Different orientations !

Batikikik · September 2010

Hello Guys!
I have a project residential Installation . which is 8,1KW
So I use 36 225Canadian Solar panels
I am gonna install 18 panels on the north facing roof , and rest 18 panel south facing roof. I know that it is better to use 2 SB4000US , 1 is separate for south 1 is for north . 2 strings of 9 in north , 2 strings of 9 inn south .
But I want to install only one SB7000US because there is not enough space for 2 inverters. In this situation I have to make 3 strings of 12 , and I will have 1 string on south 1 on north and 1 half in north half in south . I am gonna run the wires to combiner box and then go down to inverter .
Who can tell me how much will I lose production of electricity or voltage .
I mean if I will put just one 7000 in this situation loses will be too much or it is not so big difference .
Thank you!!!

niel · September 2010

Re: Different orientations !

"I am gonna install 18 panels on the north facing roof"

that would be a waste of pv. try to place these facing south too somehow even if you must pole mount them.

BB. · September 2010

Re: Different orientations !

Solar Guppy, a solar hardware designer here, perhaps can answer how you will loose... We have had the discussion here a few times here before--One of the GT Inverter mfg. wrote a white paper that said there would only be a couple percent loss with one inverter and a East/West set of panels.

SG said his experience indicates that the losses are much more--He did not quantify the amount of losses he expects, so I cannot tell you how much.

Regarding the North/South panels, what tilt are you planning on using for the North and South arrays. You are fairly well south, and a near flat (5 degree north tilt to allow for better "self cleaning"), the differences are not as large as I would have thought. Using PV Watts for Los Angeles, 4.05 kW arrays, facing south 34 degree, north 34 degree, and north at 5 degree tilt:

"Station Identification"
"City:","Los_Angeles"
"State:","California"
"Lat (deg N):", 33.93
"Long (deg W):", 118.40
"Elev (m): ", 32
"PV System Specifications"
"DC Rating:"," 4.1 kW"
"DC to AC Derate Factor:"," 0.770"
"AC Rating:"," 3.1 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 33.9"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 4.44, 406, 50.75
2, 5.35, 447, 55.88
3, 5.62, 513, 64.12
4, 6.06, 529, 66.12
5, 6.19, 555, 69.38
6, 6.17, 533, 66.62
7, 6.48, 574, 71.75
8, 6.68, 589, 73.62
9, 5.78, 493, 61.62
10, 5.43, 486, 60.75
11, 4.84, 425, 53.12
12, 4.46, 403, 50.38
"Year", 5.63, 5952, 744.00

"Station Identification"
"City:","Los_Angeles"
"Array Tilt:"," 33.9"
"Array Azimuth:"," 0.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 0.88, 46, 5.75
2, 1.55, 92, 11.50
3, 2.82, 230, 28.75
4, 4.10, 348, 43.50
5, 5.40, 491, 61.38
6, 5.78, 508, 63.50
7, 5.86, 529, 66.12
8, 4.94, 435, 54.38
9, 3.28, 261, 32.62
10, 1.93, 135, 16.88
11, 1.02, 53, 6.62
12, 0.74, 34, 4.25
"Year", 3.20, 3160, 395.00

"City:","Los_Angeles"
"Array Tilt:"," 5.0"
"Array Azimuth:"," 0.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 2.58, 221, 27.62
2, 3.57, 287, 35.88
3, 4.55, 416, 52.00
4, 5.60, 494, 61.75
5, 6.50, 591, 73.88
6, 6.75, 590, 73.75
7, 6.95, 626, 78.25
8, 6.46, 578, 72.25
9, 4.94, 423, 52.88
10, 3.87, 342, 42.75
11, 2.90, 239, 29.88
12, 2.40, 197, 24.62
"Year", 4.76, 5004, 625.50

So, you are loosing 20% year with the "north" facing" 5 degree tilt array--or ~15%...

Would you loose another 10% on the whole system due to mixing North/South arrays on one inverter??? I don't know.

If this is a ~35 degree north facing tilted roof--you are going to loose 1/2 of the year over year output.

Interesting to see that the losses/differences during the summer months are not that great (and the north 5 degree array out performs the south facing 35 degree array).

At least in Northern California, PG&E customers are (still?) forced to go on a time of use/seasonal billing plan. Given that the summer peak rates are quite a bit more for power (depending on tiered pricing)--a north facing 5 degree array may end up with an equal or better return on investment (ROI) than if everything was facing south at 35 degrees when TOU/Seasonal/Net Metering is taken into account.

Also, will these panels be mounted against a roof or tilted/elevated for better air flow (reducing panel temperatures will decrease Vmp differences and increase output over panels mounted tight against a roof with poor air circulation).

-Bill

Batikikik · September 2010

Re: Different orientations !

There is not enough space in south facing so i have no choice .
install on north facing IS NOT WASTE . I design to install it on 0 degree north and 22degree south . But owner he doesnot want 0degree because it doesnot look good so I add 3 more panels and install at 22 degree flash with roof . And the problem resolved . The only thing is the inverter . Best way is Sb4000 for 18 north and SB4000 for another 18south . But there is no space. By the way I installed same 8,1KW system it was mixed terrible half in east half in wes and half is in north , It was the worst roof in my experience . So whatever Now that system produces 44KW each day . It is in LA . 5.5hours full sun , so it means installing only one inverter LOOSING NOT MUCH . I know it as my experienc . But some people are saying your gonna loose up to 17% . But I dont belive that thats why I posted here to know your opinion guys
Thank you

Cariboocoot · September 2010

Re: Different orientations !

If you were to try putting panels on the North side at my latitude (52) it would be a real waste of money.

The closer to the Equator, the flatter the panels are, the more efficient North-facing arrays will be. Go below the Equator and it's all backwards!

Batikikik · September 2010

Re: Different orientations !

Cariboocot you are telling me common things , and you are right .
So nobody can tell me h installing one 7000 is loosing so much or no ?

mike95490 · September 2010

Re: Different orientations !

Batikikik wrote: »

Who can tell me how much will I lose production of electricity or voltage .

What's your location?

North facing panels are going to be mostly, useless.

BB. · September 2010

Re: Different orientations !

In Los Angeles, depending on the slope of the north facing panels, they can work very well in the summer. Add time of use rate plans with summer power that cost three times winter power costs--PVWATTS shows it can make economic sense (see above PVWATTS output).

-Bill

mike95490 · September 2010

Re: Different orientations !

BB. wrote: »

In Los Angeles, depending on the slope of the north facing panels, they can work very well in the summer.

That's 3 months out of the year, and with much tilt on the roof, will be useless for 3 winter months.

2 array directions will NEED 2 MPPT inputs, or 2 GT units.

My June readings show peak power only for about 2 weeks, then it rolls off.

So till we know the roof angle, or if there will be extensive racking, this is sort of pointless.

Then there is the Washing of The Panels ritual, early mornings while dew still keeps the dirt damp, and the panels are cool, and using a hose with a DI water feed, (LA has horribly "hard" water, car washing kits often have an ion exchange cartrige to prevent spots)

drees · September 2010

Re: Different orientations !

IMO, the original poster has not given us enough information to determine how well/poorly the system will work.

Need to know location (LA meaning Los Angeles or Louisiana), mounting angle of each facet, angle of roof, etc to make an accurate determination.

BB. · September 2010

Re: Different orientations !

Don't forget the original question about sharing two north south arrays on one Gt input.

Cariboocoot · September 2010

Re: Different orientations !

drees wrote: »

IMO, the original poster has not given us enough information to determine how well/poorly the system will work.

Need to know location (LA meaning Los Angeles or Louisiana), mounting angle of each facet, angle of roof, etc to make an accurate determination.

Actually he did: Los Angeles. South array at 22, North array at minus 22 (flush with roof because the homeowner didn't like the 0 degree option - me, I'd have put it at the ridge and cranked it up 22 which would look really ugly but all the panels would be facing the right way).

The South facing array is already at a compromised angle for the Latitude. The North facing array is 'facing backwards' by about 60 degrees. Off hand, you'd be lucky to get 70% from the South array and 20% from the North. Put them together into one GT inverter and you'd probably be running at 50%. Just an uneducated guess; I have no calculators available (Mac's Lab is gone!). Based on vague memories of Solar Guppy's previous explanations of this sort of situation, but with the East-West argument.

Looks to me like the North facing array is a waste of money. It will probably perform better on cloudy days than in bright sunshine.

Batikikik · September 2010

Re: Different orientations !

Guys I already provide that info but I will do it one more time Los Angeles -San Fernando Valley . array will be horizontal with roof which is 22 degree.
Question is not abpout loosing north and south . With simple calculation you can see difference between south and north facing it is simple , Also simple is if you put 0 degree tilt on north it is equivalent as 22 degree in south which is the best version . But 0 degree looks bad thats why I add 3 more panels and put on 22 degree .
Questiuon is regarding INVERTERS .
I know that best production will be is to install one inverter for 18 panels on the north and separate invereter for 18 panels in south .
BUT THERE IS NO SPACE FOR 2 INVERTERS
So I want to install ONE 7000sunny boy . and combine together 18 north with 18 south and run to inverter ..
QUESTION - ABOUT HOW MUCH WILL BE DIFFERENCE BETWEEN TWO OPTIONS
1.WITH 2 4000SUNNY BOY
2.WITH ONE 7000 SUNNY BOY

I hope I could explain the question

:D:D

mike95490 · September 2010

Re: Different orientations !

What is the brand of inverter that has several MPPT inputs ??

Batikikik · September 2010

Re: Different orientations !

Sunny boy , no it does not

drees · September 2010

Re: Different orientations !

I think you will find that in the sunny months (April-August) you won't lose too much performance.

But in the winter, you will take a severe hit in performance, especially from October-March.

Have a look at what PVwatts estimates for 2 4 kW arrays in Los Angeles - both mounted at 22*, one north, the other south:

North:

"City:","Los_Angeles" "State:","California"
"Lat (deg N):", 33.93 "Long (deg W):", 118.40
"Elev (m): ", 32
"PV System Specifications"
"DC Rating:"," 4.1 kW" "DC to AC Derate Factor:"," 0.770"
"AC Rating:"," 3.1 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 22.0" "Array Azimuth:"," 0.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 1.51, 104, 13.00
2, 2.41, 173, 21.62
3, 3.61, 318, 39.75
4, 4.83, 423, 52.88
5, 6.00, 547, 68.38
6, 6.33, 556, 69.50
7, 6.47, 584, 73.00
8, 5.71, 511, 63.88
9, 4.05, 340, 42.50
10, 2.78, 225, 28.12
11, 1.76, 120, 15.00
12, 1.27, 77, 9.62
"Year", 3.90, 3979, 497.38

South:

"City:","Los_Angeles" "State:","California"
"Lat (deg N):", 33.93 "Long (deg W):", 118.40
"Elev (m): ", 32
"PV System Specifications"
"DC Rating:"," 4.1 kW" "DC to AC Derate Factor:"," 0.770"
"AC Rating:"," 3.1 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 22.0" "Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 4.02, 366, 45.75
2, 4.99, 417, 52.12
3, 5.49, 502, 62.75
4, 6.15, 538, 67.25
5, 6.52, 587, 73.38
6, 6.59, 572, 71.50
7, 6.88, 616, 77.00
8, 6.87, 608, 76.00
9, 5.74, 490, 61.25
10, 5.14, 461, 57.62
11, 4.41, 387, 48.38
12, 3.98, 358, 44.75
"Year", 5.57, 5902, 737.75

You'll probably end up throwing away at least 25% of the arrays output year round - at which point you might as well just install 4 kW on the south slope.

So if you can't find an inverter that lets you run the strings independently, what about using micro-inverters?

They'll cost more than a single central inverter (up to twice as much) but then you won't have any issues with multiple facets. And you won't have any issues with the size of the inverter - in fact, the only additional piece of equipment you may need is a utility disconnect (in which point you'll also need a sub-panel, too).

Batikikik · September 2010

Re: Different orientations !

DEar Dress
That is right I use microinvertersbut customer doesnot wann pay that much . And it is better to put 2 3 more panel than microinverters

thank you

solarvic · September 2010

Re: Different orientations !

mike90045 wrote: »

What is the brand of inverter that has several MPPT inputs ??

Mike, It is the Power one Model Aurora that has 2 separate array imputs. solarvic

drees · September 2010

Re: Different orientations !

Batikikik wrote: »

That is right I use microinvertersbut customer doesnot wann pay that much . And it is better to put 2 3 more panel than microinverters

Frankly, I think they will find that they are paying the price for an 8 kW system and only getting a 5-6 kW system in performance.

The price difference between the SMA7000 and 32 Enphase micro inverters is about $3-4000 depending on what pricing you can get ($175-$210/ea).

225W panels cost say about $600/ea.

Let's assume the price difference is $4,000. Instead of 36 panels only get 30 and now the total price is the same and you know for sure you'll be getting maximum performance from all the panels.

At worst you end up 20% down (6.7 kW vs 8.1 kW STC) when that will be the best you *might* get from a single inverter - and real life experience from Solar Guppy indicates that you will likely do worse.

Batikikik · September 2010

Re: Different orientations !

I got your Joke !!
Ok you are right . I did my calculation again and it is true difference is not much .
I have never install micros . But I will do in this project .
Question . I have 3 strings of 12 . When I connect microinvereter I have to coonect the same way as panels ?>??I mean when you have a panel with microinveretr still you have to have 3 string each 12 . After that I will 3 strings of AC current . Then it goes to combiner box and then it goes to disconnect then meter then main ? Did I get right ?? Same wiring ?
thank you

drees · September 2010

Re: Different orientations !

It depends on the specific micro inverter you are using.

I am only familiar with Enphase products - there are a few others but I believe these are currently the most popular. They have a ton of information on their website.

With these you run 240V AC (2-hots, neutral, ground) up to the roof where you splice into a pigtail in a junction box.

The "standard" one is the M190 which you can attach up to 15 panels/inverters in a string on a 15A 240V circuit. For your 36 panel array you'd need 4 strings - you'd probably want 4 strings of 9.

They also have a "dual" micro inverter which has 2 inverters in one package - you can attach up to 10 inverters / 20 panels per string on a 20A 240V circuit - this might be preferable as it'd reduce the number AC branches you have to run.

If your utility requires you to install a utility disconnect, you'll need to combine the branch circuits in a sub-panel before routing to the disconnect.

I am still a bit surprised that there isn't room to install two regular inverters since these are what you are most familiar with...

System2 · September 2010

Re: Different orientations !

I'd rethink the north array as it's going to be money poorly spent even in LA. Can you do a partial ground or pole mount for a few extra south facing panels? You could probably get as much power out of 1/5 the north facing panels if ground/pole mounted in the proper orientation at significant cost. This would also solve the inverter problem.

Otherwise, maybe consider micro inverters for the install. I would not combine the north/south panels if it stays this way on the roof into one inverter. I also don't like the fact that you are already space "cramped" before installation. Proper planning will always allow for "extra" everything if needed down he road including electronic space!

Carlo

Batikikik · September 2010

Re: Different orientations !

Dear Carlo,
I know what are you saying but there is not enough space for 18 panels .But for me I dont consider as a waste (installing solar on north). Very often we do that , with 0 degree it is the best way . But this guy he doesnot want show roof like that , it is ok ,problem already resolved with adding couple extra panels .

Drees I am gonna use enphase 190.In this situation you dont need overcurrent protection for each string ???can you provide me some electrical diagram for micro inverters(where it goes from panel , what is the connection , what type of breaker u use how many?) ?
Thank you

BB. · September 2010

Re: Different orientations !

Here is one Enphase D380 installation manual (PDF download)... Should answer many of your questions.

-Bill

drees · September 2010

Re: Different orientations !

Batikikik wrote: »

Drees I am gonna use enphase 190.In this situation you dont need overcurrent protection for each string ???

Yes - you will be running a 240V AC line up to the roof protected with a 15A breaker up to the roof for each string - typically done with either 12-3 or 10-3 Romex into a junction box either on or under the roof depending on what you prefer.

Batikikik wrote: »

can you provide me some electrical diagram for micro inverters(where it goes from panel , what is the connection , what type of breaker u use how many?) ?

BB linked to the dual-micro inverter the M380 you probably want this one:

http://www.enphaseenergy.com/downloads/Enphase_Quick_Install_Guide.pdf

They have a lot more documentation on their support site:

http://www.enphaseenergy.com/support/downloads.cfm

Batikikik · September 2010

Re: Different orientations !

Thank you for Links .....
http://www.enphaseenergy.com/downloads/Enphase_M190_M210_User_Manual.pdf
This shows each string goes separate . I think you can combine all string up onthe roof and then run to main and put one 50A breaker,because hos showed in digram it s waste time and material. . .

BB. · September 2010

Re: Different orientations !

As long as you have a sub-panel populated with 15 2 pole breakers (combiner panel) before you hit the 50 amp branch (you cannot run a 50 amp branch directly to each inverter without the 15 amp breakers).

Each inverter is only listed (and sized for 14 or 12 AWG wire probably) for 15 amp circuits. 50 Amp is too big.

-Bill

Batikikik · September 2010

Re: Different orientations !

I dont wanna put 50abreker for each string ....3 15a for strings and one 50 for main

BB. · September 2010

Re: Different orientations !

That is fine. No 50 amp breaker direct to the Enphase.

-Bill

Batikikik · September 2010

Re: Different orientations !

But I think microinverters take much time and material for installation then regular iverters ? what you think guys?

BB. · September 2010

Re: Different orientations !

Oh we have about 50 pages of posts on why central inverters usually make more sense vs distributed micro-inverters.

In some cases micro-inverters can be ok--In any case, there are lots of people installing micro-inverters.

-Bill

Different orientations !

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