Free Online Micro-Hydro Power Calculator

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Run-of-River Micro-Hydro Power Output Calculator

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Inputs

Flow rate, Q		X
Gross head, H_gross		X
Penstock diameter, D		X
Penstock length, L		X
Pipe roughness, e (See notes)		X
Minor loss coefficient, k_m ? (See notes)		X
Kinematic viscosity, ν ?		X
Plant efficiency, η (0–1)		X

Results

Flow velocity, v	Flow velocity, v	X
Velocity check (See notes)	Velocity check (See notes)	X
Friction factor, f	Friction factor, f	X
Friction head loss, h_f	Friction head loss, h_f	X
Minor head loss, h_m	Minor head loss, h_m	X
Total penstock loss, h_L	Total penstock loss, h_L	X
Head loss check (See notes)	Head loss check (See notes)	X
Net head, H_net	Net head, H_net	X
Power output, P	Power output, P	X
Annual energy at 100% capacity	Annual energy at 100% capacity	X

Notes

Head Loss: Total penstock loss h_L = h_f + h_m, where h_f = f(L/D)(v²/2g) is Darcy-Weisbach friction loss and h_m = k_m·v²/2g covers entrance, bends, and valves. Net head H_net = H_gross − h_L.
Velocity: Check that velocity is reasonable for the available drop and pipe cost. Very low velocity may indicate oversizing; very high velocity can increase friction losses and water hammer risk.
Head Loss Target: Penstock losses below 10% of gross head are generally economic. The optimal trade-off between pipe cost and lost power often falls around 4–6% for high-value electricity sites.
Junction (Point) Losses k_m: These losses occur at pipe junctions, entrances, bends, and valves — the term “minor” is conventional but misleading; in a short penstock they can equal or exceed friction losses. Typical k values: sharp intake entrance 0.5, each 45° bend 0.2–0.3, gate valve (fully open) 0.1, butterfly valve 0.2. Sum all fittings for the total k_m. Default 1.5 assumes one entrance and two bends.
Pipe Roughness e: Typical absolute roughness: steel (new) 0.046 mm, steel (used) 0.15 mm, HDPE 0.003 mm, PVC/uPVC 0.0015 mm, concrete 0.3–3 mm. HDPE is common for small micro-hydro penstocks.
Efficiency: Typical plant efficiency η ranges from 0.70 to 0.85 for Pelton and cross-flow turbines common in micro-hydro. Use 0.75 as a conservative first estimate.
Annual Energy: Annual energy assumes continuous full-flow operation (8760 hours/year). Actual production will be lower due to seasonal flow variation, maintenance downtime, and load factor.

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