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Problems with Preexisting Hydro | 14 comments (14 topical, editorial)
Re: Problems with Preexisting Hydro (3.00 / 0) (#1)
by chainsaw (madmax424@skybest.com) on Sun Apr 13th, 2008 at 04:47:56 PM MST
(User Info)

Curious why you are using a 24 volt alternator to charge a 12 volt bank. I think the efficiently would be greatly improved not to mention a reduction in wire size and a big reduction in wire loss from 12v to 24v. Running 12 volts 285 feet is going to be tough.

Have you considered using a PMA so as to take advantage of higher voltage for the transmission distance and reducing voltage at the battery bank?

Are you using a pelton or a turgo runner?



Re: Problems with Preexisting Hydro (3.00 / 0) (#2)
by Jonesy on Sun Apr 13th, 2008 at 05:17:50 PM MST
(User Info)

I don't know what the original intent was with the design.  I basically walked into a poorly designed system.  I definately understand the implications of trying to send 12 volts this distance.  But that's what was/is here.  
The alternator produces around 15 V in operation.

For my part, I was against the 600 dollar wire upgrade, in favor of a PM alternator producing higher voltage and a method of step down.  Which, it looks like is nescisary anyway.  But, now 24 volt transmission should be sufficient, as opposed to the 120 V I figured would be needed to overcome VD in the original wire.

The turbine is the standard harris pelton.  I don't understand what pitch diameter is, but it's about 5 inches total diameter.

[ Parent ]



Re: Problems with Preexisting Hydro (3.00 / 0) (#3)
by dbcollen on Sun Apr 13th, 2008 at 07:14:19 PM MST
(User Info)

The reason for the 24 volt stator is the alternator is only spinning 1300~ rpm at Vmp, 38 feet dynamic head is not very much for a pelton runner, it should work though. with 4, 1/2 inch nozzles you would be using 118Gpm, and assuming an 85% efficient runner and a 40% efficient alternator, you have 273 watts available. A standard Delco-Remy 10si alternator is usually 25-40% effecient in use as a hydro alternator, with a custom made permanent mag alternator being 45-65% effecient. In automotive use an alternator can see 50,000+ rpm and are way more efficient at high rpm, as the field current gets cut to near nothing. most people don't realize how fast an automotive alternator is designed to spin. The alternator on my Ford has a 2.5 inch pitch diameter pulley on the alternator (4.9 inch circumference) and an 8 inch pitch diameter pulley on the crank (50.25 inch circumference) the alternator spins aprox 10x the rpm of the crankshaft, and that motor sees 7000+ rpm, which means that alternator will spin 70,000+ rpm. so running a 12 volt alt at 1300 rpm is just barely above cut in, a 24 volt stator at 1300 rpm would be equivilent to running the 12 volt at stator at 2600 rpm, and would thus require less field current.

sorry for the rambling, but I hope this helps.

Dustin

Mad River Wind and Hydro
[ Parent ]



Re: Problems with Preexisting Hydro (3.00 / 0) (#4)
by Jonesy on Sun Apr 13th, 2008 at 07:46:12 PM MST
(User Info)

Dustin, all your numbers are the same I've found, and you confirmed my assumption as to the reason for the stator.  But, like I said we only see about 100 watts.  Could the minor turbine damage account for all that difference?

[ Parent ]


Re: Problems with Preexisting Hydro (3.00 / 0) (#5)
by dbcollen on Sun Apr 13th, 2008 at 08:56:32 PM MST
(User Info)

Pitch diameter is from the radius of the center of where the  jet of water strikes the cups times 2.

As to the low output, your alternator at that head is probably lucky to be 20% efficient, cutting the expected output to 150 watts or so. Try dialing the field current with the rheostat on the turbine housing, and I adjust my nozzles by unscrewing the nozzles and putting a piece of drillrod, or a drillbit through the nozzle hole and putting the nozzle back in and use the drillrod to see where the jet of water is aimed, it should hit the center of the cups, centered on the bifercation, and all the water should hit the cup, not go past on the outside. As I recall on the harris runner the water jet should be hitting either 2 or 3 cups ay a time. It sounds as if your runner may be worn out, if you can post a picture of your runner I can tell you if it is the problem, a picture from the nozzles view would be best.

Dustin
Mad River Wind and Hydro
[ Parent ]



Re: Problems with Preexisting Hydro (3.00 / 0) (#6)
by Flux on Mon Apr 14th, 2008 at 12:57:52 AM MST
(User Info)

Can't add a lot to what Dustin has covered.

I just want to confirm that you are using a rheostat not an internal regulator ( if that alternator is normally fitted with one). You need to strike a compromise between wasted field current and turbine speed.

Also we know that you have a 24v stator but we don't know if you have a 12v or 24v field. I suspect that with your line drop you would get enough field with the 24v rotor and have to waste less in a rheo and mismatched field winding.

The 24v stator running on 12v will not be very efficient. If you had means of measuring turbine speed I would be tempted to suggest that you try to get the speed up enough to try it at 24v ( not going to work if you have a 12v field without an electronic field regulator).

Flux

[ Parent ]



Re: Problems with Preexisting Hydro (3.00 / 0) (#8)
by dbcollen on Mon Apr 14th, 2008 at 10:27:40 AM MST
(User Info)

There is no way to increase the rpm without gaining more head, or getting a smaller diameter runner. He is running the hydro at 12 volts, so the 12v rotor is fine. Switching to the 24v stator is just like winding an axial for lower cut in. There will be more I^2r losses in the stator windings, but it should be far offset by the lowering of the field current at his low output. there is also the possibility of using an Mx-60 to find the max power point, but there is the problem of huge inductive surges with the wound field when the mx60 unloads the turbine. Those surges don't happen with a PM alt, the voltage just doubles as the rpm doubles. (pelton runners typically have their max power when the cups are at 50% of jet velocity)

Dustin
Mad River Wind and Hydro
[ Parent ]



Problems with Preexisting Hydro | 14 comments (14 topical, 0 editorial)

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