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Emerging Technologies of Computation. Montek Singh COMP790-084 Sep 20, 2011. Today: Energy Harvesting Systems. Basics of energy harvesting why must some systems harvest energy? where do you scavenge energy from? Introductory case studies Philips CEA-LETI Next class: More case studies
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Emerging Technologies of Computation Montek Singh COMP790-084 Sep 20, 2011
Today: Energy Harvesting Systems • Basics of energy harvesting • why must some systems harvest energy? • where do you scavenge energy from? • Introductory case studies • Philips • CEA-LETI • Next class: • More case studies • Challenges and Benefits • Open questions
Basics of energy harvesting • What is energy harvesting? • no power supply, no batteries • somehow scavenge energy from physical env • What type of systems must harvest energy? • hard to replace/recharge batteries • hard to have batteries at all • examples?
Basics of energy harvesting • 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
Basics of energy harvesting • 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!
Basics of energy harvesting • Where do you harvest energy from? (contd.) • Biosensing: use blood glucose! • Acoustic vibrations: using piezoelectric transducers • Wind energy… • Tidal/water waves…
Case Study: Philips smartcard • Contactless smart card • basic architecture
Case Study: Philips smartcard • Why asynchronous? • async overall consumes less energy • async has better current/power profile: more spread • async has no fixed clock rate
Case Study: Philips smartcard • Graceful performance adaption with voltage
Case Study: Philips smartcard • Smart card chip layout • RAM • ROM • EEPROM • async microcontroller