Solar PV Panels

sjwajw

Had my system less than 3 weeks. Several minor hiccups such as inverter was too small for my system so has been changed to an SMA 4000. It is working brilliantly. 87kwh since 29th Nov on 3.45 system with some downtime due to problems.
I have read somewhere in my blurb that if 1 panel is in shade, this shaded panel will start to shut down the whole system to prevent damage due to something like 'the differential in generation between sunny/shaded panels'. Is this any help?? :beer:

ProfGreen

bill_on_line wrote: »

Ran the system you describe through "sunny design" with 5000tl
Typical voltage on the 7 module string is 163v dc
11 module string 299v dc

See what voltages you are getting

I have no experience as an installer but
The 163v dc is close to the default start up voltage parameter of 150v, this can be reduced to a minimum of 125v, might help the shorter string?

The supply Voltage during the day were i live is normally 248V to 250V AC. I believe high supply voltages can reduce performance, but once again not sure if this would have a great effect. Believe 253V is the maximum allowable and then you can ask the DNO to adjust the local supply voltage down.

Iain

I have now checked this over and the situation seems to be that Voltages are OK but Amp output is not. Am getting some 330 Volt from the string of 11 panels and some 167 from the string of 6. Yet am only getting from 0.2 to 1.1 Amp, which as I understand it should be in the 6-10 Amp range.. Installers seem lost as to why, and keep trying to figure out the problem (credit for effort). During some periods there is partial shading from some trees on part of the string of 11. But even the string of 6 which is mostly in full on sun does not produce a reasonable output. On sunny days I have peaked at no more than 600V (average over 1 hour) and produce less than 2 kWh in a good day.
Next they'll be searching for a faulty panel, but this is just a disappointing experience. And the weather has been unusually bright for the time of year..

don0301

hello everyone

ive just registered, and hope someone can help me with 2 queries.

i recently had solar panels fitted to my home (30/11/11)

its a 20 panel 3.9kwp system in south essex

so far my peak day generation has been 13kwh on 9/12/11

my average daily generation has been 6.75kwh

i have 2 questions:

1. i have 20x195W panels (=3.9kWp?) but the installers fitted a Fronius IG Plus 35V inverter which is rated at a maximum of 3.5KWp.
Is this right?

2. i got an owl cm160 energy monitor, which i have fitted to the live feed from the inverter inside the house fusebox. at night (when it should read 0?)it reads 113W. the inverter is rated at 0.2W in sleep mode.
i switched off all the fuse switches at the house fusebox except the inverter overnight (11 hours) and the house electric meter did not change. Can someone explain why its so innacurate and is there anything i can do to make it more consistent with what the actual meter says?

hope i got all the terminology right, im a neewbie but interested to understand and maximise the system

thanks for your help in advance

Cardew

don0301 wrote: »

hello everyone

ive just registered, and hope someone can help me with 2 queries.

i recently had solar panels fitted to my home (30/11/11)

its a 20 panel 3.9kwp system in south essex

so far my peak day generation has been 13kwh on 9/12/11

my average daily generation has been 6.75kwh

i have 2 questions:

1. i have 20x195W panels (=3.9kWp?) but the installers fitted a Fronius IG Plus 35V inverter which is rated at a maximum of 3.5KWp.
Is this right?

2. i got an owl cm160 energy monitor, which i have fitted to the live feed from the inverter inside the house fusebox. at night (when it should read 0?)it reads 113W. the inverter is rated at 0.2W in sleep mode.
i switched off all the fuse switches at the house fusebox except the inverter overnight (11 hours) and the house electric meter did not change. Can someone explain why its so innacurate and is there anything i can do to make it more consistent with what the actual meter says?

hope i got all the terminology right, im a neewbie but interested to understand and maximise the system

thanks for your help in advance

Welcome to the forum.

Firstly terminology - you are correct that your array is 3.9kWp. Your panels are actualy 195Wp. Your inverter is 3.5kW.

the 195Wp means that under laboratory conditions of sunlight, temperature etc they will produce 195 watts.

It might well be that in South Essex that your solar array will never actually produce 3.9kW if your roof is not facing directly south and hasn't the optimum pitch.

If they are optimum you may well produce slightly more than 3.9kW on a bright midsummer's day around noon. However it will be a rare occurance.


The question of an invertor with a lower kW rating than the kWp rating of the panels has been raised a couple of times on these threads, and you will need to search to get some examples.

The 'theory' behind the practice is that the lower rated invertors are slightly more efficient. Now only on those rare occasions that the kW output of your panels exceed the capacity of the invertor will the output be clipped. Thus you are trading higher efficiency for the great majority of the year for a possibly slight loss on a few occasions.

That is the theory, and we have seen little evidence to know if it is accurate, or just installer's bullsh1t to enable them to fit a cheaper inverter.

I would certainly write to them(don't phone) and get their justification on paper; they are less likely to flannel if they need to write.

On the subject of Owl monitors, like every model of this type they are useless at very low consumption. I can't find what is supposedly using 200 watts in my house

don0301

thanks for the reply cardew

and the corrections

my house is directly south (good)

but roof is steep approx 49 degrees (3 story town house)(not so good?)

i was just trying to understand why you would have mis matching inverter and panel outputs

until now i have seen the owl monitor peak at approx 3.7KW but how accurate is that? :P

until summer i guess i cant see how it is performing

was just interested to know if normal..

regarding owl i just cant understand why it reads constant 113W at night, when should be 0. i guess its more "fun " factor, than accurate measurement

so far i have generated 141.9kWh since 30/11/11

Dave_Fowler

don0301 wrote: »

thanks for the reply cardew

and the corrections

my house is directly south (good)

but roof is steep approx 49 degrees (3 story town house)(not so good?)

i was just trying to understand why you would have mis matching inverter and panel outputs

until now i have seen the owl monitor peak at approx 3.7KW but how accurate is that? :P

until summer i guess i cant see how it is performing

was just interested to know if normal..

regarding owl i just cant understand why it reads constant 113W at night, when should be 0. i guess its more "fun " factor, than accurate measurement

so far i have generated 141.9kWh since 30/11/11

The steep roof pitch will mean a better than average output during the winter months when the sun is low in the sky. During summer the output will not be as high as you would get with a roof at say 30 degrees since the sun will not be perpendicular to the panels. Probably means your inverter is well matched.

The Owl monitors, as Cardew says, are inaccurate at low levels. I have viewed the output of the current probe when the power is low. There is very little 50Hz content, but lots of spikes and general mush. The Owl box is taking this and converting it to a power reading. I would have thought that the manufacturers could have used a decent low-pass or 50Hz filter to reduce these false readings. By the way, I'm on my third Owl. The first two have failed during the first year. The transmitter continues to send but the display fails - different faults on the two faulty units. Not very good reliability.

Dave F

larkim

It its any help, my Owl meter reads 0.081 (or 0.064) almost permanently in the dark hours, clipped onto the live from the inverter. Disappointing, as it means you can't use any cumulative information about generation (the inverter is in the loft, and as it was a free install I didn't get the option to have a nice userfriendly output meter located somewhere convenient).

I have sat up in the loft when there was fluctuating sunlight, and the Owl meter (though slower to update) was consistently within about 10-20w of the reading on the Fronius inverter's display panel, so I am content that I am reading generation correctly, its just the night time usage which is bobbins.

I've also got an Owl on the live tail from the grid, which makes things even more confusing as if I'm generating 400w and using 400w it will read nil.

(I've used my boys sticker albums to tell me which meter reads which - the solar meter has a Yoda sticker, the grid meter has Darth Sidious )

Matt

Pennylane

I thought the Owl thingies were of no use now that energy is coming IN and OUT (with using solar panes) whereas before it was just OUT. You will gather I am not a scientific or technical person!:p

Dave_Fowler

Pennylane wrote: »

I thought the Owl thingies were of no use now that energy is coming IN and OUT (with using solar panes) whereas before it was just OUT. You will gather I am not a scientific or technical person!:p

An Owl placed on the output of the solar panel inverter will give you a reading of the power generated. It is useful if you do not have physical access to the inverter to read its minute-by-minute output or a wireless or wired interface direct to its data stream. The output of the inverter is one-way so long as you ignore the erroneous readings during the night time and when the generated power is below 250W.

An owl on the supply to the house has much less meaning if you don't know which way the power is flowing. If you know roughly how much power you are using and you have an Owl on the generation meter and on the mains supply meter you can surmise what the reading on the mains Owl display means (either in or out).

Dave F

munchkin88

ProfGreen wrote: »

But even the string of 6 which is mostly in full on sun does not produce a reasonable output. On sunny days I have peaked at no more than 600V (average over 1 hour) and produce less than 2 kWh in a good day.
Next they'll be searching for a faulty panel, but this is just a disappointing experience. And the weather has been unusually bright for the time of year..

Usually on the SMA inverters the minimum you can have is 8 panels per string when it comes to the TL range. We've found that the voltage is too low when any less than 8, which obviously brings down the overall generation of the system.