Renewable Energy Information

 

Micro HydroMicro Hydro

If you are lucky enough to have a permanent stream, creek or river nearby, micro hydro may solve some or all of your power needs. The power of falling water was the first means of generating commercial electricity and is still a very viable method of generation. Before you consider micro hydro here are some facts.

The power you will get from a hydro electric plant is directly proportional to three things, these are head and flow and friction loss.

Head: The height of the water source that is providing the water above the location of the generator. You must get this totally clear. This is the height where the water comes from before it begins its journey to the turbine. This height cannot be changed by re-routing pipe, changing pipe length, doing dances in circles or getting your mother in law to help. Head is related to gravity and cannot be changed! Head is simply the vertical distance between the water supply surface and the outlet that lets water into the micro hydro.

Flow: This is the amount of water available to do the work of generating the power. You will either need vast amounts of water falling a short distance or a lesser amount falling from a big height or something in between to get power from a micro hydro.

Friction loss: The amount of loss due to friction inside a pipe is considerable. Friction loss is calculated using a friction loss table and taking into consideration the length, flow, diameter and construction of the pipe. The results are given in head loss. An example of friction loss is on my micro hydro plant. This micro hydro has a 60 metre head, a 600 metre, 50 mm polyethylene drive pipe and the flow at the plant is 2 litre's per second. The head loss is around 12 metres so I have an effective head at my micro hydro is 48 metres

Measuring Head

This cannot be guessed. You can survey the distance and slope using a level and measuring tape, you can possibly use a GPS unit for larger falls or you can install a pipe, get water flowing down it, seal if off and measure the static water pressure in the pipe.

Measuring Flow

Use a bucket or other measuring device and a stop watch.

Calculating friction loss

To calculate friction loss you will need some friction loss data. This is available from pipe manufacturers, plumbers and online. Copyright prevents me providing this data here.

Calculating power available

Nothing magic here, power from falling water has energy due to gravity and it can be calculated in watts. The (metric) formula is: Head x Flow x Gravity

Head: In the example above we had an head of 60 metres, reduced to 48 metres when pipe friction loss was taken into consideration.

Flow: In the above example we had a flow of 2 litre's per second arriving at my micro hydro.

Gravity: This is the acceleration due to the earths gravitational field and is 9.81 metres per second per second. Use 9.81

Back to my micro hydro where we have a head of 48 metres, a flow of 2 litre's per second and gravity of 9.81. 48 x 2 x 9.81 = 942 watts.

But of course, 942 watts of water energy will not provide 942 watts of electricity because it needs converting into electricity via a micro hydro turbine. The conversion is at best around 50%.

942 x 50% = 471 watts and this is about what I get. This is heaps of electricity and would more than meet all my needs except for the sad fact that the creek only flows for around 3 months of the year.

The final consideration with micro hydro

This of course is the environment. Nothing like messing with a water supply to raise the ire of neighbors, water police, greenies and tree huggers. The largest environmental protest ever staged in Australia was over hydro electricity and a dam on a river ...

This was the Gordon below Franklin dam blockade in 1981 - 1983 and it was successful. Work was halted and the Franklin and Lower Gordon Rivers are now part of the world heritage listed Wild Rivers National Park, located in Southwest Tasmania.