Emerging Technologies of Computation

Montek Singh

COMP790-084Sep 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

Today: Energy Harvesting Systems

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…

Basics of energy harvesting

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

Case Study: Philips smartcard