Designing system - solark 15, strings?, shading?

[DIYsolarKY]

So I think the everyone on the forum has convinced me to go ahead and design my own and do my own DIY solar installation.

It pushed me over the edge when I got up on my standing seam roof and it was flat as a board, easy to walk on and my wife reminded me that the savings of DIY would allow us to have a massive battery bank.

House is newly built, on the grid, been in it a year, already crushing electricity, 5 girls at home, my wife too, massive house, endless list of appliances, two big AC compressors, two minisplits, washer, dryer, furnaces, in floor radiant electric heating in winter for master suite, tankless propane water heaters and propane for heating furnaces, 5 TVs, so many hair dryers... The list doesn't end

I have an option to do net metering so that is definitely the plan.

House has 400 amp service

Planning two solark 15 kpv inverters (too may positive reviews on here about this product just working well - I'm just not ready to go with the EG4 18 kpv yet, maybe 5 years from now once it has been around awhile longer and I will be kicking myself),
25-28 kw PV array, next question is where to get supplies and I need help with the design.

I have been on opensolar.com. I think I need to get on ironridge to make a more firm designs for solar racking.

I have a standing seam roof and there is an ice rail installed on the bottom near gutter with S5-T clamps and a railing system.

Can i use this as the lower rail for my panels?

I have found panels for sale by the pallet on signature solar for as low as 29 c/watt up to 52c/watt? Anywhere else I should be looking for pallets of panels?

I have been quoted for about 100 kw of use a day to get a 25-28 kw PV array.

I have been told that silfab, canadian solar, Q cells are the best quality panels, but have also been told that most panels are going to be good for 25 years and doesn't really matter what panels we get.

Opensolar.com has a function that creates strings based on the panels that are placed on the googlemaps roof.

I have basically one main SE facing section of roof and two other less optimal areas (one basically facing NE and the other SW). So three different pitches of the roof we are planning to put panels on.

I have been on my roof and done some measurements to try and confirm to help with the design.

One of the solar companies that quoted me said I need to worry about shading. They were touting using microinverters per panel or using optimizers for strings of panels.

Anyone have any feedback on why I might need optimizers? My house is nearly on top of a hill but there are some 80 ft trees just above us that shade the roof partially towards the end of the day. Does this shading mean I need optimizers? I don't really know enough about that issue. Obviously the end or beginning of each day is going to have shading issues everywhere when the sun is not more directly overhead.

I have really no idea what to do as far as string design - I have done plenty of reading here and elsewhere, but I assume this is all about how much DC voltage and amperage I can have per MPPT input into each solark input (in parallel increase amperage and in series increases voltage.)

Can I rely on the autostring function on the opensolar website, anyone bold enough to have already done this? can I just do some simple math and add up the max voltage and amperage per solar panel in each string to come up with or verify the design doesn't go over the specs on the solark inputs?

And what about getting all the proper wire sizes and lengths, I'm guessing I need ofc a large sketch of a big diagram with each string, how do I know if I need a combiner box and is that the same place a RSD goes? one solar company told me that here in kentucky that they don't even require an RSD outside, i was shocked that I guess our electric codes maybe from the stone age here.

I am looking around locally for an electrician to help connect the inverters to the main panel and meter.

I am going to fill out the net metering application and try and figure out where I need to go to get a permit for this project.

what else should I be worried about or doing in the meantime.

Any and all help is more than appreciated.

A big thanks in advance to the community of DIYers who contribute on this site. Without Will and this community no way would I consider this.

 

[pvgirl]

Partial shading will limit performance which optimizers can help. The need for optimizers is going to depend on what time shading starts to affect the panels. Also consider growth of trees which may increase shading in the future. The cost differential of optimizers over rapid shutdown only modules, plus the gain of per panel monitoring may make them worth it even without a big need for them. Sol-ark will soon be selling their own optimizer solution as an alternative to Tigo. I would confirm what code you are regulated under, as NEC 2017 and later requires panel level rapid shutdown.

I'm not sure I would trust opensolar's auto stringing. Stringing arrangement is going to be based panels direction and keeping Voc adjusted for the coldest temperature under the inverter limit, as well as making sure the panels will be within the inverters operating range. You can double check you stringing with sol-ark's panel calculator.

Wire sizes will be determined by panel choice and wiring. More then likely you won't need a combiner box.

For panels beyond online sources, look around for nearby solar and electrical distributors.

 

[DIYsolarKY]

Partial shading will limit performance which optimizers can help. The need for optimizers is going to depend on what time shading starts to affect the panels. Also consider growth of trees which may increase shading in the future. The cost differential of optimizers over rapid shutdown only modules, plus the gain of per panel monitoring may make them worth it even without a big need for them. Sol-ark will soon be selling their own optimizer solution as an alternative to Tigo. I would confirm what code you are regulated under, as NEC 2017 and later requires panel level rapid shutdown.

I'm not sure I would trust opensolar's auto stringing. Stringing arrangement is going to be based panels direction and keeping Voc adjusted for the coldest temperature under the inverter limit, as well as making sure the panels will be within the inverters operating range. You can double check you stringing with sol-ark's panel calculator.

Wire sizes will be determined by panel choice and wiring. More then likely you won't need a combiner box.

For panels beyond online sources, look around for nearby solar and electrical distributors.

Thanks for the reply.
So those trees are big huge mature trees, unlikely to grow much more, maybe I'll be surprised in 10 years.

What do you suggest for figuring out what time shade hits? And whether it is significant? Can i just go up there in the afternoon right now and take a look at 4, 5, 6 pm, i think anytime after 4 its going to be shaded on the SW and NE facing sections, but it is November so I'm sure we will get shading early during these winter months all the time. If this is the case, should I consider putting more panels on the NE facing roof pitches so I maximize my morning sun exposures and just forget about the SW ptiches that align with those trees and the shading issue?

What does panel level rapid shutdown mean? Is that just having a RSD outside for if the fire dept shows up? Again. I was shocked the installer said not required and by all means I will install whatever is the safest.

Thanks for recs on using the solark calculator as a reference for stringing.

 

[EJansen]

I have expensive panels (REC Alphas 400s) and inexpensive panels (SolarEver 410s), and though the build quality is better on the REC Alphas, the SolarEvers look better and have been performing better (however they aren't on the same roof so it's not a completely fair comparison). So far, I really like the SolarEvers. I've been talking to them directly since SignatureSolar doesn't carry them anymore (at least not the 410w variants) and they will sell directly to the public, but only full pallets. Hit me on the side if you want some POC info.

Regarding the optimizers if going with strings, I personally think they're worth it. I'm in a similar situation where I'm in a new neighborhood, but I have no trees, but things like the radon pipe shadow, bird sh*t, and clouds, in addition to the factors that PVgirl mentioned. It's really not much more expensive to add the optimization feature to the TIGOs (what I'm using) and I'm pretty sure the delta in price will pay for itself eventually. In my case, they've collected almost 15% more energy (or at least that's what's being reported).

 

[EJansen]

I have really no idea what to do as far as string design - I have done plenty of reading here and elsewhere, but I assume this is all about how much DC voltage and amperage I can have per MPPT input into each solark input (in parallel increase amperage and in series increases voltage.)

This is the calculator that I used: Solar Panel Voltage Calculator - Gold Coast Solar Power Solutions (gold-coast-solar-power-solutions.com.au)

These were the calculations using the specs on my SolarEver 410s to determine how many I could get in a string and plug into the 600V MPPTs on the EG4 18Kpv.

 

[DIYsolarKY]

I have expensive panels (REC Alphas 400s) and inexpensive panels (SolarEver 410s), and though the build quality is better on the REC Alphas, the SolarEvers look better and have been performing better (however they aren't on the same roof so it's not a completely fair comparison). So far, I really like the SolarEvers. I've been talking to them directly since SignatureSolar doesn't carry them anymore and they will sell directly to the public, but only full pallets. Hit me on the side if you want some POC info.

Regarding the optimizers if going with strings, I personally think they're worth it. I'm in a similar situation where I'm in a new neighborhood, but I have no trees, but things like the radon pipe shadow, bird sh*t, and clouds, in addition to the factors that PVgirl mentioned. It's really not much more expensive to add the optimization feature to the TIGOs (what I'm using) and I'm pretty sure the delta in price will pay for itself eventually. In my case, they've collected almost 15% more energy (or at least that's what's being reported).

View attachment 176035

Thanks for the info.
Just so it is abundantly clear to me. When you get an optimizer, you get one for every panel and then you have to get some sort of smart monitoring device that monitors all the optimizers? So if I get 62 panels, I need 62 tigos and their cloud and their TAP devices?
And their app will show you what each panel is doing, contributing and warn you when something is out of wack?

 

[EJansen]

Thanks for the info.
Just so it is abundantly clear to me. When you get an optimizer, you get one for every panel and then you have to get some sort of smart monitoring device that monitors all the optimizers? So if I get 62 panels, I need 62 tigos and their cloud and their TAP devices?
And their app will show you what each panel is doing, contributing and warn you when something is out of wack?

Yep, you'll need one per panel. I think I paid just under $38 per device for the following model:

Tigo TS4-A-O, 1500VUL/1000VTUV, 1.2M Cable,MC4; 700W Max Power

It does rapid shutdown, monitoring, and optimization. I was able to see that one of the panels was under producing and that's when I figured out that it was the radon pipe during certain times of the day.

 

[Oldphile]

I have 11 Silfab 370HC in a string and I can unequivocally state that is the limit in a cold climate. Mine hit 450 volts on the coldest day of last winter. On my second system, the installer put 12 Panasonic 400 panels in series. Yikes! Electrician measured 545 volts VOC. I suggest you use the Sol-Ark panel sizing tool

 

[Cmy]

Another place to check is suncalc.org https://tinyurl.com/ycxckm8z

Put in your address and you can vary date and time to see the shadows during the day. Try June/July and compare with winter, it may help show the tree's impact and when. I have one tree that shades the lower part of the roof during the last hour of daylight. But I am not worried about that late and, with 35 ft to the ridge, plan to keeps strings in the upper half.

 

[zanydroid]

Yep, you'll need one per panel. I think I paid just under $38 per device for the following model:

Tigo TS4-A-O, 1500VUL/1000VTUV, 1.2M Cable,MC4; 700W Max Power

It does rapid shutdown, monitoring, and optimization. I was able to see that one of the panels was under producing and that's when I figured out that it was the radon pipe during certain times of the day.

You don’t need one per panel but if you go below that you lose monitoring and you need to read the detailed install guides from TIGO. For instance if that was a series string you could have just put optimizer on that one panel. If it was series parallel then you need full deploy.

For 70 panels going to monitoring only would save $15*70 which is not nothing.

Also note SolArk is coming out with their own optimizers. Those have individual MPPT and can balance to a higher degree than TIGO because of their higher current/voltage matching range. I am not sure what the cost of the monitoring system costs in SolArk. Who knows how well they work though.