Most of the water calculations are based on a standardized temperature of 20.2 C or 68.4 F. Most water sources applicable to these small turbines run much colder. As water temperature decreases is becomes somewhat thicker. Its velocity decreases and results in a lower flow rate. There is an ugly formulae for figuring the flow rate decrease but it works out to be very close to the fluidity index if taken as a percentage. We get some of the power potential back with an increase in density. There is an intimidating calculus equation for this one. For mechanical power estimates this is adequate. Hydro-electric turbines however have an alternator attached that has a non-linear torque/output curve. The last column in the table shows what the expected power estimate should be as a percentage based on my own observations and experience on my own products as well as others.
|Water temperature||Flow rate %||Turbine|
|Temp C||Temp F||Fluidity Index||Power estimate|