[RE-wrenches] Enphase v. string inverter

[Jamie Johnson]

Nick, 

50+% greater output with enphase than unshaded kWh estimates with a string inverter?

That is what my comment referenced, the practice of some installers of taking pvwatts with a 0.85 derate(no shading) & multiplying it by 1.5 or more just to get the sale.

A kWh performance guarantee standard would eliminate this practice.

Other industries have similar standards to insure the customers receive what they paid for, why not PV?

Jamie Johnson
General Manager
SOLAR POWER ELECTRIC TM
NABCEP Certified Solar PV Installer #031310-118
(941) 380 - 0098
www.SPEFL.com
FL State Certified # EC13001765

Sent from my iPhone

On Oct 11, 2010, at 12:50 AM, Nick Soleil <nicksoleilsolar at yahoo.com> 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
> www.SPEFL.com
> Commercial & Residential
> FL State Certified # EC13001765
> 
> Sent from my iPhone
> 
> On Oct 9, 2010, at 7:07 PM, "Marco Mangelsdorf" <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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