This calculator applies freshwater gravitational power and a user-entered overall efficiency to entered flow and net head. It does not size, rate or predict an iron overshot wheel or generator system.
Iron Overshot Wheel Interactive Calculator
Explore ideal hydraulic power, assumed-efficiency shaft power, unit conversion and aggregate loss from entered net head and flow.
Equation Used
- Steady freshwater flow with density 1000 kg/m³.
- Entered H is net usable head across the wheel, not gross site elevation alone.
- Entered efficiency is a user-supplied overall water-to-shaft efficiency at the operating point.
- Flow and head occur simultaneously and tailwater does not alter the entered net head.
- No wheel diameter/width/buckets/speed, admission, leakage/ventilation, part-load curve, runaway/transients, shaft/bearing/structure, generator/transmission, civil works, hydrology, environmental or safety model.
Efficiency is an input assumption, not a prediction. Head must be the usable net elevation/energy difference at the wheel after upstream and downstream losses; flow must be simultaneously available at that head.
Water-to-shaft energy balance
Flow Q descending through net head H releases ideal hydraulic power rho g Q H. Multiplying by an entered overall efficiency gives an assumed shaft-power scenario.
The wheel sketch indicates an upper water supply but does not trace water into and out of individual buckets. Its size, speed and bucket colors are illustrative and do not change with the calculated power.
Use as a preliminary energy check
The calculation can check units and an assumed efficiency scenario from measured flow and net head. It cannot establish resource availability, select a wheel/generator, or approve civil and mechanical works.
Net head and efficiency matter
Q is converted from L/s to m³/s. Ideal power uses standard gravity and nominal freshwater density. Aggregate assumed loss is simply hydraulic power minus assumed shaft power; it does not identify leakage, exit, bearing or other loss mechanisms.
Worked example
For 80 L/s and 3.8 m net head, ideal hydraulic power is about 2.981 kW. At an assumed 80% overall efficiency, shaft power is 2.385 kW or 3.20 hp, and aggregate assumed loss is 0.596 kW.
Limits of the energy calculation
Available flow and net head can vary together through the year. Wheel geometry and operating speed affect actual efficiency, while transmission and generator losses reduce electrical output below shaft power. This calculation does not determine those characteristics or size a hydro installation.
Questions
Does efficiency come from the calculator?
No. It is entered by the user.
Can gross site head be used directly?
Only if it already equals net usable head after all losses and tailwater effects.
Does shaft power size a generator?
No. Speed, torque, transmission, generator curve and seasonal operation are absent.
References & Further Reading
- Wikipedia contributors. Water wheel. Wikipedia
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
