[RE-wrenches] Heinz 57 off-grid array - What should I do with the solar modules?

[Bob Clark]

Wrenches:

 

We were called to assess the status of an off-grid system that is not the
worst I have seen, but it comes close.

 

I have some preliminary thoughts about system redesign, but would like to
hear from the Wrenches about the array.

 

Givens:

We will not install anything unless it is to code.  It is obvious that none
of the existing system was installed to code.

We will use the existing 24V battery bank consisting of 8, Trojan L16s.  The
batteries are still “relatively fresh.”

Pump is a Franklin pump ½ hp 115VAC.  The CFs dim when the pump starts.

New load will be a GRINDER PUMP FOR SEPTIC = 2HP, 15amp (240 or 120VAC –
more than likely it will be 240V pump) – Another light dimmer!

Modest daily electrical load (estimate no more than 600 WHr/day; 25AHr) –
they are very good at managing their electrical use.

 

Solar array – to keep or replace?

8 solar modules – a Heinz 57 mix of older modules - 2 Photowatt PMX500 (Are
these modules UL listed?  There did not appear to be a rating label on the
back.) wired in series, 2 Kyocera KC120-1 wired in series, 2 Golden Genesis
PV-75 wired in series, 2 Photowatt PW 1000 12V-24V internally wired for 24V
wired in parallel with the other modules strings – all of these modules are
wired in 5 parallel strings for approximately 34.2Vmp and 20.4Imp, ~695W
(STC).   Oh, and they need a new mounting structures for the modules.

 

Should I try to work with these modules or advise the customer to start over
(any modules that are not UL listed will have to go)?

 

What is a good “rule of thumb” for a ratio of PV watts to battery bank
capacity per day of autonomy?

 

Thanks for your ideas.

 

Bob Clark

SolarWind Energy Systems, LLC

 

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