RF Energy Harvesting

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Team 2
AFRL WSN Health Diagnostic

What is energy harvesting?

The process by which energy is derived from
external sources

Why use energy harvesting?
 Renewable source
 Allows for remote charging in applications
Energy harvesters provide a very small amount
of power for low-energy electronics
 The energy source for energy harvesters is
present as ambient background and is free
 As opposed to large-scale energy
generation which costs money



Converted energy can be stored in a
capacitor for short-term use or a battery
for long-term use.
Allows for the battery (or a charger) to be
taken out of the equation of an application
since it sources energy from the
environment

Materials
 Piezoelectric
 Pyroelectric
 Photovolatics

Other
 Kinetic Energy
 RF Energy



Converts mechanical
strain to electric
current
Produces power on
the order of mW
Useful for small
applications
 Handheld devices
 Light bulbs

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Human Motion
Acoustic Noise
Vibrations
Pressure




Converts changes in
temperatures to electric
current
Stable for temperatures
above 1200 ⁰C
High thermodynamic
efficiency
Used in
 Power Plants
 Automobiles


Converts human and/or natural
motion into electric current
Found in
 Wind Turbines
 Ocean Wave Buoys
 Human Motion
Also known as solar
power
 Converts solar
radiation into DC
 Found just about
everywhere and
gaining more
popularity

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
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
Converts RF signal energy into DC power
RF energy is available in a wide array of frequency
bands due to everyday technologies
 Cell Phones
 Radio Towers
 WiFi Routers
 Laptops
 TV Signals
Only a tiny amount of power can be harvested, good for
low power applications (Ex: A WiFi router can transmit
50-100mW)
Usually very short distance, however Powercast
demonstrated energy harvesting at 1.5 miles

Our project uses RF power harvesting
technologies

Ultra-low power, battery free applications
 Perfect for wireless sensor networks

Intentional Sources
 Powercast utilizes a direct RF energy
source, dedicated to providing RF energy
for harvesting

Anticipated Ambient Sources
 Routers, cell phone transmitters

Unknown Ambient Sources
 Microwave radio links, mobile radios
Module Components & Features


Powercast P2110 Powerharvester™ Receiver
MCU: Microchip PIC24 XLP
Radio module


▪
Microchip MRF24 (802.15.4)
 RF Powerharvester
 System power: 3.3V
 Capacitor
▪


50mF (as low as 3300uF)
Discrete sensors: Temp, Humidity, Light
Wireless protocol: MiWi™ P2P

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Center Frequency = 915MHz
Intentional RF Source
Directional Antenna

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Optimized RF Powerharvesting for the
transmitter frequency
RF Powerharvesting allows for remote
placement of sensor nodes
Great performance due to a design that
focuses on minimizing power
consumption in each node
 Proprietary wireless protocol

Power harvesting technologies are
everywhere and efficiencies are vastly
improving
 Simply look at solar efficiencies

Most of the world’s energy in the future
will be generated using power harvesting
technologies
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