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If you have a creek or stream on your property that drops along its course, a microhydro system could be in your future. With the right circumstances, harnessing microhydro electricity is cheaper and more constant than either photovoltaic- or wind-powered electricity, partly because a source of flowing water is available 24/7, and not vulnerable to doldrums, clouds, or the number of daylight hours.

While a microhydro system requires a more hands-on approach than PV, it is often simpler for the system owner than harnessing wind. It can also be a great do-it-yourself project— if you have the appropriate knowledge and skills. Supplying debris-free water to the hydro turbine is the first critical step in developing a low-maintenance hydro system. This article will introduce you to several methods of constructing an intake to do just that. Keep an eye out for additional articles that will cover penstock (the pipeline to the turbine) design, and system wiring and transmission voltage considerations for high- and medium-head microhydro systems.

Creating a Diversion

If you follow a molecule of water through any high- or medium-head hydro-electric project, the first step is diverting it from its flowing source and into the penstock. A diversion can be a collection pond, a river-wide dam, or even a pile of rocks that backs up the water in a creek enough to cover an intake. A diversion can be simple or elaborate, inexpensive or costly—but it needs to suit your application in a mechanical sense and also in an ecological one—without disturbing fish or their habitat.

This article does not cover some aspects of water diversion, like dam or pond building, since their construction

A Coanda-effect hydro intake screen is great at keeping everything from fish to leaves out of the penstock.

is site specific and can be quite complex, usually requiring professional design and engineering. They also often require permission and permits from government agencies, such as your state's fish and game department, and may need to include mitigation measures to protect fish and other wildlife.

Any diversion and intake needs to be robust enough to withstand the worst that winter has to offer—or it should be removable or easy to repair. Creeks can roll boulders or float trees that can damage your intake and diversion significantly. Some creeks flow evenly year-round, while others may trickle in the summer and flood in the winter. Because every site is a little different, whatever intake method you choose will need to be adapted to work at your particular location.

An important job of an intake is to screen out rocks and other debris, 1/4-inch and larger, and anything that could lodge in the nozzles that direct the water stream onto the runner (the "wheel" in a turbine that is spun by the pressurized water). It also needs to keep out critters, like fish and other swimmers, and inhibit air bubbles from entering the pipe. For some turbine runners in high-head installations, it's also best to filter out the fines (very small particles). Included in this article are the most common intakes used for this class of hydro, with pros and cons for each. Costs will depend upon its size and the choice of materials.

Simple Pipe with Screen

Benefits: Inexpensive

Drawbacks: Requires frequent cleaning

The simplest microhydro diversions are variations of a screen-covered pipe stuck in a creek. However, they require frequent cleaning. During the first rains of the season in some locations, twice-daily cleanings may be necessary to remove leaves and debris from the screen.

If placed in the stream's direct flow, the intake should be situated at least 1 foot underwater for pipe diameters up to 4 inches. This can create cleaning issues, especially during high-water periods. Although most folks aren't interested in wading into icy waters to clean their intakes, on small creeks these diversions can be reasonably nuisance-free most of the year, and the needed materials are inexpensive. The simple screen can be used in many different situations.


Friction-fit for easy removal and cleaning

To Turbine

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1/4-inch mesh or smaller; stainless steel

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