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Small-Scale Hydroelectric Generator
Micro-hydro Basics
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| Canada and many other countries depend on large-scale hydro developments for electricity.
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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.
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| Micro-hydro systems can provide clean, environmentally friendly electricity in rural communities.
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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 flowing 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."
In this activity, you will use plastic spoons to build a model of a simple micro-hydro system. It generates surprising amounts of electricity, provided you have 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.
Making electricity
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| The completed micro-hydro turbine.
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We are surrounded by hundreds of appliances that use electricity to do work. But what is electricity? Basically, electricity is a flow of electrons in a metal wire, or some other conductor. Electrons are tiny particles found inside atoms, one of the basic building blocks of all matter. We call the
flow of electrons through any conductor a "current of electricity."
Each electron carries a tiny negative charge. When electrons move through a conductor, they produce an invisible field of magnetic force, similar to that found around a magnet. The strength of that field depends on how many electrons are in motion. You can concentrate this field by winding the wire
in which the electrons move into a tight coil with many turns. This causes many more electrons to be in motion in a small space, resulting in a stronger field. If you then place a piece of iron in the middle of the coil, the electromagnetic field will turn the iron into a powerful magnet.
While it is true that electrons moving through a conductor produce a magnetic field, the reverse is also true. You can make electrons move in a wire by "pushing" them with a moving magnet, which is how an electrical generator works. Electrical generators usually contain powerful magnets that rotate
very close to dense coils of insulated wire. The coils develop a flow of electrons that becomes an electrical current when the generator is connected to an electric circuit.
You will be building an electrical generator as part of this project. It uses moving magnets to create a current of electricity in coils of wire. This generator is technically called an alternator because the electrons move back and forth in the wire, rather than flowing in just one direction as
they do from a battery. A meter connected to the wire would show that the charge of the wire switches or alternates between positive and negative as the electrons change directions. Such an electrical current is called alternating current or AC. Household electrical current is alternating current.
Appliances have to be specially designed to use it. The other type of current is called direct current, because the electrons move in one direction only. Most battery-powered appliances such as calculators and portable CD players use direct current.
Safety Precautions
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Electric drills can cause serious eye and hand injuries. Eye protection is required, and leather gloves are recommended when drilling small parts such as corks. A cork borer can be used as a substitute but it also has risks for injury.
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Hot glue guns can cause superficial burns. Be sure glue guns are warmed up only when needed, and unplugged immediately after. Hot glue can stick to skin and clothing.
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Utility knives can be hazardous. Expose only as much blade as you need to cut the material, and fully retract the blade when not it's not in use.
Build It!
(Click to continue to the construction plans)
Test It!
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The Pembina Institute
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If all has gone well with your construction, this turbine should be able to produce significant amounts of electricity, depending on the speed of the water striking the spoons.
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Place the neck of the plastic container under a faucet and turn on the water. The rotor should spin quickly!
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Connect your micro-hydro turbine to a multi-meter and set the dial to read volts of alternating current. Measure the voltage generated by the operating turbine.
- Questions
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What variables in a micro-hydro system could you change to get more electricity from it?
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In what locations in Canada or other parts of the world would micro hydro be a good choice for clean energy?
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What practical problems would you encounter in setting up and running a micro-hydro system in a rural area ?
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Why are micro-hydro systems seen as better for the environment compared with large-scale dams?
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Use the Internet to locate distributors and manufacturers of micro-hydroelectric components. Use the search terms "micro-hydro", "pelton wheel", and "run of stream."
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