How do you get electricity from a spring?

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I received a letter from a reader today who asks:

“We have a spring with a stable 3 gpm flow and would like to use a paddle wheel to turn an 80 amp, single faze alternator, but we have a question on the gears. Does anyone know how to get the RPMs?”

Does anyone have any ideas? Is there something that would work better?

PS: I believe they’re totally off-grid.

-- Anne-marie (annemarie@tds.net), December 14, 2001

Answers

Anne Marie, first off, they will need to have a large amount of head (the elevation difference between their spring and the location of the alternator in order to generate enough power to be worth the effort.

Here's an equation which will help:

Head (feet) times flow (in gallons per minute) divided by 10 equals watts.

H = head (ft) Q = flow (gpm) W = power (watts)

H X Q ÷ 10 = W

Let's assume they have a head of 1000 feet, to make calculations simple. Then the equation gives you:

1000 X 3 ÷ 10 = W; watts equals 300.

Unfortunately, this assumes 100% efficiency, and a typical small hydro system is only 50-60%, I am told. So in this case, the actual power produced would be 150 to maybe 200 watts.

Hope this helps; the way to get the alternator was your question, though, and to do this, I advise a pelton wheel. Go to www.energyoutfitters.com and ask about a Harris Hydro setup.

No matter how much your friend may try to "gear up" this alternator, the laws of physics rule, and you CANNOT get more power out of water than the above equation calculates.

JOJ

-- joj (jump@off.c), December 14, 2001.


By the way, even if there is not enough head to generate "a lot" of power, hydro is still a very economical way to generate power. It will produce the power 24 hours per day, and does not generate less power early in the morning and late afternoon, as solar does. It's also typically way cheaper to set up than solar.

Why don't I have a 3 gpm spring? Dang!

-- joj (jump@off.c), December 14, 2001.


That's a REALLY useful amount of water on a small scale - over 4,000 gallons a day; but as joj said the energy content is likely to be effectively nil - just welling to the surface, or even if gushing out it's still going to be a thin gusher at about half a pint a second. I think they need to consider alternatives - wind-driven, solar. Heck, irrigate a market garden, and use the money to buy more solar panels; or bottle the water and sell it as spring water or mineral water. The prices people pay for bottled water it wouldn't take too many bottles to be a useful income supplement.

-- Don Armstrong (darmst@yahoo.com.au), December 14, 2001.

Anne-marie, I suspect about all you can do is give them an "A" for wishfull thinking!

Not enough flow/power to get an 80 amp alt up to any power producing speed. Gearing up--nope!

But.......If they were to think about a very small generator they might be able to get 10+ watts....don't laugh..remember this thing would be going 24/7......not much.....but a lot better nothing!

Let's all have a nice cool drink......of H2O.....

-- Jim-mi (hartalteng@voyager.net), December 14, 2001.


I assume the water flows downhill away from the spring?

There are two ways of getting sufficient head to produce useful power:

1: Run a pipe downhill from the spring until there is sufficient vertical seperation. A big diameter pipe is required to offset the evils of friction.

2: Run the water off in an as near to horizontal direction as possible until there is vertical seperation. This could be a ditch around a hill side or a wooden flume.

-- john hill (john@cnd.co.nz), December 14, 2001.



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