Micro Hydro as a Renewable Energy Alternative

Even very small streams, given enough slope, can produce electricity. Mark Weber/age fotostock/Getty

Micro hydropower, or more simply micro hydro, is a form of electricity production done at a very small scale, using power from a stream. The output of a micro hydro system is generally below 100 kilowatts, enough to provide power to a home, farm, or even a small community.

Elements of a Micro Hydro System

  • Water Intake. A pipe collects stream water, sometimes in a natural pool or a very small reservoir. The intake pipe is located below the water surface to avoid collecting air and floating debris, and above the bottom to make sure it does not pull in sand or gravel.
  • Pipe. The water then is carried downhill in a pipe, or sometimes in an open flume. The power output of the system depends greatly on the head (the vertical distance between the intake and the turbine) and the flow (in gallons per minute) permitted by the pipe. These considerations limit the availability of this type of energy to those close to a stream with a minimum of water volume and a steep enough slope.
  • Turbine. The piped water then activates a turbine, which transforms the kinetic energy of the water into rotational energy transferred through a spinning shaft to a generator. Instead of a turbine, a simple electric pump with the flow reversed can be used.
  • Regulator, Converter. The electricity produced by the generator needs to be modulated correctly to be sent to a house and used by appliances.
  • Batteries. A battery bank can be used to store electricity.

Large, more complex systems can provide all the power needs of a modern home or business.

Comparatively tiny systems of a few kilowatts (termed “pico hydro”) use a small turbine and generator (sometimes even a used car alternator), and are increasingly used in developing countries to power a few lights or a radio for several homes.

Advantages of Micro Hydroelectricity

Micro hydro systems can be designed to have little impact on the environment compared to “big hydro”.

They do not produce greenhouse gases. They often require no reservoir, but if they do, it usually holds no more than a few cubic yards of water. When installed on a larger stream where fish might live, only a fraction of the water is diverted into the pipe, having little effect on the natural water flow provided it's not impeded by a dam. Whatever the size of the stream, the system needs to be designed with in mind the protection of aquatic life and ecological processes. In addition, in many jurisdictions permits are needed for any water diversion plans.

The advantages of micro hydro scale up with the size of a system. As head and flow increase, so does power output. However, environmental impacts worsen as well. Small public utilities-scale hydroelectric projects (a few megawatts in size) can have significant impacts on streams, and if the technology was used more extensively, the cumulative environmental damages would be large. When various-sized hydroelectric projects are compared, the per-kilowatt environmental costs might be in favor of one large project (hundreds or thousands of megawatts) compared to a series of smaller utilities-scale ones (1 to 20 megawatts).

Micro hydro is very different than utilities-scale hydro in its environmental impacts, but perhaps most importantly, it differs in how it makes users more mindful of the energy they use.

Just like adopters of residential solar or wind energy, homeowners who install micro hydro projects become more aware of their energy consumption and they prioritize their energy use in a way those of us relying on public utilities do not.  


SciDevNet. 2011. Small Hydro Could Add Up to Big Damage.

US Energy Department. Microhydropower Systems.