Solar Power Production

[darrenbowsher]

I have an off grid system in the UK 4.8kw the system consist of:
2 String, each 2.4kw
2 x 5.5kw Hybrid Off Grid Invertors
1 x 10Kwh Battery DoD Set at 50%.
In September it dropped down to 78kwh.
The start up voltage is 120v with MPPT Range 120v to 500v
Any ideals why the generation is so low in September

 

[Shimmy]

Partial shading is generally the most likely culprit, but can you post the model/specs for your solar panels? Roof layout might be helpful as well.

 

[darrenbowsher]

Capacity
Parallel Capability	YES, 12units
INPUT
Nominal Voltage	230VAC
Acceptable Voltage Range	170-280 VAC (For Personal Computers),90-280 VAC (For Home Appliances)
Frequency	50/60HZ (Auto sensing)
OUTPUT
Nominal Voltage	220/230VAC ± 5%
Surge Power	10000VA
Frequency	50Hz/60Hz
Waveform	Pure Sine Wave
Transfer Time	10ms (For Personal Computers) ; 20ms (For Home Appliances)
Peak Efficiency (PV to INV)	97%
Peak Efficiency (Battery to INV)	93%
overload Protection	5s@>=150% load; 10s 110%~150% load
Crest Factor	3:01
Admissible Power Factor	0.6~1(inductive or capacitive)
BATTERY
Battery Voltage	48 VDC
Floating Charge Voltage	54 VDC
Overcharge Protection	63 VDC
Charging Method
Solar Charge & AC Charge
Solar Charge Type
Max. PV Array Power

 

[SeaGal]

What are you drawing / attempting to draw from the system? How are you measuring the production?

Being off grid, it will only generate if there is somewhere for the energy to go once the battery is charged, or is being charge at whatever the maximum charge rate of your battery is.

 

[darrenbowsher]

What are you drawing / attempting to draw from the system? How are you measuring the production?

Being off grid, it will only generate if there is somewhere for the energy to go once the battery is charged, or is being charge at whatever the maximum charge rate of your battery is.

Yes, I measure it with an electric meter which recorded the AC output DoD of 10kwH Battery is 50%, in September Solar Production was 78kwh, Grid was 156kwh. So I know there will be a difference to Ongrid, I would expect more that 78kwh in september

 

[darrenbowsher]

Partial shading is generally the most likely culprit, but can you post the model/specs for your solar panels? Roof layout might be helpful as well.

see above

 

[Solar Guppy]

Yes, I measure it with an electric meter which recorded the AC output DoD of 10kwH Battery is 50%, in September Solar Production was 78kwh, Grid was 156kwh. So I know there will be a difference to Ongrid, I would expect more that 78kwh in september

Sounds like you are not measuring the power the home used, just what is exported?

 

[Shimmy]

Your panel Vmp is ~30V, so 6 in series is right at the minimum voltage for the MPPT. When you have clouds this voltage is reduced and outside the acceptable range for the MPPT so you get no production.

Ideally you would have 7-10 panels per string.

 

[SeaGal]

I measure it with an electric meter which recorded the AC output

Do you mean AC output of the inverter to the house only usage?

Sounds like you are not measuring the power the home used, just what is exported?

I assumed it won't be able to export anything if it is off grid?

@darrenbowsher Sorry, am bit confused what exactly you are measuring? You say off-grid, yet refer to solar production and grid usage? Maybe a diagram would help. And why is battery only set to 50% DoD?

 

[darrenbowsher]

Do you mean AC output of the inverter to the house only usage?

I assumed it won't be able to export anything if it is off grid?

@darrenbowsher Sorry, am bit confused what exactly you are measuring? You say off-grid, yet refer to solar production and grid usage? Maybe a diagram would help. And why is battery only set to 50% DoD?

Yes its off grid hybrid, I can use an AC from the house when battery or solar aren't enough but cant feed back. Correct no export capability

 

[darrenbowsher]

Sounds like you are not measuring the power the home used, just what is exported?

no it doesnt export

 

[darrenbowsher]

Your panel Vmp is ~30V, so 6 in series is right at the minimum voltage for the MPPT. When you have clouds this voltage is reduced and outside the acceptable range for the MPPT so you get no production.

Ideally you would have 7-10 panels per string.

Thanks

 

[SeaGal]

OK, so you're not really measuring 'Solar Production', you're measuring just what your house is using from either:-

a) direct solar production if house load is load is less than available PV power
b) house usage from battery, but have restricted a smallish battery to only 50% DoD

Then you will need to consider :-

1) you will be drawing from the grid when your house load becomes greater than what the inverter and conjure up from PV and battery
2) you will be drawing from the grid when the battery is depleted (and at 50% DoD on a 10kWh battery we're probably only looking at between 4 and 5 kWh of available stored energy)
and
3) if the battery is full (or nearly full) and the house is not using much, the inverter will ramp down PV production to meet battery + house demand.

Now that it is October and you're probably not producing anything between about 4pm one day to 9am the next day _and_ it's probably only 60% of 4.8kW when the sun is shining this time of year, then I don't see there is necessarily a problem

It sounds to me that you need to have more finer granularity of measurement and log not only AC output, but PV generation, battery charge, discharge, SOC and grid usage - I do that with my grid-tied system using an emonPi with 5s resolution. You can then clearly see what is using power, when and from where.

 

[darrenbowsher]

OK, so you're not really measuring 'Solar Production', you're measuring just what your house is using from either:-

a) direct solar production if house load is load is less than available PV power
b) house usage from battery, but have restricted a smallish battery to only 50% DoD

Then you will need to consider :-

1) you will be drawing from the grid when your house load becomes greater than what the inverter and conjure up from PV and battery
2) you will be drawing from the grid when the battery is depleted (and at 50% DoD on a 10kWh battery we're probably only looking at between 4 and 5 kWh of available stored energy)
and
3) if the battery is full (or nearly full) and the house is not using much, the inverter will ramp down PV production to meet battery + house demand.

Now that it is October and you're probably not producing anything between about 4pm one day to 9am the next day _and_ it's probably only 60% of 4.8kW when the sun is shining this time of year, then I don't see there is necessarily a problem

It sounds to me that you need to have more finer granularity of measurement and log not only AC output, but PV generation, battery charge, discharge, SOC and grid usage - I do that with my grid-tied system using an emonPi with 5s resolution. You can then clearly see what is using power, when and from whe

 

[SeaGal]

Sorry, I don't understand what that graph is showing - it seems to be saying there is nearly 2kWh being generated per hour between 2am and 4am!!

 

[MisterSandals]

it seems to be saying there is nearly 2kWh being generated per hour between 2am and 4am!!

I suspect the x-axis is days of the month, 1-31, rather than hours of an Earth day (1-24).

 

[SeaGal]

Ah! Major blonde moment - LOL -

Though seems you've since removed the graph?

Anyway I still can't get my head around...

I would expect more that 78kwh in september

Do you have graphs showing solar production, battery usage and house draw for a period of (say) a few hours when you'd expect to be getting more than you are?

 

[WindWizard]

I don't think there is enough information provided to come to a conclusion. The MPPT Charge Controller will provide information that is useful to analyzing the issue.

A few possibilities have been discussed. Looking at the data from the MPPT Charge Controller will confirm whether or not the issue is low PV voltage.

IF OP purchases a DC clamp meter, then current and voltage can be measured at the panels. It is just a matter of troubleshooting to determine what the issue is.