Hello Joel,
The issue is that over half the array was in shade. I don't think
there would have been enough string voltage to start a string inverter.
Cheers,
Drake
At 11:33 AM 10/11/2010, you wrote:
Hello Drake,
I have observed hundreds of PV systems in the early morning and can
say without doubt that string inverters are not inherently slow to wake up.
For example, today my 12 year old SW4048 with a single crystal PV
array facing south at 12 and 18 degrees tilt and my SB2100 with a
single crystal PV array facing south at 18 degrees both were putting
out power at 7:45 am when the sun was 9 degrees above the horizon at
azimuth 105 degrees. Today the sky is clear and the sun rose in Los
Angeles at 6:57 am.
I have seen systems with 100 kW Xantrex inverters and flat Unisolar
arrays wake up before the morning sun rose above the horizon.
Granted the systems were putting out less than 5 kW, but the inverters were on.
See you all at the solar conference.
Best regards,
Joel Davidson
----- Original Message -----
From: <mailto:[email protected]>Drake
To: <mailto:[email protected]>RE-wrenches
Sent: Monday, October 11, 2010 6:39 AM
Subject: Re: [RE-wrenches] Enphase v. string inverter
I'm now monitoring a 5.376 kW system we recently installed. The sun
is barely up, with light clouds, and a portion of the array is still
in shade. The system is putting out 700 watts. A string inverter
would probably be waiting to start.
My main problem with the Enphase is the 199 watt limit to its
output. The inverters are rated for up to 235 watt modules. This
224 watt module array spends a fair amount of time at full inverter
capacity during cool sunny days. Maybe these inverters should not
be used with over 210 watt modules.
Drake
At 12:50 AM 10/11/2010, you wrote:
The main advantage of Enphase is the module level
monitoring. However, the increased output due to partial shading
can be significant. I was at a 6 year old PV site this week, and
a tree had grown up near the base of the roof. Branches were
casting a few minor shadows on the array, but was wiping out 75%
of the production. I can assure you, those 9 modules would have
been producing '50+% greater output'
Nick Soleil
Project Manager
Advanced Alternative Energy Solutions, LLC
PO Box 657
Petaluma, CA 94953
Cell: 707-321-2937
Office: 707-789-9537
Fax: 707-769-9037
From: Jamie Johnson <[email protected]>
To: RE-wrenches <[email protected]>
Sent: Sun, October 10, 2010 5:38:55 AM
Subject: Re: [RE-wrenches] Enphase v. string inverter
Marco,
The last I heard the NREL was testing enphase vs. a string
inverter, they were also suppose to test enphase vs. A competitors
module level mpp tracking. Not sure if that performance test is
complete yet.
I have seen 1 independent unshaded test ( potentially biased )
which IIRC showed enphase ~1% less than a string inverter, this
seems to match the inverters CEC rating.
What we see around here is an over estimate of kWh production by
the selling contractor using enphase, sometimes by 50+% greater
than unshaded kWh estimates.
Performance guarantees with monetary compensation back to the
customer if estimates are not met can be a good thing and improve
the industry IMHO.
Jamie Johnson
General Manager
SOLAR POWER ELECTRIC TM
NABCEP Certified Solar PV Installer #031310-118
(941) 380 - 0098
<http://www.SPEFL.com>www.SPEFL.com
Commercial & Residential
FL State Certified # EC13001765
Sent from my iPhone
On Oct 9, 2010, at 7:07 PM, "Marco Mangelsdorf"
<<mailto:[email protected]>[email protected]> wrote:
Does anyone know of any reports out there from a neutral, 3rd
party which compares an Enphase array with an array using a string
inverter with both arrays on the same unshaded surface?
Some Enphase peddlers here are saying that the energy harvest from
an Enphase system is going to be better since they supposedly come
on sooner and stay on later in the day.
One guy is actually saying that the Enphase inverters come on
before the sun comes over the horizon. Maybe from the same
family that claimed that a-Si modules produced power from the moonlight.
Thanks,
marco
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