my parents have an old mill pond on their property with a pretty decent sized dam (about 10-12' tall i'm guessing). my dad has cleaned it up and the water has been running for several months now. a LOT of water moves past the dam and we're thinking it could generate a lot of power. i'm looking at websites about hydroelectric systems for use at home, but most are for streams that do not have dams. i have no clue how much water actually comes over (in gallons per min), but it's a lot. you could easily fill up a 5 gallon bucket in seconds. water falls over in several places, one of which is about 5' wide.

have any of you done this? my dad has all these [ridiculous] ideas for "going off the grid" and/or selling energy back to the grid, but this one seems more realistic.

i'm reading this right now http://www.eere.energy.gov/consumer/your_home/electricity/index.cfm/mytopic=11050

[Edited on July 21, 2008 at 3:24 PM. Reason : -now]

7/21/2008 3:21:43 PM

i think i really like your dad

[add to my topics]

7/21/2008 3:23:23 PM

Tell me the height differential and the flow rate and i can give you and idea of the kw you could make if any .

7/21/2008 3:25:25 PM

^^yeah, at first he wanted to run his car off of water, then when i convinced him it's not as easy as that scam website sounds, he decided he'd try it w/ the lawn mower first (which he still has not done). after that he wanted to build the segway knock-off somebody mentioned on here a few weeks ago ( http://tlb.org/scooter.html ). he hasn't done that either. he's also been obsessed w/ windmills lately too.

good ideas, not so great on the follow-through. this one, however, would save him money in the long run and possibly make money by selling back to the power company...so he's a little more motivated.

^i don't know the flow rate. how could i easily measure this?

[Edited on July 21, 2008 at 3:28 PM. Reason : -]

7/21/2008 3:27:24 PM

This should help a little in regards to finding out how much water is being dispersed/flow rate.

http://ecaaser3.ecaa.ntu.edu.tw/weifang/osu/Water%20Measurement%20Units%20and%20Conversion%20Factors.pdf

[Edited on July 21, 2008 at 3:29 PM. Reason : f]

7/21/2008 3:29:07 PM

this may be feasible, but yeah, you need some numbers to determine HOW feasible...don't count on selling power back...assume a 5-year investment, and set the goal of having broken even after those 5 years on reduced or non-existent power bills

7/21/2008 3:31:45 PM

^^that just explained the units used, doesn't really explain how to get those numbers.

7/21/2008 3:34:54 PM

find a bored grad/undergrad CHE student and they should be able to tell you how much power you could get with a few measurements

(not it)

7/21/2008 3:38:33 PM

does it just come out of a pipe where you could capture all of it with a barrel easily? If so just time how long it takes to fill up the barrel. then you would have gallons/min.

7/21/2008 3:40:57 PM

I have a friend who runs his house off of a waterfall, I think they generate like 2kwh. I can give you his email if you would like. I think he bought the turbines and built the rest himself (all the piping and storage and what not.)

7/21/2008 3:41:37 PM

the numbers you would need (going off the top of my head) would be height of the falling water, how far it falls, and the flow rate. to determine the flow rate you could time how long it takes to fill a bucket, get that into gallons per minute, and then multiply by the width of the waterway. That is, by a factor of how many buckets it would take to account for the width of the waterway.

that doesn't account for power lost due to lower efficiency of the turbine, friction, and all that other mess though.

7/21/2008 3:45:50 PM

^^^no, the water flows over a dam built in the 1740s with locally quarried granite block. the blocks are 3 cubic feet, and the dam is 3 blocks thick (of course they are somewhat irregular since it was 1740something). there is a smooth section of concrete that was added to maintain it as a dam when the old mill house was removed a LONG time ago. the entire length of the dam is about 30' ish. water spills over the middle and a couple of other spots.

^^sure, i'd love to get the email address from you.

[Edited on July 21, 2008 at 3:50 PM. Reason : ]

7/21/2008 3:47:23 PM

some pix of this would be good to see what's up

7/21/2008 3:54:36 PM

this is the best i can do for right now. i don't have any good pictures on my work computer.

this is a picture of a picture, taken when i went w/ my parents to look at the house while it was on the market. the picture is retarded, and it's not how it looks now, but if you look at the distance from the top of the water, to where the water level below, it is about twice that height irl (which is about 10-12'). in that picture, it looks like it's just stormed or something. the water depth on the low side now is about 2' and very fast.



here's another picture of a picture, taken one winter before my parents owned it


there were a bunch of limbs and a couple of trees blocking the middle section. while it still flowed over in that area, there is now more water channel through that section (by original design). i'll get some new pictures in the next day or so.

[Edited on July 21, 2008 at 4:06 PM. Reason : ]

7/21/2008 4:06:10 PM

so the top edge is ~smooth? what are the dimensions and the height of the water where it goes over the wall?

7/21/2008 4:06:10 PM

yes, smooth-ish. i'd say there's about 6-8" of water (height). as far as length, i'd guess about 4-5'.

yay for estimates!

[Edited on July 21, 2008 at 4:09 PM. Reason : ]

7/21/2008 4:08:38 PM

i've been wondering about something like this for a while too...

wouldn't it be best to put a sluice gate in?

7/21/2008 4:12:02 PM

wat ?

7/21/2008 4:14:31 PM

it channels the water like this:

http://www.craftskills.biz/hydro-cameroon.htm

you should go look at yates mill pond too, you might get some ideas; even if you don't, it's a cool place to walk around

[Edited on July 21, 2008 at 4:18 PM. Reason : &]

7/21/2008 4:16:38 PM

That looks like plenty of water to power more than one household. The problem is getting the pipes to bring the water to the generator without losing water pressure. Usually pipes are laid next to the dam through the earth, but loosening up the soil of an already built dam seems like a bad idea. If you are willing then you can drill a hole in the stone for the pipes. However, if none of this is good for you, then you can bury a siphone in the earth next to the dam just deep enough that it stays below the water surface at all times, but air could get trapped and cause inefficient water flow. Either way: the bigger the pipes the better.

7/21/2008 5:08:12 PM

that seems like a pretty convoluted way to go about it

7/21/2008 5:09:52 PM

use a weir formula to calculate Flow rate

http://streams.osu.edu/book/equation_pdf/Ch8-Equations.pdf#page=2

q=C*L*H^(2/3)

where q is flow rate (cfs), C is a coefficient, L is the length of the weir (ft), and H is the height of water flowing over it (ft).

That book linked above recommends a C of 3.1, Id say lower it some because the crest is so large on your weir and its irregular (increased friction).

Id estimate your flow rate to be q= 2.5* 5ft* (.5)^(2/3) = almost 8 cfs which I think is about 60 gal/sec

Thats definitely a pretty rough estimate b/c those weir formulas are usually used on a smaller manufactured weirs.

I guess that seems pretty reasonable (maybe?). No idea what to do to actually get that into KW

7/21/2008 5:39:53 PM

your friend the b equation

7/21/2008 6:00:30 PM

^^bingo, thats what i was getting at

Quote :

"what are the dimensions and the height of the water where it goes over the wall?"

7/21/2008 6:58:37 PM

You need a sluice and a pitchback or breastshot waterwheel.

[Edited on July 21, 2008 at 7:30 PM. Reason : ]

7/21/2008 7:07:15 PM

man this one of those things i should have remembered from my ME classes..i could find it but...fuck english units

7/21/2008 7:47:17 PM

or, just time how long it takes to fill a 5 gallon bucket, or something similar. do several trials. then just use the length of the weir to find the flowrate.

say a buck is one foot wide, and the weir is 30 ft wide. multiply whatever flowrate you get by 30 ft

the weir equation above works too, but estimating the head may be more difficult than just timing/filling a bucket. to get the head, H, you need to know the distance from the crest of the weir, to the water surface, a distance far enough away from the dam to be considered level.

as water flows over the weir, the flow changes from sub to super-critical flow, meaning an increase in velocity and a decrease in flow area (the height of water over the weir).

of course, if this change is very small, it won't matter, but I don't know what you're dealing with. I've seen some pretty small weirs have a pretty large water height drop though.

i just saw the pictures. seeing those, filling a bucket method may be ok, but you need to know what the average flow over the weir is like. such as, if it's intermediate, as shown in those pictures, then the effective length of the weir would be the length of the weir that is transporting water.

using the weir equation would be a good estimate, if you can get an accurate head (don't worry about the drop in the water surface if it's really small), but again, only use the wetted length of the weir.

[Edited on July 21, 2008 at 8:38 PM. Reason : .]

7/21/2008 8:24:54 PM

This type of power generation has been becoming quite popular in underdeveloped parts of the world and even in some industrialized countries.

Alternative Energy Japan - Micro & Mini Hydroelectric

Quote :

"Japan's Daily Yomiuri reports that small-scale hydroelectric power generation is quietly becoming a big thing, with small output generators being established near mountain streams or on public water supplies. On Yakushima island, a microhydroelectric power facility was installed by the Kamiyakucho municipal government at Shirotani-Unsuikyo gorge, a densely wooded mountain area. Water flows through two 524-meter-long pipes with a diameter of 7.5 centimeters, dropping 76 meters and turning a small turbine with a diameter of 26 centimeters. The system generates 4 kilowatts of electricity, which supplies energy for a mountain office and toilets for tourists. The New Energy and Industrial Technology Development Organization (NEDO) defines microhydroelectric power facilities as having a maximum output of 100 kilowatts or less, while those with a maximum output of up to 1,000 kilowatts are called mini-hydroelectric power facilities. Small-scale hydroelectric power plants have long been regarded as suitable for producing electricity in mountainous areas, but now they are increasingly used in cities as well. In April, the Kawasaki City waterworks department and Japan Natural Energy Co. jointly installed a microhydroelectric power generator on a water pipe between a water purification plant and a distribution reservoir in the city. The site exploits a 38-meter difference in altitude between the two water facilities to distribute tap water. A pipe between the two facilities had a bypass attached on which a power generator with an output of 170 kilowatts was installed. The electricity generated on the site is sold to Tokyo Electric Power Co. Since the system is installed on a pipe used for water for domestic use--water of fairly reliable quality--it generates electricity and is virtually maintenance free. The company is currently building three similar facilities in Gunma and other prefectures in Japan and is hoping to construct 30 such facilities in the next three years. Small-scale hydroelectric power generation is possible without seriously damaging the environment. For example, it can be done by using the natural features of a mountain stream or flow from an existing dam. NEDO decided to subsidize 28 small-to-medium scale hydroelectric power facilities. A Kansai region waterworks department managed to save millions of yen on its electricity bill by using hydro-power generated electricity to pump water to its customers. The geological and geographical features of Japan mean there are countless sites where hydroelectric energy could be harnessed."

http://alt-e.blogspot.com/2004_09_01_archive.html

7/22/2008 12:13:07 AM

just get your dad a hamster wheel and hook it to a generator

7/22/2008 7:25:59 AM

OTG!

7/22/2008 5:10:40 PM

Up in the NC mountains in Dillsboro there is a hotel / inn. http://www.dillsboroinn.com/ I stayed there once. There is a waterfall right near them and they have some sort of old mill that is connected to their place, and they use the hydroelectric power to run their stuff.

I met the owners a while back, a guy & his wife, you could actually try calling them and chatting; they were really nice.

7/22/2008 5:18:51 PM