[RE-wrenches] Side-by-side microinverter, maximizer, and conventional inverter comparisons

[Joel Davidson]

Hello Bill,

Henk Oldenkamp is the inventor of the OK4U microinverter. Perhaps David Katz 
knows what Henk is up to lately. The OK4U inverter that I first tested on 
the Solec International factory roof in 1994 worked ok (as specified).

The central inverters vs. multiple small inverters side-by-side comparison 
was also in Los Angeles on a 400 kW PV array between 2 each Xantrex 100 kW 
central inverters and 74 each SMA 2500 inverters (both circa 2003). The kW 
and kWh output was the same for both configurations.

Joel Davidson

----- Original Message ----- 
From: "Bill Loesch" <solar1online at charter.net>
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Sent: Monday, May 09, 2011 7:10 AM
Subject: Re: [RE-wrenches] Side-by-side microinverter, maximizer,and 
conventional inverter comparisons


>
> Joel,
>
> As I remember Trace rebranded the (nominal 100 watt) OK4U units as 
> MicroSine
> about 2000 AD. Didn't SMA (or someone else) recently take over the OK4U
> product line?
>
> Do I understand you were not impressed with the MPPT OK4U microinverters
> performance (vs. the non-MPPT SMA?) under full sun?
>
> Do I understand correctly that you compared some 2,000 (OK4U?) 
> microinverter
> units
> with 74 transformerless (?) SMA machines?
>
> The "as much as", "up to", etc. wording is why "caveat emptor" and "Your
> Mileage May Vary" should accompany each one of those comments. Kudos
> marketing mavens.
>
> Bill Loesch
> Solar 1 - Saint Louis Solar
> 314 631 1094
>
>
>
> ----- Original Message ----- 
> From: "Joel Davidson" <joel.davidson at sbcglobal.net>
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Sent: Wednesday, May 04, 2011 8:54 AM
> Subject: [RE-wrenches] Side-by-side microinverter, maximizer,and
> conventional inverter comparisons
>
>
>> Wrenches,
>>
>> A few years ago, we compared conventional and MPPT charge controllers and
>> found power production improvement in only in unique conditions and 
>> rarely
>> over 15%. Now Microinverter and DC maximizer companies are claiming "as
> much
>> as 25%" increased electricity production and a booming market. See
>>
> http://www.interpv.net/market/market_view.asp?idx=401&code=401&part_code=01
>>
>> I've been comparing grid-connected microinverters since 1994 when Henk
> came
>> out with his OK4U and am not impressed in full-sun (no shade) 
>> comparisons.
>> In 2005, I compared a side-by-side 200 kW system with two 100 kW Xantrex
>> inverters with a 200 kW system with 74 SMA inverters and saw no 
>> difference
>> in kW or kWh.
>>
>> Have any wrenches made side-by-side comparisons? Are the claimed
>> improvements hype or real?
>>
>> Joel Davidson
>>
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