Wrenches,
Occasionally, but more frequently recently, we get
requests to turn off-grid systems into grid-tie systems. Usually this
involves sale of a property to a new owner, and either grid is brought
in to facilitate an easier sale or the new owner brings it in. Once
grid is in, the off-grid-based system is of limited utility, as the
equipment won't sell back. Most of these new owners want a
maintenance-free batteryless system.
Unfortunately, most off-grid arrays don't
easily convert, as the string sizing doesn't match. Here's my question:
I have two of these requests right now. Both are systems we installed
in the late 90s. One has ten BP 275s, one has twelve. These are
standard 12V 75W modules common to that time. I need advice on
inverters that will work with these strings.
The Sunny Boy 700, which is the only small
inverter model SMA still offers, will handle one string of up to nine
of these in our temperature range. Larger models require higher string
voltage. Fronius also requires higher voltage.
You know, it's a real problem to have to
explain to new green-oriented homeowners that there's nothing I can do
with their ten-year-old PV system to make it spin their new meter
backward. It doesn't do much for the mainstream perception of PV for
these folks.
What will work with these existing arrays,
please?
Allan Sindelar
allan_(at)_positiveenergysolar.com
NABCEP certified solar PV installer
Positive Energy, Inc.
3225A Richards Lane
Santa Fe NM 87507
505 424-1112
