Discuss My solar array doesn't seem to generate enough energy in the Electrical Forum area at ElectriciansForums.net

agybag

EF Member
Messages
12
Location
Kilmarnock
Hi,
I've recently had a 4KW PV array fitted in March this year however I don't believe it's producing the expected results. Yesterday 29/06/2019 was the hottest day so far with cloudless skies and the system at noon peaked at 2.2KW. I would expect to achieve around my peak which is set at 3.8KW. Is my system faulty and should I have the installers check out the system for any possible issues or am I expecting too much from the system ?
 

littlespark

Electrician's Arms
Messages
2,397
Location
Scottish Borders
It'll depend on the angle of the roof... the angle to the sun and any tree branch obstruction.
3.8 kW is the maximum you can generate in 100% perfect conditions.

2.2 is probably about right, not knowing the circumstances.

Also, is 2.2 the kW reading off the inverter, or off another energy monitor which may be reading generation MINUS what's being used in the house
 
OP
A

agybag

EF Member
Messages
12
Location
Kilmarnock
It'll depend on the angle of the roof... the angle to the sun and any tree branch obstruction.
3.8 kW is the maximum you can generate in 100% perfect conditions.

2.2 is probably about right, not knowing the circumstances.

Also, is 2.2 the kW reading off the inverter, or off another energy monitor which may be reading generation MINUS what's being used in the house
 
OP
A

agybag

EF Member
Messages
12
Location
Kilmarnock
Thanks for the reply,
Conditions on the day were perfect with no obstructions and south facing. 14 x315 watt panels fitted and readings taken via a solo 11 and a wattson monitor with only a difference of 30 watts between them. Max generated was around 2.2 KW which I'm sure is way under the predicted output. Since this is a new system and still in warranty I just want to ensure the output is reasonable (I expected a higher output) on a mid summer's day with no obstructions.
Regards
John
 
  • Like
Reactions: DPG

littlespark

Electrician's Arms
Messages
2,397
Location
Scottish Borders
Next time im in my attic, i'll have a look and see what my 4kW system is kicking out...

It may be you have a faulty panel which is acting as resistor to the others.
Don't go pulling out any cables.... !
 

alasdairp

Regular EF Member
Messages
132
Location
S.W. Scotland
I had one thought - could it have been limited by a high SSE network supply voltage in the area and a relatively low demand for extra power? The inverter cannot keep just pushing up the local supply voltage in order to drive out its "rated full power". Some SSE areas (and elsewhere in the UK!) run at 240 to 245 Vrms normally. The inverter will almost certainly be designed to feed a 230 volt (harmonised! ha!) supply system. As the power monitor shows generated power, did you apply some extra loads (electric fan-heater, kettle, etc) to the house wiring to see if the generated power increased? Worth trying.

I have seen serious examples of problems like this when some new bio-fuel electrical generation plants start up in lightly loaded areas in the summer - areas without adequate 11kV/33kV infrastructure to pass out the power to other areas. In one case in Cambridgeshire an 11 kV substation had to be expanded to also be a 33 kV substation to prevent regular voltage excursion exceed 253 Vrms (and often up to 258 Vrms!). I think similar problems are now becoming more common in some areas with large solar power farms. It also can occur with windfarms at times of high (good) wind and low consumption. National Grid had to regularly pay wind-farms (£10s million per year) to under-generate in order not to exceed maximum permitted system voltages.
 
OP
A

agybag

EF Member
Messages
12
Location
Kilmarnock
I had one thought - could it have been limited by a high SSE network supply voltage in the area and a relatively low demand for extra power? The inverter cannot keep just pushing up the local supply voltage in order to drive out its "rated full power". Some SSE areas (and elsewhere in the UK!) run at 240 to 245 Vrms normally. The inverter will almost certainly be designed to feed a 230 volt (harmonised! ha!) supply system. As the power monitor shows generated power, did you apply some extra loads (electric fan-heater, kettle, etc) to the house wiring to see if the generated power increased? Worth trying.

I have seen serious examples of problems like this when some new bio-fuel electrical generation plants start up in lightly loaded areas in the summer - areas without adequate 11kV/33kV infrastructure to pass out the power to other areas. In one case in Cambridgeshire an 11 kV substation had to be expanded to also be a 33 kV substation to prevent regular voltage excursion exceed 253 Vrms (and often up to 258 Vrms!). I think similar problems are now becoming more common in some areas with large solar power farms. It also can occur with windfarms at times of high (good) wind and low consumption. National Grid had to regularly pay wind-farms (£10s million per year) to under-generate in order not to exceed maximum permitted system voltages.
I'm having the engineer who installed the system over Friday morning to check the system for faults. I should say as of yesterday the solar stopped generating for no apparent reason and the meter stopped flashing but now seems to be generating again. The red light on the meter would usually flash around once every 3-4 seconds but now only flashes around once a minute. There is for sure a fault in the system
 

Paignton pete

Regular EF Member
Messages
779
Location
Over the rainbow
I had one thought - could it have been limited by a high SSE network supply voltage in the area and a relatively low demand for extra power? The inverter cannot keep just pushing up the local supply voltage in order to drive out its "rated full power". Some SSE areas (and elsewhere in the UK!) run at 240 to 245 Vrms normally. The inverter will almost certainly be designed to feed a 230 volt (harmonised! ha!) supply system. As the power monitor shows generated power, did you apply some extra loads (electric fan-heater, kettle, etc) to the house wiring to see if the generated power increased? Worth trying.

I have seen serious examples of problems like this when some new bio-fuel electrical generation plants start up in lightly loaded areas in the summer - areas without adequate 11kV/33kV infrastructure to pass out the power to other areas. In one case in Cambridgeshire an 11 kV substation had to be expanded to also be a 33 kV substation to prevent regular voltage excursion exceed 253 Vrms (and often up to 258 Vrms!). I think similar problems are now becoming more common in some areas with large solar power farms. It also can occur with windfarms at times of high (good) wind and low consumption. National Grid had to regularly pay wind-farms (£10s million per year) to under-generate in order not to exceed maximum permitted system voltages.
Wow didn’t know that could happen.
 

JimmyTheJock

New EF Member
Messages
2
Location
Caerdydd
Hmm. Have a read of the specification for the pv panels you have installed and especially their operating temperature. Not unusual to find lower output on very sunny days especially if there is little or no wind. I suspect you'll probably find you get maximum output around April or May and again in the autumn when it is a sunny but cool day.
 
OP
A

agybag

EF Member
Messages
12
Location
Kilmarnock
Hmm. Have a read of the specification for the pv panels you have installed and especially their operating temperature. Not unusual to find lower output on very sunny days especially if there is little or no wind. I suspect you'll probably find you get maximum output around April or May and again in the autumn when it is a sunny but cool day.
Hi,
As mentioned in my first message I've had the system installed since March and never been able to generate more than 2.2 KW and that's been the max ever generated. The promise of up to 3.8 KW and at 2.2 KW it's falling well short of the expected peak of 3.8 KW. I have a clear view with no obstructions and facing south with the sun around noon coming directly into my living room.
Regards
John
 

R-fur

EF Member
Messages
18
Location
Ayrshire
I agree with Alisdairp. Check the voltage if you know how to do it safely. I was at a farm once that had installed two wind turbines but they would not generate as the local voltage was too high. They had to write to SPEN to complain about the voltage. Eventually they adjusted the taps at the pole mounted transformer to reduce the voltage.
 
OP
A

agybag

EF Member
Messages
12
Location
Kilmarnock
Hmm. Have a read of the specification for the pv panels you have installed and especially their operating temperature. Not unusual to find lower output on very sunny days especially if there is little or no wind. I suspect you'll probably find you get maximum output around April or May and again in the autumn when it is a sunny but cool day.
Just checked it a moment ago and the incoming voltage is 242.5 volts
 
OP
A

agybag

EF Member
Messages
12
Location
Kilmarnock
242V should be ok. I would expect the inverter to have its upper voltage set at about 250V
OK thanks, I'll speak to the installer when he calls in on Friday as I've lost the meter flashing red light and the solar dropped out completely for a full day on Monday. I do appreciate all the help that's been given and I'll let you know the outcome after the engineers visit.
Regards
John
 

JimmyTheJock

New EF Member
Messages
2
Location
Caerdydd
I really would not get excited about seeing 242.5V as my supply here at home is presently at 252V which is not unusual as I'm only some 25m from the local 11kV/415V distribution Tx on a sunny day with (probably) very little load on it.
From experience that voltage will drop substantially on a cold winter night when people around start loading it up.
My solar 3.76kW (max) array normally peaks at around 3.4 - 3.45kW on a cool sunny day so about 92%.
I would however be concerned if a 4.41kW array is only peaking at around 2.2kW. I presume you have more that 1 inverter (I would expect 2) so can you interrogate them and see if they are both delivering roughly the same power. You would normally split the feed from the panels 50/50 between them. Is it perhaps 1 inverter that is not functioning properly? Do you have software to interrogate them?
As mentioned earlier you will see a drop in efficiency as pv panels get hot; the temperature coefficient (pMax) will be given in the data sheet but will normally be around 0.4 - 0.5% which means for every +1degC in temperature rise about the nominal (normally 25C) their output will fall by around 0.5%. Just the fact they are operating at all will cause their temperature to rise and their surface temperature will typically be well about the measured air temperature.
They are new so you would not expect degradation yet but be aware as they age the output will fall further. Most manufacturers will specify a maximum at (say) 10 & 20 years and that may well be 10% & 20% as around 1% fall in output per year of operation is fairly typical.
Hope you can resolve the problem without too much hassle but my first port of call would be the installer!
 
OP
A

agybag

EF Member
Messages
12
Location
Kilmarnock
HI all,
I had the installer here today and sure enough there's a fault with the inverter. The engineer could not fix and has passed it on to his superiors, I'll keep all concerned informed of the outcome, the system has been switched off for safety reasons as the unit was continually making a buzzing noise.
Regards
 

Steve888

EF Member
Messages
7
Location
Coventry
Hello the best way to prove the energy production is to use optimisers or a system to measure ac and Dc production. You also have to check if the panels are genuine. I had cases where peopled have been cheated with fake labels....be aware of that
 
OP
A

agybag

EF Member
Messages
12
Location
Kilmarnock
Hello the best way to prove the energy production is to use optimisers or a system to measure ac and Dc production. You also have to check if the panels are genuine. I had cases where peopled have been cheated with fake labels....be aware of that
Thanks for the info
 

Electrician Talk

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
Top