[RE-wrenches] quality off-grid PV for Africa

[Eric Youngren]

Howdy Wrenches,

First off, thanks for all of the nuggets of wisdom I have gleaned from this
list over the years.  You guys are great and I've learned important things
from you.

I am building what I hope will become a value-adding distribution company to
export off-grid PV systems and equipment to Africa and other places in the
developing world.    I want to help take the best practices and experiences
of the US off-grid industry to the people in the world that really need
it.   The quality of most PV installations I have seen in Africa is pretty
bad.   I have two 'whitepapers' on my
website<http://solarnexusinternational.com>that explain in more detail
what I mean.  What I've seen is that the PV
dealers and installers over there have access to good quality modules,
controllers and batteries but they have to go to the local markets for their
wire and BOS materials and most of that is poor quality and/or not
appropriate for DC current and voltages.  So our plan is to send complete
system packages that will include all the BOS the local installers will need
to install high quality systems that will be efficient, safe and durable.
We will also travel to give installer training workshops and possibly
develop a 'certified installer' type program for our Solar Nexus Systems
that would enable dealers to purchase materials 'a la carte' and do the
system design and integration themselves.

I'm working out the design right now for an order of 30 small (by US
standards) systems (roughly 400 W of PV, 300 W inverter, 12V PWM charge/load
control, our SolarNexus power center, 400 AH VRLA battery) that will be
installed on schools in rural Tanzania to run lighting, fans and one or two
computers.   I have some questions about best design, low cost high quality
materials and where to toe the NEC line and where its okay to ignore the US
code requirements in the name of cost efficiency and realistic risk
assessment.

Specifically,  here are some of my questions:
1.  PV combiners -   for 12V systems using 3 to 6 modules in parallel -- I'm
planning to use Midnite short TBB insulated busbars for parallel combiner
blocks,  similar in application to the old-school PDB terminal blocks but
cheaper.    I know the NEC would require individual string fusing, but is
that a concern AT ALL on 12V or 24V systems?   I have never seen a module
short out and feed current into a parallel string, but I think that's why
the code requires individual string fusing.    Has anybody seen unfused PV
combiners become a problem for 12 and 24 Volt systems?   What is the
practical limit at which it does make sense to require string circuit
protection?    Is this a case where the NEC could be optional in Africa?
(trust me, any kind of PV combiner hardware is going to be better than the
'twist and tape' methods they're using now)

2.  Meters - right now I'm planning to put Trimetrics on all of these
systems.   Obviously this will require user education for the meter to be
helpful at all.  But I feel that educated users can learn how to understand
an amp-hour meter and they need more than red, yellow and green dummy lights
to fully understand what is happening with their system.   Thoughts or
comments on that one?

3.  Lightning protection -  my kits will include ground rods and #6 bare
stranded copper wire for solid array/rack grounding and bonding for the
entire system.  To me that seems like the best defence against lightning,
but what about additional protection?   Are Delta lighting arrestors worth
the money?   Do they work?    Put it at the PV combiner or at the
controller?

Sorry for the long-winded post.    I'd appreciate any thoughts y'all might
have on anything I've mentioned here, or anything else that comes to mind.
Thanks!

best energy,
Eric

-- 
Eric Youngren
NABCEP Certified Solar PV Installer
Island Energy Systems, LLC
dba Solar Nexus International
PO Box 894
1016 Discovery Way
Eastsound, WA 98245
(360) 376-6842
www.solarnexusinternational.com
www.islandenergysystems.wordpress.com
www.solarempowerment.net
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