While most people can find sunshine or wind somewhere on their property,
only a priviledged few have a flowing stream and a slope, which are
required for micro hydro power. However, for those who have running
water on the property, this is a power source that should not be
overlooked.
Water power runs day and night, so it is excellent for off-grid systems
where it can reduce the dependency on big battery systems. It can be 10 to
100 times cheaper per watt than photovoltaic or wind turbines. More
water is available in the winter, when photovoltaic power is lowest, so
even a small micro hydro power is a very good adjunct to a solar power system.
To calculate roughly how much power your stream can generate, multiply
the cubic feet per second by the drop in feet (called the "head") and
multiply that by 67 to get watts. The number 67 includes typical
efficiencies for small hydro power turbines.
Suppose you can divert 30 gallons per minute from your stream without
drying it up and spoiling the lanscape. One gallon is 0.13368 cubic
feet, so we have 30 * 0.13368 / (60 seconds per minute), or 0.067 cubic
feet per second. If you have a 100 foot drop, you can generate about
0.067 * 100 * 67, or 449 watts.
Obviously, if you have greater flow, or a longer drop, you can generate
more power.
Some types of micro hydro turbines in use are:
- Crossflow turbines
- Pelton wheels
- Turgo wheels
- Francis turbine
- Kaplin turbine