Transcript Basic Concepts: Sources and modes of harvesting

Montek Singh
COMP790-084
Sep 20, 2011
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Basics of energy harvesting
◦ why must some systems harvest energy?
◦ where do you scavenge energy from?
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Introductory case studies
◦ Philips
◦ CEA-LETI
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Next class:
◦ More case studies
◦ Challenges and Benefits
◦ Open questions
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What is energy harvesting?
◦ no power supply, no batteries
◦ somehow scavenge energy from physical env
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What type of systems must harvest energy?
◦ hard to replace/recharge batteries
◦ hard to have batteries at all
◦ examples?
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Where do you harvest energy from?
◦ ambient light/solar: using photovoltaic cells
 range: 0.1W/sq cm direct sun; 0.1mW/sq cm indoors
 silicon solar cells only 5-20% efficiency; 0.6V/cell
◦ temperature gradients: using thermoelectric
generators
 Seebeck effect turns temp gradients into electricity
 few hundred mV with a few Kelvin gradient
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Where do you harvest energy from? (contd.)
◦ Vibration energy: using electrostatic transducers
 below 100Hz
◦ RF power: using tuned antenna
 if 2W emitted by reader: 0.5-2mW harvested
at 1-2 meters distance
 used in RFID tagging
◦ Inertial kinetic energy: from human body
 using knee brace, backpack, etc.
 Seiko automatic watches!
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Where do you harvest energy from? (contd.)
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Biosensing: use blood glucose!
Acoustic vibrations: using piezoelectric transducers
Wind energy…
Tidal/water waves…
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Contactless smart card
◦ basic architecture
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Why asynchronous?
◦ async overall consumes less energy
◦ async has better current/power profile: more
spread
◦ async has no fixed clock rate
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Graceful performance adaption with voltage
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Smart card chip layout
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RAM
ROM
EEPROM
async microcontroller