Today we’ll pick up our discussion of hydroelectric generator systems where we left off in our last post. Let’s discuss the power output to be expected from a water source. To determine that, we first need to know the flow rate and the head (difference in elevation over which the water will travel in a pipe to get to the turbine. The most efficient type of wheel – the pelton turbine – will require a minimum head of about 20 feet (at least 50 feet is better). You can still generate electricity with less head, but you’ll need to turn to a reaction or propellor type of turbine, and you will see less power output. To determine the head, simply measure the difference in elevation from the pipe intake to the location where the turbine will be mounted. The flow rate can be determined quite simply with the use of a bucket and a stop watch. Simply measure the amount of water delivered per minute.
Now to determine how much power the water source will produce, use this equation:
Net Head (in feet) X Flow (gallons per minute) / 10 = Power (Watts)
Keep in mind that “net” head means we have to account for friction loss in the pipe using a friction loos flow chart. The larger the pipe, the less friction loss.
So if we have 50 feet of net head and 100 gallons per minute, the expected power output woud be 500 watts, or 1/2 Kilowatt.
The cost for a domestic micro hydro system (including hydrogenerator, charge control, batteries, and inverter) can be anywhere from $4,000 – $6,500.00 depending on the type of components you select. This does not include pipe which would vary from site to site.
