Sanyo Hit-N system instaleed, results

[dennis2011]

Yes Kate, even small shadows affect system disproportionatley. My roof is only 33 degrees pitch, the shallower the better for a dual east/west. Did you know that even a flat roof gives 90% of the return of a due south roof? With east/west you get a longer more even production day without the big midday spike. Even in June with the sun directly overhead the sunlight is striking each panel at a glancing angle, hence one of the explanations for the 85% figure.
In the case of your installation you could have considered 6 panels on the south face plus 8 panels on the east face. You might have saved nearly £1000 on the install cost with very little reduction in annual output. The inverter still copes ok with 2 unequal strings. East is slightly better than West for 2 reasons. Firstly east roofs are usually colder than west roofs. Secondly due to the azimuth angle (tilt of the earth) changing through the seasons the sun rises closer to the South East on December 21st but closer to the North East on June 21st. June is one of the peak months for solar production.

 

[kate.harrison1]

Yes Kate, even small shadows affect system disproportionatley. My roof is only 33 degrees pitch, the shallower the better for a dual east/west. Did you know that even a flat roof gives 90% of the return of a due south roof? With east/west you get a longer more even production day without the big midday spike. Even in June with the sun directly overhead the sunlight is striking each panel at a glancing angle, hence one of the explanations for the 85% figure.
In the case of your installation you could have considered 6 panels on the south face plus 8 panels on the east face. You might have saved nearly £1000 on the install cost with very little reduction in annual output. The inverter still copes ok with 2 unequal strings. East is slightly better than West for 2 reasons. Firstly east roofs are usually colder than west roofs. Secondly due to the azimuth angle (tilt of the earth) changing through the seasons the sun rises closer to the South East on December 21st but closer to the North East on June 21st. June is one of the peak months for solar production.

Yes, hindsight is a wonderful thing! I was lead to believe by all four installers who quoted that the e/w was best for my property and that unequal strings would not work satisactorily. As a lay person, I found it hard to argue! The £1000 saving would presumably have been on the 2 extra panels as I would still have required two faces of scaffolding.

Do you really think 4000TL would work effectively with an e string of 8 panels in one track and a s string of 6 in the other? I suppose I could always argue that I was ill-advised and ask them th move them but I would have damaged roofing felt on one aspect and 2 spare panels, not to mention the fact that all installers, mine included will be going flat out in the foreseeable future.

Do you think a few scaffold poles might really affect output?

 

[series530]

Hi Kate,

the effects of shading can be very significant and, to my thinking, have even more effect as a percentage of output when the amount of energy available through sunlight is lower.

The following is a case in point. It references page 4 but you may want to read the whole thread so as to get the complete picture and some of the hypothesis presented.

http://www.electriciansforums.net/photovoltaic-solar-panels-green-energy-forum/41299-effects-shading-4.html

Once up and running (hopefully next week), I plan to investigate the effects of shading further as I will be able to analyse panel by panel. Unfortunately though, the week after, I'll be away during the week on business for quite some time, so the data may be a little slow in coming to the forum.

 

[dennis2011]

Yes, I estimated the saving as the cost + installation of 2 extra panels. Most twin input inverters should cope well with unequal string provided the necessary parameters are met. One of these is the start up voltage, in other words how much voltage is needed to get the inverter to start producing electricity. If this is too high for your panels than your inverter wiil only start up when your panels are producing peak voltage, or in extreme cases, on a badly designed system, the inverter would not start at all. Sanyo HIT panels produce about 30 volts per panel so your string of 8 panels will produce 240 volts and the string of 6 panels would produce 180 volts. I do not know the specs for the Sunny Boy 4000TL but for the Aurora PVI 3.6 it is factory set at 200 volts per input BUT it can be easily adjusted by the installer right down to 140 volts individually for each input. I would have suggested something like 140 volts for the 6 panel string and 180 volts for the 8 panel string.
I know it can be tedious, and it is not meant as a criticism of you, it's just the way I am, but I like to find out things myself as much as possible before I have any work done, so that I can clearly understand the pro and cons of various quotes.

 

[kate.harrison1]

Hi Dennis,
I too am fairly careful with my homework prior to decision making, but some of the nitty gritty electrical stuff was rather out of my comfort zone and, as I was consistently being told by all that it would be better to have the higher number of panels in equal strings on e/w than trying to squeeze a smaller number onto the south facing hip and some more on one of the other pitches. Perhaps I placed too much confidence in the expertise of the installers' advice but I can't really justify changing it all now! perhaps removing the scaffold poles will make a difference but I doubt anyone's system is doing more than a couple of Kw in this damp grey weather and I shall have to wait for spring and summer.

I have a growing list of questions to ask my installer, perhaps the one concerning me the most is about earthing. I have been reading threads on here and on other forums suggesting that the TL inverters must be earthed in a specific way. When I asked my electrician and installer, they said that no special earthing arrangements were required. I don't like to doubt their professionalism and have been given sheets of paper with the results of electrical tests etc so its not as if they haven't paid attention to it all. Of course the problem now is that they will all be manicly busy for the next few weeks and probably wont be too keen to come and answer my (perhaps unnecessary) questions!

 

[dennis2011]

At the end of the day I am sure you will be pleased with the output of your system on an annual basis and will will give you a good indexed-linked rate of return. We are now in the 4 worst months of the year for solar generation. We really need some frosty but very sunny days!
I am not an electrician, but do have a scientific background and have looked into earth bonding of arrays. It only occurs with TL (transformerless) inverters and advice varies from manufacturer to manufacturer. It's very complicated, something to do with 'galvanic separation' - don't understand it fully.
Some makers like SMA, who make yours, state that earth bonding is not needed, which is reassuring for you to know. Fronius, another popular make definitely do recommend earth bonding. All the roof rails are joined together with earthing wire and taken to an earthing stake hammered into the ground. It's not a big leakage if any, Fronius explained it to me as just a 'tickle'. But if someone is up there on ladders, say cleaning your gutters and rests his hand on one of the panels, then the surprise of the very mild shock could make him fall off his ladder. It's the falling of the ladder which is the potentially dangerous bit!

 

[kate.harrison1]

Thank you. That makes me feel somewhat reassured! Another question though now about lightning> What is the effect if any, on a solar array and its component wiring etc of a highly charged electrical storm? Are we m,ore likely to be strush due to all the extra metal on the roof, and what happens if we are?

You can tell I'm having sleepless night can't you?! Someetimes, info read on these kind of forums can be rather worrying.

Btw, on my array production, today we have not seen even a glimmer of sun here in Hertfordshire and it is pretty gloomy. My Sunny Beam thingy says we are producing a pretty consistent C500Wh so I guess thats about what to expect in these conditions. Probably going to do <2 Kw again today.

 

[dennis2011]

Quite sunny in Shropshire today - at the moment done 3.4kw which makes up for dark dismal yesterday - only about 1kw.
I wouldn't worry too much about the lightening - the panels may be metal framed but not the highest thing on your roof, usually the chimney. I think if you check with your insurance policy you will find that the panels are now covered as part of your building insurance, as part of your house structure. So if some bits fell of an aeroplane or lighting srtuck and damaged your panels then I am fairly certain you would be able to claim on your house insurance. I haven't heard of any panels being hit by anything sinister, giant hailstones in some countries, bird droppings here. Try not to worry!