25kw solar output

[point1st]

I have two solar arrays with 72 solar panels total for 25,200w ... I am looking to see if anyone else has a 25kw system and want to find out what the system should be able to produce on feedback to the grid on a bright sunny day everything optimal. 23 to 24kw? TY

[J.P.M.]

I have two solar arrays with 72 solar panels total for 25,200w ... I am looking to see if anyone else has a 25kw system and want to find out what the system should be able to produce on feedback to the grid on a bright sunny day everything optimal. 23 to 24kw? TY

See PVWatts. Get the input as close to your array's parameters as possible and use a 10 % system loss parameter. Model each array separately and sum the results.

With good inputs you'll likely get within 5 % or so of your long term output. any actual individual year's output will probably be +/- 10% of what PVWatts models. Any 30 day period will likely be +/- 30 % of the model's output for the same 30 day period. any individual day's output will have little to no probability of matching what the model spits out.

And/Or, look into something called PVOutput.org and look for arrays in your area of similar size, and orientation (tilt and azimuth).

[foo1bar]

And/Or, look into something called PVOutput.org and look for arrays in your area of similar size, and orientation (tilt and azimuth).

I'd look for similar orientation and scale by DC wattage.

25kW is really large for a residential system - but I think it is small for most commercial systems. So I don't think you'll find similar size *and* same orientation nearby.

And I'd second looking at pvwatts.

[bcroe]

I have two solar arrays with 72 solar panels total for 25,200w ... I am looking to see if anyone else has a 25kw system and want to find out what the system should be able to produce on feedback to the grid on a bright sunny day everything optimal. 23 to 24kw? TY

PVWatts is designed to give you typical output over time and expected
weather conditions. It is not designed to show peak power on a bright
sunny day everything optimal. For that reason I was unable to use it for
design work here. Bruce Roe

[J.P.M.]

PVWatts is designed to give you typical output over time and expected
weather conditions. It is not designed to show peak power on a bright
sunny day everything optimal. For that reason I was unable to use it for
design work here. Bruce Roe

True, and doing it is a bastardization of the model, but it can be used to give reasonable approximations of what to expect on/around any particular clear day.

Use the hourly output option and look for clear days around the date(s) sought. It's a bit klunky to do it that way, but it does about as much as the OP probably needs or I bet he understands.

I've got my own software written years ago before PVWatts or SAM that I've used for design purposes and it does just what the OP seems to be asking - for clear day output in 1 minute, 1 hour or all day summations for any location and array orientation, but the file is too big to put on line.

PVWatts can get him where he wants to be for about 20 minutes worth of learning and $0.00 spent.

[SolTex]

I am new to this forum, and new to PV systems, but I'm learning a lot from the threads here

Why doesn't someone ask the OP about his inverters? Is his system max output not ultimately limited by the max AC output of his inverters? I assume his inverter (or inverters) are slightly undersized in relation to his total panel DC ( nominal) rating.

[RichardCullip]

I took a look at my hourly data for the last year. Interesting to see the maximum for a given hour was 3.88kWh. This is for a system that has 4.04kW of panels connected to a 3.8kW inverter. So, for at least one hour in the last year I got 102% of the inverter rating or 96% of the panel wattage. This system is installed on a south facing roof in the sunny San Diego area with no shade issues.

That being said, I don't normally pay attention to the hourly output but rather pay attention to the monthly totals as I reconcile my SDG&E bill each month.

[J.P.M.]

I took a look at my hourly data for the last year. Interesting to see the maximum for a given hour was 3.88kWh. This is for a system that has 4.04kW of panels connected to a 3.8kW inverter. So, for at least one hour in the last year I got 102% of the inverter rating or 96% of the panel wattage. This system is installed on a south facing roof in the sunny San Diego area with no shade issues.

That being said, I don't normally pay attention to the hourly output but rather pay attention to the monthly totals as I reconcile my SDG&E bill each month.

Usually, people who are nominally savvy about PV know that (and you/re more savvy than the average bear), provided the array is operating in a normal way and under cloudless skies, max. hourly or instantaneous output isn't much of a measure of much of anything more than how clear the atmosphere is.

Richard: Just for goofs and giggles, do you know what date/time that was ?

[RichardCullip]

Richard: Just for goofs and giggles, do you know what date/time that was ?

J.P.M - it was the Noon hour on 4/27/21

[bcroe]

Why doesn't someone ask the PO about his inverters? Is his system max output not ultimately limited by the max AC output of his inverters? I assume his inverter (or inverters) are slightly undersized in relation to his total panel DC( nominal) rating.

The inverters will clamp the AC output power, mine run about 101% of rating as
I keep them them in clipping up to 8 hours a day. No damage to the Fronius pair
in nearly 9 years. The DC generated will need to be around 5% more to cancel
wiring loses and inverter efficiency. Bruce Roe

[J.P.M.]

Richard: Thank you. I'm in La Quinta until 04/17 or so. I'll check and see what I've got for that date when I get back to N. County. Some data I've got here from the Davis instrument on the roof back there shows a partly cloudy day with irradiance running high/low most of the day with a max. GHI irradiance at 1250 hrs. P.D.T. of 1,125 W/m^2 and lots of minute to minute variation between ~220 W/m^2 and 1,050 W/m^2, so, lots of cloud reflections. I don't have access to the Sunpower monitor as I left my passwords at the other house.

It'll be interesting to see how the specific outputs compare.

Note to readers: Richard and I live about 6 or so miles apart at almost the same longitude. I used to be able to see his array from my kitchen with binoculars until a tree grew in the field of view.

Regards,

J.P.M.

[TheEmrys]

Note to readers: Richard and I live about 6 or so miles apart at almost the same longitude. I used to be able to see his array from my kitchen with binoculars until a tree grew in the field of view.

I realize I am an odd person, but I found the thought of you sitting in your kitchen watching someone else's panels through binoculars hilarious.

[J.P.M.]

I realize I am an odd person, but I found the thought of you sitting in your kitchen watching someone else's panels through binoculars hilarious.

Me too, especially after the tree blocked my view, but it's something to do between times when I'm abducted by the aliens. The anal probes were tough to get use to (reminded me of working life before I retired) but at least now they let me drive the spaceship.

At this stage of my life I'm down to more time than money, more money than brains and running out of all three faster than I thought would happen so I've got to prioritize.

But all that is off topic, so, back to the OP's concerns.

[point1st]

Thank you all for your input and that's the reason why I didn't mention the inverters to begin with because I believe they are a bit undersized. I looked at a few systems from those links provided and it appears that they reach about 90 - 92% of what the array is capable of. I looked at systems where the inverter has greater capacity than the array is stated to have. I have 2 Sol-Ark 12k in parallel. My system is doing about 76-77% of the rated output or about 19-19.3kw Should be able to get about 23k from what I'm seeing if the inverters would allow it. I noticed they were flatlining on the graph. I talked with Sol-Ark and they limit to 9k and 3k to battery. I never owned solar before but am learning and a company installed it for me. I told them I wanted 25kw output. I'm disappointed with the whole ordeal but I need to get it working the way I wanted it to. Understand that either I will have to install another Sol-Ark12k in parallel or go to something else.

[Will792]

Thank you all for your input and that's the reason why I didn't mention the inverters to begin with because I believe they are a bit undersized. I looked at a few systems from those links provided and it appears that they reach about 90 - 92% of what the array is capable of. I looked at systems where the inverter has greater capacity than the array is stated to have. I have 2 Sol-Ark 12k in parallel. My system is doing about 76-77% of the rated output or about 19-19.3kw Should be able to get about 23k from what I'm seeing if the inverters would allow it. I noticed they were flatlining on the graph. I talked with Sol-Ark and they limit to 9k and 3k to battery. I never owned solar before but am learning and a company installed it for me. I told them I wanted 25kw output. I'm disappointed with the whole ordeal but I need to get it working the way I wanted it to. Understand that either I will have to install another Sol-Ark12k in parallel or go to something else.

Most people would consider your observation as a sign of good design. The intent of optimal AC(inverter) to DC (panels) ratio is to optimize cost, not to be able to squeeze out every single KWh during some hours when panels produce more power, i.e. mid May afternoon. Since PV system output varies greatly sizing AC for panels peak production creates oversize condition most of the time. Additional cost can be applied to extra panels or extra AC capacity. I think math area for this type of calculation is called linear optimization. I read several white papers that calculated optimal AC to DC ratio and it was in 1.35-1.5 range. Most PV designers use 1.25 ratio.