RF Energy Harvesting

PowerPoint PresentationEnergy Harvesting from the environment and daily activities
Eisa Zarepour
PHD Candidate
School of Computer Science and Engineering, University of New South
Wales, Sydney, Australia.
Outline
The concept
From Temperature variation
From Pressure variation
From humidity variation
Few Nano-scale EHs Schemas
Energy Harvesting
Ambient Energy sources
…
Energy harvesting (also known as power harvesting or energy scavenging) is the process by which energy is derived from external sources.
The concept
Energy Harvesting
Example
Harvesting energy from
Ambient RF Energy sources
The concept
Base station
School of Computer Science and Engineering
Received power from Radio Frequency radiations can be harvested as a signal = energy +/ data.
Received Power
According to the IEEE 802.11 standard, every compliant Access Point (AP) periodically sends out management frames called beacon frames.
The purpose of beacon frames is to advertise the presence of an AP in an area, its capabilities, and some configuration and security information to the client devices.
The time interval between two consecutive beacon frames is called the beacon interval which is a configurable parameters that determine the beacon rate per second (β).
β is usually between 10-50.
Each beacon contains around 63 bytes information or 500 bits.
As transmitter is using an electromagnetic wave to represent and transfer a bit, the energy of each single bit can be harvested at the receiver.
How we can harvest energy from an anonymous access point?
Beacons
The Beacon will be relatively constant in length. You can calculate it as follows:
802.11 MAC header: 24 bytes
Fixed Beacon fields: 11 bytes
Variable fields:
SSID: 2 bytes plus the number of bytes in the SSID
Supported rates: 6 bytes
DS parameters: 3 bytes
Country: 6 bytes (optional)
FCS (fixed field): 4 bytes
Total: 61 bytes plus the number of bytes in the SSID
Beacon structure
The signal strength of AP is usually in dBm (Android also gives in dBm). We can use below conversion to make it appropriate for the second equation:
P(W) = 1W · 10(P_dBm / 10) / 1000 = 10((P_dBm - 30) / 10)
For example, the equivalent Watt of a -60 dBm signal is one nano Watt (10-9 W).
Energy calculations
Energy calculations
An example
Let us assume we have this trace of RSS for a given AP over time .
t1
t2
Time Stamp
RSS (dBm)
RF Energy Harvesting
In Android , you can use startScan/getScanResults methods from WiFiManger class to discover the available access points and then identify their specs such as SSID and strength in dB (lab2).
MobileWiFi framework is the framework that manages WiFi functionality on iOS.
More information
1- While you are walking or travelling via a vehicle, find out all available wireless access points around you every second.
2- For each access point extract and save these information ( from lab 2):
Network name (field: SSID)
Signal strength in dBm (filed: level)
3- Save all data from step two in an excel or csv file including these columns:
Date and Time in the format of yyyy-MM-dd HH:mm:ss
Position data from GPS including longitude, latitude and speed ( from lab3 )
Network name (SSID)
Why we need to record frequency of APs and also the location data ?
Performing further analysis on the types of APs based on their frequencies.
Performing location analysis which can help to find the potential area for harvesting RF energy (e.g. academic area, train stations, etc.)
Other possibility for harvesting energy in daily activities
Variation in Temperature
Variation in Pressure
Variation in Humidity
User activity (kinetic)
Power can be harvested from temperature variation via Pyroelectric Generators
The detectable current i(t) of a pyroelectric material is proportional to the rate of change of its temperature and can be expressed as:
PC is the pyroelectric current coefficient and A is the surface area of the electrode connected to the pyroelectric material
Pyroelectric voltage at time t can be calculated as:
PV is pyroelectric voltage coefficient, rd is the Debye length of ZnO and T(t) is the variation of temperature at time interval of [t-1; t] in Kelvin
From Temperature Variation
You can read the ambient air temperature and device temperature via these two sensors:
1- Read the output of those two temperature sensors every second
2- Save the resulted data in an excel file including these columns:
Ambient air temperature
Power can be harvested from atmospheric pressure variation
For a fixed volume V of gas, the change in energy ΔE due to a change in pressure ΔP is ( reference ): ΔE= ΔPV (pressure in Pascal)
For example, local pressure can change around 30−40 mbar (3−4 kPa) during cyclonic weather events, a more typical daily pressure change is 3 mbar (300 Pa). With a device volume of 1 cm^3 this will provide 300 mJ/cm3 (around 3nW per day)
You can read the atmospheric air pressure via barometer sensor( TYPE_PRESSURE )
More information
From Atmospheric Pressure Variation
1- Read the output of barometer sensor every minutes.
Ambient air pressure
Power can be harvested from relative humidity changes
The ability to obtain a potential difference across membranes separating two aqueous solutions of differing salt concentrations has been known for over half a century.
Based on this concept, several approaches have been proposed to use humidity changes to make such potential difference. For example, a solid-state electrochemical cell can benefit from changes in the relative humidity of the surrounding environment to produce electricity ( Reference ) and the resulted voltage would be:
V is the theoretical membrane potential (J C-1 or V), R is the gas constant (J mol -1 K-1), T is the absolute temperature (in Kelvin, K), z is the electrochemical valence, F is Faraday's constant (C mol-1).
1% variation in humidity can creates around maximum of 0.4mV potential difference.
From Humidity Variation
You can read the Ambient relative humidity from the mobile sensor ( TYPE_RELATIVE_HUMIDITY ) in %.
More information:
Where
F is Faraday's constant : 9.65*104
Z is the electrochemical valence: around 32.5 in the aforementioned paper.
T is temperature in Kelvin which can be measured via phone sensor or use a constant of 305K as an average normal weather temperature.
From Humidity Variation
1- Read the output of humidity and temperature sensor every minutes.
Relative humidity in %
Instruction
Some Nano-scale Energy Harvesting Devices
*
“ Pyroelectric Nanogenerators for Harvesting Thermoelectric Energy ”Ya Yang, Wenxi Guo, Ken C. Pradel, Guang Zhu, Yusheng Zhou, Yan Zhang, Youfan Hu, Long Lin, and Zhong Lin Wang, Nano Letters, 2012, 12 (6), 2833–2838
“ Harvesting vibration energy by a triple-cantilever based triboelectric nanogenerator "Weiqing Yang, Jun Chen, Guang Zhu, Xiaonan Wen, Peng Bai, Yuanjie Su, Yuan Lin, and Zhonglin Wang, Nano Research, Online
From thermal and motion
*
“ Self-Powered Magnetic Sensor Based on a Triboelectric Nanogenerator "Ya Yang, Long Lin, Yue Zhang, Qingshen Jing, Te-Chien Hou, and Zhong Lin Wang,ACS NANO, 2012, Online
“ Nano-Newton Transverse Force Sensor Using a Vertical GaN Nanowire based on the Piezotronic Effect "Yu Sheng Zhou, Ronan Hinchet, Ya Yang, Gustavo Ardila, Rudeesun Songmuang, Fang Zhang, Yan Zhang, Weihua Han, Ken Pradel, Laurent Montès, Mireille Mouis, and Zhong Lin Wang, Advanced Materials, 2012, Online
From magnetic field and gravity
Energy Harvesting for NSNs (2)
*
“ Multi-layered disk triboelectric nanogenerator for harvesting hydropower "Yannan Xie, Sihong Wang, Simiao Niu, Long Lin, Qingshen Jing, Yuanjie Su, Zhengyun Wu, Zhong Lin Wang, Nano Energy, 2014, 6, 129–136
From water wave and hydropower
Energy Harvesting for NSNs (3)
*
Hybrid schemas (1)
*
“ Flexible hybrid cell for simultaneously harvesting thermal and mechanical energies "Sangmin Lee, Sung-Hwan Bae, Long Lin, Seunghyun Ahn, Chan Park, Sang-Woo Kim, Seung Nam Cha, Young Jun Park, Zhong Lin Wang, Nano Energy, 2013, 2, 817-825
Hybrid schemas (2)
*

Date post:	30-Sep-2015
Category:	Documents
Upload:	naga-karthik
View:	22 times
Download:	0 times

RF Energy Harvesting

Documents