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several question for hydroelectric project

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Hi all, I'm new here and a novice at electronics. I'm looking for some help on a project that I "volunteered" for at my children's school. I of course want this to be safe and hopefully work, so I thought I would ask some experts.

I am working on a renewable electricity project for a class, and we have decided to do hydroelectric as we have a good source nearby. I have worked on the basics of the project and have a steady water power source.

My thought is to use a DC motor (perm mag) to charge a set of batteries. Here are my initial thoughts of what I need.

I am able to change any of these items as I have not actually started purchasing any of this material yet. Of course, price is a factor as we have a limited budget and I can only chip in so much to the overall project.

This is what I think I need in order to get this to work. Any feedback or noticing red flags that make this unsafe would be appreciated.

1) 12V DC motor _ Full Load Amps - 4.51 ( – Item # 3XE20)
Will be geared to spin at it 1725 RPMs (RPMs listed on motor when 12V is applied to it)

2) Diode between motor and battery to keep batteries from spinning motor
Question - size/type diode needed

3) Charge Controller to dump excess load when batteries are full
Question – recommendations? I am thinking of something like the Flexcharge 25 Ampere Alternative Energy Battery Charge Controller

4) Battery (or bank of batteries)
12V Deep Cycle (Golf Cart) AGM Battery
Specification/type of battery can be changed
Question – recommendations of type, size, AH of batteries to be used?

5) Inverter

So I hope that is enough information of what I think I should be using for this project. If anyone would be willing to help lead me in the right direction the kids and especially I would be quite appreciative.

The information you've provided doesn't seem too bad, though it may be worth checking now, whether you can actually get the motor spinning at 1,725rpm and producing 12V using your arrangement of gears etc.

The diode you use just needs to be rated for the voltage / current it'll operate at (I'd recommend at least a 25% margin of error though, to be on the safe side). Bear in mind the voltage drop of the diode also.

That's a pretty big battery, and it's 12V - unless you're confident you can generate well over 12V, it may be difficult to charge, especially with the voltage drop from the diode. Depending on how much current you can get from this source, 28AH may also be too high capacity to be worth using.

I don't know much about charge controllers so I can't help you there.

Why the inverter? What are you planning on powering from this supply? Is it going to be a substitute for a mains supply?
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To charge a 12 volt battery, you need to take it to 13.8 volts. This plus the diode drop, you are talking between 14 to 14.5 volts depending on the diode forward drop, check the datasheet. I would suggest a schottky diode.

Thus the motor would have to spin faster... assuming that the voltage change is linear with RPMs (no saturation effects), it would have to spin at

1725 * (14.5/12) = 2084 RPM
Just an idea: you will probably need a protection circuit for when it rains and the river swells up!

I hope the river is big because doing the math shows you will need a lot of torque to get the rotor spinning at desired speed :)
Do you have details of the water source? Like available height (top to bottom) and volume (Liters/Second). To give you a feeling for the numbers, if you have a waterfall of height 3M and 2Lt/S flow over it then the maximum power available (100% efficient) is MGH = Mass*Gravity*Height = 2*9.81*3 = ~60W. You'll be lucky to get 25% efficiency and so your output will be ~15W. Is your water source similar, smaller or bigger than the example.

Numbers and calculation off the top of my head and so could be completely wrong. :D

A lot of hydro hobbyests use the alternator and voltage regulator taken out of a scrap car to charge the battery. The alternator is relatively efficient at lower RPMs and can usually be directly attached to the axle of a pelton wheel or similar small turbine that spins at fairly low speeds. This kind of setup is quite simple, and all the electronics you need comes straight out of wrecked car, so should be cheap.
Indeed, your suggestion is a good one. Since a vehicle alternator has a variable field (which is controlled by the voltage regulator), it can maintain accurate voltage regulation over a very wide speed range.
Something that a permanent magnet DC motor won't do, as its output voltage will be proportional to the actual RPM, since the field is constant and fixed by the P.M.
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Hey everybody, thanks for the feedback. I just got the DC motor and will give it a try this weekend just to see what I get out of it. I think I know to not expect to much.

I also talked to my car mechanic and discussed using an alternator for this project. That does sound like a possibility since some of the new ones put out 14-15V and plenty of amps.

They said that the alternator can sense the voltage and stop charging if the battery gets up to the proper charge. I still have some investigating to do on this, but think this would be the way to go.

Does anyone know if there would be a need for a diode in this scenario of using an alternator? My understanding is that there could be one built into the alternator to keep power from flowing back.

I would think I would also not need the charge controller since that function would be built into the alternator.
What height of water do you have and what flowrate?

Re the alternator, most modern alternators have a solid state rect/reg unit built in or riveted to the back, they will be fine BUT it will require quite a lot of revs to get any decent power out of it.

If you post more details about the water source it would be easier to suggest a good generator setup.

i have seen a similar idea in a an american website, they made such products for campers in remote areas.

The alternator was mounted in between two small floating pontoons that are sufficient enough to keep the alternator and the wiring assembly afloat. The advantage here is that when the water level rises the pontoons lift up keeping the alternator from submerging.

I also remember seeing a funnel like guide in front of the alternator. This not only increased the amount of water flowing over the turbine but also increased the speed of flow, this way the spped of the alternator was more or less steady.

Its possible some ideas may have been patented...but I think you can check this out..

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