Thursday, February 7, 2013

OK, You've measured head and flow, what's next?

Assuming you have some good figures for head and flow your next step should be penstock sizing. Go bigger when in doubt. The pipe doesn't cost much more compared to the labor.  If you had 200' of head, that's great, how long a pipe will you need? Have you measured the flow through a couple of seasons? If you email me some pictures with someone standing in the stream I can give you a ball park flow figure.  
Also check with local water resources authorities for flow data. Or take some rough seasonal measurements as explained on my blog. You'll want to size your power plant so that you will have enough water to run 95% of the time. This is why sometimes it is better to have two turbines of different sizes so when you don't have enough water to run the bigger unit you can at least make some power with the reduced water flow in the smaller unit. The head is constant, but the flow is the variable to be able to adapt to. The best way to adapt using a PaT is to have two.
Pump/motor working asTurbine/generator units are cheap and it is nice to have two PaTs in the powerhouse, one for low flow and one for high flow. It also gives you a backup power source incase of breakdown, maintenance or repairs.

Concentrate, and don't skimp, on the  intake structure, penstock and powerhouse first. If you run out of money with those three items, just get a split case pump on Ebay save the $9K to 12K you'd be paying for an 'engineered system'.  For this site you would be looking for a 3X4X12 with a 20 to 40 HP, 3 phase motor. An 'end suction' centrifugal pump will also work but is somewhat less robust. 

Here is a source of used steel pipe on my Blog.

How far a distance is your planned home from the planned powerhouse? I'm asking because most 3 phase motors can be set up for 480V so you can transmit power over longer distances with thinner wire and then using a step-down transformer at the house will give you better regulation plus the standard 240V/120V service.



Hi Rob,

firstly great informative blog.

I've got a little stream that has a an average of 5L/s flow rate fairly consistently each year.

The head can be as low as 60m or 1000m as the land is sloping in such a good way that it is very good to have a very high head system built for increased power.

I want to build a micro hydro system that would have sufficient power for 9 houses in my village using this little stream.

The approximate maximum distance the power has to travel from the turbine/generator is 3km.

This may be much to ask but I'm would really need an expert to help me out on this but I will just shoot anyway:
(1)what system would be suitable for a 5l/s flow rate and a 500m-1000m head?
(2) what size of pipe diameter do I need?

I hope you would have time to reply to me.

Thanks you.


Rob said...

Hi MS,

I will need more information to help you. How long is the pipe? You will want to maximize the head, so if you can get 1000m vertical how long a pipe will you need?
Please email me directly at