With a quarter century of experience designing, installing and operating microhydroelectric projects, Scott Davis is exceedingly qualified to author a practical handbook for developing a small, residential-scale source of electricity from flowing water. 

Based in British Columbia, where he is co-founder of the renewable energy advocacy group Friends of Renewable Energy BC, Davis' case studies and advice on government regulations and incentives are largely centered on western Canada, but the basic principles of hydropower site assessment and the systems available for creating and storing power are applicable on almost any site that has flowing water.

"In a typical system, water leaves a stream through an intake ditch or canal," Davis explains. "Water is brought to the forebay, where intake screens remove debris that could clog the jets of the turbines. Water flows from the intake through the penstock to the turbine and generator unit, where power is generated. The power is transmitted to a battery/inverter subsystem near the point of use."

Davis' guide systematically explains how to assess your personal energy needs and then calculate a site's potential for meeting those needs. This is followed by an introduction to the various technologies now available for microhydro projects, advice on how to select the one most appropriate, instructions for getting the project started and, finally, some case studies.

Davis cautions his readers to be realistic about their expectations for microhydro. In most cases, for instance, residential microhydro is not going to provide enough power to heat a home through the winter. But it can probably keep the lights on and the laptop running and help cook a few meals.

"Good essential service (lights and music) for an off-grid household can be supplied, whether with wind, PV, or microhydro, or some combination, with a few dozen kilowatt hours per month. Prospective microhydro developers should realize what small levels of continuous power are actually required for a high level of service," Davis points out.

While the wind generators are subject to the whims of nature and solar systems depend on the clear light of day, microhydro power generation is generally constant, making it the world's largest -- and cleanest -- source of renewable energy.