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600watt panel = ? real life ac power

kaseywantssolar

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Hi folks, newbie question just to help me get started. I started a small grid tie system with 600 w panels and a grid tie microinverter. The microinverter monitoring software and an ac power meter both agree that the absolute maximum power generated is approx 370 Watts. Now i live in Singapore and thats when the sun is scorching, beating down directly overhead to the panels and with no cloud cover. A bit underwhelming to say the least ….

Is there something wrong ? Or is this actually already great ? Being my first solar foray n all, i really dont have any context to be able to guess, so your opinions would be really welcome!

Should i be happy because if the panels are 600W pk DC, this means that the maximum theoretical power i can generate would be 300 Watts AC (measured RMS) ??

But if thats true, why dont i see this point referenced in the ‘sizing your solar system“ type articles ? These typically talk about inverter losses, shade, etc.… but don’t point out that if you want to generate 2kw AC you need 4kw DC pk panels at a minimum…

What am I missing ?
 
You are in hot zone, high temperature affect the PV output.
You also have system and conversion loss to factor in.
What is the STC (Standard Test Condition) and PTC rating of the panel?
 
Thank you for those links ! They seem to account for maybe 2x% losses ? i seem to be generating only 55% of the panels rating in bright sunshine and that has me stumped…
 
and i also used a gtb-600 wifi version …
 
Should i be happy because if the panels are 600W pk DC, this means that the maximum theoretical power i can generate would be 300 Watts AC (measured RMS) ??
What is the voltage of your panel(s)/array?
I would think a 600W panel to have a high voltage. The micro inverter ad shows 50V max so wondering if excess is being clipped or if high voltage negatively affecting MPPT algorithm.

Happen to have pic of inverter monitor software (grasping for clues)?
 
Thanks all for the help. I wanted to get a sense if you folks felt getting 370 watts AC out of a 600 w panel (in direct sunlight) was reasonable. Based on the responses im getting, maybe its NOT. i started with a few panels just to get a feel of things hence my question...

Here is how the microinverter grid tied system is set up:
The microinverter has 4 x mppt inputs.
2x150w in series into each mppt input. (at the moment, two of the 4 inputs are unused)
Each input max is 60V and the series panel OC V is 2x27v measured in direct sunlight = 54V

The panels:
150W ETFE SOLAR PANEL
Max Power Pmax: 150W
Max Power voltage Vmp: 24V
Max Power Current Imp: 6.2A
Open Circuit Voltage Voc 26V
Open Circuit Current Imp: 6.8A

What do you folks think is a reasonable amount of AC power i should expect (peak) from this system?
 
Ahhh, so you dont have a 600w PV Panel, you have 4x 150w panels making a 600w PV Array.
 
The panels:
Ok so you have flexible solar panels. There have been many reports of some being over hyped. Can you check the volts and amps of an individual panel?

Also, how long is the wire run from your panels to micro inverter? What wire gauge and connectors are you using?
 
Spec from Aliexpress: Inverter Maximum output efficiency is 95% at best, so real world at best may be 90% or less, so you can easily loose 10% of power, and you are not going to get full PV panel rated output either in the real world.
Does the MPPT/Inverter come with interface so you can see PV input Voltage and PV current?
 
but don’t point out that if you want to generate 2kw AC you need 4kw DC pk panels at a minimum…
AC & DC power, volt to volt, are very close to each other. Why AC is read as rms & not peak to peak if I recollect correctly.
Those of us that match the load with the PV output for direct to water heating realise the PV max output rating is only at a very narrow band:


The general consensus is double the number of panels to give double the wattage of your matched element to get a good result on a sunny day. For your 900w24v element you need 9 of your 200w panels.

I can not remember actually seeing the sun in the week I spent in Singapore,. So apart from the heat, and PV makers claims, you also have that tropical humid sky to lower the pv output.
 
OK, two things here:
1. You are using flexible panels. I also have some of these, 4x100w, and I'm barely getting 180w AC out of them at full sunlight, when hot.
From my experience, the wattage stated for these panels are pretty much theoretical. When I checked open circuit voltage, and short circuit current of each one separately, I was only able to get around 88w DC, when they were in full sunlight but still cold.

As stated above, solar panel power will go down as heat rises, and these flexible panels are no exception (maybe even worse, depending how you mounted them and how much air flow they get).
In my case that is only 45% efficiency from peak DC STC rating to actual AC output, when hot outside (35° C) for these flexible panels, which have some air circulation but probably not enough.

2. I have used exactly the same two microinverters you used, and got similar results with both of them with the flexible panels.

The Sun microinverter is alot better quality than those no-name inverters which heat up pretty quickly, and will stop producing power for about 10 minutes when they reach their temperature threshold. This could happen multiple times a day.

I also have two 455w Longi glass panels, but they peak at about 370w AC each, when hot.
Alot better than the flexible panels, but still less than expected.
That is around 82% efficiency from peak DC STC rating to actual AC output, when hot outside (35° C).
I think you need to take into consideration that the DC output has losses because of panel heatup, and there are losses also when converting to AC.
Especially if you aren't running the microinverter close to it its maximum load, it's effiency drop will be larger.
 
BTW, when I connected all panels in parallel to the GTB-600's two inputs (total wattage over 1000w DC) I was only able to get 535w AC at the maximum, and that caused it to heat up like crazy, stopping AC output ever few hours to cool down as I mentioned.
These are really a waste of money. I really regret buying them (had two 600w, and one 1200w that didn't work well with my glass panels).

I ended up getting the SUN 2000w G3, which is alot better, and has alot more info to display on the app.
 
Thanks indeed!

1. The smaller WVC and GTB inverters are a waste of money indeed - i just chalk it upto learning costs myself. As with you, i found them cutting out a number of times during the day until it cooled down each time. And that was nowhere near its rated 600W either!

2. The output im getting seems then to be what meetyg experienced for the flexi panels too. Sigh. Somewhat more expensive lesson vs the $70 inverter but the panels wont be wasted. I just won’t get anymore of them for now. A company called Utica in Sg seems to have a few glass types on offer so i’ll poke around there and see,

3. The iphone app on the SUN 2000W wants a password that i dont have, so for now, the only system telemetry i have is from the GTB (ouput side only) which isnt very useful. As soon as i find a nice chunky load, ill measure the panels and report back for posterity’s sake.

4. The setup wiring is 8awg, mc4, solder/heatshrink and about 3m long from panel to inverter. Its grid tied to the rest of my home, so theres plenty of load drawing from the inverter :)

Cheers for now from sometimesunnypore …
 
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To use the telemetry functions, you need to connect your inverter to WIFI using the app.

If I recall correctly, the username and password for the built-in web console was admin/admin (which you change later on).
 
Each input max is 60V and the series panel OC V is 2x27v measured in direct sunlight = 54V

The panels:

Max Power voltage Vmp: 24V

"
Min/Max Starting Voltage​
22-50V​
"

This could cause it to not turn on. Any chance only one of two MPPT inputs is running, and other is not due to excessive input voltage?

I don't find max survivable input voltage in inverter spec.

"
Max Power voltage Vmp: 24V
Open Circuit Voltage Voc 26V
"

Would not have expected those to be so close.
26V x 2 = 52V, close to the 54V you observed.
I don't expect you to get even higher voltage in the hot weather of Singapore. Probably panel spec is incorrect.
Ordinarily we warn people about Voc rising another 10% to 15% in freezing weather and killing the inverter or SCC, but not likely a problem you will have.
 
Ok so you have flexible solar panels. There have been many reports of some being over hyped. Can you check the volts and amps of an individual panel?

Also, how long is the wire run from your panels to micro inverter? What wire gauge and connectors are you using?
At least panels in his links have the needed surface area to theoretically produce the advertised power. (Unlike 500*1000mm=0.5m2 panels that claim 200w output)
 
I finally managed to get the Solarman software working with the Deye Inverter. It seems like the iphone app is harder to use compared to the android version. It didnt help also that the website has two home monitoring versions - only one of which works for me. I may just write up a few notes to save others the headache…

Anyway, in terms of telemetry, the software is wayyyy better than the smart life used for the cheaper GTB type inverters, BUT is nowhere near real time. The smart life was easy to setup and basically gave me a second by second readout of the output current, voltage and power (but nothing else, and no graphs)

I’m probably going to get one of these wifi AC meters to satisfy the tweakers itch …


looks like it will do the trick.

Ive attached what the Solarman readouts show on a rainy cloudy day…. the output wattage looks suspect as its a bit more than the sum of the input power - almost certainly quite inaccurate due to the low ac currents at the output.

Well either that … or I’ve discovered a perpetual motion machine ?

I’ll take some screenshots when its super sunny just to close the loop on these flex panels.
I’ve got some 420w regular panels on order for comparison too….

The gui of this solarman app is nice but the erratic and slow updates is not.…
 

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There is supposed to be a "local mode" in the app where it connects directly to the microinverter, and doesn't route through the Solarman Cloud services. But I hadn't had the time to fiddle with it and get it working.
I'm not sure but maybe that would give more real time stats rather than every few minutes. But I suppose that would only work if both the phone and the inverter are connected to the same WiFi network at the time.

I like the fact that I can connect from anywhere to the Solarman website (https://home.solarmanpv.com) and see that stats.
 
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