University of Rhode Island
Biomedical Engineering
Andrew Seitler
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Thermoelectric – Body heat
Photovoltaic – Light (Artificial and Solar)
Electrostatic – Electric Potential change
Electromagnetic – Vibration
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Heat Transfer is the transfer of thermal
energy from a hot mass to a cooler mass.
The human body generates constant heat
Sleeping 250 Btu/hr (75 watts)
Awake 400 Btu/hr (120 watts)
Light work/exercise 650 Btu/hr (190 watts)
Heavy work/exercise 2400 Btu/hr (700 watts)
Majority of Heat escapes through the head
λ thermal conductivity
σ electrical conductivity
S, Seebeck Coefficient
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Any light source can be used to generate
energy even at small invisible amounts.
Artificial Lights generate a constant 60 Hz
signal along with a small amount of photons.
The sun generates energy commonly called
solar radiation, easily transferred by heat; far
more efficiently harvested by photovoltaic.
Photovoltaic devices are made of silicon and
convert solar radiation directly into energy or
electrical current.
h, Planck's constant
Φ, work function
f, frequency
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Stationary or slow moving electric charges
Electric charges are constantly changing on
the human body.
◦ Contact with objects that have a higher or lower
charge cause electric charges to transfer.
◦ Neurons and electrical impulses
◦ Special vibrating piezoelectric devices can be tuned
to pick up these changes.
Q, Electrical Charges
R, distance between charges
Ε0,Permittivity Constant
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Motors are designed to turn when current is
applied; they allow for current generation
when they are turned.
Piezoelectric devices create vibrations or can
be used to vibrate and generate energy based
on frequencies readily available.
Mass driven magnets
◦ Human motion
◦ Walking
◦ Exercising
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Human created ambient energy
◦ Radio Towers
◦ Cell phone Towers
◦ Television Stations
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Solar Radiation
◦ Creation of Heat
◦ Photon vibrations
◦ High Energy Radiation
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Currently energy harvesting used for sensors.
◦ Mostly military use for listening devices
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Piezoelectric’s currently in use
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Radioisotopes
Vibrations
Charged Battery
Coupled Capacitors
Energy Source
Challenge
Estimated Power
(in 1 cm3 or 1 cm 2)
Light
Conform to small
surface area
10µW – 15mW
(outdoors: 0.15mW-15mW)
(indoors: <10µW)
Vibrations
Variability of
Vibration
1µW – 200 µW
(Piezoelectric: 200µW)
(Electrostatic: 50µW-100 µW)
(Electromagnetic: <1µW)
Thermal
Small thermal
gradients
15µW
(10 degree C gradient)
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Smaller Devices
Energy Farming becomes more efficient
Piezoelectric devices can automatically tune
Possibility to listen to and transfer energy
from High energy electromagnetic radiation.
Heat from current devices transfer to power
themselves.
Reduce need for batteries
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http://spectrum.ieee.org/semiconductors/de
vices/wireless-sensors-that-live-forever
http://spectrum.ieee.org/energy/renewables
/putting-wireless-power-to-work
http://earth2tech.com/2008/12/17/chipcompanies-eye-energy-harvesting/