find an inexpensive generator for small hydro

[deb]

Hi,

I am designing an inexpensive water current turbine. At this point, my problem is to find a cheap generator. Thanks to a website, several solutions are under consideration.

-    Second-hand alternator for vehicles.

The biggest problem with using car alternators for hydro power is that they are designed to rotate at too high a speed to be practical in hydro power applications without significant modifications.

-    Home-made permanent magnet alternator

Could be very interesting if I had enough time to built one myselves

A PMG construction manual is available on a website with some recommendations in using it for hydro power.

-    Induction motor conversion alternators

Apparently, it's the same amount of work to build an efficient alternator from scratch as it is to convert an induction motor, and the home-made alternators perform much better.

-    DC generators

Most are not good at low rpm.        

If someone have an other idea, I would be grateful to heard other opinion or experience.

[Norm]

  A car alternator is still about the best choice as you may find ...they really don't have to spin that fast as you will find if you do a search here or on Google.

              ( :>) Norm

[deb]

Well, I have made research on internet and the car alternator is not really the best choice... Here what i found on a website....

"The reason is that the field coils need energy, about 30 watts is typical. This means in slow speeds you will lose almost all the energy produced by the water turbine in the field coils. You will have to gear up a car alternator to at least 2000 RPM. No matter what water turbine design you choose, it is unlikely to be more than one tenth that speed, so you will need 10 to 1 or more gear ratio. This will magnify friction losses and make startup harder."

Are they wrong?

[wdyasq]

Your internet search showed one version of someones 'truth'.  Another problem with an automobile alternator is expected life span.  Using just a few assumptions one might say a car alternator needs rebuilding every 100,000 miles or so.  That would be about 2,000 hours at 50 MPH.  Or, 83 days if it was running 24/7.  That makes replacement or rebuild 4-5 times a year in addition to the power drain of the field coils.

Some here have had good luck with conversions.  Industrial motors are designed to run for many hours a day many years with minimal maintainence.  Only time will tell if these conversions will last as long once modified.  But, the bearings and cases are a good start. The bearings are properly aligned and have a good record in their original use.

Homebuilt PMA alternators are just that.  They are another 'unproven' hand built or modified device.  With professional attitudes and skills, my opinion is it would be  as reliable as a motor conversion.

One could purchase a prebuilt PMA alternator/motor.  One company building them is: http://www.ecycle.com/motorgenerator/default.htm .  Although not inexpensive, they can be made to generate electricity at almost any speed.

Good luck,

Ron

[deb]

Thank you very much Ron for the prebuilt PMA alternator/motor company. I think it is exactly what I need.

[Vtbsr]

Hi Deb, I am running a Harris pelton www.harrishydro.com. They can rewind the car alt to your voltage. I have foung that you have to rebuild once a year. You can get better top and bottom bearings and  brush holder assembly. What kind of head and flow do you have? You need to know the distance from the turbine to the batteries to design for volt loss. The harris has a 4" dia pelton that is direct mounted to alt. You dont need to gear up. If you have grid power you cound use  a induction AC motor. You have to  spin motor faster than its run speed to make power flow. good luck

[johnlm]

You did not mention how much power you are wanting to produce.  Your choice of an alternator is very dependent on the power.  If all you are looking for is 20-30 watts a box fan motor (like the ones on 1960-1990 model 20inch breeze boxes) can be modified to aPMA in about 1-2 hours, using commonly available ceramic magnets, 2 inch dia washers from your hardware store and some epoxy; and depending on how you use the existing windings will get to 12V at around 250 RPM (around 500 rpm if you divide the main windings in half and wire up in parallel for more output current).  One can get 25-30 watts (2-3 amps at 12V) at around 1000 RPM.  If the maximum output of the water turbine is 200 RPM as you suggested then a more moderate gear up is required.  If you are wanting several hundred watts at 200 RPM then likely one of the homemade axial machines as described on this site will likely be a good choice.

I have reworked car alternators (including rewinding and changing them over to permanent magnets to get rid of the field requirement) that will get to 12V at around 300 RPM and put out 150 W at 800 rpm.  But it takes maybe 10 hours of work (probably more the first time) to do this.

johnlm

[deb]

Hi,

You may not have well understood. I am building a water current turbine. In consequence, I have no head. The flow is on average almost 0.9 m3/s. In restricting the flowing area, I can have more than 3.5m/s.

I could use an induction AC motor, but I prefer to build the turbine as if I was not grid connected. It could be more useful...

[FishbonzWV]

Deb

I've got some used 48V pm brush motors.

They are 4" diam  x  9" long

Chucked up in a drill press

RPM     Vo        attached to 12V 34AH Batt

440.    20.?? (forgot)  2.5 A
     
540.    21.86           3.2 A
     
     

About 50 Watts at 540

Bonz

[nack]

You might also consider the GarboGen garbage disposal conversion.  I don't really know much about it, but the circuits I have seen suggest that it pulls output current from the start and run windings, and produces pretty good output on a tiny mill.  I would probably just make an axial flux PM alternator, because then you can make it as stout as it needs to be for the environment it lives in.

[deb]

A mistake...Sorry.

The flow is only 0.19m3/s.

I expect 200W maximum but I want the generator to produce electricity even for low speeds.

 

[Dennis]

   I have a no-head design called a Gravity wheel that I have put together. It is based on the ancient design of the Persian waterwheel, the first vertical wheel ever made.

   With this design you do not have to worry about generator speed as much, it lifts the water, then you just use an off the shelf turbine/generator unit.

  Please see my site at http://WildWaterPower.com

  I have a patent pending, so if you deside to use this design you have to call me and we will discuss the matter.

-Dennis

[Nando]

Deb:

I have a Brushless 3 Phase Motor ( Smart Drive) that is capable of producing around 1 watt per RPM so at 1000 RPM , 1 KW is generated.

If this range of power is good for you, let me know and I can send photos for your perusal.

Also you can email direct to me : nando37 -at- comcast -dot- net

Nando

[Nando]

Deb:

I am added a new photo

Nando