1. Energy Harvesting and Potential
University of Rhode Island
Biomedical Engineering
Andrew Seitler

2. Sources Energy can be Harvested
Thermoelectric – Body heat
Photovoltaic – Light (Artificial and Solar)
Electrostatic – Electric Potential change
Electromagnetic – Vibration

3. Thermoelectric Energy
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

4. Thermoelectric energy transfer

5. Photovoltaic Energy
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

6. Electrostatic Energy 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

7. Electromagnetic Energy
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

8. Piezoelectric Energy Transfer

9. Ambient Energy in Environment
Human created ambient energy
Radio Towers
Cell phone Towers
Television Stations
Solar Radiation
Creation of Heat
Photon vibrations
High Energy Radiation

10. Current Devices Currently energy harvesting used for sensors.
Mostly military use for listening devices
Piezoelectric’s currently in use
Radioisotopes
Vibrations
Charged Battery
Coupled Capacitors

11. Challenges from different Sources
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)

12. Future Possibilities 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

13. Works Cited
vices/wireless-sensors-that-live-forever
/putting-wireless-power-to-work
companies-eye-energy-harvesting/