Engineers Without Borders-USA2008 International Conference

University of Minnesota Chapter

Solar-Powered Well Pump and Water Tower

Amponsah, Ghana

Spring ’06 to Summer ‘07

Agenda

• Community Needs

• Site Visit

• Design

• Implementation

• Challenges

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

Site Visit - Summer 2006

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

Pump

• Grundfos SQFlex-1111GPM 30-300 VDC / 90-240 VACMultiple Protections

Solar Array

8 Panel Array

BP 3115J, 115 W

12 V, 7 A Nominal

Implementation- Summer 2007

Raising the Water Tank

Implementation

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

Challenge 1: Shipping

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

Max exposure to the sunAbove jungle canopyReduced potential of theft

• 6500 L Polytank (10L/person /day)

Challenge 2: TowerChallenge 2: Tower

Challenge 2: TowerChallenge 2: Tower

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

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

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

Concluding Remarks

Contact Information

Presenter:

Nathan Knutson

knut0293@umn.edu

Chapter:

www.tc.umn.edu/~ewb

President:

Brian Bell bell0384@umn.edu