Energy Harvesting and CONASENSE

Prof. Dr. Mehmet ŞafakHacettepe 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

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.

Supply Demand

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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 ambientsources and converting into electricalenergy for immediate use or storing forfuture 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

bodyX. 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 GeneratorsRunning 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 GeneratorsWalking 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 life-

time of the sensor networkR. 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 piezopotentialgated 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 2W from an integrated nanogenerator of a sheet of 1 cm2 in size using a self-powered 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 ratesJ. 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. 2012WPMC 2012, 24-27 Sept. 2012 28

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-your-hands.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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