engineers without borders-usa 2008 international conference
TRANSCRIPT
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Engineers Without Borders-USA2008 International Conference
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University of Minnesota Chapter
Solar-Powered Well Pump and Water Tower
Amponsah, Ghana
Spring ’06 to Summer ‘07
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Agenda
• Community Needs
• Site Visit
• Design
• Implementation
• Challenges
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Community Needs
600+ students & villagers w/o clean water
Pit latrines w/o wash station
Result:Lost time in class due to diarrheal illnessGender inequality from fetching waterRare but still present: Guinea Worm
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Site Visit - Summer 2006
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VillageAbove-ground water tower
Grundfos submersible
pump
M/F sanitary toilets
Hand washing station
Biomass compost pens
Soccer field / P.E. field
Irrigated farmland for school crops
main school building
main school building
drying slab for crops and bricks
drying slab for crops and bricks
secondary
classrooms
secondary
classrooms
Control Boxw
ater line
water line
water line
Solar panel array
water faucet
water faucet
Design Layout
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Pump
• Grundfos SQFlex-1111GPM 30-300 VDC / 90-240 VACMultiple Protections
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Solar Array
8 Panel Array
BP 3115J, 115 W
12 V, 7 A Nominal
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Implementation- Summer 2007
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Raising the Water Tank
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Implementation
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Perfect or Far From?
Major Challenges:Major Challenges:
1 Transport1 Transport2 Wrong Tower2 Wrong Tower3 Incorrect Schematics3 Incorrect Schematics4 Well Log Inaccurate4 Well Log Inaccurate
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Challenge 1: Shipping
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Challenge 2: TowerChallenge 2: Tower
Main structure after our modificationsStructure present
when team arrived
10 ft10 ft
10 ft10 ft
10 ft10 ft
Seal Welds
Added Cross-Bracing
Added Footings w/ Rebar
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Max exposure to the sunAbove jungle canopyReduced potential of theft
• 6500 L Polytank (10L/person /day)
Challenge 2: TowerChallenge 2: Tower
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Challenge 2: TowerChallenge 2: Tower
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Designs are often modified in the field -- previous structural/failure analysis is no longer accurateDesign failures occur despite the strength of your materials
3D FVM study of 80 fps (59 mph) wind gust directed towards the lofted edge of the solar panel assembly - to be coupled with structural analysis to determine strains on mounting brackets.
necessary to prevent necessary to prevent catastrophic accidentscatastrophic accidents
Retroactive Design AnalysisRetroactive Design Analysis
Failure analysis can direct Failure analysis can direct your in-country collaborator’s your in-country collaborator’s attention to features prone to attention to features prone to failure failure
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Challenge 3: Incorrect SchematicsChallenge 3: Incorrect Schematics
2 Parallel 4-Panel Banks 8 Panels in Series
Result: 125 Watts in full cloud cover
Result: Random pumpshut-off in 50% sunlight
48 V 96 V
48V @ 14 A = 672 watts 96V @ 7 A = 672 watts
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Challenge 4: Well PerformanceChallenge 4: Well Performance
Valve to limit well outputPump Duty Cycle:
5 Gpm Lockout Lockout Lockout
2 Gpm
We had to limit well output due to incorrect well log
( = pumping, =Low Well Alarm)
Time
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Concluding Remarks
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Contact Information
Presenter:
Nathan Knutson
Chapter:
www.tc.umn.edu/~ewb
President:
Brian Bell [email protected]