[RE-wrenches] P1 micro performance

[Drake]

It would be good to quantify the amount of peak 
energy that is lost through power limiting. We 
have a 2160 Watt array on a 40 degree pitched 
roof with a SB 2500HF US inverter. The other day 
I watched the meter hover over 2000 W and peak at 
2490 W. It was a clear, cold day. It runs in the 
STC range and higher many days in the spring.

I have one Enphase customer with a ground mount 
with Sharp 224s and Enphase 190s. The inverters 
can stay pegged for 4 hours at a time in the spring.

Emacs!


The graph above was from a day with some clouds, 
but still power limited much of the day.

It would be good to get a better understanding of 
the annual percentage effect. Enphase claims an 
overall power increase, even with this effect. 
Undersized string inverters are clearly an issue.

Drake



At 12:37 AM 3/22/2013, you wrote:
>Thanks for sharing the screen capture, Marco.
>
>Interesting issues to think about here. This is 
>actually prime clipping season in many places 
>(not sure about Hawaii) due to the cool weather. 
>While there are more sun-hours in the summer, 
>the cell temperatures are often high enough that 
>you won't tend to see rated power out of the modules.
>
>While I'm not running performance models for 
>work, the people who do are routinely increasing 
>dc-to-ac ratios, often as high as 1.4-to-1. 
>Having said that, most inverters aren't installed on a roof. (Not yet anyway.)
>
>I'd probably lean to a more conservative sizing 
>ratio for micros. While I can imagine some 
>scenarios where I'd be comfortable with a 215 W 
>micro on a 265 W module—like a flat roof install 
>in Vermont, which reportedly doesn't see 1,000 
>W/m^2 very often—I wouldn't try that here in Texas.
>
>On Mar 21, 2013, at 7:54 PM, Marco Mangelsdorf wrote:
>
>>Check out the output of the modules below at 
>>1PM on this Spring equinox for this system here in Hilo, Hawaii.
>>
>>These mods are SunPower 245s with the Power-One 
>>micro 250s.  Notice that the AC outputs below are 223 watts and higher.
>>
>>If we had installed Enphase M215s instead, the 
>>max output possible would be ~ 224 watts.
>>
>>If there’s clipping this early in the year, 
>>imagine the degree to which the clipping will 
>>be increasing in the months to come as the solar insolation increases.
>>
>>And these mods were “only” 245s.  Enphase 
>>states that their M215s are fine with modules 
>>up to 265 watts!  Imagine the amount of 
>>clipping taking place when that kind of pairing takes place.
>>
>>marco
>>
>><image005.png>
>><image006.png>
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