Solar output confusion

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Solar output confusion

Postby engineern6719 » Mon Jul 23, 2018 6:49 pm

Apologies if posting in the wrong area.Not quite 12 months ago we had a 5.4 kw solar system fitted.Its a single phase inverter integrated into a three phase electrical system.The three phase meters were replaced with a single net meter displaying import and export figures.Checking inverter output during this winter period on average it’s around 23-24 kWh hours per day.Pre solar our average daily usage during winter was 15.5 kWh per day.However since our last meter read 35 days ago we have only exported 1kwh to the grid.
To me this doesn’t sound right.Could somebody please advise me if my thinking is right or wrong.
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Re: Solar output confusion

Postby Gordon-Loomberah » Tue Jul 24, 2018 9:01 am

Welcome to the Energy Matters Forums Engineern6719 :)

It certainly does sound as if something is amiss, but without comprehensive system monitoring, it can be quite difficult to determine what is going on.
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Re: Solar output confusion

Postby engineern6719 » Tue Jul 24, 2018 12:33 pm

I made a complaint to the retail supplier just before the end of the last billing cycle for the same problem.They asked me to keep a log for a week to 10 days recording and photographing readings three times a day.I don’t know how they did it but they concluded from this information that the system was serviceable.To me a complete waste of time.To have the meter in the meter box checked they want to charge me $460.
All I want is somebody to explain to me if the system is serviceable why the discrepancy in the figures but the only people you can talk to are non technical staff.Frustrating.
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Re: Solar output confusion

Postby Gordon-Loomberah » Tue Jul 24, 2018 5:29 pm

Was your average daily winter energy usage 15.5kWh in total for all 3 phases, or just the phase the solar is now on?
Did you get rid of 2 supply phases, or did they install a new 3ph meter, which just has solar on one phase, the other 2 being supply only? Perhaps the meter nets out solar and total usage across all 3 phases?
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Re: Solar output confusion

Postby engineern6719 » Tue Jul 24, 2018 6:48 pm

My average daily usage quoted was for the 3 phases taken from a pre-solar bill during the winter period.The three phases were retained.The three meters were replaced with a single “net” meter which has a single lcd display.The display cycles between import and export.Whether its true or not I was told that the meter totals the usage across the three phases.Solar production is subtracted from the usage.If there is excess solar it’s exported to the grid.Ifthere is insufficient solar for daily usage it’s imported off the grid.
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Re: Solar output confusion

Postby Gordon-Loomberah » Tue Jul 24, 2018 7:24 pm

If you only exported 1kWh, then the display should be showing power being imported almost the entire time. Is that the case when you look at the meter? Typically usage must be well in excess of your generation to result in almost no exports over a month.
How many kWh have you imported during the past 35 days?
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Re: Solar output confusion

Postby engineern6719 » Tue Jul 24, 2018 8:40 pm

Over the 35 day period we have imported 411 kWh which equates to 11.7 kWh per day on average.From those figures the solar would be providing some of the power but not as much as I thought it would.
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Re: Solar output confusion

Postby Gordon-Loomberah » Tue Jul 24, 2018 10:10 pm

Are you sure your PV system has been producing 23-24kWh/day at this time of year? I don't know where you are located, but that sort of output from a 5kW system suggests somewhere very sunny, and not in the south of Australia.
If it is producing that output on average in July, then it appears you are using a lot more energy than you thought.
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Re: Solar output confusion

Postby engineern6719 » Tue Jul 24, 2018 10:59 pm

I live in north west Sydney.The 23-24 kWh daily solar production that I quoted earlier is taken off the inverter via wifi.Am I interpreting these figures correctly.
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Re: Solar output confusion

Postby Gordon-Loomberah » Wed Jul 25, 2018 9:25 am

It has certainly been sunnier than average for much of NSW lately, see below graph for Richmond RAAF base, which should be similar to your location- very near the the highest recorded sunny weather for July.

RichmondRAAF-2018solar.gif


Even so 23-24kWh/day seems a little on the high side for an average, but not unrealistic for sunny cool days.

However, having loads greater than solar production for the entire day for a whole month, to allow only 1kWh of export seems highly unlikely. I assume that you don't have the inverter set to limit exporting?

Any idea how you could be using more than twice this: "Pre solar our average daily usage during winter was 15.5 kWh per day."

I think you need to install a monitoring system so that you can determine what is really going on.
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