Author Topic: Simple Methods for Determining Head/Fall and Penstock Length  (Read 1901 times)

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Simple Methods for Determining Head/Fall and Penstock Length
« on: April 02, 2015, 12:55:22 PM »
Determining Head/Fall for high fall sites in the U.S.:
1. Get the Geological Survey map for your site.
2. Find your intake site and note the nearest elevation contour.
3. Find your turbine site and note the nearest elevation contour.
4. Subtract the turbine site elevation contour from the intake site elevation contour. This is your head/fall accurate within +/- two times the contour spacing (usually 10 feet).
Note: this should be adequate for evaluation and system design where head/fall exceeds 100 feet. It may be adequate for evaluation for medium head/fall sites, say 50 to 100 feet.

Determining Head/Fall for Medium and Low fall sites in the U.S. and any site anywhere.:
1. Get a water level from the hardware store or make your own. All that's needed is 1/4" clear vinyl tubing. Length needs to suit your site. 25 feet may do for short distances and longer than 100 feet gets awkward in most terrain. You will also need a measuring device.
2. Arrange a date with a survey partner. It's possible to do it alone, but far more difficult and way less fun.
3. Start at your intake site. Move toward your turbine site as directly as possible. Move downhill as far as the tube allows and/or you can still measure from the water level to the ground. While it is possible to start down and work up, it means someone has to stand reaching and watching up while the other proceeds uphill. Not fun.
4. Write down each measurement as you go and total them up at the end.
Note: A builder's transit level will allow sighting over greater distance and if you also have a survey rod greater drops up to 15 feet. However, a water level can see around corners and through brush and trees.

Estimating penstock length for U.S. sites.:
1. Get the Geological Survey Map for your site.
2. Note the scale and determine how accurate you plan to be.
3. Set a drawing compass to some fraction or multiple of the map scale.
4. Use the compass to follow the terrain between your intake and turbine sites. If you haven't done this before, a walking motion is used. Plant both compass points, raise one end, swivel it around the other, plant it, then repeat for the other point. Count the segments and multiply by scale to determine overall distance.
5. Add the head/fall to compensate for extra penstock needed to travel down.
Note: this method should be adequate for evaluation and planning. Actually measuring the planned path is recommended before ordering supplies.