Energy Harvesting and CONASENSE
Prof. Dr. Mehmet Şafak
Hacettepe University
Ankara, Turkey
Outline
• Energy in wireless nodes
– Demand vs supply
• Energy supply
– Battery
– Energy harvesting
• Energy-efficient designs
• Nanogenerators and nanopiezotronics
– Operation in THz band
• Conclusions
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Energy Consumption
• Energy consumption of wireless
sensor/communication nodes is crucial in
CONASENSE applications.
– Life-time
– Cost of maintainence and replacement
– Difficulty/inconveniance of reaching densely
populated nodes
– Independent, sustainable and continuous
operation
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General Structure of a Wireless Node
Demand
Supply
D. Niyato, E. Hossain, M.M. Rashid and V. K. Bhargava, Wireless sensor networks with energy
harvesting technologies: a game-theoretic approach to optimal energy management, IEEE
Wireless Communications, August 2007, pp. 90-96.
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Energy Requirements by Wireless
Transceivers
• Energy is required by sensor, processing
unit, buffer management and transceiver
Transceiver
Frequency
Bit Rate
Output Power Range
IEEE
802.15.1
(Bluetooth)
ISM Band
(2.4-2.5 GHz)
1 Mbps
 20 dBm
(100 mW)
10-30 m
IEEE
802.15.4
(Zigbee)
ISM Band
(2.4-2.5 GHz)
250 kbps
 3 dBm
(2 mW)
10-30 m
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Energy Consumption
• To minimize energy consumption in sensor
networks, one can
– reduce the number of bits to transmit
– choose best adaptive coding/modulation strategy
– use efficient transmission scheduling
– exploit power saving modes (sleep/listen)
periodically
– use energy efficient routing and MAC
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Energy Supply: Harvesting vs Battery
• Required energy can be obtained either from
batteries or by harvesting.
• Energy harvesting systems generate their own
energy
– Energy harvesting is still in its infancy
– Sufficiency and continuity pose serious problems
– Sensor applications are well-suited to energy
harvesting because they typically require low
throughputs
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Battery–Driven Systems
• Battery-driven systems use stored chemical energy
– Finite lifetime
– Regular maintenance/replacement is difficult/costly when
systems are remotely located
• Higher battery capacity implies increased cost
• Low-duty cycle implies decreased sensing reliability
• Higher transmission range implies higher power
requirement
• Lower transmission range implies more hops and
higher energy usage at multiple nodes.
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Rechargeable Battery Technologies
for Energy Storing
S. Sudevalayam and P. Kulkarni, Energy Harvesting Sensor Nodes: Surveys and
Implications, IEEE Communications Surveys & Tutorials, vol.13, no.3, 3rd Quarter 2011.
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Energy Harvesting
the collection of energy from ambient
sources and converting into electrical
energy for immediate use or storing for
future use
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Energy Harvesting
• Available energy sources
–
–
–
–
thermal (including solar energy and human body)
vibrational/mechanical
chemical
wind, etc.
• Energy harvesting sensor nodes
–
–
–
–
piezoelectric materials (vibrational energy)
thermocouples (thermal energy)
photovoltaic cells (solar radiation)
wind turbines (wind energy)
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RF Energy Harvesting
• Based on Faraday’s law
– Distant-charging sensor
nodes, RFID tags,
wireless transmitters
– Output voltage (0.5 V)
Magnetic coupling between RFID
tag and reader loop antennas
S. Sudevalayam and P. Kulkarni, Energy Harvesting Sensor Nodes: Surveys and
Implications, IEEE Comm. Surveys & Tutorials, vol.13, no.3, 3rd Quarter 2011.
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Vibration Energy Harvesting
• Piezoelectric materials (generators) directly
convert a mechanical vibration to a relatively high
voltage:
–
–
–
–
Output voltage (1-20 V)
Output current (1-100 A)
RF transmit with a duty cycle less than 3 %
Examples
• sensors in railway/road tunnels,
• shoe-powered RF tag system,
• self-powered door bells
M. Kroener, Energy harvesting technologies: energy sources, generators and management for
wireless autonomous applications, 2012 9th Int. Multi-Conf. Systems, Signals and Devices (SSD),
pp.1-4.
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Thermal Energy Harvesting
• A simple thermal energy (TE) generator is made by heating one face
of TE module and cooling the other face, causing an electric current
through a load connected to its terminals
• TE generator:
– long life cycle, no moving parts, simple and high reliability.
– low efficiency (5-6 %  10 %)
• Examples:
– Seiko thermic watch: 22 W harvested drives the watch and charges a
4.5 mAh lithium-ion battery
– Retrieve energy from waste heat in industrial applications
– Efficient solar thermal energy harvesting systems
– Harvest energy from small temperature gradients between the human
body
X. Lu and S.-H. Yang, Thermal energy harvesting for WSNs, 2010 IEEE Int. Conf. Systems, Man &
Cybernatics (SMC), pp.3045-3052.
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Thermal Energy Harvesting
• Energy harvesting from human body
– inertial kinetic energy and/or thermoelectric energy
• Human power:
– uncontrollable by user: blood pressure, body heat,
breath
– user controllable: finger motion, paddling (bycle
dynamo), walking (shoes)
• Wearable bio-sensors
– gloves, wrist-watches, rings, patches, earlobes,
intelligent clothes, eye-glasses, accelerometers
– glucose monitor, pulse sensor, electrocardiograph,
oxygen-level monitor, temperature sensor, respiratory
meter
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Thermal and Kinetic Energy Generators
Running Subject
Performance of thermal and inertial kinetic energy generators on
a running subject with realistic device effectiveness
P.D. Mitcheson, Energy harvesting for human wearable and implantable bio-sensors, 2010 Annual
Int. Conf. IEEE Eng. Medicine and Biology Society (EMBS) , pp.3432-3436.
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Thermal and Kinetic Energy Generators
Walking Subject
Performance of thermal and inertial kinetic energy generators on
a walking subject with realistic device effectiveness
P.D. Mitcheson, Energy harvesting for human wearable and implantable bio-sensors, 2010 Annual
Int. Conf. IEEE Eng. Medicine and Biology Society (EMBS) , pp.3432-3436.
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Characterization of Energy Sources
S. Sudevalayam and P. Kulkarni, Energy Harvesting Sensor Nodes: Surveys and Implications, IEEE
Communications Surveys & Tutorials, vol.13, no.3, 3rd Quarter 2011
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Energy-Efficient Designs
• Infinite amount of energy available to a node,
but
– energy generation is not continuous
– rate of energy generation can be limited
• Energy storage helps
• Energy consumption policy: Maximize the lifetime of the sensor network
R. Rajesh, V. Sharma and P. Viswanath, Capacity of fading Gaussian channel with an energy
harvesting sensor node, IEEE Globecom 2011.
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Energy-Efficient Designs
• Energy generation profile of the harvesting source
must be matched with the energy consumption profile
of the sensor node.
• This requires a system-level approach involving
– variation-tolerant architectures
– ultra-low voltage circuits
– highly digital RF circuits
• This can result in more than an order of magnitude
energy reduction compared to present systems
A. P. Chandrakasan , D. C. Daly, J. Kwong and Y. K. Ramadass, Next-generation micro-power
systems, 2008 IEEE Symposium on VLSI circuits digest of technical papers, pp.2-5.
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Energy-Efficient Designs-DSP
• DSP architecture and circuits should be energy
efficient, energy scalable, and robust to variations
in the transducer output voltage
• Energy scalability
– Because of unpredictable and time-varying nature of
the harvested energy
• Energy-scalable hardware should include
techniques for approximate processing
– Trade-off between power and arithmetic precision
DSPs for energy harvesting sensors, Applications and Architectures, IEEE
Pervasive Computing, July-September 2005, pp. 72-79.
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Energy-Efficient Designs
• Energy harvesting technology is far from
satisfying present needs
• Densely populated low-cost sensor nodes can
operate with power dissipation 100 W.
– Projects: PicoRadio (Berkeley), AMPS (MIT),
WSSN (ICT Vienna) and GAP4S (UT Dallas)
– This may be possible with energy harvesting
M. Tacca, P. Monti and A. Fumagalli, Cooperative and reliable ARQ protocols for
energy harvesting wireless sensor nodes, IEEE Trans. Wireless Communications,
vol.6, no.7, pp. 2519-2529, July 2007.
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Nanogenerators and Nanopiezotronics
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Nanogenerators and Nanopiezotronics
• Nano-sized sensing/communicating devices
can detect and measure new types of events
at nanoscale
• Energy consumption is low
• Energy harvesting provides independent,
sustainable, maintenance-free, continuous
operation
• Communication between sensor nodes is in
the terahertz (THz) band
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Nanogenerators and Nanopiezotronics
• A piezoelectric potential is created at the terminals of a
piezoelectric material once it is subjected to a strain ( e.g.,
body motion, muscle stretching, breathing, sonic waves ..)
due to the polarization of the ions in the crystal.
• This potential can have two functions:
– ‘It can drive a transient flow of the electrons in the external
circuit, which is a process of generating electric energy. This is
the fundamental principle of the nanogenerator’.
– ‘It can gate the flow of charge carriers flowing through the
material if it is a semiconductor, resulting in piezopotential
gated field effect transistors, diodes and sensors. This is the
principle of piezotronics’.
Z.L. Wang, Top emerging technologies for self-powered nanosystems: nanogenerators and
nanopiezotronics, 3rd Int. Nanoelectronics Conf. (INEC), pp.63-64, 2010.
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Nanogenerators and Nanopiezotronics
• State-of-the-art in 2011:
– It is demonstrated that a gentle straining can output 1-3 V
with an instantaneous power of 2W from an integrated
nanogenerator of a sheet of 1 cm2 in size using a selfpowered nanosensor.
• Potential applications for MEMS that require power
levels in the range W to mW.
• Future of nanotechnology research is likely to focus on
integration of nanosensors into nanosystems acting like
living species with sensing, communicating, controlling
and responding.
Z.L. Wang, Nanogenerators for self-powering nanosystems and piezotronics for smart
MEMS/NEMS, IEEE 24th Int. Conf. MEMS, pp. 115-120, 2011.
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Nanogenerators and Nanopiezotronics
• Nanogenerators can be used for
– independent, sustainable, maintain-free, continuous
operation of implantable biosensors for intra-body
drug delivery, health monitoring and medical imaging
systems
– environmental research (distributed air pollution
control)
– defense and military technology (surveillance
networks against new types of nuclear, biological and
chemical attacks at nanoscale, home security)
– communications at very high data rates
J. M. Jornet and I. F. Akyıldız, Joint energy harvesting and communication analysis for perpetual
wireless nanosensor networks in the Terahertz band, IEEE Trans. Nanotechnology, vol.11, no.3,
pp.570-580, May 2012.
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THz Band (300 GHz-3 THz)
•
•
•
•
Wavelenth: 1mm - 0.1 mm (non-ionizing radiation)
Used in radioastronomy and space-remote sensing
IR band of solar spectrum lies within THz band
Vulnerabilities:
– Very high atmospheric absorption (>100 dB/km) and
attenuation due to rain, fog etc.
• Identifying hazardous materials from a distance is not easy
• THz (through-wall) imaging very difficult
• Suitable for medical surface imaging (like skin cancer)
– Lack of THz sources
• Compact, solid-state, room-temperature transceivers not available
C. M. Armstrong, The truth about terahertz, IEEE Spectrum, pp.28-33, Sept. 2012
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Atmospheric Absorption in THz Band
Atmospheric
absorption
due to water
vapor and
oxygen at
horizontal
transmission
at sea level
and normal
humidity
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Rain Attenuation in THz Band
Specific attenuation
due to rain
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Future of Nanogenerators
• Nanogenerators and nanopiezotronics (coupled
piezoelectric and electronics properties) are listed
among the top 10 emerging technologies:
• New Scientists (Top 10 Future Technologies)
– http://www.newscientist.com/article/mg20126921.80
0-ten-scifi-devices-that-could-soon-be-in-yourhands.html?full=true
• MIT Technology Review (Top 10 Emerging
Technology in 2009)
– http://www.technologyreview.com/video/?vid=257
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Conclusions
• Battery-driven systems are not suitable in many
applications.
• Energy harvesting technology is in its infancy but
is promising.
• Sensor applications are well-suited to energy
harvesting
• Efficient designs for low-power systems and
harvesting technologies are required.
• Micro- and nano-systems are promising for
CONASENSE applications in mid- to far-terms.
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