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Ed, P.E.
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17 Ft hole, grid synchro
Ed, P.E.   11/17/2011 1:48:46 PM
I caught that they dug a 17-Ft hole, and combined with the 10 Ft drop they mentioned, there could be a roughly 25-Ft head of water with the turbine down at the bottom of the hole.  About 12 PSI.  Also, induction motors, run as motors, turn at a slip frequency a bit slower than the 60 Hz driving them.  BUT, when you run them for a bit as a motor and they achieve near synchro speed, 1750 RPM or so, then try to spin the shaft faster than that, you will push power into the grid as a generator once you try to turn it faster than 1800 RPM.  The grid is bigger than the motor, so the grid prevents the motor from going as a generator faster than the 60 Hz grid frequency, but power will flow into the grid as you push harder.  This was a Motors Lab exercise we did at the University of Idaho back in the 70s.  Of course, if the grid drops, the motor will run overspeed because the hydro turbine wants to spin it faster than 1800 RPM, so the need for shutdown controls.  This project is a LOT of work, but very nice.  Here in  California, the utility companies might not accept a home-grown control system for Netmetering or grid-tie operation.  I have always wanted to do a hydro generator system, but here in the Mojave Desert, we have no water....

Ann R. Thryft
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Re: Probably Not Commercially Viable...
Ann R. Thryft   11/17/2011 12:53:07 PM
When I was wondering whether the creek in back of our house would support a system like this, even a very small one, I was also wondering about potential difficulties with local and state zoning requirements.

Anybody have any ideas? I know that in our area I found out we're a protected salmon run, so that tosses that idea out the window.

bob from maine
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Payback for low-head hydro
bob from maine   11/17/2011 12:51:54 PM
My 20 year old analysys of low-head hyrdo didn't come up with a service period that equalled or exceeded the payback. Power companies are notably fickle about allowing any frequency other than 60HZ, so generating AC, converting to DC, then back to 220VAC/60.00HZ was a significant expense. Older turbine water wheels had adjustable 'vanes' that kept speed constant independant of load but their accuracy was unacceptable; most newer wheels use a 'throttle' plate to control input flow which greatly reduces the efficiency of the set-up, though if flow can be held constant, speed can be controlled varying the field to control load.  Finding and rehabing a hundred year old bronze 20-50HP turbine was the best economic solution, though these are few and far between. In Maine, fish are more important than electricity, so we're tearing down 100 year old hydro dams in hopes there is a 100 year old salmon who may want to come home to spawn. Several of my fellow hyrdo co-conspirators genrate DC and use that to run resistive heat, controlling indoor temperature by opening or closing windows. Assuming you own a dam which will supply minimum flow, can find an old turbine wheel, can cludge-up the necessary controlls to meet the grid requirements, can meet the environmental concerns, can do most of the labor yourself, you still have to be aware that the government in all its wisdom will change the rules and remove the requirement that the power company must pay you at their 'cogeneration' rate, rather than some other contrived rate. Like electric cars, the analysis of the economics for hydro power is more emotional than economic. I congratulate the writer on an apparent successful installatioin, other than the typo of water flow, the research looks good, though I don't see how he controlls frequency to meet the grid requirements.

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Re: lets check the math
Sport   11/17/2011 12:09:35 PM
Indeed.  I did a quick check. First, I assume the typo of minutes vs. seconds. 2 gallons per sec is about 16 pounds per sec over a 2 ft drop is 32 pound-ft/sec is about 43 watts at near 100% efficiency.

The basic premis is all wrong.  You can't do a whole lot with 40W but it might be better than nothing in some circumstances.

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Re: The numbers don't add up;
David12345   11/17/2011 12:02:18 PM
I read the article as saying that technically you CAN generate electricity with as little as 2 gpm and only 2 feet of head.  This doesn't necessarily mean it is economically attractive, or even that much of a benefit.  I gather that in this application they have 10 feet of head and run close to 320 gpm, when generating 20KW.  It sounds like the lake does not always have enough flow to permit continuous generation at this rate. The use of three 15 HP motors is to adequately load the 50 HP turbine. 

This was an interesting article.  I have been very interested in low rise lakes for storing wind or solar photovoltaic energy.  When you have wind or sun, you can drive pumps to pump up to a reservoir/lake/tank from a lower lake or river. Then you can generate hydroelectric power when you need it, or when the peak load gives the best payback to feed the grid.  The "potential energy" of gravity on water may be more cost effective than batteries.

Larry J Manson
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lets check the math
Larry J Manson   11/17/2011 10:31:09 AM
40 cubic feet per second is 320 gallons per second.

This is 2,560 pounds per second, with a 10 food drop, that is 25,600 foot pounds per second or 34.7 killowatts.  If an efficiency is achieved of 57%, you have 20 kw.  

I have no concept of achievable efficiencies.

320 gallons per second and 10 foot drop is a far cry from the teaser of 2 gallons per minute and 2 foot drop.

2 gallons per minute with a 2 foot drop gives .72 watts prior to taking in account inefficiencies.  

Please let me know, if I am in error in this reasoning.

Despite these little physics differences, it is still a very interesting application.






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Re: Details on smaller application
BobGroh   11/17/2011 10:10:57 AM
If you are interested in small hydroelectric installations, spend some time on the internet and following some of the other links provided by the other post'ers (is that a word??). 

I did a short analyisis on a similar system for my brother who has a trout farm down south  - he has a fair amount of water flowing (the details are buried away someplace on this computer) and he thought that maybe he could make some money from that by selling (or at least 'replacing') electrical power.  Unfortunately, from the information I could find, the ROI was clearly NOT in his favor even for a mainly DYI system.

The author's system is impressive - very impressive.  But I doubt if it makes economic sense IMHO.

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Probably Not Commercially Viable...
dchristopherson   11/17/2011 9:59:58 AM
This is a great DIY project, but it probably doesn't scale well to similar sized commercial applications.  I'm thinking mainly because of labor costs involved.  It sounds like the two brothers did most of the work, with no costs associated with their time.  Labor costs alone can be a very significant cost in projects like this.  Many applications may also require the design services of professional engineers (structrual, electrical and mechanical), another significant cost. 

Incentives (and hardware requirements) vary from utility to utility, also.  Sounds like these guys got the best of both worlds...simple grid-tie in requirements and very attractive buy-back rates for surplus power.  In some areas its exactly opposite.  Very expensive equipment required for grid connection and buy back rates less than what you typically pay as a consumer.

And even a 100W generating system may require the same level of automation and control of this 20kW system.  This means that there is really no way for the 2 gpm / 2 ft. drop system to have ANY payback if you want to make it grid-connected.  But, if all you want is a stand alone system to charge up your cordless drill, you're off the races.  A simple water wheel and a DC motor will get you up and running without even needing a dam.

I don't mean to be a pessemist, but there are real technical and regulatory barriers to this kind of thing.  The real success story in this applciation is the amount of time and effort (the perspiration) that these two guys put into the job.  Kudos to them.

Ray Jorgenson
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Re: Micro
Ray Jorgenson   11/17/2011 9:50:11 AM
Home Power magazine has a wealth of information on small hydro plants, as well as PV and solar hot water. A mature & well respected magazine.    homepower.com

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Details on smaller application
mikec711   11/17/2011 9:34:16 AM
Still trying to understand the ROI if I do have a creek without that nice dam the guys had to work with.  Thanks to my beavers ... I've got some 3 foot drops (some of the year) and good volume (but not 40 cubic feet per second).  I also have an issue that the creek is a good distance from the house and/or grid.  Would love to see more detail from the perspective of implementation.

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