Montek Singh COMP Sep 20, 2011

 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

 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?

 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

 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!

 Where do you harvest energy from? (contd.) ◦ Biosensing: use blood glucose! ◦ Acoustic vibrations: using piezoelectric transducers ◦ Wind energy… ◦ Tidal/water waves…

 Contactless smart card ◦ basic architecture

 Why asynchronous? ◦ async overall consumes less energy ◦ async has better current/power profile: more spread ◦ async has no fixed clock rate

 Graceful performance adaption with voltage

 Smart card chip layout ◦ RAM ◦ ROM ◦ EEPROM ◦ async microcontroller