Energy Harvesting for Mobile Computing Joe Paradiso Responsive ...
Energy Harvesting for Mobile Computing Joe Paradiso Responsive ...
Energy Harvesting for Mobile Computing Joe Paradiso Responsive ...
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<strong>Energy</strong> <strong>Harvesting</strong> <strong>for</strong> <strong>Mobile</strong> <strong>Computing</strong><br />
<strong>Joe</strong> <strong>Paradiso</strong><br />
<strong>Responsive</strong> Environments Group, MIT Media Lab<br />
http://www.media.mit.edu/resenv DCU 6/05
Source Material…<br />
IEEE Pervasive <strong>Computing</strong> Magazine, February 2005<br />
Chapter 45 in “Low Power Electronics Design,”<br />
Christian Piguet, editor – CRC Press, Fall 2004<br />
Systems <strong>for</strong> Human-Powered <strong>Mobile</strong> <strong>Computing</strong> J.A. <strong>Paradiso</strong><br />
To appear in Proc. IEEE Design Automation Conference (DAC), July 2006
Smart Sensors and HCI<br />
• Electronics are cheaper, smaller, more capable, lower power...<br />
– Intelligence, sensing, communication, processing…<br />
• Move off desktop into "things” & environments<br />
• Entirely different “input devices” & modalities enabled<br />
Shift toward fine-grained, distributed interfaces<br />
• Ubiquitous <strong>Computing</strong> (PARC/Weiser)<br />
• Things That Think (ML)<br />
• Disappearing Computer (EU)<br />
• Invisible <strong>Computing</strong> (Microsoft)<br />
• Pervasive <strong>Computing</strong> (IBM)<br />
Sensing, communications, power management, context (AI) are key
Batteries<br />
Batteries improve relatively slowly<br />
• Can exploit other chemical reactions<br />
–Fuel Cells<br />
–Microengines<br />
• Clever power management and<br />
circuit design can reduce power<br />
requirements<br />
– Low voltage, clock scaling, large<br />
feature size, adiabatic computing,<br />
analog processing, keep everything off<br />
<strong>Energy</strong> harvesting may become practical…
4/04<br />
©<br />
MIT-ML<br />
iSun – 2 Watts<br />
Solar Cells<br />
Media Lab’s Locust Position Beacon<br />
• 10-20% efficiency <strong>for</strong> commercial modules<br />
• Common polycrystalline Si modules are ~16-17% (mass produced,<br />
cheap process, a few 1$'s a Watt total)<br />
• Monocrystalline Si are a little closer to 20%.<br />
• IC grade Si and fab processes, ~24% is possible but expensive.<br />
• Stacked multi-junction cells, and cells using other materials and<br />
structures get over 30% but are very expensive or still in the lab<br />
– 10-100 mW/cm 2 in bright sun<br />
– 10-100 μW/cm 2 in an office<br />
An option if the light and area are there<br />
JAP<br />
Franhofer ISE Freiberg<br />
1 Watt under halogen<br />
20% eff.<br />
5
The Hat is an apt location…<br />
Mainly Chillers
Ambient RF<br />
• Power density ~ E2 /Z0 – (Field strength) 2 over 377 Ohms<br />
– Would like to see fields of 10 V/m at antenna<br />
• 26 μW/cm2 Flashing Antenna Top<br />
– Not seen in typical urban environments<br />
• Except close to cell phone transmitters<br />
• AM Crystal radios yield under 1 mW (typically 20 μW) w. large<br />
antenna and good ground.<br />
Need large collection area and/or need to be very close to transmitter<br />
Mickle et al (US Patent 6,856,291) - U. Pittsburgh - highly resonant regenerative<br />
antenna with an effective cross section that is much larger than its geometric area<br />
(perhaps by a factor of 1000 or more)
Bill Brown<br />
Microwave-powered helicopter, 1964<br />
Beaming Power<br />
Wireless humidity sensor<br />
Martinez, 2002<br />
• Beaming power has a long history (Tesla, etc)<br />
• Rectannas can approach 80-90+% efficiency<br />
• Low power apps common in everyday environments<br />
– RFID (chips use 1 to 100 μW)<br />
• RF-powered sensors coming off the horizon<br />
– Passive LC and SAW devices, sensor chips<br />
– Wireless tire pressure and tire friction sensors<br />
– Implantable sensors <strong>for</strong> monitoring in vivo blood pressure<br />
RFID Tags
4/04<br />
©<br />
MIT-ML<br />
Human <strong>Energy</strong> Expenditure<br />
People dissipate<br />
between 100-<br />
1000 Watts<br />
Perhaps one can<br />
steal Watt or<br />
two?<br />
JAP<br />
9
Where to Tap the Power<br />
Caution: Thad’s<br />
numbers tend to be<br />
optimistic!<br />
Watt-level available<br />
Thad Starner, Human-Powered Wearable <strong>Computing</strong>, IBM Systems Journal 35, pp. 618-629 (1996).
In Vivo Fuel Cells Adam Heller, UT Austin<br />
• Extrapolating from electrochemical<br />
detection of glucose (TheraSense)<br />
– Adapt techniques <strong>for</strong> more power<br />
– Make a sugar-burning bio fuel cell<br />
• Composite electrodes and conductive gels<br />
– Biologically transparent system<br />
– Build into a vascular stent<br />
– Generate electricity from glucose and O2 in<br />
blood<br />
• 1 cm long x 4 mm wide<br />
• Can (theoretically) produce up to 1 mW<br />
– 1-3 weeks of power from equal-size battery<br />
• 1-2 μW <strong>for</strong> 1 week at a 0.5 V demonstrated in<br />
2002 (in a grape)<br />
• US Patent 6,531,239<br />
• In-vitro low power or low duty-cycle<br />
medical systems<br />
– Low-bandwidth biosensors<br />
– Valve <strong>for</strong> the incontinent
4/04<br />
©<br />
MIT-ML<br />
Thermal Powered Systems<br />
• Carnot Efficiency <strong>for</strong> human body at 20° C<br />
– 5.5% (drops to 3.2% at 27° C)<br />
• Today’s thermopiles have
Seiko SII Thermic ® Heat-Powered Watch<br />
Booster IC<br />
Thermal energy watch<br />
Watch movement<br />
Battery<br />
arm<br />
2.14mm<br />
Heat flow<br />
1.7mm 2.14mm<br />
2.36mm<br />
Thermoelectric module<br />
Adiabatic<br />
case<br />
1.27mm<br />
Thermoelectric unit<br />
Thermoelectric (Photo)<br />
• Uses 10 Thermoelectric modules and a booster IC<br />
• Runs off body heat<br />
Low T, limited surface area, low efficiency -> Microwatts...
Thermo Life Generator<br />
• Thermo Life <strong>Energy</strong> Corporation<br />
– Applied Digital Solutions (Dr.Ingo Stark)<br />
– Dense array of Bi 2 Te 3 thermopiles deposited onto thin film<br />
• Most efficient at temperatures of 0 to 100 degrees Celsius<br />
• 10 μA or more @ 3 volts (6 V OC) when in contact with<br />
the body (5°C T)<br />
• 60 μW/cm 2<br />
• Thin film battery charging<br />
– Front Edge’s Nano<strong>Energy</strong><br />
• Medical monitor powering, biosensors
The ETA Autoquartz Self-Winding Electric Watch<br />
The Swatch Group (SMH)
4/04<br />
©<br />
MIT-ML<br />
The ETA Autoquartz Mechanism<br />
Proof Mass winds spring, which pulses generator<br />
JAP<br />
16
The Autoquartz Generator Per<strong>for</strong>mance<br />
Generator always run at<br />
optimum rate (10-15K RPM)<br />
Power stored on spring until<br />
threshold is exceeded<br />
Generator pulsed <strong>for</strong> 50 msec<br />
Yields 6 mA at >16 Volts<br />
~100 mW peak power!<br />
Current integrated onto<br />
capacitor
KINETIC outline<br />
diagram<br />
Gear train<br />
Rotor<br />
Stator<br />
Seiko AGS System<br />
Oscillating weight<br />
Coil<br />
Charge control<br />
circuit<br />
Secondary<br />
power supply<br />
Drive circuit<br />
• Proof mass oscillation directly cranks generator<br />
– Little intervening mechanics<br />
– Charge accumulated on capacitor<br />
• Power Output:<br />
–5 μW average when the watch is worn<br />
– 1 mW or more when the watch is <strong>for</strong>cibly shaken<br />
Stator<br />
Oblique view<br />
Rotor<br />
Coil<br />
Oscillating<br />
weight<br />
Oscillating<br />
weight gear<br />
Transmission gear
4/04<br />
©<br />
MIT-ML<br />
Seiko Experimental AGS <strong>for</strong> Marine Mammals<br />
• Uses watch AGS components<br />
– Power Output is 5 to 10 mW<br />
JAP<br />
19
Magnetic and Electrostatic Microgenerators<br />
• Many, many devices in current literature<br />
– Chandrakasan, Roundy/Wright, Mitcheson, El-Hamadi, James,Yates, Li,<br />
Taishiro, Ching, Miyazaki, Goerge…<br />
• Powers range 10’s-100’s of μW<br />
• Most employ spring return<br />
– Mechanically resonant, 10’s of Hz – several kHz<br />
• Others use bistable action return w/o spring<br />
– Mitcheson 2004 – broadband<br />
• Magnetic generators can approach 1 mW<br />
– 100-500 Hz, 25-200 μm motion, ~1 cm3 (court. Mitchenson)<br />
• Electrostatic generators tend to produce 100 μW<br />
– Simple to integrate onto MEMS<br />
– Need bootstrap supply<br />
– Constant charge (sliding) and constant voltage (pressing) modes<br />
36 mW @ 12.6 kHz<br />
Beeby et al<br />
Southampton<br />
6 μW @ 6 Hz<br />
Miao et al<br />
Imperial College
MEMs Driven Condensor Power Supply<br />
84<br />
mg<br />
• MEMs motor in reverse…<br />
– Special power-control electronics designed & fabbed<br />
–8 μW indicated @ 2.5 kHz, 500 μm motion<br />
– Could tile <strong>for</strong> more power<br />
– Provides power <strong>for</strong> their sub μW “picoJoule DSP”<br />
– Vision of power, sensing, and processing on one chip<br />
Anantha Chandrakasan, Jeff Lang - MIT MTL
Inertial Microgenerators (piezo)<br />
• Ho, 1961<br />
– Claimed 150 μW when<br />
coupled to 80 Hz heartbeats<br />
• Roundy & Wright, 2003<br />
– PZT bimorph<br />
– 100 μW when shaken at<br />
resonance<br />
– Building MEMs structure w.<br />
80 μW per cm 3 (@ 800 Hz)<br />
– Berkeley group also making<br />
tunable cantilevers
4/04<br />
©<br />
MIT-ML<br />
Microgenerator Per<strong>for</strong>mance<br />
1 cm 3 devices<br />
•For human body motion (Hz-level excitation)<br />
–Few μW/cm 3<br />
•For machine excitation (kHz-level excitation)<br />
–Hundreds of μW/cm 3<br />
Tends to go as w 3 and y 0 2<br />
Personal comm, Paul Mitcheson, Imperial College UK<br />
JAP<br />
23
4/04<br />
©<br />
MIT-ML<br />
Shake-Driven Flashlights<br />
Weighs150 grams and produces 200 mW with a steady shake at its<br />
mechanical resonance (roughly 3.3 Hz) - 2 mW/cm 3<br />
Dual microgenerator in AAA <strong>for</strong>m factor - 28 μW @ 70 Hz<br />
Yuen et al, CU Hong Kong, 2005 (note that AAA battery would last 15 years)<br />
JAP<br />
24
4/04<br />
©<br />
MIT-ML<br />
Commercial Microgenerators<br />
The PMG7 is designed to resonate at mains<br />
frequency (50 or 60Hz) with a bandwidth of<br />
0.2Hz giving excellent per<strong>for</strong>mance on any<br />
AC synchronous motor powered equipment.<br />
Output is from 0.1mW to several mW power<br />
depending on the level of vibration (eg up to<br />
5mW at 100mg or 400μW at 25mg).<br />
FerroSolutions, Cambridge MA Perpetuum, Southampton UK<br />
Both Magnetic<br />
JAP<br />
25
4/04<br />
©<br />
MIT-ML<br />
Power Backpacks<br />
Larry Rome, University of Pennsylvania, 2005<br />
5 cm up-down hip movement from walking reacting<br />
with 20-38 kg inertial load generated up to 7 Watts<br />
JAP<br />
26
4/04<br />
©<br />
MIT-ML<br />
Reaction Force (% of body weight)<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
Heel Strike<br />
Heel Strike Toe Off<br />
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9<br />
Time (seconds)<br />
• Force at heel strike and toe off exceeds 100%<br />
– Heel can compress by 1 cm – Watts possible?<br />
100%<br />
Body Weight<br />
JAP<br />
27
Power <strong>Harvesting</strong> Insoles - 1998<br />
PVDF Stave<br />
Molded into sole<br />
<strong>Energy</strong> from bend<br />
P peak 10 mW<br />
1 mW<br />
“Thunder” PZT<br />
Clamshell Unimorph<br />
Under insole<br />
Pressed by heel<br />
P peak 50 mW<br />
10 mW<br />
Raw Power<br />
circa 1% efficient<br />
Unnoticable<br />
<strong>Responsive</strong> Environments Group<br />
MIT Media Lab<br />
1998 IEEE Wearable <strong>Computing</strong> Conference
Application: Batteryless RF Tag<br />
• Use Piezo-shoes to charge up capacitor after several steps<br />
• When voltage surpasses 14 volts, activate 5 V regulator<br />
– Send 12-bit ID 6-7 times with 310 MHz ASK transmitter<br />
• After 3-6 steps, we provide 3 mA <strong>for</strong> 0.5 sec<br />
– Capacitor back in charge mode after dropping below output<br />
<strong>Responsive</strong> Environments Group - MIT Media Lab
4/04<br />
©<br />
MIT-ML<br />
Rotary Magnetic Generator Retrofit<br />
<strong>Responsive</strong> Environments Group - MIT Media Lab - 1998<br />
• Attaches lever-driven flywheel/generator to shoe<br />
- 3 cm deflection, bulky<br />
- Suboptimal (e.g., better integration, hydraulics...)<br />
• Produces a quarter watt average ( 1 W peak), but very obtrusive!<br />
JAP<br />
30
Better Generator Integration<br />
Jeff Hayashida’s BS thesis - 1999<br />
• Mechanical generators entirely in insole<br />
• Produces about 60 mW average power<br />
• Use of a spring to store energy between footfalls can bring a Watt<br />
• Mechanically complex and fragile…
Mechanical Boot Generators…<br />
Lakic, 1989<br />
Lakic, 1986<br />
Barbieri, 1925<br />
Mainly foot warming<br />
applications<br />
Landry, 2001<br />
Chin, 1996
Trevor Baylis’<br />
Electric Shoe<br />
Company<br />
• Piezoelectric “crystal” struck with each footfall<br />
• Claims to generate 100-150 mW<br />
• Used in walk across Namibian Desert, summer 2000<br />
– Cellphone battery partially (e.g.,
4/04<br />
©<br />
MIT-ML<br />
Passive Hydraulic Chopping to Excite PZT at Resonance<br />
• Antaki, et al., 1995<br />
– Passive hydraulic resonant excitation of<br />
piezoceramic stack during heel compression<br />
– Big, kludgy shoe<br />
• Developed to power artifical organs<br />
• Developed order of 0.2 – 0.7 Watt average power<br />
• 2 Watts from simulated “jogging”<br />
JAP<br />
34
4/04<br />
©<br />
MIT-ML<br />
Active Hydraulic Chopping at Heel Strike<br />
• Heel compresses Hydraulic bladder by 8 mm<br />
– μ-hydraulic transducers hammer PZT stack<br />
– Many charge-pump cycles per footstep<br />
– Piezo driven at resonance frequency (20 kHz)<br />
• PZT generators occupy 1-cm cube<br />
– Each produces a watt<br />
• 40% efficiency<br />
– 3 per shoe gives 3 watts total<br />
• Components Tested<br />
– Fully integrated?<br />
8 mm<br />
JAP<br />
35
4/04<br />
©<br />
MIT-ML<br />
Dielectric Elastomers under the heel<br />
2-4 mm<br />
• Electrostatic generator with silicone rubber or flex<br />
acrylic elastomer between the plates<br />
– Placed under heel<br />
– 2-4 mm of squeeze gives 50-100% area strain<br />
– 4 kV across them!<br />
– Saw 0.8 Watt per shoe (2 Hz pace, 3 mm deflection)<br />
– Estimate that 1 Watt is possible with more deflection<br />
Ron Pelrine, Roy Kornbluh - SRI International<br />
JAP<br />
36
150 g, 200 mW, 2 Hz<br />
Commercial Active Power Generation<br />
Cranking and Shaking<br />
• 60 turns (1 min) stores 0.6 Watt-hr<br />
• 40% efficient<br />
• Today’s laptop supply roughly 30-50 W-hr<br />
• 1 hour of more of winding (w. heavy spring!)<br />
Freeplay (Baygen)<br />
• Innovative Technologies Sidewinder<br />
• 80 g, 2 mins cranking gives >6 mins cellphone talk
4/04<br />
©<br />
MIT-ML<br />
Windup Flashlights in History<br />
VanDeventer, 1916<br />
Mining applications…<br />
Luzy, 1922<br />
JAP<br />
38
4/04<br />
©<br />
MIT-ML<br />
Nissho Engineering (AladdinPower)<br />
Tug Power<br />
Pull ring to spin flywheel & generator<br />
80 g, 2.5 W<br />
AladdinPower<br />
Squeeze<br />
1.6 W, 1.5 Hz<br />
Step Charger<br />
6 Watts<br />
JAP<br />
39
$100 Laptop (OLPC Foundation)<br />
<strong>Computing</strong> <strong>for</strong> every child on the planet<br />
Power & networking are main technical challenges<br />
New display, efficient electronics and software aim at ~1 Watt<br />
Cheap environmental power needed as infrastructure is unreliable<br />
Originally crank, now pedal doubling as power x<strong>for</strong>mer or dual pulchain, etc.
4/04<br />
©<br />
MIT-ML<br />
The Electric Bolo<br />
• Saul Griffith (MIT Media Lab)<br />
• 100-200 g proof mass, .3-.5 meter radius, 1-2 Hz rate<br />
• Claims approx. 3-5 Watts...<br />
JAP<br />
41
Johnson, et al., Transmitter Circuit,<br />
US Patent No. 3,796,958, March 12, 1974.<br />
Zenith ‘Space Command”<br />
Self-Powered Buttons<br />
Crisan, A. (Compaq), Typing Power,<br />
US Patent No. 5,911,529, June 15, 1999<br />
Pipi "Kodomo No Omocha" pager toy
4/04<br />
©<br />
MIT-ML<br />
Voltage (V)<br />
14<br />
12<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
-2<br />
-5.6<br />
Self-powered buttons<br />
16.4<br />
Strike Occurrence<br />
Tank Capacitor Voltage<br />
38.4<br />
60.4<br />
82.4<br />
104<br />
126<br />
3 Volt Regulator Output<br />
148<br />
170<br />
192<br />
214<br />
• ~0.5 mJ at 3 Volts per push<br />
• Sends 12-bit RFID 12 x throughout floor (50 ft.)<br />
• No need <strong>for</strong> battery, wire… Mark Feldmeier<br />
236<br />
Time (msec)<br />
Serial ID Code<br />
258<br />
280<br />
302<br />
324<br />
346<br />
368<br />
Spring 2001<br />
390<br />
412<br />
434<br />
JAP<br />
43
4/04<br />
©<br />
MIT-ML<br />
Cleaner Prototypes<br />
CES Show - 2004 EnOcean device<br />
uses bistable PZT<br />
bimorph cantilever<br />
JAP<br />
44
4/04<br />
©<br />
MIT-ML<br />
Power <strong>Harvesting</strong> – Wireless, Batteryless Window Switch<br />
with ALPS Automotive<br />
• Command window up-stop-down<br />
• No battery, no wire<br />
– Power harvested from single push<br />
– Eliminate need <strong>for</strong> complex wire harness<br />
Mark Feldmeier<br />
JAP<br />
45
AES Roadmap<br />
“
Mobility in Sensor Networks<br />
• Forefront research where sensor nets meet robotics<br />
and control<br />
• Sensor clusters move to places to optimally:<br />
– Measure dynamic phenomena<br />
– Position relays to repair or patch broken network<br />
– Dump in<strong>for</strong>mation at access points (portals)<br />
– Get recovered or recharged<br />
What does power harvesting<br />
mean in a mobile system?<br />
<strong>Energy</strong> cost of moving atoms is much<br />
higher than moving bits…
Parasitic Mobility in Sensor Networks<br />
Implications<br />
- Sensor clusters hitch rides to places<br />
where they need to be to optimally:<br />
- Measure relevant phenomena<br />
- Relay in<strong>for</strong>mation peer-peer<br />
- Dump in<strong>for</strong>mation into portals<br />
- Get recovered or recharged<br />
- Rapid diffusion of sensors across an environment<br />
- System self-organizes to auto-dispatch nodes to desired regions<br />
Innovations and Architecture<br />
- Interpretation of <strong>Energy</strong> <strong>Harvesting</strong> in mobile networks<br />
- Two flavors:<br />
- The Tick (e.g., jumps onto a car, attaches magnetically, then disengages)<br />
- The Bur (e.g., sticks to passing object, then shakes off)<br />
- Contains GPS, RF, basic sensor suite<br />
Phoresis<br />
<strong>Paradiso</strong> & Laibowitz
4/04<br />
©<br />
MIT-ML<br />
Parasitic Mobility Research (ParaMoR)<br />
• Paramor Hardware – small nodes<br />
with sensor suite (light, microphone,<br />
inertial, proximity, temperature,<br />
heat), GPS, RF communication,<br />
rechargeable power source, and<br />
minimal actuation <strong>for</strong><br />
attachment/detachment<br />
• Active nodes (ticks)<br />
• Passive nodes (burs)<br />
• Value-added nodes (pens)<br />
• ParaSim – Software<br />
simulator to study behavior<br />
and evaluate control<br />
algorithms <strong>for</strong> parasitically<br />
mobile sensor nodes<br />
Active Node<br />
JAP<br />
Passive Node<br />
Mat Laibowitz<br />
49
4/04<br />
©<br />
MIT-ML<br />
Symbiotic Node Tests<br />
Accls<br />
Light<br />
Zone #<br />
Node 7<br />
Only<br />
JAP<br />
50
4/04<br />
©<br />
MIT-ML<br />
Power <strong>Harvesting</strong> Summary<br />
JAP<br />
51
4/04<br />
©<br />
MIT-ML<br />
Summary<br />
• Environmental energy μw-W<br />
• Biofuel cells μw<br />
• Thermal conversion μw<br />
• Inertial energy harvesting<br />
• Heel strike generators mW-W<br />
• Deliberately Powered Systems<br />
μw - mW<br />
W<br />
JAP<br />
Human-Powered Systems<br />
52
4/04<br />
©<br />
MIT-ML<br />
Humanity’s Destiny?<br />
JAP<br />
53
4/04<br />
©<br />
MIT-ML<br />
Resting Humans are dim bulbs (100 W)<br />
They will use us in more creative ways...<br />
JAP<br />
54
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