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Forum Index : Other Stuff : Solar powered roof ventilator

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M Del
Senior Member

Joined: 09/04/2012
Location: Australia
Posts: 155
Posted: 11:57pm 28 Jan 2013
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Hi Guys, After the heat we had a couple of weeks ago I have been researching powered roof ventilators (My two wirly birds could not keep up ) Powered units are not cheap by any means.

I am going to try a 10" fan from a car radiator and power it from a solar panel.
The fan draws 5 amps and requires an 8 amp fuse. I can get a 40watt panel fairly cheap or go larger if required.
My thinking behind using the 40watt panel is that the fan will never quite get up to full speed, therefor it should have an extended life cycle.

Is my thinking correct or am I going to kill the fan in some way? There is bound to be something I have not thought of.

cheers
Mark

Mark
 
Downwind

Guru

Joined: 09/09/2009
Location: Australia
Posts: 2333
Posted: 12:18am 29 Jan 2013
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My concern would be the power dissipated through the motor prior to enough voltage/current to actually move the motor, as the sun started to produce power through the panel this would be lost into the motor windings until the power was great enough to drive the motor, im not sure if that would cause problems or not.

If it was me i would add a voltage switch so the panel voltage needed to be high enough before the motor turned on, something like an opamp switch or even a good old 555 timer chip would do it.

Another view to back off the power requirements with a fan is to shroud the outer ends of the fan blade on the suction side to restrict the air entry hole size, as the fan will only draw full power with moving maximum air.

Pete.
Sometimes it just works
 
jack fork stik
Newbie

Joined: 08/12/2012
Location: Australia
Posts: 34
Posted: 05:29am 29 Jan 2013
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sounds like a job for a minimiser/maximiser to stop the fan from trying to startup when theres not enough volts/amps to do the job.do a search for diy solar hot water or solar powered cooler and its a aussie site
 
M Del
Senior Member

Joined: 09/04/2012
Location: Australia
Posts: 155
Posted: 09:04pm 29 Jan 2013
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Thanks for that guys. Knew there was something I forgot. I think a 555 timer will do the trick, but I will look into the other items and come up with a plan.

cheers
Mark

Mark
 
norcold

Guru

Joined: 06/02/2011
Location: Australia
Posts: 670
Posted: 09:54pm 29 Jan 2013
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futurlec.com.au have a 6amp motor solar maximiser in kit form, should be just what you require, otherwise the motor may never start.
We come from the land downunder.
Vic
 
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