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Hydro John
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Posted: 01 November 2011 at 12:25am | IP Logged Quote Hydro John

Hi Everyone,

I am working on a micro hydro system. I am using a 60 series (36 poles) Fisher & Paykel motor as a generator and a home made pelton wheel that I made from pvc elbows. The F&P is turning about 285 rpm and producing 128v on each phase with a 13 watt light bulb wired into each phase. The system is about 400 feet from my house and I would like to be able to use this power in my home. I am new to all this and not sure where to go from here. I thought about hooking up a preheater to heat water, but don't know if it could be done with the 3 phase AC that the F&K produces. Also I thought about changing the AC to DC with 3 ph rectifier and charge a battery, but the DC voltage produced would be much higher than 12,24 or 48 volts. Could I charge a battery with high voltage DC? Any suggestions would be appreciated. I have read about all kinds of controlers, inverters, MPPTs and other electronic gadgets and now I am totally confused. Hope someone can steer me in the right direction. If anyone is interested, I will be glad to post some pictures, that is if I can figure out how to do it. Thanks



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BobMann
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Posted: 01 November 2011 at 12:53am | IP Logged Quote BobMann

Hello I can help you very easy here seeing you are in the USA.

I would keep the AC 3 phase all the way to the home 400 ft is far but will work.

You will need a controller and rectifier. I would then use a grid tie to help off set the home enegy bill.

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Hydro John
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Posted: 01 November 2011 at 1:04am | IP Logged Quote Hydro John

Hey Bob,

Thanks for the reply. I have a rectifier salvaged from a gm alternator. Would that be OK? What kind of controller would I need and will I be able to connect it directly to the grid through my home power panel? Hope I don't sound too dumb.
Thanks again,

John
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Don B
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Posted: 01 November 2011 at 6:30pm | IP Logged Quote Don B

Hi John,

A few comments that might help. First, Bob Mann is correct when he says that you should keep the feed to your house as 3 phase all the way to minimize voltage drop and losses.

I assume that the 128V that you are measuring is with the 13 Watt light globes connected? If you try to measure the Volts with no load then at all they will be much higher.

You could use the 3 phase supply to heat water, but you would then need 3 heater elements - one for each phase. Note also that a 117V (?) heater element will be a much greater load than your light bulbs, and may even stall the turbine.

If you want to rectify the three phases to DC then you will need a rectifier with 6 diodes. Each diode will have to have a voltage rating of probably around 200 Volts or better, and be suitable to carry the current involved, which will depend on what your turbine can do with a bigger load connected. Even so, even 1 Amp rated diodes would probably be adequate at the voltage that you are operating at.

I am not familiar with the GM alternator that you mention, but if it is an automotive type then the diodes would not be suitably voltage rated.

By the way, voltages of 128V at AC or DC can be deadly, so be very careful never to work on any wiring with the turbine operating.

If you do fit a rectifier, then you could use the resulting DC to heat water, and at least for that you would only need one element connected to the DC output.

If you want to look into things like a grid tie inverter, or charging batteries, then I strongly recommend that you talk to someone locally with some expertise in the matter.

Regards

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Posted: 01 November 2011 at 8:29pm | IP Logged Quote davef

Have you got an idea of what your head is and flowrate? IE, how much mechanical power you will be able to harness.

A test, is to rectify the 3 phase AC and place various loads on your system to determine where your maximum power point is. OR, you can load the system up with different wattage bulbs and record both the AC voltage and AC current. You can also tweak the rotor speed as well as how the stator is placed relative to the rotor (shimming the rotor). EcoInnovation NZ describes the procedures for these tests.

If you are running this unit at an appropriate speed, ie frequency, there is an option to use 3 toroidal transformers to get you down to a reasonable voltage before rectification.

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Hydro John
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Posted: 01 November 2011 at 9:19pm | IP Logged Quote Hydro John

Thanks everybody,

Penstock: 400 ' (buried 4" PVC)

Head: 20'

Flow: Minimum is about 50 gpm; Maximum is 300 gpm (depends on how much rain). Thinking about building a dam to give a constant flow and also increase head to 30'.

I have run several test with different bulbs hooked up to each phase of the 3 phase wild AC. The maximum without stalling is three 13 watt bulbs, one hooked to each phase. Any more begins to stall the turbine. The RPMs of the turbine is 285 RPMs loaded with the three 13 watt bulbs.

Yesterday, I hooked up the GM 3 ph rectifier. Recorded 390 DC volts with no load. I then connected a dead 12 battery. First recorded voltage was 12.1 volts. Subsequent readings continued to increase to 12.6 volts over about 30 min. I didn't really know what I was doing, so I terminated my test. Please let me know if I did anything right or if all was wrong.

I like the idea of using a water heating element, but the AC heating elements that I have access to would be too high wattage and would probably stall my turbine. I don't know about a DC element, are they available in low wattage or would that matter? I also like the idea of a grid tie inverter, but I don't have access to anyone with this expertise in my area. I have read EcoInnovation NZ article on tweaking turbine with washers, but I'm thinking I have other problems before I begin fine tuning. Maybe I'm wrong, don't know.

Two questions I have:

1. Can I charge a 12, 24 or 48 volt battery bank with the 390 volt DC produced by my turbine?
2. Can I hook my wild AC 3 phase to a grid tie inverter?

If either of these is possible, what do I need to do to accomplish my objective?

Thanks again




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Posted: 01 November 2011 at 10:14pm | IP Logged Quote Gizmo

Bob Mann would be the one to talk to here. He's got some very good figures using a F&P Smartdrive and a programmable grid tie inverter. With a hydro you should be able to reach 600 or more RPM, its wild AC, but the gridtie Bob used can harness that sort of power.

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BobMann
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Posted: 01 November 2011 at 10:55pm | IP Logged Quote BobMann

Gizmo wrote:
Bob Mann would be the one to talk to here. He's got some very good figures using a F&P Smartdrive and a programmable grid tie inverter. With a hydro you should be able to reach 600 or more RPM, its wild AC, but the gridtie Bob used can harness that sort of power.

Glenn

Thanks for the good words.
I will but a parts list up for him today.
I had talked of a Smart Controller Steve is working on. The bourds are on the way and parts list on order.
It will work here slike as S--t here is what it can do.
Real world testing using my Mann Smart Drive and Modifed blades will start next week at a few location.



I've just finished drawing the schematics for the MPPT and I wanted to list all the features and get some input before I start routing the board. I currently have 8 IO signals left over on the microcontroller so maybe someone can think of a good use .



MPPT Features



The MPPT controller board was designed for maximum flexibility. The board is very custimizable and can be used in many ways and it purchased in kit form or bare board, the user can make decisions about the input range, output range, on board memory, etc.

Power Input: The on board 3 phase rectifier uses 6 15A 600v diodes that have only a 1v drop at 10 amps. This means the capacity of the rectifier as a whole is around 45 amps. The user can substitue in other diodes (for instance lower voltage and more current) as long as they are in the TO-220 package. The rectifier also contains a circuit that lets the microcontroller count AC pulses as a way to measure actual turbine RPMs. If the user doesn't want to use the on board rectifier, DC power can be brought in through another connecton. The disadvantage of this is there is no way to count RPMs.



The CPU and other electronics on the board are powered by a power supply that can run on 10 600v, from either the output or from the input. In battery charging systems this will allow the controller to stay alive even with no wind. The power usage should be less than 5 watts or 83 milliams.



The CPU is a 40 Mhz Pic microcontroller with USB interface, PWM outputs, 8 analog inputs, etc. The firmware in the microcontroller will be flash programmable via the USB interface so people can flash in updates or their own firmware.



The USB interface goes through a chip that isolates the ground of the controller and the ground of your computer by up to 2500 volts. This will prevent damage to your computer if your turbine ground is floating. [However there is still danger to you, if you let that happen.] The interface will be USB2.0.



The power switching can handle up to 600v on the input and 60 amps. (Based on the size of 3 transistors.) Three transistors are used in parallel, and if your turbine puts out less current, some of the transistors can be left off the board to save money. The output can also go up to 600v, but this circuit can only convert voltages downward, not boost them up.

The switching circuit uses synchronous rectification, which means instead of a diode completing the circuit when the inductor is providing current, some transistors are turned on instead so there is less of a voltage drop and more efficiency. Again 3 transistors are used for this purpose and some can be left off for lower current applications. In an emergency both sets of transistors can be turned on at the same time, and the turbine will be shorted making it stop.

There are analog circuits to monitor input voltage, input current, output voltage and output current. The stock configuration will read voltages up to 400v and currents to 60a, but I will include a spread sheet that will help you tune these inputs for lower voltage or current applications by changing some resistor values. These inputs go into a 10 bit A/D converter so there are 1024 levels. If the range is 400v then the resolution is 0.4 volts. If you tun it down to 50 volts the resolution will be .05 volts.

There is an input on the board for an anemometer that closes a connection as it rotates. This can be used to log wind speed with the other data.

There are 6 locations for memory chips. These can either be populated with 4Mx8 flash or 16Kx8 ram. The flash is permament but slow. Flash can also only be rewritten about 10000 times. The RAM is fast but forgets when power goes off. Chips can be mixed and matched as needed.

There are 2 LEDs on the board, but I have 8 spare IO on the processor so I may add a few more LEDs for status displays, etc.

There are 3 off board components. These are the input cap, the inductor, and the output cap. Depending on the user's turbine, these can range from fairly small and inexpensive components, to large expensive components. I could not come up with selections that would please everyone. With high current inputs the input cap can have a large effect on board efficiency. I will provide a spread sheet that will help with the selection of these components.

I have only thought about the firmware and haven't written anything yet but I'm thinking that the controller could learn about the turbine through trial and error and record it's experiences in the RAM, then as it gets more data is can use that information to peak power track. This board should be able to be programmed as a battery charge controller or as a board to drive a low cost GTI.

I'm thinking that the firmware, and any associated software will be open source with the GNU license. That way people can modify it as needed. Also the software's interface to the board will be documented.

=========================================

If anyone has any comments or suggested features, now is the time to let me know, before I start routing the board.
Steve's infomation above.
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Posted: 01 November 2011 at 10:57pm | IP Logged Quote Gizmo

Hi Bob

I would post the MPPT stuff on a new thread to keep this one on topic.

Glenn

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Hydro John
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Posted: 02 November 2011 at 4:14am | IP Logged Quote Hydro John



Hey everybody,

Thanks so much for all the info. I am very anxious to see the parts list from Bob. In the mean time I am going to try to attach some pictures of my Micro Hydro. It's pretty crude now, but hope to make improvements as the projects proceeds.


GM 3Ph rectifier



F&P generator mounted in plywood box. Used bottom of washing machine for bearing mount.



Home made pelton wheel. The nozzle is 3/4" hole drilled in a 1" PVC cap. I used 1" PVC elbows for cups and 1/8" aluminum (salvaged from old highway sign)for wheel. Aluminum wheel is 10" dia and total outside dia is 13 1/4". I'm sure a pelton wheel from EcoInnovation would be much more efficient.



Another photo of pelton wheel. The cups are glued together and attached to the wheel with rivets.


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Posted: 02 November 2011 at 6:56pm | IP Logged Quote davef

Your head 7 metres and flowrate about 4 litres per second.

7m * 4L/s * 9.81m/s squared * 50% = 140 Watts. Your penstock losses are quite small with that size of pipe. As you are getting something like 3 * 13 = 39Watts, there should be some optimisation opportunities.


Two questions I have:

1. Can I charge a 12, 24 or 48 volt battery bank with the 390 volt DC produced by my turbine?
2. Can I hook my wild AC 3 phase to a grid tie inverter?


1. I wouldn't do that. To get maximum power out of the system you want to make some attempt at "matching" the source to the load. Or you waste power in the generator internal impedance, which gets dissipated as heat.

2. I wouldn't even consider this as this power level. Also you are not generating 3 phase AC at the power line frequency, so some "conversion" would be necessary.

I would suggest reading about rotor sizing, rotor speed and nozzle sizing. If you search carefully on the EcoInnovation site you should find quite a bit of free information.

Increasing the head another 10' is a good move, a 30% increase in power. If the minimum flowrate is 50gpm, unless you have a lot of storage you are not going to get much more than 50gpm. A days storage at 50gpm = 72,000 gallons, etc.

Neat idea for the buckets!

Good luck,
Dave
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Posted: 02 November 2011 at 8:11pm | IP Logged Quote Don B

Hi again John,

I would like to endorse Dave's remarks - particularly about rotor sizing, speed, and nozzle sizing. It really is worth doing a little research here.

While your Pelton wheel buckets look well done, it seems that your turbine diameter was dictated by the size of the piece of aluminium that you had to hand. If you could make your turbine diameter larger, then you would get more torque, although this may be at the cost of the turbine (and hence the alternator) speed.

The nozzle is also worth more experiment. Your nozzle appears to be something that would be quite hydraulically "lossy", and you might well be able to gain some significant performance improvement by re-designing it. The best nozzles are more like a needle valve, with a tapered (ie venturi like) transition between the penstock diameter and the nozzle diameter, ideally with a central "needle" for adjustment and throttling.

If you look at an adjustable garden hose nozzle, you will get some idea of shapes that are reasonably efficient. Just improving the characteristics of your nozzle may well give you a substantial performance increase without doing anything else.

One further comment from one of your earlier posts. There is no such thing as an AC or a DC heating element - it does not matter whether the current is AC or DC - it heats them just the same. Ohms law is the operative principle here.

Note though that most heating elements would be of the order of 1,000 Watts or more so that, even if you find one with, say, a 220 Volt or higher voltage rating, the load on your turbine with one of these fed with DC would be way higher than the present 39 Watts worth of lamps that you are running.

Regards

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