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 alohaspirit 12-12-2009 12:27 AM

rain catchment + water turbine = Pico Hydro Power

a recent project in rain collection got me interested in Pico Hydro Power

it rained the other day and filled a 50 gallon drum in 10 minutes

so why not make some electricity too?

has anyone had any experience in this?

Pico hydro - Wikipedia, the free encyclopedia

Make: Online : Bucket-borne hydroelectric generator

 Piwoslaw 12-12-2009 03:25 PM

Unless you live in a place where it rains often, then this may not be cost-effective. The output would not be kilowatts, but only a few watts. How often does it pour, and for how long (answer may vary denpending on where you live)? Most rain is not more than a drizzle for hours at a time, and there is not much energy in a gutter that is just dripping, probably not enough to overcome internal friction. Collecting water on the roof until there is a certain amount and then letting it rush down onto the turbine may be better, but holding a ton of water on the roof isn't a good idea.

On the other hand, maybe there is a better way to it? Maybe a formula for how much power is to be had per roof area, where the inputs are volume of water per area unit per time unit (how intense) and head of water (height difference between roof and turbine). Very interesting... Now I have something to think about :)

 Bicycle Bob 12-12-2009 03:57 PM

It is pretty easy to calculate from gallons of water to pounds, and measure the vertical fall, etc, to get the potential HP (33,000 lb-ft per minute) and get from there to watts. One problem with tiny pelton wheels is that as you scale down, the boundary layer in the nozzle starts to dominate, and efficiency drops. I'm fond of systems with stored water and two ponds or tanks separated in elevation instead of a battery to store available wind power or whatever. However, for low-draw, on-demand generators, I think we will find that small, positive displacement diaphragm pumps will be very suitable, running backwards.

 alohaspirit 12-12-2009 06:36 PM

Quote:
 Originally Posted by Piwoslaw (Post 147004) Unless you live in a place where it rains often, then this may not be cost-effective. The output would not be kilowatts, but only a few watts. How often does it pour, and for how long (answer may vary denpending on where you live)? Most rain is not more than a drizzle for hours at a time, and there is not much energy in a gutter that is just dripping, probably not enough to overcome internal friction. Collecting water on the roof until there is a certain amount and then letting it rush down onto the turbine may be better, but holding a ton of water on the roof isn't a good idea.

thats kinda what i was thinking about

collecting water in tank/drums and once the level is high enough,
releasing a valve to push the water towards the turbine

it may only be for x amount of time, but its power

might be good when theres a flood and the power goes out

why dont water towers use these?

and it rains a lot in hawaii

The average annual rainfall over the entire state
is equivalent to 8,000 billion gallons of water

 Bicycle Bob 12-12-2009 07:05 PM

Water towers are only tall enough to generate the desired working pressure for sprinklers, etc. There would be no point in pumping water to a higher tower and then recovering some of the pump power with a turbine.

 alohaspirit 12-12-2009 08:05 PM

Quote:
 Originally Posted by Bicycle Bob (Post 147039) Water towers are only tall enough to generate the desired working pressure for sprinklers, etc. There would be no point in pumping water to a higher tower and then recovering some of the pump power with a turbine.
no pumps

i meant water reservoirs not filled through a pump

just by rainfall

 brucey 12-12-2009 08:28 PM

It's a neat idea but I feel like others have said, it's awful complicated set up with many moving parts (things to break). It can charge 11 cell phones which was the intended purpose I guess, but that's still only like 50 watts max. (Total guess there)

Thats almost a single light bulb and only during peak rainfall.

Wouldn't a solar cell phone be better? How big of a panel is necessary to get the 5V 0.7A necessary to charge a phone?

(3.5Watts)

 alohaspirit 12-12-2009 09:08 PM

i believe there are \$20 pico generators that have an output of 300-500 watts

 thatguitarguy 12-12-2009 10:16 PM

Believe it or not, in Colorado it's illegal to catch rainwater unless you have water rights, and hardly anyone in Colorado has the water rights to their own property. I know people who've gotten in trouble catching rainwater to water their horses and trees.

Water law in the west is complex, and mostly ridiculous.

 Christ 12-13-2009 12:33 AM

Hm... Seems like rain water isn't really property water until it reaches the property... so if you're catching it out of the air, and the water rights apply to water on the property, it's not really subject to water rights laws, eh?

I mean, unless Colorado's title laws allow land ownership to the area of the land deed, including area below ground and above ground, in which case, whoever owns the water rights to that property would still have property rights to the water falling from the sky.

However, if CO's deeds don't include the area above the land in their ownership (which must be in detail, of course), noone can say anything about capturing rain water, as ownership doesn't take place until it becomes property water.

Someone should look into that, really.

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