[RE-wrenches] 14 PV-Powered Fans- best method?

Dave Click daveclick at fsec.ucf.edu
Mon Sep 14 07:11:46 PDT 2009


Hi all,

I'm working on a project for a state park, where they're looking to add 
some PV-powered fans to a outdoor bus stop. The customer is hoping to 
have the fans spin more quickly as irradiance increases, and they want a 
master cutoff switch. I'm initially planning to use 2 10W modules 
(series to 24V) powering each of 14 Nextek (http://www.nextekpower.com/) 
DC-powered Gossamer fans, since that seemed to be the easiest way.

However, I'd like something that looks better than 30 of those small 
modules (best 10W module I found that can do 24V is series-connected 
Sunwize modules with semicircle cells) up there on the roof. I was 
thinking about having a 24V module or two up there that backfeeds the 
output of a 14-pole source circuit combiner, with each pole a 1A breaker 
feeding a fan. Then I got concerned that if a breaker or two ever 
tripped (hopefully each fan presents an equal load to the PV, but 
still), the remaining breakers would trip as it tried to feed 200W 
through fewer and fewer loads.

Any recommended method for implementing this, and for installing the 
cutoff switch in the first scenario? For the second scenario, I'd 
probably just use an unfused safety switch on the PV output.

Thanks,
Dave



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