I agree with Rob that for small systems it is much simpler and more reliable to regulate the power rather than the water flow. Most of these small systems will be used for battery charging, but the power may be delivered as AC at higher voltage. In such cases there is an easy way to regulate the system by putting the dump load across the AC line rather than the DC.
Rather than deal in general terms I'll explain how my recently modified system is set up. Power comes from the turbine driven induction motor as 3 phase AC at about 167V. [A side note: It is at 167V because it then goes to 3 transformers setup as 240V (delta) primaries and 32V wye/star secondaries then to a 3 phase bridge rectifier with the output connected to a 48V (56V typical) battery bank. Unlike single phase, where the RMS voltage of the rectified sinewave DC output is exactly the same as the RMS AC input, in 3 phase the DC output voltage is 1.35 times the leg to leg AC voltage. So, the battery clamps the rectifier output to 48-56V depending on state of charge, which means the AC phase to phase input is ~52/1.35 = 38.6Vac, which means each of the transformer secondaries forming the wye/star is 38.6/sqrt(3) = 22.3Vac, that means the primaries are 240*22.3/32 = 167V. If I had used nominal 24V output transformers in wye to the 3 phase bridge, the primaries would run closer to the rated voltage. 24*1.35*sqrt(3) = 56.1V ] I used a solar charge controller, Morningstar TS-45 and configured it in diversion load mode with its inputs connected to the battery +/- and outputs connected to two resistors in series. These resistors can be relatively low wattage, sized for only 30-50mA. For example with 60V peak battery equalization voltage, split across two resistors 50mA*30V = 1.5W and 30V/0.05A = 600ohm. So you could go with two standard value 680 ohm or even 1k-ohm resistors rated at 5W or 10W connected in series and connected across the TS-45 load +/- terminals. Clearly this won't dissipate much power, but it does provide a 24-28Vdc signal between the load (-) terminal and the point between the two resistors which I use to fire AC solid state relays (SSRs). If you have a 12 or 24V battery bank you can fire the 3-32Vdc triggered type AC SSR directly from the TS-45 output terminals. If you have higher than a 48V battery bank use more of the resistors in series and take the SSR trigger (+) signal from the opposite lead of the resistor connected to the (-) terminal. Now, whenever the battery bank voltage is at the control limit, the TS-45 in trying to dump power actually just sends a signal to trigger the SSRs. The SSRs are connected to AC line voltage from the hydro on one side, and a load resistor on the other side. You can find these relays rated to 25A (using a heat sink) at 240V for about $20 each at most electrical supply places. I had previously used some old oven and drier heating elements, but they took up too much space on the wall. So I put three 300W 16ohm edgewound and enamel coated resistors in series across the 167V from the hydro. That will dump in my case ~580W, but it is easy enough to size these resistors to dump what power you need at the generator line voltage. I purchased the resistors from digikey.com The 300W version are $16.48 each, part number FVE-300-xx (xx is resistance in ohms from 0.5, 1.2, 2.0, 5.0, 8.0, 10, 12, 16, and 20). A larger 1000W resistor (black silicone finish rather than enamel coated) is available for $51.50 each, part number FSE1000-xxx (-.25, .50, 1.0, 3.5, 4.5, 10, 15). Both also have a mounting kit available. Of course if you have a useful AC load of appropriate power and voltage rating that can be connected and disconnected such as a water heater use it. So, in simple terms, the PV load controller senses battery voltage, triggers SSRs which connect an the AC diversion load across the lines from the hydro. Joe http://h-hydro.com --- In [email protected], [EMAIL PROTECTED] wrote: > > A quick general note regarding regulation. It is my experience that in smaller > systems regulation is best done at the electrical output end rather then water > intake end. A power diverter using IGBT or TRIAC power elements, or even > relays, is by far the cheapest and most reliable way to govern the output of < > 5 kilowatt output systems. In the < 100 volt range these units are available > off the shelf from many vendors, while the 120V and up systems are more costly > and somewhat harder to to source. At the end of the day they are still a better > investment if only for the reason that you might still want one even with a > water flow diverter installed, in case the valve sticks open. > > Rob > > > > Quoting tom kasmer <[EMAIL PROTECTED]>: > > > > > > > > > > > > > > > using a PM motor as a generator has the following > > > > tenet. It has > > > > no regulation mechanism other than shaft speed, so > > > > here's what I suggest. You could rig up a smart bypass > > > > of the flow to regulate the speed so as to regulate > > > > the output power. Im sure that a magnetically coupled > > > > rotor excitation will indeed be expensive. > > > > Having a lot of experience in the fields of > > > > electricity and magnetism, unless this fancy generator > > > > has a few successful years > > > > of use in the field, I would stay away from it. You > > > > will have little or no recourse if it fails since is > > > > not in a car. Tom > > > > > > > > --- williameverettstone <[EMAIL PROTECTED]> wrote: > > > > > > > > > Thanks for the reply. > > > > > > > > > > 50gpm is the minimum flow even in times of drought. > > > > > > > > > > Several formulas on the net showed we could expect > > > > > to produce about 20 > > > > > watts w/ 50gpm and 4-5' head. This equates to 1.6 > > > > > amps at 12 volts. I > > > > > figured 1-1.5 just to be realistic. > > > > > > > > > > Thanks for the advice on PM motors, I'll check them > > > > > out. Since posting > > > > > I found that Delco has come out with brushless > > > > > alternators available > > > > > in 12, 24 and 48 volts. I'm waiting for a quote on > > > > > one now, rewound to > > > > > produce at lower RPM. I expect it's going to be too > > > > > pricey. > > > > > > > > > > Thanks again. > > > > > > > > > > > > > > > > > > > > --- In [email protected], tom kasmer > > > > > <[EMAIL PROTECTED]> wrote: > > > > > > > > > > > > > > > > > > my experience witn GM alternators is that the > > > > > brushes > > > > > > will last > > > > > > about 150,000 miles + or -. That is a half year of > > > > > > steady driving. The alternator is subjected to > > > > > > underhood temperature extreemes and wild > > > > > > accelerations. In an outdoor enclosed housing, > > > > > > running at a fairly constant speed, you might get > > > > > a > > > > > > year of 24/7. > > > > > > Your 1-1.5 amps sounds low. How did you get that > > > > > > number? As far as PM generators, any PM motor will > > > > > > work nicely as a generator. > > > > > > 4 feet of head is only 2 psi of pressure. How much > > > > > > total flow > > > > > > does the creek have worst case drought time? Is > > > > > that > > > > > > the 50 gpm number? If you are limited to this > > > > > level of > > > > > > power, that is about > > > > > > 20 watts best case with an automotive generator. > > > > > You > > > > > > might better spend your budget on a photovoltaic > > > > > array > > > > > > and settle for > > > > > > daylight only solar power with less hassle. Im not > > > > > an > > > > > > expert in microhydro power so others may do > > > > > better. > > > > > > Tom Kasmer > > > > > > > > > > > > --- williameverettstone <[EMAIL PROTECTED]> wrote: > > > > > > > > > > > > > Hi All, > > > > > > > I have a situation with minimum 50gpm flow year > > > > > > > round (I have been > > > > > > > measuring for 5 years, through drought and > > > > > different > > > > > > > seasons). > > > > > > > > > > > > > > My wife and I are planning to rebuild the > > > > > remnants > > > > > > > of a small dam on > > > > > > > the creek which would provide about 4' head. We > > > > > > > estimate we could > > > > > > > generate 1 to 1.5 amps here. > > > > > > > > > > > > > > We are on a budget, and a prebuilt micro hydro > > > > > unit > > > > > > > is out of the > > > > > > > question, at least the ones I've seen so far > > > > > ($1,000 > > > > > > > and up). > > > > > > > > > > > > > > If we were to use an off the shelf auto/truck > > > > > > > alternator w/ brushes, > > > > > > > how long can we expect the brushes to last > > > > > running > > > > > > > 24/7? Are PM > > > > > > > alternators available, and how pricey are they? > > > > > > > > > > > > > > My second dilemma is predicting the best turbine > > > > > > > type and size, and > > > > > > > pulley ratio to obtain the highest RPM at the > > > > > > > alternator with the > > > > > > > available water flow. Is there a method to help > > > > > make > > > > > > > these decisions? > > > > > > > If we fabricate some sort of squirrel cage type > > > > > > > turbine, how do I > > > > > > > decide the optimum radius of the unit? > > > > > > > > > > > > > > Thanks so much for any help! > > > > > > > Bill ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. 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