Powering Mesh Networks for Environmental Sensing in Remote Areas

Department of Electrical and Computer Engineering Graduate Studies

Doug Frome

2 April 2013

Introduction - MESA Project

– Mountainous Ecosystem Sensor Array

• Three dimensional monitoring of the ecosystem

• 78 sensors total – 26 per site – 3 sites (Micro-Nets)

• Located in the Frank Church Wilderness of No Return in the State of Idaho

MESA project Goals • To achieve real time wireless three dimensional monitoring of

a mountainous ecosystem.

• To make the system autonomous such that maintenance of the system is only required once per year.

• To physically install the system and have it functioning within one year.

• To have all sensors tested for precision and be within 10% tolerance of all other like sensors.

• To receive all data generated by all of the sensors with minimal interruptions.

• To develop a system to manage and store the data generated by the sensors in the project.

• To comply with all the minimum impact requirements in the Wilderness Act of 1964.

Mid site Upper site

Lower site

½ crown height

5

Sensor Sensor

#

CO2 (2 min) 1

Air T/RH (2 min) 2

soil h20/T (30 min) 3

WXT520 4

Net Radiation (2 min) 5

Snow Depth (2 hr) 6

Dendrometer (1 hr) 8

Leaf Wetness (2 min) 9

4

9 5

8

5

9 2 1

4

9 1

2m

½ crown radius

½ crown radius

Full crown radius

123W

Camo Solar Panel in Tree

Wind Turbine

Main Tree Sensor Locations

Aluminum Pipe

1

10W 10W 10W

8 8

6 6 6

3m 3m

3

3

3

3

3

3

3

3 ½ crown radius

Sensor Sensor

#

CO2 (2 min) 1

Air T/RH (2 min) 2

soil h20/T (30 min) 3

WXT520 4

Net Radiation (2 min) 5

Snow Depth (2 hr) 6

Dendrometer (1 hr) 8

Leaf Wetness (2 min) 9

Tree #1 Tree #2 Dead Snag

Tree #3

Solar Panel in Tree

Aluminum Pipe

50cm 50cm

Standards for mounting Equipment

• Can not harm the trees

• Has to have low visibility

• Animal proof

• Must be transportable by:

–human, mule, car, and small plane

Top Assembly – Main Tree

• Assembled in lowered position, then raised.

• Extension beam

gets equipment out of branches.

• As simple as this looks; it took a long time to get the design right.

Fastening the Main Mast • Mast pipe is secured by

two sets of tree braces with crosspieces.

• Crosspiece U-bolts hold mast pipe.

View of Tree braces, crosspiece, and mast pipes

Solar Panel in Main Tree • Meets min. impact • Camouflage • Black pipe • Low Visibility

• Tangential Tree Mount (Left)

• Radial Tree Mount (Below)

• Tree Braces • Ratchet Straps • Strut (Bolted) • Pipe Clamps • Anodized pipe and powder

coated strut (Low Visibility) Meets min. Impact Req.

Tertiary Tree – Snow Depth Sensor & Solar Panel

Nu-Rail allows two axis rotation for positioning of snow depth sensors parallel with the ground. Solar panel also has two directions of rotation.

Sensor Sensor # Wh/day sample time

CO2 1 24 2 min

Air T/RH 2 0.029 2 min

soil h20/T 3 0.0048 30 min

WXT 4 1.68 2 min

Net Radiation 5 0 2 min

Snow Depth 6 0.006 2 hrs

Dendrometer 8 0.0001667 1 hrs

Leaf Wetness 9 0.007 2 min

Intelemote (no sensors)3.3V A 1.251 X

Intelemote (no sensors)5.0V B 1.896 X

Intelecell (no sensors) C 15.533 X

DC-DC Converter D 6 X

Vegetronix RS-232 Board E 0.24 X

OWL radiometer Board F 0.16 X

Predicted Power Consumption

Note that the biggest power consumers are the CO2 sensor and the I-cell

Main Tree Sensor #s Wh/year Wh/day # motes

Top 1,4,5,9,C,F 15103.7 41.38 1 cell

Mid Canopy 1,2,9,B,D 11655.18 31.932 1 mote

Base of Canopy 5,9,B,D 2884.595 7.903 1 mote

Base of Tree 1,4,5,8,B,B,B,D,D,D 18019.38085 49.3681667 3 motes

Main Tree Total: 47662.85585 130.5831667

Other Trees Sensor #s Wh/year Wh/day # motes

Tree 1 3,3,3,3,6,6,8,A,A,E 1012.278846 2.7733667 2 motes

Tree 2 3,3,3,3,6,A,E 553.413 1.5162 1 mote

Tree 3 8,A 456.6758455 1.2511667 1 mote

Predicted Power Consumption Per Power System

Wh/day Ah/day @12V W continious I continuous Wh/5days Ah/5days @ 12V

Main Tree 130.5832 10.88193056 5.440965279 0.453413773 652.915834 54.40965279

Wh/day Ah/day @3.3V W continuous I continuous Wh/5days Ah/5days @ 3.3V

Tree 1 2.773367 0.840414152 0.115556946 0.035017256 13.8668335 4.202070758

Tree 2 1.5162 0.459454545 0.063175 0.019143939 7.581 2.297272727

Tree 3 1.251167 0.379141424 0.052131946 0.015797559 6.2558335 1.895707121

Predicted Power and Current

Measured Power and current Wh/day Ah/day @12V W continious I continuous Wh/5days Ah/5days @ 12V

Main Tree 113.9328 9.4944 4.7472 0.3956 569.664 47.472

Wh/day Ah/day @3.3V W continuous I continuous Wh/5days Ah/5days @ 3.3V

Tree 1 2.66904 0.8088 0.11121 0.0337 13.3452 4.044

Tree 2 1.80576 0.5472 0.07524 0.0228 9.0288 2.736

Tree 3 1.09296 0.3312 0.04554 0.0138 5.4648 1.656

Measured Ah/5days values are used for battery bank sizing

Ah/5days @ 12V Battery Bank Size Ah

Main Tree 47.472 118.68

Ah/5days @ 3.3V Battery Bank Size Ah

Tree 1 4.044 10.11

Tree 2 2.736 6.84

Tree 3 1.656 4.14

Battery Bank Size = [Amp Hours Needed for 5 days/60%]*1.5

Values in the first column were taken from the table on the previous slide.

Batteries – Lead acid

• Sealed AGM used – does not leak acid during transport

• No need to refill fluids, no maintenance

– Lithium-ion

• Lithium iron phosphate (LiFePO4) used because of superior fire safety

• Other types of Lithium-ion batteries are pyrophoric

– Nickel

• cadmium, nickel-metal hydride

• Not used because of temperature and memory effects

Battery Configurations

• Main Tree

– Deka AGM

– 3 parallel 55Ah 12V batteries

– 165Ah total (main bus)

• Peripheral trees

– A123-26650 LiFePO4

– 4 parallel 2.5Ah 3.3V

– 10Ah total (per tree)

Battery Bank Size Ah

Main Tree = 118.68

Tree 1 = 10.11

Tree 2 = 6.84

Tree 3 = 4.14

Minimum Calculated Bank Size:

Main Tree Power System

Diode blocks reverse current flow into solar panels at night.

Main bus and Forgen wires are in 12-4 SJOW cable

Tertiary trees have similar power system, but no wind turbine.

Wire

gauge

ohms

@ 75ft

ohms

@ 100ft

V drop @ 75ft

@400mA

V drop @ 100ft

@ 400mA

P loss (Watts)

@ 75ft

P loss (Watts)

@ 100ft

10 0.0749175 0.09989 0.029967 0.039956 0.0119868 0.0159824

12 0.1191 0.1588 0.04764 0.06352 0.019056 0.025408

14 0.189375 0.2525 0.07575 0.101 0.0303 0.0404

22 1.2105 1.614 0.4842 0.6456 0.19368 0.25824

24 1.92525 2.567 0.7701 1.0268 0.30804 0.41072

Main Bus Voltage Drop Considerations: • 12 gauge wire was chosen • Less than a tenth of a volt drop across a 100 foot bus • 25mW of power consumption • Bus Current = 9.4944Ah/24h ≈ 400mA (Based off of measured current)

Solar Considerations:

• The Solar panel does not produce sufficient power when light is below a certain thresh-hold.

• Can not harvest all of the light in a day; low levels of radiance are not usable.

STAR 123 Warner Energy Panel • Vmpp = 20.95V • Impp = 5.93A • Nominal Power = 123W

1.9A @ 300W/m^2

Radiance (Mid Site) 12/2/12 – 12/6/12

0

100

200

300

400

500

600

700

6:00 7:12 8:24 9:36 10:48 12:00 13:12 14:24 15:36 16:48

12/6/2012

12/5/2012

12/4/2012

12/3/2012

12/2/2012

• Assume 12/3/2012 is a sunny day in December at MESA Mid Site with 2.5 hours of radiance above 300W/m^2

• Estimate 1.5 sunny December days out of every 5 days = bad weather

• This results in (1.5days)*(2.5hr/day) ≈ 3.75hr/5days of radiance greater than 300W/m^2

W/m

^2

Time of Day

Horizon H-series: days of operation @ full power

Norco Cylinder

Size

Volume (Liters)

@ 0.5atm

Days of Operation

H-12 (12 Watts)

Days of Operation

H-20 (20 Watts)

Days of Operation

H-30 (30 Watts)

Q 4528 17.47 11.23 7.48

S 8490 32.75 21.05 14.03

K 12452 48.04 30.88 20.59

• The Main Tree power consumption is 4.75W continuous.

• The “K” cylinder would power the main tree for 121.36 days if

the H-12 fuel cell was used.

• (12W/4.75W)*48.04days = 121.36days

Equipment

Definition of a Mesh Network

• The definition of a mesh network is a Local Area Network (LAN) where each node can operate as an independent router.

• This means that if one of the routers is removed, then the others readjust and re-route the network transmissions.

• For the MESA project, these nodes are referred to as “motes” or “i-cells”.

Mesh Networks in the MESA system

mote

mote

mote mote

mote

• Mote mesh system uses the Xbee-Pro® Radio and Digi-mesh algorithm.

• I-cell mesh system uses the Zigbee X-Tend® radio and a mesh algorithm developed by Intelesense.

• Each I-cell has a Xbee-Pro® Radio to mesh with motes.

XBee-PRO® 900/DigiMesh™ 900 OEM RF Modules

• 900MHz Radio • Proprietary Driver • Indoor/Urban: up to

450ft (140m) • Outdoor line-of-sight: up

to 1.8 miles (3 km) • Transmit Power Output:

50 mW (+17dBm) • Receiver Sensitivity: -100

dBm • RF Data Rate: 156.25

kbps

The main features of the Digi-mesh protocol are:

• The network is self healing.

• Peer-to-peer architecture.

• Route Discovery

• Selective Acknowledgements: –Only the destination mote will reply

to a route request

• Sleep modes

Sensor Interface – Radiometer & Soil

Radiometer Data Path

Radiometer OWL

(OP Amps)

Spark Fun RS232

converter

Intelecell

Low Voltage Signals

3V RS232

12V RS232

Intelecell

Soil Sensor Data Path

Veggie Tronix

SDI Bus

RS232 Bus

Soil

Sen

sors

LEM schematic – Power Monitoring

Questions ???