Well summarized. I think your mileage would vary based on the
anti-islanding algorithm used in the inverter and the generator's
ability to regulate frequency. So while it may "work" in that an
inverter syncs to a small generator's output, it's very unlikely that
reverse current backfed into the generator was considered during the
generator design. Feeding 3kW of PV back into a generator that had 6kW
of load isn't going to drop your fuel consumption by 50%, either. Given
that the best case scenario is marginal fuel savings and the worst-case
scenario is a fried regulator board taking your generator offline when
you need it most, I'd keep them separated.
DKC
On 2012/12/13 10:18, August Goers wrote:
Hi All --
Thanks for the feedback. Yea, we've always used Sunny Islands with
batteries for anything that needs to run off grid. This was more of just
a theoretical question. From what I heard, it sounds like the excess
current from the PV might damage the generator (or I suppose anything
running in the house) and this will result in higher voltage. Best case,
the inverter will cycle on and off. V = I*R. Worst case something blows up.
Thanks, August
*From:*re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>
[mailto:re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>] *On Behalf Of *Greg
Seelhorst
*Sent:* Wednesday, December 12, 2012 8:18 PM
*To:* 'RE-wrenches'
*Subject:* Re: [RE-wrenches] off grid PV connected to generator
August –
I’ve seen this scenario and it is not pretty like William suggests.
From what I’ve seen, the problem is not so much the power of the PV
being more than the generator, but moreso if the 1) generator is
synchronous or non-synchronous with the inverted AC (sine wave) and 2)
if the loads are less than the PV. The generator will ‘create’ the
voltage and run even if there are zero loads. The inverted AC (from PV)
wants to push current onto the ‘local grid’ and if there are no loads
(nor heat sink diversion or batteries to charge) then the current will
try to backfeed the generator.
My recommendation is to get a critical loads panel for the generator
only back-up, or go grid-tie with back-up using a Sunny Island, or the
like, that make the switch seamless during an outage.
*Greg Seelhorst*
/Designer/Project Manager/
NABCEP Certified Solar PV Installer™
*POSITIVE ENERGY, Inc.*
510 S. Main Street
Las Cruces, New Mexico 88001*
*Cell: 575-650-1883
Office: 575-524-2030
FAX:575-915-1788
*g...@positiveenergysolar.com* <mailto:g...@positiveenergysolar.com>
www.positiveenergysolar.com </www.positiveenergysolar.com>
*http://www.positiveenergysolar.com/images/stories/PE-logotype.png*
<http://www.positiveenergysolar.com/>
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