diy solar

diy solar

Trying to understand our system better

Craig at Mansfield

New Member
Joined
Dec 25, 2021
Messages
6
Hello, I’m new to this forum and am trying to get more information to understand my system. We have 38 panels, an LG Battery and 6Kwt inverter. Our system cuts itself off from the grid if the grid goes down and runs couple dedicated circuits. We have Solar Edge monitoring through the web but I’d like to try to understand little more.

Is there a way we can ascertain average daily figures for production, consumption etc..?

How come our system sometimes produces more than 6 Kwts (sometimes shows 11-12Kwts solar production) but lately seems to max out at 6Kwts?

How come even when our batteries are charged and the system is putting power back into the grid we still draw power from the grid?

I think I should be able to get these answers from our installers but so far not much luck!
 
For anyone to provide any sort of valid response, we will need to know what equipment you have and how it is setup. Please provide Make / Model of all the solar gear installed, any configuration information provided etc.
Your LOCATION (nearest large city, state/province) is also important.
Also if you know what angles / direction / degrees your solar panels are aimed at etc...
More info provided the better responses you will get.
 
For anyone to provide any sort of valid response, we will need to know what equipment you have and how it is setup. Please provide Make / Model of all the solar gear installed, any configuration information provided etc.
Your LOCATION (nearest large city, state/province) is also important.
Also if you know what angles / direction / degrees your solar panels are aimed at etc...
More info provided the better responses you will get.
 

Attachments

  • STC Assignment Form PV Solar.pdf
    5.7 MB · Views: 15
Welcome to the forums!

"Kwts" isn't really a measure. A kilowatt (kW) is a measure of power and a kilowatt-hour (kWh) is a measure of energy. You pay for kWh, but devices are typically measured in kW (and how much energy they use depends on how long they're run). Not trying to knitpick, but if you use kW when you mean kWh folks might assume you're talking about something else and give you the wrong answer.

We have 38 panels, an LG Battery and 6Kwt inverter.
From your attachment, you have a 24 panel array capable of producing a maximum of 7.8 kW (kilowatts) at STC.

Is there a way we can ascertain average daily figures for production, consumption etc..?
You can use a tool like SAM to give you what's expected for your area. You can keep a record of kWhs consumed/produced off the grid meter with pencil & paper, but I use RF. If you have current transducers (CTs) you can keep a record independent from SolarEdge's monitoring. SolarEdge might have an interface allowing you to get to the raw data. The nice thing I've heard about SolarEdge is you can get per panel information, so probably the first thing to look at is to see if the panels are all roughly producing the same.

How come our system sometimes produces more than 6 Kwts (sometimes shows 11-12Kwts solar production) but lately seems to max out at 6Kwts?
Looks like the installation is in Australia, so using an insolation calculator, and assuming the panels are aligned for year-round optimization (you might be optimized to the season when you use the most power) then the insolation for December is your best month, around 5 and the worst month is June around 2.8. So, you should see between (5x7.8=) 39 kWh/d to (2.8x7.8=)21 kWh/d. Of course, if you have any shade it'll be a lot worse.

If you mean kW, then the power is at the maximum during solar noon and from your attachment should usually be less than 7.8 kW. Panels are rated at "standard temperature and conditions", which you almost never see (possibly for 15 minutes around solar noon on a perfect day).

How come even when our batteries are charged and the system is putting power back into the grid we still draw power from the grid?
It's probably time-averaged. For example, in a 15 min period, you might take some from the grid and put some on the grid, so during that period it appears to go both ways.

Hope that helps!
 
Welcome to the forums!

"Kwts" isn't really a measure. A kilowatt (kW) is a measure of power and a kilowatt-hour (kWh) is a measure of energy. You pay for kWh, but devices are typically measured in kW (and how much energy they use depends on how long they're run). Not trying to knitpick, but if you use kW when you mean kWh folks might assume you're talking about something else and give you the wrong answer.

OK noted, thanks.

From your attachment, you have a 24 panel array capable of producing a maximum of 7.8 kW (kilowatts) at STC.

We have 38 panels, I just added one of the submission forms to show the system - I should have added screen shot of array display which I add now.

You can use a tool like SAM to give you what's expected for your area. You can keep a record of kWhs consumed/produced off the grid meter with pencil & paper, but I use RF. If you have current transducers (CTs) you can keep a record independent from SolarEdge's monitoring. SolarEdge might have an interface allowing you to get to the raw data. The nice thing I've heard about SolarEdge is you can get per panel information, so probably the first thing to look at is to see if the panels are all roughly producing the same.

Ok will see how I can pull the info out, I went to the RF site, and my brain hurts!

Looks like the installation is in Australia, so using an insolation calculator, and assuming the panels are aligned for year-round optimization (you might be optimized to the season when you use the most power) then the insolation for December is your best month, around 5 and the worst month is June around 2.8. So, you should see between (5x7.8=) 39 kWh/d to (2.8x7.8=)21 kWh/d. Of course, if you have any shade it'll be a lot worse.

If you mean kW, then the power is at the maximum during solar noon and from your attachment should usually be less than 7.8 kW. Panels are rated at "standard temperature and conditions", which you almost never see (possibly for 15 minutes around solar noon on a perfect day).


It's probably time-averaged. For example, in a 15 min period, you might take some from the grid and put some on the grid, so during that period it appears to go both ways.

Hope that helps! Thanks, appreciate you taking the time, I'll have to work a little more to understand why I'd take anything from the grid when we're showing excess of power production and full batteries.

1
Welcome to the forums!

"Kwts" isn't really a measure. A kilowatt (kW) is a measure of power and a kilowatt-hour (kWh) is a measure of energy. You pay for kWh, but devices are typically measured in kW (and how much energy they use depends on how long they're run). Not trying to knitpick, but if you use kW when you mean kWh folks might assume you're talking about something else and give you the wrong answer.


From your attachment, you have a 24 panel array capable of producing a maximum of 7.8 kW (kilowatts) at STC.


You can use a tool like SAM to give you what's expected for your area. You can keep a record of kWhs consumed/produced off the grid meter with pencil & paper, but I use RF. If you have current transducers (CTs) you can keep a record independent from SolarEdge's monitoring. SolarEdge might have an interface allowing you to get to the raw data. The nice thing I've heard about SolarEdge is you can get per panel information, so probably the first thing to look at is to see if the panels are all roughly producing the same.


Looks like the installation is in Australia, so using an insolation calculator, and assuming the panels are aligned for year-round optimization (you might be optimized to the season when you use the most power) then the insolation for December is your best month, around 5 and the worst month is June around 2.8. So, you should see between (5x7.8=) 39 kWh/d to (2.8x7.8=)21 kWh/d. Of course, if you have any shade it'll be a lot worse.

If you mean kW, then the power is at the maximum during solar noon and from your attachment should usually be less than 7.8 kW. Panels are rated at "standard temperature and conditions", which you almost never see (possibly for 15 minutes around solar noon on a perfect day).


It's probably time-averaged. For example, in a 15 min period, you might take some from the grid and put some on the grid, so during that period it appears to go both ways.

Hope that helps!
 

Attachments

  • Screen Shot 2021-12-27 at 9.24.27 am.png
    Screen Shot 2021-12-27 at 9.24.27 am.png
    476.5 KB · Views: 10
For anyone to provide any sort of valid response, we will need to know what equipment you have and how it is setup. Please provide Make / Model of all the solar gear installed, any configuration information provided etc.
Your LOCATION (nearest large city, state/province) is also important.
Also if you know what angles / direction / degrees your solar panels are aimed at etc...
More info provided the better responses you will get.
Thanks Steve, noted!
 
I went to the RF site, and my brain hurts!
It's not as bad as it seems. Mainly you just follow beMasher's instructions and play around with it a bit. It was fun!

But then, I also wrote my own monitoring code and I measure my solar panel's output by comparing it to nearby weather stations from weather underground. Basically, you know the area of your panels (meters squared), a weather underground site that reports the watts/meter-squared gives you current power, so (Watts/m² actual) x (m² of array) = watts your array sees. Panels start out around 20% efficient (and lose a bit each year) and you lose some based on an imperfect tilt angle. But the (watts your array puts out) ÷ (watts-at-current-conditions) gives you your actual efficiency (which will change with the seasons as the sun's relative angle to your panel changes). They should be closest to your panel's specs at solar noon (about 1 pm today for you).
 
It's not as bad as it seems. Mainly you just follow beMasher's instructions and play around with it a bit. It was fun!

But then, I also wrote my own monitoring code and I measure my solar panel's output by comparing it to nearby weather stations from weather underground. Basically, you know the area of your panels (meters squared), a weather underground site that reports the watts/meter-squared gives you current power, so (Watts/m² actual) x (m² of array) = watts your array sees. Panels start out around 20% efficient (and lose a bit each year) and you lose some based on an imperfect tilt angle. But the (watts your array puts out) ÷ (watts-at-current-conditions) gives you your actual efficiency (which will change with the seasons as the sun's relative angle to your panel changes). They should be closest to your panel's specs at solar noon (about 1 pm today for you).
20% efficient to start with? That’s not so encouraging. Thanks for your reply, appreciate you taking the time.
 
20% efficient to start with? That’s not so encouraging. Thanks for your reply, appreciate you taking the time.

Not encouraging? fairly fantastic, actually.

You could convert sunlight to heat more efficiently.
The trick with PV is first select a bandgap of energy, then harvest that much energy from each photon. An IR photon has less energy, passes through silicon without interacting. Higher energy photons give you one electron with bandgap energy, but excess energy is wasted as heat.

You can get more efficient PV, which is accomplished with multiple thin-film layers each harvesting different energy photons. But you'll spend more money per kWh doing it. Might save space and weight, if that is important to you.

Single-crystal silicon PV panels can be bought for around $0.50/W, and will produce power for about $0.025/kWh (amortized over 10 years, even less over their 25 to 40 year lifespan)

Don't worry about "efficiency" until after the power from sunlight has been harvested and turned into electricity. Just worry about $/kWh.
You can worry about efficiency using the electricity.
 
How come our system sometimes produces more than 6 Kwts (sometimes shows 11-12Kwts solar production) but lately seems to max out at 6Kwts?

Probably "Insolation", how much sun intensity you get during the current season. Check an on-line insolation calculator for your panel angle and this month (for sun angle).

But it can be a fault in the equipment. I found one wire open circuit, so I was getting power from only half an array.
Another array with older panels, I found reduced current from one string.
A clamp DC ammeter is good to compare PV string current, if you have multiple strings.
 
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