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Overview: Micro Hydropower Hot

Most of the global hydro power that is used in the world is produced by large-scale hydroelectric plants. We see them as dams and are quite common place in countries with large water resources (Sweden, Egypt, Canada and so on). A lesser known technology, but a growing segment, is micro-hydro. It is much smaller in scale than its bigger brother.

Using micro-hydro systems have a minimal environmental impact, but are limited by the resource requirement. It is water specific. Unlike wind or sun that are omnipresent, with variation in intensity, water resource is either present or not with little variation. Another pro is that is affordable when compared to other small-scale renewable energy systems. The greatest advantage of micro-hydro is that it produces power continuously 24 hours a day, 7 days a week, making it incredibly predictable.

 

Micro-hydro functions through small turbines. Small turbines are turned by falling or moving water. The turning motion drives a generator which produces electricity. The turbines need two things to generate power: head and flow.

 

To measure head, you can gauge height difference just by observation. To accurately measure head, run a pipe between 2 people, with a pressure gauge on the bottom. Fill with water. Every 1 psi equals 2.31 feet. So take the gauge reading, multiply it by 2.31 feet/psi and you will get how many feet of head you have.

 

Measuring flow is even easier, take any size bucket and measure its capacity. In this example I will use a 5 litre bucket. Find a collection point and time how long it takes for the bucket to fill up.  Take the capacity and divide it by the time it took to collect (as a fraction of a minute). You will then get the flow in litres per minute. There are different methods for larger more complicated streams, there is the float method and a weir.

 

Every micro-hydro system has an intake, protected by a filter and silt trap. The intake has an input side which is the flow from the stream or dam and an output pipe which is known as the start of the penstock. Remember, larger flows require larger silt traps. The penstock delivers clean, pressurised water to a turbine. Flow through the penstock pipe is controlled by the nozzle size. Take the minimum flow of the stream and use half of the stream flow as a rule of thumb.

 

The potential power in watts is a tenth (an efficiency indicator) of the result of Net Head (feet) multiplied by the Flow (LPM).

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