Real Power for 5kw System

System

Hi. I just found this site and this is my first post. I live about 40 miles south east of Phoenix in Queen Creek Arizona.

My 5KW GT system was commissioned on Dec 28 and here are the Daily KW as displayed on the inverter.

Date

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Daily Total

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Time On-Line
12/28/09

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5.004

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8:20

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Cloudy all day
12/29/09

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14.499

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9:47

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Partly cloudy
12/30/09

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15.295

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9:52

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Partly cloudy
12/31/09

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23.885

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9:58

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Sunny
1/1/10

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22.634

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10:03

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Sunny
1/2/10

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23.262

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9:55

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Sunny
1/3/10

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23.421

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9:57

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Sunny

I have 26 BP Solar Panels Model SX3190B and a Xantrex GT5.0 Inverter.

The peak power at around noon on a sunny day is about 3400W

Do these numbers look right or should it be closer to 5000W?

Thanks,
Roger

BB.

Re: Real Power for 5kw System

I like to compare against the PV Watts program. Using 5kW and defaults for everything else (assuming facing south at 33.5 degree tilt):

"Station Identification"
"City:","Phoenix"
"State:","Arizona"
"Lat (deg N):", 33.43
"Long (deg W):", 112.02
"Elev (m): ", 339
"PV System Specifications"
"DC Rating:"," 5.0 kW"
"DC to AC Derate Factor:"," 0.770"
"AC Rating:"," 3.8 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 33.5"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:"," 8.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 5.09, 564, 47.94
2, 6.06, 608, 51.68
3, 6.61, 708, 60.18
4, 7.54, 766, 65.11
5, 7.53, 773, 65.70
6, 7.28, 699, 59.41
7, 7.13, 711, 60.44
8, 7.17, 720, 61.20
9, 7.15, 696, 59.16
10, 6.75, 707, 60.09
11, 5.59, 587, 49.90
12, 4.88, 547, 46.49
"Year", 6.57, 8085, 687.23

For December/January (this is a ~20 year average)--call it 555 kWHrs per month or:

555kWhrs per month / 30 days per month = 18.5 kWhrs per day

You can look at the hourly data output and see what each "average" day would output (load in spread sheet for total per day/week/etc. comparisons).

From the same site, they also have nice PDF files of the data... And you can visually see how much variation per day over 20 years there is.

For January, over the years, the long term monthly average power varies between ~4.0 and ~6.3 Hours per day of sun with an average of ~5.2 hours of sun...

So, it looks like weather wise, you can easily see +/- 20% variation from year to year results in power output.

Looks like a good start.

With solar--your mileage may vary.

-Bill

PS: From the hourly data--just a quick look shows that you should see an average maximum in early January of ~3,600 watts average for an hour...

mike95490

Re: Real Power for 5kw System

rcrawford wrote: »

The peak power at around noon on a sunny day is about 3400W
Do these numbers look right or should it be closer to 5000W?

I'd not expect to get more than 80% of the sticker mileage !

4940 x 80% = 3952w would be the VERY BEST expected, at the 6 days your panels are aimed perfectly at the sun for 20 minutes. I'm assuming they are fixed on the roof, and not on a tracker, so they only give peak output as the sun moves perpendicular to the panels.
My 4.5KW array seldom got over 3.5KW output, except for a couple days when the sun was perfect.