Microhydro Flow, nozzles

Site Assessment: Flow 5-gallon bucket –Small stream, small waterfall Float –Larger, flat, uniform stream V-notch Weir Rectangular Weir

5 gallon bucket This may be tricky… Small stream, little waterfall Most typical method for microhydro

5 gallon bucket If the measured flow using a 5 gallon bucket and a stop watch was 5 gallons in 1.5 seconds, how many GPM would this be?

5 gallon bucket If the measured flow using a 5 gallon bucket and a stop watch was 5 gallons in 1.5 seconds, how many GPM would this be?

Float method Big, flat, uniform creek

Float method Flow (ft 3 /s) = Velocity (ft/s) x Cross Sectional Area (ft 2 )

Float method 1.Calculate the average depth Lay a board across the stream, measure the depth every foot, average the depths

Float method 2.Calculate the cross sectional area Area (ft 2 ) = Average depth (ft) x Width (ft) If XS is too irregular, divide into rectangles and sum em’ up

Float Method 3.Calculate velocity Measure where you measured the area, an orange makes a good float, start well upstream, a 10’ span is good, average multiple measurements

Float method 4. Correct for Friction Flow (ft 3 /s) = Velocity (ft/s) x Cross Sectional Area (ft 3 ) x.83 Multiply x 0.83 to correct for friction on the bottom of the stream

Float Method So, if these guys measure this 3’ wide stream and get an average depth of 8” and it takes an orange an average 5 seconds to go 10 feet, what is the flow in GPM? 1 ft 3 = 7.48 gallons

Float Method So, if these guys measure this 3’ wide stream and get an average depth of 8” and it takes an orange an average 5 seconds to go 10 feet, what is the flow in GPM? Area = 3’ x 8” x (1’/12”) = 2 ft 2 Velocity = 10 ft/5 s = 2 ft/s Flow = 2 ft 2 x 2 ft/ s = 4 ft 3 /s 4 ft 3 /s x 7.48 gal/1 ft 3 x 60s/1 min = 1795 gpm Correct for friction, 1795 gpm x.83 = 1490 gpm Complicated but easier than this…

Weir Method For larger flows or more accurate measurements Small –V-notch Larger –Rectangular All you needs is depth and the table

Weir depth measurement With V-notch or Rectangular weirs, drive a stake in the ground level with the bottom of the weir for depth measurement The stake should be behind the weir about 4x the depth of water through the weir

V-notch Weir

Using the V-notch weir chart, determine what a stream’s flow rate would be in GPM if the depth of the water was 5.5 inches.

Rectangular Weir Using the Weir chart, determine what a stream’s flow rate would be in GPM if the depth of the water above the weir notch was 3 inches and the weir notch was 4" wide.

Nozzles Generally, single nozzle systems with under 2000 feet of penstock require a 2" pipe. A two nozzle system needs a 3" pipe and 4 nozzle systems require a 4" pipe. This will keep pipe losses under 25%.

Nozzles What size nozzles and how many would you recommend if one wants to use about ½ of a stream with 260 GPM of measured flow with 100 ft of head (pelton wheel)?

Nozzles Maximum efficient flow at various heads From Harris Hydro (FIGURES IN GALLONS/MIN) FEET OF NET HEAD # of nozzles

Nozzles NOZZLE FLOW CHART – from ES & D FLOW RATE IN U.S. GALLONS PER MINUTE Head Feet PSINozzle Diameter, inches RPM 1/83/161/45/163/87/161/25/83/47/