Freeze Resistant Rainwater Turbine

25 acre feet of water... is this the storage volume or discharge volume? Per year? Per day? 25 acre feet of water discharged at a regular rate over a year is about 120 ft³/hour.

What is the water head?

Offhand, this sounds like a non-starter.

25 acrefeet of water per year. The drop to the exit of the property is 20 feet. I'd have to run 300 ' of plastic trough.

Rainfall is highest in the spring and summer when I am out there, most years. Less rain is in the fall when it is too cool for me to be out there, anyway. Last week the farm pond was totally full. Some summers like last year are very dry, I can't expect much then. This year has been very wet, but I cant find statistics. Average was showing 50" rain per year in Charlestown 7 miles down the road. This year was way above average rainfall. 6 acres drain into the pond.

Those old wood wheels with the wooden troughs on grist mills look mighty freeze resistant, but the volume they use is much bigger.

It's hard to beat $400 per year .....anything you could build that would be reliable would be expensive...What about a generator? What is your power requirement?

As you described, it wouldn't run in winter anyway. If the hard freeze was going to blow the casing, then there wouldn't be water flow for your trickle chargers and such.

After the freeze, then there would be a significant time delay till the system flowed. As previously stated. "Sounds like a non starter."

The open top pelton wheel shown in his patent drawing might withstand a freeze. I'll look at doing that. I had seen a cone wheel (foucault? it was French) where water drained on it from the top, but making it was a problem. Pulling stainless steel sheet around into a cone to weld it would probably require a lot of fixturing and hydraulic or screw forces. Welding a steel sheet cone to a 2" stainless shaft would also be a real trick with a 240 amp welder. A pelton wheel could be made of steel pipe 6" long, and some sheet formed with my hydraulic bearing press. I might be able to roll 6" wide steel into a cylinder; I'm experimenting today with rolling bicycle fenders without a motor to drive the steel, just a plate with bearings mounted on shoulder bolts.

Losing power in the winter freeze is not a problem, I don't live out there. I can't afford to heat the drafty trailer, it was costing the previous owner $500 a month for heat and A?C. I do use power in the winter to charge tractor batteries, which can stand a month off without serious deterioration IMHO. I already bought a 200W solar panel which might provide enough trickle charge on winter days. A water wheel could be turned up to start the refrigerator when I am out there, then throttled back when only the fan and lights are running. No A/C is required out there.

Building the plastic trough would help preserve my limestone hill anyway, wheel or not. In the creek on the other side of the property the gulley is worn down 25' to the underlying shale rock.

A generator would just be stolen when I am not there. Hauling in fuel would be a nuisance, I ride out there on a bicycle, and don't use a car. Hauling fuel for the lawnmower is hard enough. The thieves took my jon-boat (which I never used), lantern, this fall the turkey roasting pot. They stole the wire out of the community center down the road. "Fortunately" my trailer has aluminum wire, which has reliability of connection problems but won't be stolen. A pelton wheel could be just too weird to steal, not to mention the location is 500' off the road. An old Ford alternator would also not be too much of a temptation. The wire, I could bury. I already have bought 700' of 12 ga underground burial 2+ground wire.

Somebody a couple of years ago was stealing $200 of electricity a month in January and February. I went out there in the winter, no sign of an inhabitant, like trash in the trailer. Somebody ice fishing with an extension cord and space heater, perhaps? The lawnmower shed is near the pond, with an electrical outlet. I shut the electricity off now in the cold months, pull the main breakers out of the panel, and hide them.

Thanks for reading and thinking.

I can think of a lot of things that are cup-shaped that you could attach to a wheel. PVC end caps would work but they are expensive.

_{Please, no jokes about cup-shaped things, I am already in trouble}

Go ye to the second hand store and find a suitable wheel maybe from a cart or tricycle etc.. Also find ye some spoons with suitable metal handles that can be twisted and screwed to the face of your found wheel with the business end configured suitably to catch water. I think you can fashion this to your needs.

We are working with a very small water volume. If the entire water volume is released steadily, freely, constantly, for 6 months instead of 12 months, he has about one quart of water (at about 10 psi) per minute.

A leaky toilet comes to mind, except more pressure.

A lesson learned Doorman, This would be on the scale of a gerbil exercise wheel.

25 acre feet = about 8,146,285 gallons. This is the quart?

Uh-oh...

Let's see... 25 acre-foot of water per year, 1,089,000 ft³.
(1,089,000/Yr) / 365 days / (24 hrs/day) = 124 ft³ /hr +/-. So...

Uh-oh... there aren't 7.48 ft³ in a gallon, are there? Other way 'round.

I divided instead of multiply... Steady state discharge is about 900 gallon/hr. or about 15 gal/minute.

That would be a leaky toilet indeed! Good catch.

Still not much to work with, but a LOT better that my previous wildly inaccurate statement.

15 US gal per minute is about 0.06 cubic metre per second. 20 ft drop is about 6 metres, or a pressure difference of around 60000N/m2. Multiply those together and apply a harvesting efficiency of, say, 30% gives an output of a kilowatt. At say 12p per kWh the savings to be made are around £1000 per year. You could justify spending no more than £3-4000 on capital equipment to achieve that saving.

Several key pieces of information were omitted in your project decription:

(1) Does the pond totally freeze, or just freeze over in winter?

(2) Do you have the capability of trenching in your supply pipe below the freeze line in the ground, and also burying the turbine below grade with insulating protection?

(3) 25 acre feet per year is 1,089,000 ft³/year, 6,783,202 gallons/year (774 gal/hr), 12.9 gpm. That volume over a 20 ft drop is capable of 35.9 ft-lb/sec, which is precisely 0.065 British Horsepower, . This is the average power your unit is capable of, specifically 49 Watt. Note that I did not factor in efficiency, which will be south of 80% for such a low head operation. You might be able to net 37 W electric for charging batteries.

My suggestion: bury the transfer pipe (and have the intake well below water level, with an inline strainer and valve for servicing). Keep all your equipment below freeze level and use the best available insulation practices. If you can, also install some vertical drill holes to circulate this water through (with minimal head loss obviously), in order to help raise the temperature above freezing in your turbine room. No guarantees, but it might just work.

A look at these figures may allow greater latitude http://www.wvu.edu/~exten/infores/pubs/ageng/epp13.pdf

Yes, if the source of rainfall results in a large inconsistency in flow rate, then the OP might want to consider increasing the storage capacity in some manner, but will still need a diversion channel during high flow periods, in which case, erosion of his land is still going to take place.