IEEE Wireless Communications - April 2017 - page 36

IEEE Wireless Communications • April 2017
1536-1284/17/$25.00 © 2017 IEEE
Electric-field energy harvesting (EFEH) can be
considered as an emerging and promising alter-
native for self-sustainable next-generation WSNs.
Unlike conventional harvesting methods that rely
on ambient variables, EFEH provides more reliable
and durable operation as it is operable with any
voltage-applied conductive material. Therefore,
it is better suited for advanced throughput and
applications requiring a certain QoS. In this arti-
cle, we introduce this newly emerging WSN para-
digm, and focus on enabling EFEH technology for
smart grid architectures, such as home, building,
and near area networks, where the field intensity
is relatively low. To this end, a practical methodol-
ogy and a general use implementation framework
have been developed for low-voltage applications
by regarding compelling design issues and chal-
lenging source scarcity. The proposed double-lay-
er harvester model is experimentally evaluated. Its
performance in terms of implementation flexibil-
ity, sensor lifetime, and communication through-
put is investigated. In addition, current challenges,
open issues, and future research directions are
discussed for the design of more enhanced EFEH
wireless networks.
The ubiquitous structure of wireless sensor nodes
has markedly altered monitoring and surveillance
systems, and accelerated the utilization of wireless
sensor networks (WSNs). To ensure high-accuracy
data collection and enhanced communication
quality, sensors can even be deployed in the thou-
sands. However, energizing these excessive num-
bers of sensors can constrain the performance
of the communication. Although the majority of
wireless nodes operate discontinuously, a typi-
cal battery tends to deplete within a year. There-
fore, an auxiliary or distinct power source must
be employed. To avoid battery deployment, heat,
electromagnetic, and kinetic energy come into
prominence to run the nodes autonomously.
Even though the harvesting methods are
broadly comparable in cost and lifetime with
commercial general use batteries, the power to
be extracted by harvesting might not always be
continuous, and its magnitude may alter markedly
depending on the ambient factors. These issues
have directed research efforts to find more reli-
able sources in terms of energy availability and
endurance. In this regard, electric-field stands as
the most promising candidate with the character-
istics of ambient variable independence, sufficient
power rating, low complexity, and excellent ener-
gy continuity.
Electric-field energy harvesting (EFEH) is first
proposed for high and middle voltage (HV/MV)
overhead power lines by considering the sur-
rounding electric field in abundance. The empir-
ical results revealed the competence of EFEH in
providing advanced situational awareness and
increased asset security, which accordingly moti-
vated the utility companies to utilize it. As one
of the main purposes of the smart grid (SG) con-
cept is to consume the available energy as effi-
ciently as possible [1], EFEH wireless networks
seem promising to prevent waste, minimize loss,
and increase operational efficiency. The net-
works structured with specialized sensors, such
as light, temperature, humidity, and presence, can
also sense an indoor environment, process the
gathered parameters, and notify an upper-level
authority for decision making procedures. By this
means, such systems as air conditioning, heating,
and lighting can be deactivated in the case of no
human presence or when they no longer need
to operate. Accordingly, a detailed consumption
profile can be constituted to both notify the utility
for demand-response management and guide the
customer for future saving behaviors.
Although there are already some preliminary
efforts to implement EFEH in low-voltage systems,
there is currently no study intended explicitly to
build wireless networks by regarding the varying
energy needs of differentiated network compo-
nents. We therefore focus on how to optimize
the design of the harvester for supporting vast
network topologies by allocating different levels
of power and to meet the requirements of spe-
cific applications. For this purpose, we propose
a multi-layer harvesting model and a practical,
general-use implementation framework by elabo-
rating on the current challenges of this fundamen-
tally new networking paradigm to enable sensor
energization in smart home, smart building, and
SG scenarios.
The remainder of this article is organized as
follows. We commence with a literature review
of existing energy harvesting techniques. Then we
extend our study to the basic principles of EFEH
including its basis, main constraints, and applica-
ble procedures. In the next section, we point out
the issues related to low-voltage application, and
propose a multi-layer harvester model to increase
etinkaya and
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The authors are with Koc
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