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Energy/Electricity Storage and Use/Grid Connection => Off-Grid, Batteries & Inverters => Topic started by: billi on January 26, 2009, 09:00:24 AM



Title: electric motor as a generator
Post by: billi on January 26, 2009, 09:00:24 AM
which electric motor can i use to generate electricity

I would like to play a bid  and built my own micro hydro turgo generator ( i guess around 1500 RPM)

All parts are easy to find , but have a problem to find a good affordable DC generator ..... to charge a 24 volt battery

Sure could search for a lorry alternator (but they have brushes ?) and i think quite open

Windturbine ones are not fast spinning

So can i not just use an electic motor (magnet) and use it as a generator ?  I hope to generate  between 100-300 watt

Thanks Billi



Title: Re: electric motor as a generator
Post by: Richard Owen on January 26, 2009, 10:10:07 AM
Don't know much about DC.

Do your inverters/chargers have the capacity to take an AC input?

If so, the easiest way to diy is to use an induction motor as a generator. There's even a book on the subject

(http://lh4.ggpht.com/_c2XWxGvDCVM/SDv4pCXEoMI/AAAAAAAAAPs/bnry8lsjKbU/s288/DSC02513.JPG)

If your gear can't take an AC input, I don't think it's hard to rectify a generators AC to DC.

I'm sure others will describe a simpler solution.


Title: Re: electric motor as a generator
Post by: stephend on January 26, 2009, 10:21:48 AM
Futurenergy sell the generator component of their wind turbines as a separate part - outputs 24v or 48v DC.  (I've no idea whether the torque and RPM's of a hydro system would match that of a wind turbine...)



Title: Re: electric motor as a generator
Post by: billi on January 26, 2009, 06:45:25 PM
Quote
Do your inverters/chargers have the capacity to take an AC input?

Thats possible , but cause i only think of  100-300 watt it would cause to too much switching in the inverter , cause the let me say 150 watt of the turbine are supplied to the house and then power assisted  by the battery   and i have a 1.1 kwh waterturbine that will go on the AC side of my system ( feeded by a lake that i will drain only occasionally to charge the battery /instead of a diesel backup) or to run a heatpump of it

So try to get a trickle DC charging idea running when lake is overflowing .....

Anyhow thanks for the input

Stephend i have seen the futerenegy ones , but think i would need gearing then ....


billi





Title: Re: electric motor as a generator
Post by: guydewdney on January 26, 2009, 06:49:15 PM
Whats wrong with brushes? Most alternators on trucks, which run for thousands of hours - and the replacements are cheap and easily available.

(unlike the replacements on my new motor - a 50hp(37kw) 300v 1000 rpm - which retail at 800 quid!  :o )


Title: Re: electric motor as a generator
Post by: billi on January 26, 2009, 10:43:35 PM
i think my move will be towards a DC generator (PM)  like the one in my Motorwind turbine   .... they say its  rated 1.5 A regardless  of volts upto 95 volts  and use a solar MPPT tracker to charge the 24 volt battery

so the same generator at 70 volt produces about 100 watt   and only around  40 watt at 24 volt  bike:

Just thinking



Title: Re: electric motor as a generator
Post by: stephend on January 27, 2009, 09:59:57 AM
The guys at volvoxengineering have recently announced a 48V DC diesel/veg oil generator.  Since they build these themselves they might be able to source just the alternator for you.



Title: Re: electric motor as a generator
Post by: sunshinekid on January 27, 2009, 08:49:11 PM
You could just make a generator.   I've never done it myself, but read about using a wooden circular disc with around 10 holes drilled around the edge and neodymium (rare earth) magnets glued in the holes.

On another wooden disc, you glue hand-wound coils.  Then using the shaft and bearings from some other motor, you have a completely brushless generator.

Sound like fun?

Steve