monitoring solar production/potential

[gamb00ler]

I have 11kW of panels feeding into a 10kW inverter (SMILE-T10-HV-INV).

 

The software they have provided shows how much power the panels are pumping into the house load and/or batteries.

When the batteries are full and the house load is low, the software only displays the amount of solar production that is being used.  I cannot see what the current maximum solar production could be.  I know some of the potential output is discarded because no place to expend it.

 

Is there a way to see the maximum panel output that is possible under the current conditions?

 

I can think of a few low priority power expenditures that I could use to increase the current load and consume the power that is currently being discarded.  IE time shifting consumption.

 

Edited August 12, 2023 by gamb00ler

[Bandersnatch]

16 hours ago, gamb00ler said:

I have 11kW of panels feeding into a 10kW inverter (SMILE-T10-HV-INV).

 

The software they have provided shows how much power the panels are pumping into the house load and/or batteries.

When the batteries are full and the house load is low, the software only displays the amount of solar production that is being used.  I cannot see what the current maximum solar production could be.  I know some of the potential output is discarded because no place to expend it.

 

Is there a way to see the maximum panel output that is possible under the current conditions?

 

I can think of a few low priority power expenditures that I could use to increase the current load and consume the power that is currently being discarded.  IE time shifting consumption.

 

I have a similar problem. The software that came with my Growatt inverters (I have 3x5kW in parallel) only shows power that is consumed.

 

In addition to powering the house, I also am also able to power my EV and electric motorbike, but the system was designed to power an electric SUV and an electric pickup truck  - when one becomes available in Thailand. So I would like to know how much power my system is making in total to know if that is possible.

 

As I over the 5kW maximum for single phase, I am not allowed to feed back to the grid, so currently excess production is curtailed.

 

I am also trying load shifting with various appliances like my ice maker, robovac and Dyson charging that are on timers to run in the middle of the day 

 

 

 

Edited August 13, 2023 by Bandersnatch

[KhunLA]

@gamb00ler

Ours also only registers production for use, now.  Before we got the digital meter, we did export on a few days.

 

Our system is 9.7kWh of panels w/8kW inverter, and on our best export day, and on a crappy weather day, as peaks & valleys show, we exported 26.8kWh.

 

Max production hours seemed to be from 1000-1400, with inverter maxing output of 8.8kWh, if sunny.  We could probably have an excess of 30kWh, if sunny with our usage.  Max production maybe around the 60kWh mark on sunny day.  

This shows we can hit max production around 1000 hrs, previous graph as late as 1400 hrs

Edited August 13, 2023 by KhunLA

[Muhendis]

Power is not discarded. Solar panels produce enough power for the loads which are applied to them.

There is a maximum limit to this, dictated by the area of the panels, which will not be exceeded.

It follows from this that you cannot measure the power from the panels which is not being used.

Best for estimation is written on the label stuck on the rear of the panel (PMax).

Subtract from this the thermal derating figure according to the panel temperature then subtract a further amount which is 1%/year (some newer panels are better than this) to get the probable potential output.

[McTavish]

Output from my 10kw Deye was only showing Production/Consumption until I started feeding back to grid (shhhh) and I got a surprise at midday to see 7.37kw being produced out of 12 (x 550w) Longi PV's = 608w per panel 

The panels were 100% aimed at the midday sun and it was a totally clear sky.  

[007 RED]

OK, my small scale system is not in the big boy's league, but the Sofar 2.2kW GTI does seem to give me feedback as to what my 4 x 415W panels, which are connected in series are producing, as can be seen from the graph below which I downloaded from the monitoring facility a few minutes ago.

 

Obviously the 'big dips' in the current produced by the array is a result of some 'white/grey fluffy stuff floating overhead'.

[bluejets]

What your graph shows is not only what the panels are producing per se but, the load connected ( current) which is varying anywhere between 2 and 10 amps over a 4 hour ( approx) period. 

Voltage is fairly constant over the sample period @ around the 120v dc input level.

 

Your assumption about clouds being the source of the current fluctuations is incorrect.

 

When panels are initially installed it is a common practice/requirement to measure and record the panels "short circuit " current which is an indicator of their capacity.

[Muhendis]

1 hour ago, bluejets said:

Your assumption about clouds being the source of the current fluctuations is incorrect.

The amount of electricity the panel produces relates directly to the amount of sunlight falling on the panels.

If the OP is using pretty well all the panels can produce under good sunlight light conditions and a cloud passes over, there is every likelihood that the output from the panels will fall below the power demand. In that case the current will fluctuate.

Fix for this is more panels.

Edited August 14, 2023 by Muhendis

[KhunLA]

1 hour ago, bluejets said:

Your assumption about clouds being the source of the current fluctuations is incorrect.

Clouds, rain, even high pollution levels block the sun's rays from hitting the panels.   Very real production fluctuation because of it.   I can look at the inverter showing real time drop in production as sunlight is blocked by clouds.

 

As stated, if needed, simple solution would be more panels.  Thankfully not needed, as when the sun isn't brutally hot, no need to run the ACs as abusive when temps are high.

 

Of course if need to charge your EV, and didn't plan it well, may need to supplement with the grid.  Advantage of having 2 EVs, as 1 is always topped up.

Edited August 14, 2023 by KhunLA

[Fruit Trader]

4 hours ago, bluejets said:

What your graph shows is not only what the panels are producing per se but, the load connected ( current) which is varying anywhere between 2 and 10 amps over a 4 hour ( approx) period. 

Voltage is fairly constant over the sample period @ around the 120v dc input level.

 

Your assumption about clouds being the source of the current fluctuations is incorrect.

 

When panels are initially installed it is a common practice/requirement to measure and record the panels "short circuit " current which is an indicator of their capacity.

It's very likely this inverter is exporting which means all energy being produced will be consumed. If this is the case, current variations will be from cloud movements and the constant voltage from the inverters control of power point. 

[007 RED]

3 hours ago, bluejets said:

Your assumption about clouds being the source of the current fluctuations is i

As others have pointed out, your 'assertion' is not correct. 

 

FYI... Yesterday during the time frame illustrated by the graph which I showed above, there were intermittent clouds from late morning through to mid afternoon which blocked the sunlight hitting the panels.  As a result, it could be clearly seen that there were a consistent drops in the current produced by the array as the cloud(s) blocked sunlight hitting the panels and a clear return of current produced once the cloud cleared .

 

As a further example, take a look at the graph below.  FYI....On the 3rd August (in my location West of BKK) it was a very overcast day. 

 

On the 3rd, my small scale system only managed to produce a measly 3.79 units all day.  You will notice that at approximately 15:11 hrs the system almost 'closed down'.  This being as a result of a torrential rain/thunder storm which lasted for several hours. 

 

Using your assertion, the heavy clouds should have had no affect whatsoever on my system's ability to produce electricity and they should have merrily produced power throughout the storm .  I wish.

[007 RED]

5 minutes ago, Fruit Trader said:

It's very likely this inverter is exporting which means all energy being produced will be consumed. If this is the case, current variations will be from cloud movements and the constant voltage from the inverters control of power point. 

You've 'hit the nail on the head'.  My small scale GTI system is normally allowed to export any surplus electricity to the grid.  The exception being the day when the meter reader comes, then it's definitely switched into NO EXPORT mode to stop the disc spinning backwards.

[Fruit Trader]

1 hour ago, 007 RED said:

You've 'hit the nail on the head'.  My small scale GTI system is normally allowed to export any surplus electricity to the grid.  The exception being the day when the meter reader comes, then it's definitely switched into NO EXPORT mode to stop the disc spinning backwards.

I have not done much reading in these threads but interesting to discover a Sofar KTL-G3 series user.

 

I have some history with this series of Sofar inverters which use passive cooling only. I would be interested to know if your inverter logs 'Temperature De-rating' errors on very hot days. If your inverter is located outside in the shade you probably never see this error.

Along with a few guys in a small group, we also use Sofar KTL-G3 inverters (3.3kW version) one for each phase feeding our work sheds. They are de-rated for no export but rarely does the situation arise where we don't use all solar production.

 

Only problems we have had with these inverters are over temperature de-rating solved with extra cooling, over grid voltage solved by changing country code and extracting Modbus information from Sofar technical.

 

Below I show a mod done to all inverters. Electronic controlled cooling fans below the heat sink which includes modified mounting bracket to increase spacing. 

 

 

 

 

Back to the subject of this thread, how to see the maximum panel output that is possible under the current conditions.

To find potential power output above actual consumption would require a known reference. This might be a small loaded collector mounted next to the main string.

 

 

 

 

[gamb00ler]

Could I get a simple device to measure the sun's observable brightness that will produce an output that can be periodically (ever second?) sampled by computer?

 

By using that light meter one should be able to relate that to your solar production.  Once you calculate the appropriate conversion factor from light meter to solar production one could accurately predict what the solar installation could produce at each meter sample time.

[Fruit Trader]

2 hours ago, gamb00ler said:

Could I get a simple device to measure the sun's observable brightness that will produce an output that can be periodically (ever second?) sampled by computer?

 

By using that light meter one should be able to relate that to your solar production.  Once you calculate the appropriate conversion factor from light meter to solar production one could accurately predict what the solar installation could produce at each meter sample time.

Not difficult to create a reference and calculate potential capacity. With this continuously varying potential capacity how would you increase consumption to match?

 

To make a prediction one would also need to know the sky conditions and make a calculated guess what the next time window is likely to deliver.  

[JBChiangRai]

There is no way to tell what the maximum output could be if you’re not using all the potential power.

 

The most effective way to use all the potential power is the export to the grid surplus power.

 

I did assemble a contactor with an adjustable over/under voltage protection device so when the grid voltage hit 245v the contactor tripped allowing power to charge my EV but the car errors after a short while when it trips too often, I could use it for corridor air cons etc but rewiring the breakers sounds too much like work.

 

I do export but turn it off on meter reading day.

[Fruit Trader]

14 minutes ago, JBChiangRai said:

There is no way to tell what the maximum output could be if you’re not using all the potential power.

Potential output can be calcualted from a known reference. The result can be found using a lookup table or real time calculation. 

[JBChiangRai]

18 minutes ago, Fruit Trader said:

Potential output can be calcualted from a known reference. The result can be found using a lookup table or real time calculation. 

Not really a workable solution, it won’t account for atmospheric pollution.

[Fruit Trader]

2 minutes ago, JBChiangRai said:

Not really a workable solution, it won’t account for atmospheric pollution.

Both reference and production array face the same conditions.

[JBChiangRai]

5 minutes ago, Fruit Trader said:

Both reference and production array face the same conditions.

OK I see what you mean. Hard work though. 

 

 

[Fruit Trader]

Just now, JBChiangRai said:

OK I see what you mean. Hard work though. 

 

 

But better than saying it cant be done.

 

I have done it using strings that are not even on the same plane. Very easy for those who have the ability to collect and manipulate data. I believe there are several on this forum.

[gamb00ler]

2 hours ago, Fruit Trader said:

Not difficult to create a reference and calculate potential capacity. With this continuously varying potential capacity how would you increase consumption to match?

 

To make a prediction one would also need to know the sky conditions and make a calculated guess what the next time window is likely to deliver.  

There are time flexible loads that I would use, such as laundry (especially the electric dryer), ironing, etc.  I sometimes pre-cool the portion of the house our son and DIL will want to cool off when they get home from work.  Our house is fairly well insulated so the pre-cooling can be effective for a few hours.

 

You make a good point about needing to pay attention to the potential for cloud cover or rain to reduce PV output.

[gamb00ler]

1 hour ago, Fruit Trader said:

Very easy for those who have the ability to collect and manipulate data. I believe there are several on this forum.

yeah.... math is one of my favorite flavours!  (ooops... I used the non-US spelling)

Edited September 14, 2023 by gamb00ler

[Crossy]

OK, now I'm holding the correct end of the stick ???? 

 

I'm not sure you'll be able to simply use light intensity. It might be possible to use a small panel with its own MPPT and a constant-voltage load like a battery would be (or even use a battery provided it never gets fully charged - use it for your outside lights perhaps).

EDIT Check online for "shunt voltage regulators"

 

You can then measure the power going into the load and extrapolate to the potential available from your array.

 

How you actually apply that to your loads is then "simply" a matter of determining which load best suits the current conditions.

 

The problem is always going to be that, unless you have dynamically adjustable loads (think big light dimmer on a water heater) you're always going to be either over using (and drawing from the grid or your batteries) or under using and throwing away potential energy.

 

Interesting problem ???? 

 

[KhunLA]

12 hours ago, JBChiangRai said:

Not really a workable solution, it won’t account for atmospheric pollution.

@gamb00ler 

Agree, as a few variables unseen, especially pollution.  When AQI is 100, it definitely knocks production down a notch.  Upper clouds, humidity.  

 

Still amazed by how much it will produce on overcast, even if a lite rain.  Then other days you think, what's going on.  Give me some juice.

 

After a year of use, I'm pretty good at estimating how the day is going, and whether to plug the EV in or not.  Unless sunny out, isn't even a consideration till about 0900 hrs.  

 

As soon as the panels are producing 2.5kWh in excess of the load, I know I'm good to charge the EV (@2.3kwh), and the ESSs will top up during prime sun exposure hrs.  Unless it gets heavier overcast.

 

Overcast days, you just need to pay attention, load, EV, hmm ... bake some bread (2.2kWh), not forgetting the 2 ACs are running, but overcast, so not drawing a lot.  Wife is ironing clothes, washing clothes. 

 

Then you hop in shower (3.5kWh), and your drawing off you ESSs ???? for 5 ish minutes.

 

Funny looking at 1st month (Aug 2022) installed, 350kWh, playing conservation, only using ACs when needing    Then last month, 1 year later, about 750kWh, with a couple days out of the house, and it's who cares, ACs on, and not even in the house..

[KhunLA]

Or ... could just get a pair of those adjustable sunglasses, and look up, see how dark they get ????

[Crossy]

42 minutes ago, KhunLA said:

Still amazed by how much it will produce on overcast, even if a lite rain.  Then other days you think, what's going on.  Give me some juice.

 

Yeah, there are evidently many, many factors operating here, some of which would appear to be less than obvious.

 

Sunny day with thin, high, cloud seems to slug it more than more obvious clouds, most odd.

 

@gamb00lerare you looking for an automatic adjustment, or just a way of guestimating your current potential generation??

 

 

[carlyai]

Another factor that may/may not cause a problem is atmosphere temperature inversions.

In my case, in a previous life, I worked for the PMG in Radio Systems Design. So before we installed telephone/television microwave systems we analysed the radio path. We could see what happened to the microwave signal over different weather and seasons.

Different microwave frequencies fade at different rates. Sometimes we could see that the atmospheric  propergation  cause the signal to 'bend' and completely miss the parabolic dish.

As microwave signals fade at different rates we would either change the path or install space or frequency diversion to 'catch' the signal.

Maybe the sun's rays hitting the panels vary slightly due to atmospheric propergation conditions?

 

 

 

[JBChiangRai]

My system has 3 of 6Kw grid-tied inverters on singe phase that I have adjusted the shutdown if grid-over-voltage, inverter 2 set 1 volt higher than inverter 1, inverter 3 set 1 volt higher than inverter 2.

 

On a sunny day, inverter 1 shuts down if we’re not using enough power followed by inverter 2.  Running a couple of air cons is enough to keep 2 inverters running (multi-purpose room, wine cellar/electric & battery room/computer server room has an air con running 24/7). Charging an EV keeps all 3 running.

[JBChiangRai]

5 hours ago, carlyai said:

Another factor that may/may not cause a problem is atmosphere temperature inversions.

In my case, in a previous life, I worked for the PMG in Radio Systems Design. So before we installed telephone/television microwave systems we analysed the radio path. We could see what happened to the microwave signal over different weather and seasons.

Different microwave frequencies fade at different rates. Sometimes we could see that the atmospheric  propergation  cause the signal to 'bend' and completely miss the parabolic dish.

As microwave signals fade at different rates we would either change the path or install space or frequency diversion to 'catch' the signal.

Maybe the sun's rays hitting the panels vary slightly due to atmospheric propergation conditions?

 

 

 

And UFO’s blocking the sunlight is also important.