Wednesday, October 3, 2012

Micro-hydro Basics

large-scale hydro developments for electricity
Most machines that make electricity need some form of mechanical energy to get things started. Mechanical energy spins the generator to make the electricity. In the case of hydroelectricity, the mechanical energy comes from large volumes of falling water. For more than 100 years, the simplest way to produce the volumes of falling water needed to make electricity has been to build a dam. A dam stops the natural flow of a river, building up a deep reservoir behind it. However, large dams and reservoirs are not always appropriate, especially in the more ecologically sensitive areas of the planet.

Micro-hydro systems can provide clean,
environmentally friendly electricity in rural communities
For making small amounts of electricity without building a dam, the small-scale hydroelectric generator is often the best solution, especially where fast-flowing streams on steep slopes are close by. A small-scale hydro system usually consists of an enclosed water wheel or turbine, which is made to spin by jets of high velocity water. The water is taken from the stream and moved down slope to the turbine through a long pipe called a penstock. Water fl owing through the penstock picks up speed, and is directed at the blades of the turbine by nozzles. The turbine spins continuously, as long as there is water to drive it. The turbine is connected to an electrical generator, and the electricity is then available for running appliances or charging batteries. The spent water is returned to the stream. This kind of system is called a “micro-hydro” system, “run-of-stream hydro” or “low-impact hydro.”

The completed micro-hydro turbine.
In this activity, we will use plastic spoons to build a model of a simple micro-hydro system. It generates surprising amounts of electricity, provided us a supply of pressurized water, such as from a lab sink. This model closely resembles real micro-hydro designs, and can produce enough electricity to light a small light bulb.

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