frictional losses anybody?

[Zero]

I've installed 150m of 2 inch / 50mm plastic pipe for my micro hydro project, I have about 80 foot/25m of head, if I add more pipe I can get more head but I'm sure I read somewhere that over a certain length the frictional losses add up to 100% and there is nothing more to be gained, can anybody tell me the losses for 2 inch pipe?

Ta,

Zero.

[John II]

Hi Zero: I think that one will also need to know your anticipated flow through your two inch pipe in "cubic feet per minute" in order to properly answer your question ?

Also I assume you are using plastic pipe ? It's friction head loss is less than metal pipe.

John II

[tinker]

Check here:  http://www.irrigationtutorial.com/polyloss.htm

[Ungrounded Lightning Rod]

Note that 1 PSI is 2.31 feet of head.  So at 80 feet of head you've got 34.63 at zero flow.  That's a lot, and with a 2" pipe you should get some decent flows.

492 feet is quite a bit, but let's see...  Run it at 50 GPM (the maximum recommended flow rate for 2" pipe).  34.63 - (4.92 * 1.98) = 24.89 PSI.  You'll only lose about 2/5 of your head.

Available power = flow (cu ft / sec) * head (feet) / 8.8.  (Neglects mill efficiency)

50. gpm * .13368 = 6.684 cfs.
    
24. 89 psi * 2.31 = 57.5 feet of head
    
57. 5 * 6.648 / 8.8 = 43.4 hp
    
43. 4 * 745.7 = 32,392 watts.
    
    

Even assuming only 66 percent efficiency for the mill and genny that's over 21 KILOwatts.  (There's a LOT of power in moving water.)  Even a "normal" city-dweller's energy-inefficient house tends to average a kilowatt or so.

So I don't think you need to run more pipe.  Even if you decide to go with electric heat in the winter.  B-)

Somebody want to check my numbers?

[LEXX]

That seems high but the numbers look right.  One question: Is this a year-round flowing stream?  If so it looks like your power and heating problems are gone!

[Zero]

Thanks for the help guys. It is plastic pipe I'm using.

Something I've never understood is this - is the 'flow rate' the flow thru the open pipe or thru the nozzle / turbine? if it's the latter how can you know this before you have it?

My stream flows all year round but drops down to around 20 gal/min in dry spells, so I'm building a small pelton wheel to run at that rate so it will run all year round, does that sound right?

How do I calculate the size of pelton runner and diameter of nozzle to get the best efficiency?

Ta,

Zero.

[Nando]

Zero:

You need to tell me what is the water usage you have now and the water usage you like to have with the additional head.

The losses depend on the water flow, and normally, the  best water flow is 2/3 of the static pressure.

Static Pressure for 25 meters is 35.5 PSI so 2 / 3 * 35.5 = 23.7 PSI which represents 16.7 meters head and the optimal velocity = sqroot( 2 * 16.7 * 9.81 ) = 17.5 meters / sec.

The maximum flow = PI * R^2 * Velocity = 3.14 * 0.025^2 * 17.5 m/s = 34 l/s

Now how much water are you using.

I have data for pressure drop based on l/s that can as well calculate the available power, though  not close to me, it may take a couple of days to get it.

If you need further assistance contact directly

Regards

Nando

nando37 at comcast dot net

[acowie]

Yes, but at 20 gallons per minute stream flow (1.5 litres/sec) it starts looking different. Assuming that for the sake of the environment you're only diverting 10% of the flow then you're down to .15 litre per second - at that rate with the head you've got then it's lightbulb material - fortunately it's 24/7 so if you learn to conserve, have a good battery bank, good controls then it all works. My hydro is a feed from a permanent creek which sometimes flow at such a rate that could flood an entire city. Fortunately, it's "normal" rate is about 20 litres /sec which affords a constant charging of my battery bank - with 80m of head it sure helps. Added to this I've got 2kW of solar panels, 1kw wind power, solar hot water system, and a battery bank that should have given me a hernia (dingy trips and uphill walks). After all this, people can still outstrip the system - the answer to all this and it's what most people should address first is CONSERVATION. It doesn't matter if it's your power, money, or so on - the message should be CONSERVATION. Think about what you really need to live on - basically if you strip out the rest and start from there it's not too much - the view from my place is great and doesn't rely on electricity! After haaving returned to New Zealand from Guangzhou in China lasst month it's good to see the star again.

Cheers - keep pumping outt clean power!