I've done some research and I'm tenatively planning on a system of eighteen Sanyo 180W modules (3240W) and one SunTie XR 2500W. I have roof space and plans to grow to 36 modules & 2 ST XRs in the future.

Sanyo 180W Data sheet

My questions:

1. The Sanyo Vpm is 54V and Voc is 66.4V. This appears to be a perfect match for the ST XR with 18 strings of one panel each.

Am I correct in the design or are there things I'm missing?

2. The SMA string calculator shows a Minimum Peak Power Voltage range of 380-744v for 10 modules from 104-32F or 38-74V/module. The ST XR data sheet show a MPPT voltage range of 44-85V.

What will happen at high temperatures if the MPPT voltage drops out of range?

3. Given that I am in a hot dry area (SoCal) would misting sprinklers above or below the system increase the efficiency of the system via evaporative cooling?

Thanks,
Sean

You'll be running at the Sunties power limit allot if what I have read about the Sanyo HIT's are true ! ... You might want to start with 16 and add if there is headroom



Yes ... This is correct



From everything I have read , the Sanyo's out perform there name plate ratings and tempature has a minimal effect on the mppt. the Suntie will track down to 42 volts , but it does need the voltage to go above 50 volts to start operating

Running at 54 Volts is right at the Sunties peak effiency point !




Generally yes with Si panels , but the misting equipment and maintaince is usally considered to cost more than just adding panels to make-up the difference gained by hot vs. cool panels , also water is becomming expensive !

Solar Guppy,

Thanks for the quick response. That helps a lot.

The PTC of they Sanyos is reported at 168.1 which gives me an array of 3025W and SMA reports a 2x9 panel array as having a peak output of 2705W at 104F. It's in a less than optimal location facing east with a 16 degree roof tilt which will probably cut output even more. Not great, but all I have to work with.

Having played with a spreadsheet, sun angles and many many sine/cosine calculations I'm looking at only 369 hours/year that I'd have a chance to be over 2500W array output. Assuming the SMA figure is accurate, I'm looking at approx 13KWh/year lost due to inverter clipping.

At the low end with 18 panels I'm looking at 668 hours/year averaging 630W array output. At that level I'm losing 147KWh in inverter effeciency. With a 16 panel array I'd lose an additional 17KWh making the 18 panel array look better.

A few more questions if you don't mind:

1. Since I am planning single panel strings what will shading of a single panel do to the output of the array? I'm assuming it will not affect the remainder.

2. What exactly happens when the MMPT voltage is lower than 42V? Does the inverter hold at 42V and operate less efficiently or does it track below 42V and drop offline?

3. Do you have any idea what sun angle is required to wake the system up? 50V is 75% Voc of the Sanyo panels but I can't find any documentation on sun angle vs voltage/output. In the winter the system may not wake up until 11am or later.

4. Any retailer recommendations? I want to ensure I get the GP version of the ST XR. Also I'm planning on a self install so I'd like to work with a company that will recommend the small bits I won't know I need until I'm on the roof.

Thanks,
Sean

That is for Si , NOT HIT , there is a difference !

Sanyo claims you will get at minimum PTC at tempature , its a Asi/Si hybird panel



With which inverter ? , the Sunnyboy reports 2-3% high on it's power output , which also has the side effect of it being really a 2425 watt output , not 2500 watt inverter

If you have the money , Sure go for the biggest area you want , worst that will happen is you might get that second inverter if the panels are as powerful as I have heard



bypass diode will kick-in , shouldn't be an issue , the non-shaded cells will just produce closer to VOC , net resultis you just loss that single panels production



it will hold the voltage if the arrays is producing any reasonable amount of power , there is noway , you will see this low of a voltage from the Sanyos



even the smallest of direct sunlight will make the panels produce VOC .. will not be an issue with 16-18 panels




All your BOS (balance of system) componets , you can get from home depot , I used gutter mount clips for my arrays mounts and even had a civil engineer sign off on them to make the building department happy , see my photo-gallery from the main solar-guppy page

Sun Electric had a good deal a month ago for 1100 dollars , try them , maybe others can suggest places to get them now ...

Guppy,

All my work has been on paper and I have zero real world experience. I apologize if I have offended you. My base assumption was that any 2500W inverter would clip at 2500W. I wasn't aware that the SMA started clipping even earlier.

The SMA Sizing guide has a specific entry for the Sanyo HIP-J54B. The Fronius tool shows significantly different data.

Imp: 3.33A
Vmp: 54V (180W)
Vmp @ 122F: 50.4V (168W)
Vmp @ 158F: 47.4V (158W)

The 122F output matches PTC and a 16 panel array @ 158F is still 2525W.

I used the cosine of the sun angle as array output starting point. So a 45 degree angle I assumed would give 70.7%. I also used the SMA number of 2705 @ 104F as my peak. PTC @ 104F means I'm looking at clipping at 83% of peak array output (3KW).

The State of CA gives rebates based upon the array output, so I'm trying to minimize inverter costs. Based upon your comments I'm definately shrinking down to two 16 panel arrays.

Two more questions:

1. Is it possible to use the the internal PV array fuses and the bypass terminals at the same time?

2. Comparing the Fronious to the SunTie, the IG 3000 is 94% at 75% load vs 90% on the California website. It requires strings of six panels compared to single panel strings for the STXR. Is there any way to approximate the loss to the other five panels when one is shaded?

Thanks,
Sean

I'm not in anyway offended ! , SMA has long been aware that they report high in AC values ... They just think it's a non-issue and this example would show it to be at a dis-advantage to the Suntie in this one example




Your getting way to deep and into the weeds here. First off , cosine is a good quick calculator BUT , this is used for power calculations , VOC is pretty independent of isolation (direct sunshine) .. You should have no issues with the Suntie and it's operational range with the HIT panels , they appear very well matched.



Techincally Yes , I don't know what the code requirements would be ... all of your panels will have to have their own fuses , you will need an external combiner for sure



On Shading , you should only lose the power of the panel shaded with the Suntie , as the sting slenght increase in number of panels , you will lose most of the production from the string , even with bypass diodes !. This is because the mppt point of the string with the shaded panel will be lower that the other strings ... it will match the voltage , but power output will be 50-90% less , depends on the number of panels that make up the string (percentage thing)


I would not take that as fact , The Fronious has a peak of 94% with the required US isolation transformer , they claim 96% without one .. even the Sunnyboy which is 94%+ only claims ~93% for the CA list ...

It's looks spec wise like a good inverter , all I can say is there are few if any installed in the US and the Sunite has a couple thousand. I still use the Sunties and we have had no failures of my 4 units or any of the 10 beta sites in 1.5 years (Keep in mind I talking about my redesigned GP/UPG) I have no data to make a judgement on way or another ... at least with the Suntie , you know I'll always answer technical questions

This is the exact system I have decided to install. I will start with 16 panels arranged landscape style in an 8 wide by 2 tall array (35ft wide by 6 ft tall) on a 40' by 25' south facing roof at a 30 deg angle. With these Sanyo HIT 180 modules, I have room to have a 4 inverter 10KW system.

I have three important questions on this configuration:

1. Any suggestions on the parallel connections of the 18 panels? (Mfg specification requires a 15A fuse/cb on each panel, but the output specs are for only 3.6 A maximum output.) Should I use the MC connectors attached to the panels and extend them to a combiner box, or wire directly from the internal terminals of the PV junction box to the combiner. Since these are 48 volt panels, is it proper to parallel two or four panels and then run to the combiner box?

2. I plan to install the Sunties in an air-conditioned utility room on the second floor in the geographical center of the roof to help minimize lead length. Since the ambient temperature of the room will be 75 or less, will the performance of the Suntie improve at higher PV wattage conditions? If the inverter is working at a 90% efficienty at 2500 watts, will the inverter produce 250 watts of heat in the utility room? It is my understanding that without the rainshield, the unit will run cooler.

3. The initial array segment will be placed on the highest part of the roof. I want to be sure the array is properly grounded for lighting protection. Is it proper for the ground to run from the array, inside to the Suntie, and then to the main circuit breaker box ground point, or directly from the array down the roof to the ground point with another ground from the Suntie to the main ground?

Any thoughts or wiring suggestions would be appreciated.

SolarNewbie,

I've actually changed my design slightly. I'm planning a 36 panel system with three inverters each having a 12 panel array. The main reason for that is the 6 fuse combiner internally. I'm planning on combining pairs of panels at the array with MC combiners and running them back using #10 cable with MC connectors. A 25' run is still less than 1% volatage drop for two panels.

I used this page to check voltage drop:
http://www.jhlarson.com/ind_table1.htm

I'm planning on growing my array to 3x16 in the future when I have more funds. For that I'll probably need an external combiner like the TCB-6.

As for your inverters, why install them inside? I'm planning on mounting mine on the outside wall right below the array. Attempting to cool the inverters using their own electricty is probably more of a loss than operating them in a hotter environment.

Sean