Post on 09-Apr-2020
transcript
1Challenge the future
Indoor solar energy harvesting
for sensor network router nodesAbhiman Hande, Todd Polk, William Walker,
Dinesh Bhatia – University of Texas at Dallas
2007
Speaker: Victor Spiridon
2Challenge the future
Free Solar EnergyWhy not harvest it for WSN
3Challenge the future
Outline
• Challenges of Indoor solar energy harvesting
• Indoor solar energy applications
• Implementation
• Experimental results
• Conclusions
• Personal conclusions
4Challenge the future
Outline
• Challenges of Indoor solar energy harvesting
• Indoor solar energy applications
• Implementation
• Experimental results
• Conclusions
• Personal conclusions
5Challenge the future
Harvesting solar energy
• Solar panel size
• Duty cycle
• Energy storage• Rechargeable batteries
• Capacitors
• Backup energy.
6Challenge the future
Harvesting solar energy… indoors
• Light intensity:• Outdoor: 100-1000 W/m2
• Indoor: 1-10 W/m2
• Cell efficiency:• Monocrystaline silicon cells: 1-3%
• Amorphous silicon cells: 3-7%
• Trade-off: price vs. panel size (no. of panels).
7Challenge the future
Outline
• Challenges of Indoor solar energy harvesting
• Indoor solar energy application
• Implementation
• Experimental results
• Conclusions
• Personal conclusions
8Challenge the future
Suited ApplicationsBuildings with “always on” lights
• Hospital & industrial environments
9Challenge the future
Outline
• Challenges of Indoor solar energy harvesting
• Indoor solar energy applications
• Implementation
• Experimental results
• Conclusions
• Personal conclusions
10Challenge the future
Harvesting system:
Hardware
• Crossbow MICAz• Chipcon CC2420, Zigbee radio
• ATMega 128L
• Size: 2.5” x 2.25” x 1”
• Solar Cell• Solar World 4-4.0-100 monocrystaline
• Size: 3.75” x 2.5”
• Ultracapacitors:• 2 x Maxwell PC5-5, 5 Vdc, 2 F, in parallel
• Philips 34W fluorescent lights.
11Challenge the future
Harvesting system:
Solar cells
• Output: 2 mA @ 3.2 VDC
• Needed: 25 mA @ ~3 VDC
• V – I profile @ 1 cm
from the light source
12 cells
12Challenge the future
Harvesting system:
Dual Router Algorithm
• 100% availability for receiving sensor packets
• Minimize no. of solar cells / router node
• 50% duty cycle
• Alternative Sleep/Wake Routine
• Partner searching
• 1 second interval (reasons?).
13Challenge the future
Start Initialize RouterNode Parameters
Locate Network
Determine shortest path to Base Station
Acquire ID from Base
Find a Route Partner
Start/Resume Sleep/Wake Routine
Forward message
Already Received
ID?
Route Partner stillAvailable?
Message to be
forwarded?
Lost network
connection?
No
No
No
No
Yes
Yes
Yes
Yes
Router Node Flowchart
14Challenge the future
Start
Initialize SensorNode Parameters
Locate Network
Determine shortest path to
base
Send Sensor Reading
Go to SleepWake Up
Sensor Node Flowchart
15Challenge the future
Harvesting system:
Circuit + battery back-up
16Challenge the future
Prototype router node
17Challenge the future
Outline
• Challenges of Indoor solar energy harvesting
• Indoor solar energy applications
• Implementation
• Experimental results
• Conclusions
• Personal conclusions
18Challenge the future
Experimental results
• Determining the no. of solar cells• Experiment with a variable power source
• Current 12 mA, 14mA (with PM circuit)
• 8 solar cells – just to be sure
• PM circuit efficiency @ 25 mA load• Drop of 60 mV & 5 mA 82%
• Q1 pmos (on): 50 mV drop @ 25 mA
• Leakage through Zener diode: 10 mV
• Ripple through a charge/discharge cycle• 15 mV – 0.5%. – due to high capacity.
19Challenge the future
The solar cell set up
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Testing application
• 1 sensor node, 2 router nodes (1 pair)
• Sensing data: Vload reading• Sensor: each 10s
• Router: each 25s
• Results over 24h confirmed the system’s robustness
• Vload stabilized at 3 Vdc
• Similar results with 2 router pairs.
21Challenge the future
Outline
• Challenges of Indoor solar energy harvesting
• Indoor solar energy applications
• Implementation
• Experimental results
• Conclusions
• Personal conclusions
22Challenge the future
Conclusions
• The harvesting technique is effective
• 50% duty cycle – reduced no. of solar cells
• Efficiency of power management circuit: 82%
• The network protocol – fairly robust
• Vload stabilized at about 3 Vdc
• Future Work: Interface the MICAz sensor node• A&D Medical UA767PC BP monitorBlood pressure, heart rate.
23Challenge the future
Outline
• Challenges of Indoor solar energy harvesting
• Indoor solar energy applications
• Implementation
• Experimental results
• Conclusions
• Personal conclusions
24Challenge the future
Personal conclusions
• No. of solar panels fairly large
• Router node – always close to light source• Why not use power from the grid?
• 100% routing availability is not needed• Same functionality: sync-ed nodes
• TinyDB
• Thorough system testing.
25Challenge the future
Requiered experiments
• Power w.r.t. the distance from light
• Node survival on back-up power
• Influence of temp over solar cell efficiency• Above 40°- 1% less power / degree
• Network protocol testing over a complex topology
• Power usage at low / high traffic
• Is initial capacitator charging time neglectable?.
26Challenge the future
Questions…
27Challenge the future
R1
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R1 – Ch 2, 3 ; R2 – Ch 1, 4
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Test app
30Challenge the future
No. of solar cells testing circuit
31Challenge the future
Solar panel power – temperature
relations