvesting sensor nodes: Surveyand implications,” Communications Surveys Tutorials, IEEE, vol. 13,no. 3, pp. 443 –461, quarter 2011.[2] A. V. Taddeo, M. Mura, and A. Ferrante, “Qos and security in energy-harvesting wireless sensor networks,” in SECRYPT, S. K. Katsikas andP. Samarati, Eds. SciTePress, 2010, pp. 241–250.

Energy-Harvesting Wireless Sensor Networks

http://orbit.dtu.dk/ws/files/51114015/EWSN12_abstract.pdf

Energy-Harvesting Wireless Sensor Networks

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology