EERE: Energy Basics

Microhydropower

Microhydropower systems are small hydroelectric power systems of less than 100 kW used to produce mechanical energy or electricity for farms, ranches, homes, and villages.

How a Microhydropower System Works

All hydropower systems use the energy of flowing water to produce electricity or mechanical energy. Although there are several ways to harness moving water to produce energy, "run-of-the-river systems," which do not require large storage reservoirs, are most often used for microhydropower systems.

Illustration of an example microhydropower system. A river flows down from some hills. The river first flows through an intake, which is indicated as two white walls on each side of the river. The intake diverts water to a canal. From the canal, the water travels to a forebay, which looks like a white, rectangular, aboveground pool. A pipeline, called a penstock, extends from the forebay to a building, called the powerhouse. You can see inside the powerhouse, which contains a turbine and other electric generation equipment. The water flows in and out of the powerhouse, returning to the river. Power lines also extend from the powerhouse, along and through two electrical towers, to a house that sits near the river's edge.

For run-of-the-river microhydropower systems, a portion of a river's water is diverted to a water conveyance—a channel, pipeline, or pressurized pipeline (called a penstock)—that delivers it to a turbine or waterwheel. The moving water rotates the wheel or turbine, which spins a shaft. The motion of the shaft can be used for mechanical processes, such as pumping water, or it can be used to power an alternator or generator to generate electricity.

Microhydropower System Components

Run-of-the-river microhydropower systems consist of:

A water conveyance, which is a channel, pipeline, or pressurized pipeline (penstock) that delivers the water
A turbine, pump, or waterwheel, which transforms the energy of flowing water into rotational energy
An alternator or generator, which transforms the rotational energy into electricity
A regulator, which controls the generator
Wiring, which delivers the electricity.

Many systems also use an inverter to convert the low-voltage direct current (DC) electricity produced by the system into 120 or 240 V of alternating current (AC) electricity.

Commercially available turbines and generators are usually sold as a package. Do-it-yourself systems require careful matching of a generator with the turbine horsepower and speed.

Whether a microhydropower system will be grid-connected or stand-alone will determine its final balance of system components. For example, some stand-alone systems use batteries to store the electricity generated by the system. However, because hydropower resources tend to be more seasonal in nature than wind or solar resources, batteries may not always be practical. If batteries are used, they should be located as close to the turbine as possible because it is difficult to transmit low-voltage power over long distances.

Dams or diversion structures are rarely used in microhydropower projects. They are an added expense and require professional assistance from a civil engineer. In addition, dams increase the potential for environmental and maintenance problems.