Help understanding power generation and usage

[statman78]

We just had 20 solar panels installed on our house in Chiang Rai.  The charts showing how much power is generated and how much we use do not make sense.  No matter how much power we generate our total consumption is always greater.  See the 2 charts below from yesterday and this morning. From today’s chart it shows consumption of about 2kW at 9:00 am with consumption being under 1kW over night.  Nothing has been turned on during this time.  The only change is that the yard lights which are on overnight were turned off about 6:30 this morning.  The spikes are when I was making breakfast.  In the full chart from yesterday it can be seen that consumption follows the generation curve but is always above it.  Why???  I studied mechanical engineering, not electrical and it was many years ago.  The only reason I can think of is that we are drawing some power directly from the grid.

 

I’m sure there are people who can help me understand this.  We are also contacting the people who installed the system.

 

 

 

[KhunLA]

If conx to grid, then yes, drawing from.   Turn the grid off, if possible for your solar production/consumption.

 

Your app may have filters to show all, consumed, produced, exported, purchased.   Mine does.

 

Assuming you don't have ESS/batteries for storage of excess produced. Our system produces just enough to cover consumption, once batteries topped up, as we don't export, or import, since we have grid turned off.

 

Prior to that, new digital meter and grid tie in, the app showed consumption/production & import/export from grid.

 

Now basically off grid, so production is usually a tad more than consumption.  

 

 

 

 

[KhunLA]

If can't turn grid off, simply note the meter reading before production/sunrise, then at sunset.   Should be within the ballpark of your consumption vs production difference.

 

 

[statman78]

4 minutes ago, KhunLA said:

If can't turn grid off, simply note the meter reading before production/sunrise, then at sunset.   Should be within the ballpark of your consumption vs production.

 

 

KhunLA,

 

Thanks for the info.  We can’t turn off the grid.  So I will do as you suggested.  We don’t have batteries for storage of excess.  Also we are waiting for approval from the power company to export the excess back to the grid.  Does this mean any excess power we generate is wasted until we can “sell” it back to the power company?  Also, would the gap between the lines disappear during those times when we generate more power than we use and are approved to send it back to the power company for credit?

[KhunLA]

38 minutes ago, statman78 said:

KhunLA,

 

Thanks for the info.  We can’t turn off the grid.  So I will do as you suggested.  We don’t have batteries for storage of excess.  Also we are waiting for approval from the power company to export the excess back to the grid.  Does this mean any excess power we generate is wasted until we can “sell” it back to the power company?  Also, would the gap between the lines disappear during those times when we generate more power than we use and are approved to send it back to the power company for credit?

If exporting & not compensated ... yes, wasted production.  You should be able to turn export off in the inverter's settings.

 

All things being equal, your system will generate whatever the load is.   With grid tie in, if not generating enough, then draws off the grid, and the opposite, when generating  more than needed, will export excess to the grid.

 

I labelled the graph to help explain, and added the night time.

 

When have ESS/battery storage of excess, our system production goes to load & batteries, till topped up, then simply allows in, as much is needed for the house load.  Since grid turned off, overnight, we'll draw off the ESS/battery storage till start producing enough after sunrise, about 0700 hrs for us.   Stops producing enough about 1700 hrs, so back to the ESS. 

 

So we're about 10hr on solar, 14 hrs on ESS.

[JBChiangRai]

There are some tests you can do, it looks to me like you are exporting to the grid (because otherwise I'd expect your PV production to plateau rather than follow the typical sunlight production bell shape), assuming you have a spinning wheel meter, it should be going backwards at peak times, if you have a digital meter, maybe it records import and export separately.

 

Check your meter reading(s) at midnight and again at midnight the next day and see how they compare to your charts.

 

 

It does also look like either a bug in the graphing software, it's probably adding PV production to Consumption to give you the Red line or more likely the CT Transformer is on the wrong leg (PEA/House).

 

 

[KhunLA]

Look at your last bill / meter reading.  You do NOT want to go into the negative.   So need to pay attention to what you are exporting.  

 

Are the components of your system approved components by PEA standards, on their list.  Did you/wife apply for grid feed in compensation or your installer, if using.

 

If applied, and not approved to export for compensation, I would expect a digital meter will be installed in the near future.  Stay on the positive side of your meter reading, till PEA makes a decision on you application for feed in compensation.

 

Take note when you meter was read last, and don't export couple days before or after that date.  You don't want them to see the meter running in reverse.

[statman78]

47 minutes ago, KhunLA said:

Look at your last bill / meter reading.  You do NOT want to go into the negative.   So need to pay attention to what you are exporting.  

 

Are the components of your system approved components by PEA standards, on their list.  Did you/wife apply for grid feed in compensation or your installer, if using.

 

If applied, and not approved to export for compensation, I would expect a digital meter will be installed in the near future.  Stay on the positive side of your meter reading, till PEA makes a decision on you application for feed in compensation.

 

Take note when you meter was read last, and don't export couple days before or after that date.  You don't want them to see the meter running in reverse.

Thanks again for the info.  Great stuff.  The installer did all of the paperwork.  Our system does meet PEA standards.  According to the installer it has been taking 6-8 months for approval to export for compensation..  I’ll make sure we keep an eye on the meter.

[statman78]

1 hour ago, JBChiangRai said:

There are some tests you can do, it looks to me like you are exporting to the grid (because otherwise I'd expect your PV production to plateau rather than follow the typical sunlight production bell shape), assuming you have a spinning wheel meter, it should be going backwards at peak times, if you have a digital meter, maybe it records import and export separately.

 

Check your meter reading(s) at midnight and again at midnight the next day and see how they compare to your charts.

 

 

It does also look like either a bug in the graphing software, it's probably adding PV production to Consumption to give you the Red line or more likely the CT Transformer is on the wrong leg (PEA/House).

 

 

I’ll check the meter to see how it compares to the charts.  Right now we are waiting approval for export.  Ty our comment  about adding PV production to consumption is interesting.  when looking at the chart from yesterday I see that the gap between the 2 lines is larger during the time we are consuming more power due to the swimming pool pump being on.  I’ll also have the installer look at all of the connections.

 

Thanks!

[Crossy]

Do you have a normal disc-type meter or an electronic one?

 

The disc meters actually go backwards when exporting so it's easy to see.

 

By the way, one member has been waiting >2 YEARS for his export meter!

[JBChiangRai]

15 minutes ago, Crossy said:

By the way, one member has been waiting >2 YEARS for his export meter!

When you don't want one, they fit one immediately, when you do want one, you can't get one.

 

TiT

[statman78]

3 hours ago, Crossy said:

Do you have a normal disc-type meter or an electronic one?

 

The disc meters actually go backwards when exporting so it's easy to see.

 

By the way, one member has been waiting >2 YEARS for his export meter!

I have a disc type meter.  Based on the great comments and suggestions I received today I went out a couple of times to check at saw that it was going backwards.  As was suggested earlier the chart I originally posted looks like PV production is added to consumption which makes it look like I am consuming more than I’m producing.  Since the meter was running backwards this is not the case.  I also have a graphic that shows how much power I’m using from my system and how much I am drawing from the grid and any time.  This graphic also must be wrong since it shows I am drawing power from the grid when I can plainly see that my meter is running backwards.

 

As mentioned earlier I’ll need to watch this when it comes time for the monthly meter reading since I haven’t been approved to export my excess.

 

Thanks to all who replied!

[Crossy]

I wonder if (like others have said) your CT is on the wrong lead or is the wrong way round.

 

Definitely time to get your installer involved.

 

[KhunLA]

10 minutes ago, statman78 said:

This graphic also must be wrong since it shows I am drawing power from the grid when I can plainly see that my meter is running backwards.

 

As mentioned earlier I’ll need to watch this when it comes time for the monthly meter reading since I haven’t been approved to export my excess.

 

Thanks to all who replied!

That doesn't sound right at all.   As suggested, ring up your installer to check over things.

 

When things are running consistent A$$ backwards, make a short vid of you inverter screen & meter running backwards.   So he believes you know what your suggesting ????

[Muhendis]

5 hours ago, JBChiangRai said:

When you don't want one, they fit one immediately, when you do want one, you can't get one.

 

TiT

That is so true.

It took seven years to finally get my normal rate meter fitted but would you believe it took 'em just ten minutes to remove it the other day.

My dearly beloved forgot to pay the January bill of 82Bht.

When you want something forever is the shortest time. On the other end of the scale, greased lightning looks so slow.

[BritManToo]

9 hours ago, statman78 said:

n the full chart from yesterday it can be seen that consumption follows the generation curve but is always above it.  Why???

It's because they connected this little current measuring coil with the wires the wrong way round.

 

[asf6]

Hi Statman,

Interesting graphs. Here's what I learned from them. 

 

1) Your solar cell system has a maximum output of 4kw, which it achieved at around midday. 

2) Your solar cell system produced electricity for about 12 hours and nothing for about 12 hours. 

3) The amount of electricity it produced between 6.30am and 6.30pm averaged about 2kw for those 12hrs, so approximately 24kwh, which compares to the yield stated on the graph (24.71kwh).

4) From 6.30pm to 6.30am, you consumed about 10 kwh of energy - 6kwh from 6.30pm to midnight and 4kwh from midnight to 6.30am. 

 

Interesting thread.

 

 

[JBChiangRai]

11 hours ago, BritManToo said:

It's because they connected this little current measuring coil with the wires the wrong way round.

 

It produces AC, so it's not connected with the wires the wrong way round, it's over the wrong wire

[Crossy]

17 minutes ago, JBChiangRai said:

It produces AC, so it's not connected with the wires the wrong way round, it's over the wrong wire

 

Whilst it does produce AC, it's the phase of that AC relative to the mains voltage that tells the inverter which way the energy is flowing. It definitely matters which way round it goes.

 

But you are right, it could well be on the wrong wire.

[a340bangla1]

Statman,

 

it looks to me like us, you have a Huawei inverter, at least the software looks the same as ours. That page you took the screenshot of has an upper part, that normally shows the flow of electricity. Load on the lower left side, supply from solar from the top and grid from the right. Like this:

 

 

In case you are feeding to the grid, this will be shown by the small arrows going down from your system.

 

Here are my curves from some days ago (we have a 5 kW system and is is quite hazy these days here in Pattaya).

 

 

If I were feeding back to the net, the blue line would turn green (which I - of course - would never do).

[statman78]

19 hours ago, a340bangla1 said:

Statman,

 

it looks to me like us, you have a Huawei inverter, at least the software looks the same as ours. That page you took the screenshot of has an upper part, that normally shows the flow of electricity. Load on the lower left side, supply from solar from the top and grid from the right. Like this:

 

 

In case you are feeding to the grid, this will be shown by the small arrows going down from your system.

 

Here are my curves from some days ago (we have a 5 kW system and is is quite hazy these days here in Pattaya).

 

 

If I were feeding back to the net, the blue line would turn green (which I - of course - would never do).

Yes we have the same system as you have.  Your top diagram shows that you are using power from the system and from the grid based on the direction the arrows move.  Ours shows the same.  The strange part is that while our diagram shows we are getting power from the grid, at the same time I can look at our meter and is running backwards so we are exporting power back to the grid.  When the sun goes down the meter runs in the forward direction so we are using power from the grid.  For the last couple of days I’ve been going out and checking the meter at the same time everyday.  Overall we are using a little more power from the grid than what we are sending back since the meter reading is a bit higher everyday.

[a340bangla1]

Can you say how much is shown as coming from the grid in a situation when the meter is running backwards ?

[statman78]

20 hours ago, a340bangla1 said:

Can you say how much is shown as coming from the grid in a situation when the meter is running backwards ?

It varies but ranges from .9kW to 2kW depending on how much power my system is generating 

[KhunLA]

22 hours ago, a340bangla1 said:

Can you say how much is shown as coming from the grid in a situation when the meter is running backwards ?

My inverter shows how much/what and where it's going in every direction in real time.  panels, grid, battery, load (house).   On the inverter panel, and app. along with totals currently used/using and for the day.   Not sure about the inverter, but app stores it all in memory, for years.

 

Depending on need, in real time, the 'arrow' may reverse direction as we're looking at, if sun is blocked by a cloud and load is drawn from elsewhere (grid or battery) which we prioritize in the settings.  Solar-battery-grid for us, till battery at certain %, then grid if no solar.

 

Luckily, yet to 'need' the grid overnight or at all, since solar installed.

[Crossy]

@statman78 can you post a photo of where your CT is positioned?

 

Any joy with the installer?

[a340bangla1]

Statman,

 

I seem to be fresh out of ideas. This is what I am seeing this morning:

I can associate events in the house with this graph: aircon in bedroom switched off, espresso machine heated up, pool pump started, sprinklers and deep well pump coming on and turning off..... Consumption from PV is reduced when consumers go off. All as it should be. I have turned feed to the grid off for the time being.

 

So I could not imagine what could be wrong in your system.

One thing might be worthwhile to try though: You could turn of the feed to the grid for a while and turn it back on after some time to see if this changes anything.

 

KhunLA:

 

Unfortunately, data is going to and stored on the Huawei server, the graph is updated every 5 minutes. Of course, the arrows also show direction of feed, but not in (real) real time.

 

I intensely dislike having my data in China, but what can I do ? This is one thing about Huawei...

 

 

[statman78]

28 minutes ago, Crossy said:

@statman78 can you post a photo of where your CT is positioned?

 

Any joy with the installer?

I’ll post a photo later since I am in Bangkok now and the system is on our house in Chiang Rai.

The installer did a great job.  It took 2 days to install everything.  

[JBChiangRai]

34 minutes ago, statman78 said:

I’ll post a photo later since I am in Bangkok now and the system is on our house in Chiang Rai.

The installer did a great job.  It took 2 days to install everything.  

Can I ask who you used? and what it cost?

[Crossy]

44 minutes ago, statman78 said:

I’ll post a photo later since I am in Bangkok now and the system is on our house in Chiang Rai.

The installer did a great job.  It took 2 days to install everything.  

 

No problem. I'm sure your man did a good job, but we all make mistakes, and simply getting the CT wires reversed isn't beyond the realms of possibility.

 

One easy test you could do is actually set the inverter to not export, then check what the meter is doing.