[RE-wrenches] Enphase v. string inverter

[Drake]

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 <jjohnson at spefl.com>
>To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>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:marco at pvthawaii.com>marco at pvthawaii.com> 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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