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Electricity you can make at home? It's not so hard to imagine. You can tap the gravity of almost any body of running water and turn it into hydropower.
Different kinds of turbines exist for different water conditions. The flow rate, the density of the water, the head—or height of the drop (if there is one)—and the acceleration of gravity all factor into the generation of power from a turbine. So maximizing the power available from a water flow is just about getting the appropriate turbine to match these conditions.
For example, a high head turbine, often an impulse turbine, operates in open air, and uses a nozzle to convert low-velocity water into a high-speed jet. The nozzle is aimed so that the water hits the blades with maximum force, and then exits the turbine—power generated—the same as it entered, only with diminished energy.
A low head turbine, often a reaction turbine, can be used even where water is slow moving. These turbines are immersed in water and by using larger pipes and housed in larger casings, the turbines capture a greater amount of flow and thus maximize the amount of energy they are able to produce. Think of it like a boat propeller: the water hits the runner blades, causing the turbine rotor to rotate, in turn driving the electrical generator.
Minimal impact
At this point, the electricity is generated, the water has done its job, and exits through an opening at the bottom—this is the best part about hydropower is that it is a totally clean, renewable resource (provided we don't squander our water supplies in other ways, which is perhaps not a safe assumption).
Major hydropower projects that rely on dams are a different story: dams around the world have caused large-scale problems both socially and environmentally, as they disrupt ecosystems and displaced millions of people. But small turbines do not interrupt the flow of water and do not emit any pollution, and enough of them could contribute to a system of distributed power, which is a direction that some energy experts advocate we move toward.
There's also a "cross-flow turbine"—the recent turbine of choice for turbine the Planet Mechanics team. The cross-flow, according to the Energy Bible:
uses a drum shaped runner much like the wheel on an old paddle wheel steamboat. A vertical rectangular nozzle is used with this type of turbine to drive a jet of water along the full length of the runner. One advantage of this type of turbine is that it can be used in situations where you have significant flow but not enough head pressure to use a high head turbine.
Next home project?
So if you live near running water, even if it's a slow-moving stream, check out some turbine how-to guides online, maybe your next home project could be to generate your own electricity!
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