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Hello All
I'm very new to the whole area of back yard power generation, but as I typically do I've jumped in with both feet. I have a creek that runs year round at ~70-120 GPM. I have 120 ft of head with a pen stock of about 220ft of 2.5 inch PVC pipe. The penstock is connected with two 10mm nozzles and it acts on an 8 inch pelton wheel. I bought an F&P stator from Randy's Workshop (60s Fisher & Paykel motor) and rewired into a star configuration (as per his rewire diagram on his site).
Before I fitted the stator/magnetic rotor to the F&P shaft (i.e. with no load) the shaft spun at ~2000rpm with tons of torque. After I fitted the stator/magnetic rotor to the shaft and connected it to a nearly dead 110 amp hr 8D battery the rpm dropped off to 100rpm and is really hard to turn (I know there is a term for this “field…something”).
My question is:
1) I need to rewire the stator so that I am able to get the rpms up to a more efficient level (450 rpm I think is the target). Given I’ll likely be charging a four 8D bank (12 volt system….although I’m thinking of changing to a 24volt config) connected to pre hot water heater what rewire configuration is best for the stator…
2) Am I missing a piece of equipment that governs the draw on the gen?
As I said, I am really new to this so basic diagrams of a rewire would be great.
Thanks!
Nick
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:03pm 29 Mar 2013
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Try running the system with no load at 2,000 rpm and see what dc voltage you are getting.
It will probably be surprisingly high! (be careful).
That will also give us some idea of how to reconnect the windings to reach your target voltage, and 24v will run at lower current, and be more efficient in many ways.
By having less windings in series, and more in parallel, it will produce a lower output voltage and higher output current, and the speed will come up into a much more efficient operating range.
What you need to do is try several different combinations of connections experimentally to see which produces the highest wattage output.
This is well worth doing, because hydro systems generally run at a constant speed, and if you can optimise the coil connections, it is extra free power output. Cheers, Tony.
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 11:21pm 29 Mar 2013
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Best to decide if you want 12 or 24 volt system before rewiring the stator.
What is the present rewire you have, as i have no idea what "rewired into a star configuration (as per his rewire diagram on his site). " means (im to lazy to look it up)
Rather than spin it at 2000 rpm unloaded and work with high voltage, its far safer to use a calculator, connect your meter across the DC output best to add a capacitor of approx 1000uf across the DC output as well, as it will smooth out the meter readings.
Then spin the alternator by hand, its easy to spin at around 60 rpm (1 rev per second) we find it easy to dial in that rpm mentally with body movement, it dont need to be 100% accurate.
Then divide you meter voltage by 60 (rpm) to get volts per 1 revolution of the shaft.
Now work out what rpm will give you cutin voltage to the battery voltage used.
Perhaps the present stator wiring will better suit a 24v system.
Most information around on F&P rewires are for wind turbines and target a cutin speed of around 100 rpm, that's because wind is not a constant force and dont have the energy or torque of hydro.
Another test you can try is to back off the magnet hub, this simply means un-doing the nut that holds the hub to the shaft so it moves the magnets out away from the stator some, the less magnet area covering the stator the lower the output current and hence less loading on the alternator = higher rpm.
Its not the best solution, but a easy adjustment to let you get this working better until you decide on the rewire solution.
Your aim is to achieve cutin around the target rpm that produces the best torque, You quote @450 rpm, so if you look to a rewire for say 400 rpm cutin at X voltage, than 450 rpm should give reasonable power output.
Again it comes back to what cutin voltage do you want (12, 24v) as for the same stator rewire 12v will load (cutin) at around 1/2 the rpm of a 24v system.
Remember the above test/calculation to establish volts per rpm.
Pete.Sometimes it just works
Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566
Posted: 07:04pm 02 Apr 2013
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nicholasgeo;
Welcome to the forum.
Just a suggestion, The F&P alternator is a Low speed machine and will output its rated load at 1000 rpm easily.
It may be wise to use the turbine speed to double the torque input to the F&P Shaft.
A gear reduction box 2:1 Ratio or close. This would ease the load on the turbine.
I would love to have your Water source and Head, "What a setup"
--------------Cheers, RoeTime has proven that I am blind to the Obvious, some of the above may be True?
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:01pm 07 Apr 2013
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Roe has a point...
And increasing the diameter of your Pelton wheel may be a less troublesome alternative than a gearbox.Cheers, Tony.
jebz Regular Member Joined: 13/06/2011 Location: AustraliaPosts: 79
Posted: 03:49am 09 Apr 2013
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A MPPT battery charger can adjust the power drawn from the generator to maximise it's power delivery. A starting point can be obtained by using various dummy loads to plot the current and voltage outputs to obtain the maximum power attainable. For medium power testing light bulbs can be used in series and parallel to create many test loads.
Hello
Thanks for the many posts. I've been working away on the “Beta set-up” and adjusting nozzle types and recording the voltage. To date with my flow (60 gallons/ sec) with 120 ft. of head a 12mm nozzle works the best.
Thanks for the advice Pete aka “Downwind”
--I am getting 142 volts at 1amp. I’m using a barb type connector fitting for abs connections as the nozzels. Needless to say the aiming of the nozzles has been problematic and I need to make an adjuster fitting to “aim” the jet flow. Currently the jet is to high and I’m loosing about ¼ of the stream of water.
I settled on a 2 coils in series or “6X2C” rewire on the stator, this seems to work well for a high-speed 24-volt system. I’ve modified the weldment from Randy’s workshop to hold the pelton wheel shaft and generator and am using this with a water meter box with an 8inch pelton wheel (with no gearing). I was given 45, 100Ah 1.2-volt batteries NiCad batteries and am using them for my battery bank.
Thanks for the response “Jebz”
My past problems with charging the battery were due to the big draw on the Gen…therefore the battery was acting as an electromagnetic break…something I didn’t understand. Jebz, You suggest a MPPT to solve this problem. I’ve looked at them and they seem to be a bit pricey. Do you know of a lower cost unit or recommend a piece of equipment that will limit the “draw” on the generator? I guess like all the set-ups people have made I’ll have the highest draws during the waking hours and then low to no draw during the night. This will allow the battery bank to recharge during the night…well at least I hope. I was hoping to find a piece of equipment like a battery charger I use to charge a car battery….It produces either 2amps or 6 amps at 12 volts. Is there not something that will restrict the “draw” (in my case) to 24-volts at roughly 2.5 amps…Again, this may seem like a dim question, so excuse my ignorance.
Cheers, Nick
Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566
Posted: 07:17pm 14 Apr 2013
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nicholasgeo
Hi again;
You have the Potential of generating 35 Kw.
Your post states 60 Gal. Sec. with a Head of 120 Ft.
60 Gal of water weighs 498 US pounds. 52.17 Pounds Sq In.pressure at 120 Ft.
This is 25980 ft. pounds Sec.
33000 ft.pounds Minute is one Hp.
so 60 seconds at 25980 ft. lbs = 1558839 ft. pounds Minute / 33000 = 46.9 HP.
46.9 * 746 = 35000 watts.
It is difficult to offer meaningful advise, Your Nozzle size seems a bit small to pass 60 gal. a sec. and your 8" turbine is way too small for this water source.
If you are working with what you can afford then disregard the Rambling above.
Wire some of your coils parallel and omit connecting some of them to pick up the amps and drop the voltage. Keep at it, You will overcome.
----------Cheers. Roe Edited by Greenbelt 2013-04-17Time has proven that I am blind to the Obvious, some of the above may be True?
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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