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DIY: Make Electricity Using Your Backyard Stream


Here’s a simplistic and yet encouraging way of making yourself a water powered power station, by using a stream in the back of your house. The idea is taken from an Off-Grid.net article. In fact, the idea is not new at all: even the Romans used it thousands of years ago to power their mechanical systems, that although being mechanical, were not primitive at all, and secured a pretty good level of comfort back then.

The main idea is simple: find yourself a river, make sure its falling abruptly enough to have the necessary speed and velocity to spin your turbine, and make the necessary piping and flow control system.

Mountainous and hilly sites are best suited for this type of renewable energy. The first parameter you have to take into account is the height from where you want your water to fall from. If it’s higher than 3m, you have a high head micro-hydroturbine. If it’s between 0.6 – 3m you have a low head hydroturbine. The first is to be preferred because the power of the stream needed is much reduced. High head hydroturbines compensate the lack of volume with the power of gravity.

You have to measure the size of your piping, and the water flow that comes to you from that stream. There are several methods for doing this, and I will quote Off-Grid.net here, because their explanation is the best (I couldn’t find a better one):

1. The bucket method which involves damming your stream to divert its flow into a bucket or container. The rate at which the container fills is the flow rate. If you used a 5 gallon bucket and it was filled in one minute then your flow rate would be 5 gallons a minute.

2. As long as the water isn’t fast flowing and/or over your calves you can use weighted-float method. This involves measuring the depths of the waterway across its width. To do this you will need: a helper, tape measure, yardstick, weighted-float (a plastic bottle halfway filled with water will do), stopwatch, and graph paper. Then to calculate the flow for a cross section of the waterway at its lowest water level you need to:

  1. Find the most uniform depth and straightest stretch of the waterway
  2. Measure the width of the waterway at the narrowest point
  3. Use the yardstick vertically to measure the depth at 1ft increments. You may wish to use a string stretched across to mark the increments.
  4. Plot the measurements on the paper to give you a cross section diagram of the waterway
  5. Calculate the area of each section by determining the areas of the rectangles (area = length i— width) and right triangles (area = ½ base i— height) in each section
  6. From the section you measured mark a point at least 20ft upstream
  7. From there release your weighted-float and time how long it takes to reach your measured part of the waterway. Be careful to not let the weighted-float drag on the streambed at anytime.
  8. To get your flow velocity divide the distance between the two points by the seconds it took the float to travel. Doing this multiple times and using the average will you give you a better measurement
  9. Multiply the velocity average by the cross-sectional area of the stream
  10. Finally you need to account for the roughness of the bed of the waterway. You will need to multiple the results by either 0.6, for many rough stones on the bottom, 0.7, for only small to medium stones on the bottom, or 0.8, for a smooth sandy type bottom.

Once you have the flow and head calculations you can estimate the power outage for a standard microhydropower system, which has about 53% efficiency. To do this you multiply the net head by the flow then divide by 10 to get the output in watts.

net head [(feet) i— flow (gpm)] i· 10 = W”

So, here it is! An electricity making system right out of your river’s stream! It has almost no impact on the environment, and it can free you from the grid partly or completely (depending on your needs and the water velocity).


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