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diy solar

Finally, the start of my 25kw Ground Mount grid-tie system

Hedges said:
Height of things like weeds or other shade would be the main concern.

My original arrays used 18' Unirac rails, which I think were custom cut to fit 8, 120W panels. Standard sizes seem to include 17' and 20'.
They come within about 18" or 2' of the ground.

What is your panel electrical (series/parallel) configuration?
By making two physical arrays of different orientations (e.g. 10:00 AM and 4:00 PM sun would be 90 degrees apart), parallel strings peak at different times, delivering more watt hours for a given peak wattage. Total available watt-hours/day would be less than with ideal orientation, but utilization of inverter could be about 40% higher because peak is 70% as high.
Depending on ratings of MPPT inputs, you may be able to have each string on its own input. Multiple strings of different orientation wired in parallel will capture about 2% less due to not quite operating at Vmp (unless shadows fall on a string, making loss greater.)

With mounts costing $0.15/watt, panels costing $0.20/watt, and inverters $0.15/watt (approximate), this should deliver more energy per dollar. Also, more energy within maximum power allowed to backfeed, or maximum charge rate of a battery backup system. Battery backup would be kept fully charged later into the evening, reducing capacity used at night.
Click to expand...
Where are you getting panels that cost $.20/watt? The best I've been quoted is a little under $0.50/watt on the panels. The fronius inverters are roughly $0.25/W and I haven't priced out the ground mount, but let's say the one from blue sun is $4k with freight for 25kw then that would be about $0.16/W.

On the surface, without digging into it deeply, I was thinking of doing 16-17 panels in series and then putting them all on their own MPPT inputs. Each series run (5) would get a run back to the inverters. There would be two series per inverter (15k fronius primo). I'm not set in stone on the fronius inverter at this point, but kind of what I've been going with. For the system I'm doing, it made more sense to go with a larger output capable inverter with a higher DC voltage rating.

Right now, the field I'm putting the panels in is in full sun (745AM). It will then start to get shaded around 7-8PM. There are no trees or obstacles in the way except the very beginning and the very end of the day.
 
I think MSRP of 7.7 kW Sunny Boy is around $2500 so $0.33/watt, and street price may be $1800 so $0.25/watt.

I think you're right, most new panels are around $0.50/watt.
Some of the guys may have ordered direct from China considerably cheaper, but tariffs and shipping are more of a problem now.
SanTan has some new that were likely leftovers from large install projects. Those seem to be close to $0.50.
Even the premium used ones like SunPower are $0.40. You may find some bargains (with labels intact, not like the SanTan/Trina panels with UL labels removed.)

Solar Panels | SanTan Solar

store.santansolar.com store.santansolar.com
 
@Hedges

Thanks for confirming. I was beginning to think I was missing something as far as price goes.

What's your opinion with possibly going with the BlueSun panels?
 
What angle would I want to put my panels at? From my understanding, if you're going to only have one tilt angle and you would want to use your latitude as the angle. For me, this would be 47.5 degrees. Is this correct or is there a better way to go about this?
 
I don't know much about most panels.
Various degradation mechanisms exist, sometimes excessively rapid at least under certain conditions.
This post has a link to reports you can download, read about those issues and see which brands were high scoring.

diysolarforum.com

Is there a reliable resource to compare panel makes/models

Well that sounds like a heck of a deal! Glad you placed your order and can't wait to see how it all works. That is a very good price, and I should not be surprised but that confirms they get a great deal when they upgrade. I wonder if they went with Trina on the replacement units? Any idea?
diysolarforum.com diysolarforum.com
 
live4soccer7 said:
What angle would I want to put my panels at? From my understanding, if you're going to only have one tilt angle and you would want to use your latitude as the angle. For me, this would be 47.5 degrees. Is this correct or is there a better way to go about this?
Click to expand...

Yes, that is close if goal is to maximize Wh/year.
But if orientation is something other than true South (not magnetic), a different tilt would be better.
You can find "insolation" calculators. Most just use your location, while some may know weather history.
Obviously hills or morning fog affects what orientation is ideal.

You may favor summer production if time of use means bigger credit. Or if high A/C use. For off-grid/backup, perhaps more winter power is desired. Typically at my latitude, 5.5 hours effective average sun year round, maybe 7 hours summer 2 hours winter. A different tilt can shift that.
 
@Hedges Thank you again. My goal based on the way my grid tie works is to simply produce as much wh/year. Time of day and use are irrelevant in my case.

The sunmodo rack only allows for a 35* tilt.
 
I haven't seen anything saying not. It should really come down to voltage drop. If necessary, I cant get them a little closer.
 
@MarkSolar Was it more efficient to run the wire to the service panel from the inverter than the PV wires to an inverter near the service panel?
 
The inverter is in a barn that already had a subpanel fed from the house service panel. The subpanel wiring had been there for years so no new wiring was required. If I didn't already have the barn subpanel, I would have run high voltage DC from the array up to the house and put the inverter next to the main service panel. If you use micro inverters, you're stuck at the relatively low 240v AC so the wire size can get pretty large over long distances. I think power optimizers keep the voltage fairly high all the time, they might be worth a look if you have really long DC runs.
 
I would rather run PV wires the long distance.

1) PV voltage (for string inverter) is higher than AC voltage, so less loss.
2) Voltage drop in PV has no impact in functionality unless it drops below MPPT minimum, while AC voltage at panel is typically already above nominal due to power you feed, and at inverter is even higher. If that gets too high, it disconnects.

My inverters are about 30' away. I have 25' of 2 awg to PV panel and 5' branch circuits to each inverter.
 
@Hedges That was my thinking as well. Higher voltage and less current for the longer runs would result in less loss.

Any opinions on the SOLIS inverters? Bluesun would be provide this inverter to me. I'm very tempted to get their system. I'm looking at about $1 a watt for all materials minus conduit, premits, etc.... Probably another few thousand. I really should have done all this last summer when the PV price was about half what it is now.

I didn't get everything done that I wanted to this week, but I got a lot of new information regarding permitting and documentation from the Utility company. I have also gotten a better idea on what I need to get done in order to submit that information successfully. Our ground mounts in WA (Spokane County) have to be "engineered" Sunmodo and Unirac both make this easy. I may be buying the PV stuff from bluesun and then going with the rack system from a local company since it doesn't appear that bluesun provides these engineering documents. I have asked them, but we will see.
 
I don't know Solis, have only used SMA.
$1/watt was about my estimate including conduit and mounting hardware. Maybe prices went up, glad I bought what I did when I did.

If you get grid-tie inverters, make sure they do frequency-watts so you can add battery backup with AC coupling.

We (San Jose, Calif) get away without mechanical permits if size of ground mounts is within non-permit structure dimensions.
 
I'll have to call the county to make sure on the requirements for permitting. It was just what I was reading online on their site.

$1/watt is before any rebates/tax credits. take 26% off that and then I'll be able to get an extra 5% off. The $1/w is without sales tax, which I shouldn't have to pay in WA state.

I'll definitely check to make sure they have frequency-watts. I'm completely unfamiliar with that, so I'll start reading up and seeing if the models I'm looking at have it.

It's hard to beat the price of this inverter with a 10 yr warranty:
thepowerstore.com

Solis 10kW Single Phase Solar Inverter 4 MPPT 208/240VAC with internal Sunspec MLRSD transmitter (SKU Part Number Solis-1P10K-4G-US-SPRT)

Solis 10kW Single Phase Solar Inverter 4 MPPT 208/240VAC with internal Sunspec MLRSD transmitter (SKU Part Number Solis-1P10K-4G-US-SPRT)
thepowerstore.com thepowerstore.com

I haven't dug into specs, but if that's a good option it would save me quite a bit of money. I have also found wire cheaper as well. That won't be a huge savings overall, but still some.

I'll be creating a cost sheet soon as I begin to hammer down all the suppliers or potential suppliers and their pricing.
 
"CA Rule 21 Phase I-III compliant ) and UL 1741 (SA) certified"

Perhaps "Phase I-III" covers frequency-watts, I'm not sure.

Here's SMA Sunny Island, a battery inverter which provides backup and manages AC coupled PV inverters. Several other brands do too. The way it works is battery inverter disconnects from utility grid if that fails and forms a local grid. It raises frequency above 60 Hz to request reduced power, and the GT PV inverters ramp down their output in response, matching load consumption.

Without "frequency-watts", GT Inverter just drops offline or 5 minutes, and battery cycles up and down.

 
SteinVT said:
I'm in the middle of building up a ground mount system similar to MarkSolar's. It's a Sunmodo rack with Adani bifacial panels, all purchased from my local CED Greentech in Burlington Vermont. Originally I was going to go the cement route, but I am very happy with the ground screws. A crew came in with a big Bobcat and put in the 16 screws in a couple of hours. Using the calculator on the Sunmobo website suggested a bunch of concrete would be needed. I would still be digging.

The screws were put in accurately enough that only minimal screwing around was needed to get everything lined up. Here is a picture of our work in progress. This represents 2 and 1/2 days of work by myself and my very understanding wife.
View attachment 60948

We had to leave on a trip but will be back new week and we hope to finish it up. Still working on the design for the connection to the house. - Mark
Click to expand...

That is wrong on several levels. As those panels are affected by wind and snow loading, all the stress is being put on the glass instead of being transferred to the frame. If you're in a cold area and the ground freezes, movement of the structure could cause those panels to become loose.

I strongly suggest you look at the mounting directions for the panels.. you could be voiding your warranty doing it that way.
 
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