New 11kW Ground Mount in N San Diego

[Poway]

Looking comments on the following configurations... And PM of recommended installers (thejq any recommendations?)

Ground Mount. Perfect conditions (point south or slightly west... any elevation... no obstructions)

11.95 kW DC
28x SunPower 427W Panels
Solar Edge P400 Optimizers
SE11400 inverter (is this to small for the 11.95 DC if so could drop to 26 panels 11.1KW?)

10.8 KW DC
36x LG 300W Panels
Solar Edge P300 Optimizers (or should I still use P400 optimizers?)
SE11400 inverter

10.8 KW DC
36x LG 300W Panels
Enphase M250 (will these clip ... do I need to use lower wattage panels given ideal pointing of array?)


Thanks

[Poway]

11.95 kW DC
28x SunPower 427W Panels
Solar Edge P400 Optimizers
SE11400 inverter (is this to small for the 11.95 DC if so could drop to 26 panels 11.1KW?)

Thanks

Sorry (New Kid Error) the first option should have read

11.12 kW DC
34x SunPower 327W Panels
Solar Edge P400 Optimizers
SE11400 inverter

[logdin]

Cost is always a factor. Can you provide that? All of the components are from quality companies.

[sensij]

I'm I would guess they are all on the expensive end of what we see reported for prices here, especially the sunpower option. A quote with Canadian solar, solarworld, q-cells, or some other less premium panel would probably round out the options better.

Clipping on any of those systems will be low, probably affecting annual production by much less than 1%. Solaredge in particular designs up to 125% of the inverter size. What is your annual electricty usage? Can you reduce it? Do you really need a system that big?

[carlsbad]

Any particular reasons of choosing SunPower panels for a ground-mount system? I looked into SunPower briefly due to roof space constraints but wasn't able to justify the additional payback period. The specs on the SP panels are tempting though.

[thejq]

SunPower is probably over kill for the price, normally at about 15-20% premium, unless you're really short on space. As for LG vs. other brands, if the price is just slightly higher (<5%), I'd go for LG any day. With ground mount I don't think space is an issue. For reference, here's San Diego's pvoutput page, http://pvoutput.org/listteam.jsp?tid=859 . Find a sunny day for good comparisons, and click on efficiency to rank systems from high to low and move your mouse over the top 20 systems and see what brand of panels work best in San Diego in general. Mine is called Carlsbad 4.8KW. For 300W panels, I think both P300 or P400 should be fine. The latter is just $10/each more. I will PM you my installer info.

10.8 KW DC
36x LG 300W Panels
Enphase M250 (will these clip ... do I need to use lower wattage panels given ideal pointing of array?)

I know others may disagree, but I personally never want to see clipping. Not only you're losing power at the time you're paid the most (assuming you're on some type of TOU plan), having the inverter working at peak for extended period of time doesn't sound good to me either.

[Poway]

DC Oversizing

I know others may disagree, but I personally never want to see clipping. Not only you're losing power at the time you're paid the most (assuming you're on some type of TOU plan), having the inverter working at peak for extended period of time doesn't sound good to me either.

We both may be wrong but I agree completely. SolarEdge has guidelines that allow DC panel rating to be 135% of AC output rating (they call this DC oversizing). This is probably not a problem in other areas of the country or on roofs with not the best orientation. But in my case I have unobsturcted view to the South and since I'm doing a ground mount.. can have perfect elevation/Azimuth angles.. Also the panels I'm buying are 0-+5% so I think at least in early years there would be alot of clipping so I will not do DC oversizing.

[thejq]

We both may be wrong but I agree completely. SolarEdge has guidelines that allow DC panel rating to be 135% of AC output rating (they call this DC oversizing). This is probably not a problem in other areas of the country or on roofs with not the best orientation. But in my case I have unobsturcted view to the South and since I'm doing a ground mount.. can have perfect elevation/Azimuth angles.. Also the panels I'm buying are 0-+5% so I think at least in early years there would be alot of clipping so I will not do DC oversizing.

Since you have plenty of space, SW might be better for you, assuming you will be on either DR-SES (solar) or EV-TOU plan. Both pay the most in the afternoon. One reason some people might consider oversizing is to avoid having to upgrade (or derate) the switch panel, especially for bigger installations.

[HX_Guy]

11.95 kW DC
28x SunPower 427W Panels
Solar Edge P400 Optimizers
SE11400 inverter (is this to small for the 11.95 DC if so could drop to 26 panels 11.1KW?)

10.8 KW DC
36x LG 300W Panels
Solar Edge P300 Optimizers (or should I still use P400 optimizers?)
SE11400 inverter

10.8 KW DC
36x LG 300W Panels
Enphase M250 (will these clip ... do I need to use lower wattage panels given ideal pointing of array?)


Thanks

As others have said, I think the SunPower are overkill. They are good panels no doubt but it seems their niche is if you're short on roof space, otherwise theyll produce pretty much the same as an LG, Canadian Solar, etc panel.

Go with the P400 optimizers even if you use 300W panels. They are only a few bucks more per unit so it won't cost much at all.

Also as mentioned, I would not want any clipping at all. Even if it's only a percent or two of annual production, why have any clipping at all if it's not necessary?

[sensij]

Also as mentioned, I would not want any clipping at all. Even if it's only a percent or two of annual production, why have any clipping at all if it's not necessary?

Usually the clipping involved in these threads is less than 1%, and closer to 0.1%. Like every other design decision, it is a question of what pay for what you get. If minimizing losses without respect to cost was the goal, everyone would be wiring their systems with 4/0 conductors, and would be on the roof every night cleaning the panels. Those two things could easily add up to a percent or two of annual production... yet, they aren't done because it isn't worth the time or effort. Same thing with some of the clipping decisions, except people get emotional about it when they see a flat-topped output and decide they want that bell curve at any cost.

[sensij]

Go with the P400 optimizers even if you use 300W panels. They are only a few bucks more per unit so it won't cost much at all.

Why spend that extra money? The P300 and P400 are rated for the exact same output power.... 15 A @ 60 V. The P400 has a wider input voltage range to accommodate the higher voltage 72 or 96 cell panels, but if the temperature corrected Voc of your panel is less than 48 V, there is nothing to be gained by going with the P400. All you are doing is forcing the optimizer to perform MPPT over a larger voltage range, which is pointless since the panel will never operate in the upper level of that range.

[HX_Guy]

Future proofing is my thought process. It could literally costs less than $100 extra for all the optimizers but you'd have some flexibility if you ever want to switch panels to a larger version.

[thejq]

Usually the clipping involved in these threads is less than 1%, and closer to 0.1%. Like every other design decision, it is a question of what pay for what you get. If minimizing losses without respect to cost was the goal, everyone would be wiring their systems with 4/0 conductors, and would be on the roof every night cleaning the panels. Those two things could easily add up to a percent or two of annual production... yet, they aren't done because it isn't worth the time or effort. Same thing with some of the clipping decisions, except people get emotional about it when they see a flat-topped output and decide they want that bell curve at any cost.

Not sure where you got the 1% from. Just for kicks, I looked at my outputs today (first sunny day of March). For my 16x300W panels (http://pvoutput.org/intraday.jsp?id=...88&dt=20150303), if I had gotten M250 micro-inverter, anything above 4KW will be clipped (in fact, since not all panels reaches 250W at the same time, the actual clipping point is slightly less, but that's beside the point). So today, I would have clipped from 11:30 to 1:30 for 0.353 KWh which's 1.2% of my total production today. According to PVWatt, during June/July/Aug the production should be 50% higher than today. For simplicity and be pessimistic, I'm going to assume the production curve is a triangle (in stead of bell curve). After a few geometric manipulations, increasing the total production by 50% would result in about 3.74% clipping in those 3 months. Since I'm expecting to produce 1000KWh / month, I'd be losing 112 KWh (or *$.49 = $55) in just those 3 months. If again pessimistically assume the rest of the year altogether, I loose 1/2 that due to clipping, then for the year I would have lost $83. Of course there're lots of hand waving here, but since I've been pretty pessimistic in my logic, that number is likely the lower bound for me. I guess I'll know more precise numbers as the summer rolls around.

[Poway]

P300 is being discontinued (as you note the P400 provides a superset of capability)

Why spend that extra money? The P300 and P400 are rated for the exact same output power.... 15 A @ 60 V. The P400 has a wider input voltage range to accommodate the higher voltage 72 or 96 cell panels, but if the temperature corrected Voc of your panel is less than 48 V, there is nothing to be gained by going with the P400. All you are doing is forcing the optimizer to perform MPPT over a larger voltage range, which is pointless since the panel will never operate in the upper level of that range.

Two quotes I received noted that the P300 was being discontinued. One of the quotes originally said P300 but was updated to P400 with no cost change due to P300 being discontinued (so I think it is probably really being discontinued)

[sensij]

Two quotes I received noted that the P300 was being discontinued. One of the quotes originally said P300 but was updated to P400 with no cost change due to P300 being discontinued (so I think it is probably really being discontinued)

Thanks for the information. SolarEdge collapsed what had been a P350 (for 72 cell panels) and a P500 (for 96 cell panels) into the P400 not long ago, and it sounds like they are streamlining further. If less inventories part numebrs and more standardized manufacturing brings the cost down, great. I don't think it changes my position... if the P300 is available for less money and is appropriate for the panel being installed, I would still choose it. If one fails in the future, swapping a P400 in is not a problem (the optimizers don't all have to match), and SolarEdge has already shown they may maintain backward compatibility in future upgrades, like they did when they moved from the OP series optimizers to the P series. No guarantees, of course.

I'm not sure that future proofing against installing 72 cell panels in the future is where I would choose to spend extra money; if 72 cell panels make sense in the future, they probably would have made since now in the original installation. For the most part, panel efficiency has improved over time leading to more current out of the cells, but only a very small increase in voltage. I would guess that the 48 V max of the P300 still has some room to run, but once it is no longer available, there is no longer a decision to make.