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: Drake
To: 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
www.SPEFL.com
Commercial & Residential
FL State Certified # EC13001765
Sent from my iPhone
On Oct 9, 2010, at 7:07 PM, "Marco Mangelsdorf" <[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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