Micro hydro systems generate electricity from flowing water, typically from a stream or spring on the property. Micro hydro is the most consistent and efficient renewable energy source for homesteads with a suitable water resource. A well-designed system can produce power 24 hours per day, year-round, with 50 to 70 percent system efficiency compared to 15 to 20 percent for Solar PV.
A micro hydro system has four main components: a water intake and penstock (pipe), a turbine, a generator or alternator, and a controller. The intake includes a screen to exclude debris and a settling basin to remove sediment. The penstock carries water downhill to the turbine, creating pressure from the vertical drop (head). The turbine converts the water's energy into mechanical rotation, which drives the generator.
Pelton turbines use one or more nozzles that direct a jet of water against spoon-shaped buckets on the runner. They are used for high-head, low-flow sites with a head of 10 to 200 meters and flow of 1 to 50 liters per second. Pelton turbines are the most common type for homestead micro hydro.
Turgo turbines are similar to Pelton but use a different runner design that handles higher flow rates. They are used for medium-head sites of 5 to 50 meters. Crossflow turbines operate efficiently over a wider range of flows and are used for low to medium head sites. Propeller turbines are used for low-head, high-flow sites.
A successful micro hydro site requires three elements: adequate head (vertical drop), adequate flow, and year-round water availability. Head is measured as the vertical distance from the intake to the turbine. A head of 10 meters can generate usable power with a flow of 5 liters per second. Flow is measured during the dry season to ensure year-round operation. The minimum flow for a practical system is 2 to 5 liters per second.