| Wind systems for pumping water: A training manual |
TOTAL TIME: 2 Hours
OBJECTIVES: Familiarize participants with the strengths and characteristics of the local materials.
Discover what is available in the way of local building materials.
MATERIALS: Small poles, pipe, bamboo, and whatever materials you wish to examine and test to use in wind system construction.
Step 1: 30 minutes
Walk around the site looking at the types of materials available for use. Comment on and discuss the uses, qualities, strengths and weaknesses of the various types of materials represented.
Step 2: 15 minutes
Explain the method of destructive testing-pushing things to their limits.
Step 3: 15 minutes
Test some poles by supporting them at varying distances horizontally along their lengths and having someone stand on the middle of the poles.
Step 4: 5 minutes
Make some educated guesses at the stresses involved.
Step 5: 30 minutes
Discuss the forces on a mill and give some idea of the size of the forces-wind load and centrifugal load on the rotor and tower, as well as the pump loads.
Approximate stresses on the windmill are given in the handout titled "Rules of Thumb for Wind Waterpumps"
Step 6: 25 minutes
Test more materials for strength and flexibility.
RESOURCES: Copies of Attachment 7-A
Material Strengths & Testing
RULES OF THUMB FOR WIND WATERPUMPS
Centrifugal Force - (assuming a rotor tip speed ratio of approximately 1)
1 pound at one foot from the hub exerts with a force of 55 pounds in a 60 mph wind.
1 kilogram at 1 meter from the hub exerts with a force of 180 kilograms in a 100 km. per hour wind.
Maximum Windmill Drag Approximation - (in a 60+ mph (100+ km. per hour) wind)
10 pounds per square foot
45 kilograms per square meter
Power Calculation -
One horsepower is equal to lifting 400 gallons of water to a height of 10 feet in one minute.
One horsepower is equal to lifting 1500 liters of water to a height of 3 meters in one minute.
This formula is for theoretical horsepower and does not include the efficiency (or inefficiency) of the pump or the hydraulic friction losses in the pipe or the mechanical friction. For real life, use about one quarter of these figures for single acting pumps, and one half of these figures for double acting pumps.
A 2" pump puts out a quart for every 18 inches of stroke
A 2" x 2" square pump puts out a quart in 14" of stroke
A 3" pump puts out a quart for every 8 inches of stroke
A 5 cm. pump puts out a liter for every 50 cm. of stroke
A 5 cm. x 5 cm. pump puts out a liter each 40 em. of stroke
A 8 cm. pump puts out a liter for every 20 cm. of stroke