Questions on 25kW Residential Cap in NY

[bcroe]

Bruce, no offense was intended and I hope none was taken. I just wanted to understand your reporting standards because I know you put a lot of thought into your system setup. I also thought there was some esoteric reason that was beyond my grasp.

But I am glad you brought up snowfall. You have posted many times about placing a open divider between panels so that snow can either fall or be moved easily through the middle of the array. So far so good and I get that and it does make sense. But what concerns me is that providing that space you allow for a higher likelihood of damage to the panels during the snow removal process.

I use a snow broom as I assume you do too. As I move about the array the broom sometimes slips off the edge, when that happens the handle usually comes in contact with the panel. Most of the time I catch it, but not always. That force on the panel especially in extreme cold is not good. By placing a divider in the array I would now have dramatically increased the edge area and thus more opportunity for the broom to slip off the panels, especially toward the end of the cleaning when I'm tired.

Just wondered if you noticed that effect last winter?

Dan, I don't take PVOutput very seriously, but its a quick handy way to get curves and comparisons over
days, months, or years. They have no idea what is going on here, and I'm not interested in their judgment.

In the near future I will be trying out landscape mounts, only 2 high. That provides a center gap for snow,
but also a place for a tilt pivot close to the center of gravity. I concluded a bunch of low arrays don't take
any more space than a very high one, at least after the first. That makes them easier to tilt, but it also
means the vertical snow removal distance is only 39 inches. So the total snow being pushed at a time is
far less, as is the distance, and my pushing effort. AND the reach distance is reduced, so the pole will
be easier to control.

There will be seasonable tilt changes; if it becomes simple enough, maybe vertical
or slightly over vertical positioning for some storms.

So far no panel has been damaged, but if one is, it'll beg attention to the snow removal tool. Last
winter clearing time was reduced from 90 min to 40 min and with less effort, and I didn't need to
blow much snow away from the array base. Bruce Roe

[DrLumen]

Bruce, no offense was intended and I hope none was taken. I just wanted to understand your reporting standards because I know you put a lot of thought into your system setup. I also thought there was some esoteric reason that was beyond my grasp.

But I am glad you brought up snowfall. You have posted many times about placing a open divider between panels so that snow can either fall or be moved easily through the middle of the array. So far so good and I get that and it does make sense. But what concerns me is that providing that space you allow for a higher likelihood of damage to the panels during the snow removal process.

I use a snow broom as I assume you do too. As I move about the array the broom sometimes slips off the edge, when that happens the handle usually comes in contact with the panel. Most of the time I catch it, but not always. That force on the panel especially in extreme cold is not good. By placing a divider in the array I would now have dramatically increased the edge area and thus more opportunity for the broom to slip off the panels, especially toward the end of the cleaning when I'm tired.

Just wondered if you noticed that effect last winter?

Maybe wrap some rags, towels or pool noodle around the handle to soften any possible impact? Just a thought...

[DanS26]

I pretty much explained that last time you asked. I don't know what their "efficiency" is about, but
my ideas are quite different. Like, how many minutes per KW does it take to clear a 6" snowfall?
Bruce Roe

Bruce, no offense was intended and I hope none was taken. I just wanted to understand your reporting standards because I know you put a lot of thought into your system setup. I also thought there was some esoteric reason that was beyond my grasp.

But I am glad you brought up snowfall. You have posted many times about placing a open divider between panels so that snow can either fall or be moved easily through the middle of the array. So far so good and I get that and it does make sense. But what concerns me is that providing that space you allow for a higher likelihood of damage to the panels during the snow removal process.

I use a snow broom as I assume you do too. As I move about the array the broom sometimes slips off the edge, when that happens the handle usually comes in contact with the panel. Most of the time I catch it, but not always. That force on the panel especially in extreme cold is not good. By placing a divider in the array I would now have dramatically increased the edge area and thus more opportunity for the broom to slip off the panels, especially toward the end of the cleaning when I'm tired.

Just wondered if you noticed that effect last winter?

[DrLumen]

Out of curiosity, I had to go look up my limit is here. A measly 10kW. Also, the way my interconnect agreement is written, it appears to be based strictly on the nameplate wattage as a hard limit. Perhaps the OP needs to research a bit more to see if the utility is imposing a 'hard' limit or a production limit. If they use the nameplate specs then solar hours (like in bcroe's system) won't matter and trackers would appear to be a better solution.

[J.P.M.]

I guess we have different objectives, nothing wrong with that. My objective in part is to use PV to
generate all the house energy needs. The 15KW inverter plant needs to working as hard as possible.
A standard SW desert system does poorly in northern IL, so I am investigating ways to better adapt it.
Bruce Roe

No knock on my end either. NOMB and hail the freedom. But I can see a lot that could have been done to reduce cost and maint., particularly snow removal. BTW, I'm not in the desert. I lived in one of the cloudiest, snowiest places in the U.S. for close to 50 years and did a lot of stuff similar to you but on a smaller scale. I get your climate and approach. Hat's off pardner !

[tyab]

Bruce has explained his design many times - to maximize the overall daily output for the AC output he is installed for. Thus the high DC to AC ratio and he is trying to minimize clipping - and overall cost is not his primary concern but he has reduced costs with that wood mounting on the east/west panels. Combined with his snow conditions and desired to have ease of clearing - it works for him. Two thumbs up as far as I am concerned. I don't think anyone would recommend it to the vast majority of solar customers but I could see edge cases of potential solar users that may have the same sort of desires. Clearly his ability to clear snow is vastly superior to most others (myself included). As far as PV output - its pointless to try and rate systems since anyone can put in any numbers they want.

Back to the OP - the OP Has clearly defined his energy problem in prior posts - very low efficiency and very large historical castle where he is under many restrictions on types of improvements. I'm taking a wild stab here but given the OP's usage, they are not as cost sensitive as other folks might be - but they would like to knock down what must be an extremely high electrical bill - but hey - he gets to live in a castle - how cool is that! Especially for his kids (another assumption).

25 will be your maximum size for residential zoning - here in PG&E land its 30. If you desire a larger system, have a chat with the building department about seeing what regulations are required to have a commercial hookup and a chat with the PoCo about a commercial account. Maybe it can happen that way - and given your historical status maybe that can help with the zoning.

[bcroe]

Bruce: on efficiency, I think what Dan S26 is getting at is that fewer stated panels can mean less stated capacity for more output I believe that will distort any efficiency numbers, or lead to confusion.

After looking at all you've done, it's clear to those who know a bit about solar design that you're not doing what you've done with an eye toward maximizing output per PV area. Maybe you're pursuing some design goal dealing with less variability for more of the day perhaps, for whatever reasons. But if you're grid tied without limits to feed-in quantities, Maybe I'm missing a lot, but I've never seen the sense of what you're doing from a cost effectiveness point of view, nor heard/read what your design goals are, but I suspect, whatever they are, they aren't about cost.

Not knocking it mind you, I just don't get it.

I guess we have different objectives, nothing wrong with that. My objective in part is to use PV to
generate all the house energy needs. The 15KW inverter plant needs to working as hard as possible.
A standard SW desert system does poorly in northern IL, so I am investigating ways to better adapt it.
Bruce Roe

[pclausen]

Now you are opening up other options. My idea was to increase hours with panels, without investing more
in the inverter plant. That keeps your peak power at the same limit. Changing things at the AC level will
require a complete rework.

I have no plans to change anything about the 80 South facing panels with micro inverters that consists of 6 strings, each feeding a 20A breaker in the shop sub-panel.

My thinking was to add a 20 panel East facing string and 20 panel West facing string, each feeding into separate MPPT inputs on say a SMA Sunny Buy 7.0. And then connect the SMA to the 2nd set of taps on the secondary 400A meter base at the shop via a separate, fused service disconnect.

Is there an issue with mixing brand A micro inverters with brand B string inverter behind a single residential 400A service? Since all grid tied inverters, regardless of brand, independently manages its relationship to the grid, I would not think this should be a concern.

[J.P.M.]

I pretty much explained that last time you asked. I don't know what their "efficiency" is about, but
my ideas are quite different. Like, how many minutes per KW does it take to clear a 6" snowfall?
Bruce Roe

Bruce: on efficiency, I think what Dan S26 is getting at is that fewer stated panels can mean less stated capacity for more output I believe that will distort any efficiency numbers, or lead to confusion.

After looking at all you've done, it's clear to those who know a bit about solar design that you're not doing what you've done with an eye toward maximizing output per PV area. Maybe you're pursuing some design goal dealing with less variability for more of the day perhaps, for whatever reasons. But if you're grid tied without limits to feed-in quantities, Maybe I'm missing a lot, but I've never seen the sense of what you're doing from a cost effectiveness point of view, nor heard/read what your design goals are, but I suspect, whatever they are, they aren't about cost.

Not knocking it mind you, I just don't get it.

[bcroe]

Bruce, love your experiment with lengthening "sun hours" with the East West facing arrays. Don't know about the financial returns on an investment like that but from a production standpoint it does maximize the sunlight hitting the earth at your location.

I have always wondered.....and I mentioned this to you before.....why on PVOutput you do not disclose your East West arrays, only the south facing array as your installed production base....but then post production of all the panels no matter what orientation? This really distorts the efficiency of your installed production base. Not calling you out on this but just trying to understand your thinking on reporting to PVOutput in this manner.

Years ago a moderator on this site named "russ" said you cannot believe anything you see on PVOutput......maybe he was talking about this kind of reporting.

I pretty much explained that last time you asked. I don't know what their "efficiency" is about, but
my ideas are quite different. Like, how many minutes per KW does it take to clear a 6" snowfall?
Bruce Roe

[DanS26]

Now you are opening up other options. My idea was to increase hours with panels, without investing more
in the inverter plant. That keeps your peak power at the same limit. Changing things at the AC level will
require a complete rework.

Strings lend themselves to the kind of experiment I'm doing, but don't deal well with shadows. My curve
above no doubt will change with latitude, and it will change with seasons. Probably there will be experiments
with the tilt over months. The E-W panel arrangement produces enough power here, I was planning to
remove some S panels. Just what is the best winter arrangement isn't clear, considering the clouds
and short sun days. Bruce Roe

Bruce, love your experiment with lengthening "sun hours" with the East West facing arrays. Don't know about the financial returns on an investment like that but from a production standpoint it does maximize the sunlight hitting the earth at your location.

I have always wondered.....and I mentioned this to you before.....why on PVOutput you do not disclose your East West arrays, only the south facing array as your installed production base....but then post production of all the panels no matter what orientation? This really distorts the efficiency of your installed production base. Not calling you out on this but just trying to understand your thinking on reporting to PVOutput in this manner.

Years ago a moderator on this site named "russ" said you cannot believe anything you see on PVOutput......maybe he was talking about this kind of reporting.

[bcroe]

Now you are opening up other options. My idea was to increase hours with panels, without investing more
in the inverter plant. That keeps your peak power at the same limit. Changing things at the AC level will
require a complete rework.

Strings lend themselves to the kind of experiment I'm doing, but don't deal well with shadows. My curve
above no doubt will change with latitude, and it will change with seasons. Probably there will be experiments
with the tilt over months. The E-W panel arrangement produces enough power here, I was planning to
remove some S panels. Just what is the best winter arrangement isn't clear, considering the clouds
and short sun days. Bruce Roe

[pclausen]

Thanks Bruce. I see plenty of those parallel adapters in "the bay". Cool. So I was walking around trying to decide where to put these E-W panels and if I should do one more array pointing South as well.

So here's a shot from abut 300' in front of the shop building:



So I was thinking the E - W arrays could start where the front of the trailer is, and then go back towards to camera. I do have some pretty tall trees, especially towards the East. Here's a shot showing them:



And a shot from the house looking down, showing the "valley" on the other side of the shop where I was planning to put the E - W panels.



I'm also thinking I can get away with putting up another South facing 24 panel array behind the existing one.

Here's a graph showing my production and consumption this afternoon:



So I'm only putting 9kW onto the grid, well below my 20kW limit. Being that it is quite hot today, the panels aren't all that efficient. Here's another shot from a few weeks ago, on a cool day, when the sun just came out from behind some clouds:



Here I was putting about 11kW into the grid, again well below my 20kW limit.

So I have a pretty constant 7 - 8 kW load from the miners before HVAC and other household appliances. They all run some flavor of Linux with watchdogs that would restart them if they sensed a given rig wasn't mining. So it is very unlikely that some/all of the miners would die during high noon one day. But even if they did, the conditions would have to be perfect to me to spike over 20kWh.

So I would my spare microinverters for the 2nd ground mounted South facing array, which will be close to the shop and easy to wire to the existing 200A sub-panel at the shop. It has 225A bus bars, and the main breaker inside it has already been downgraded to 150A. My voltage runs high from the POCO, typically 250 volt, even at night when the panels are pulling it up. So 104 panels @ 260W = 27,040 DC Watts. Divide that by 250V and you get 108A AC before losses. So I think having a total of 104 micro inverter based panels will work just now.

For the E - W facing panels, I'm thinking that it would be better to go with a single large inverter. If I was to go with 20 panels East and 20 panels West, I should only need to size the inverter to be able to handle 24 panels, correct? So let's say I went with 275W panels, that would require about a 7 kW inverter.

I have not looked into a DC array before, but given the 400 ft run up the house, I'd want to run as close to 600V as possible, right. So that would be about 20 panels, correct?

I still have all the literature from the county inspector, that includes a thorough section on DC. Since my current system is all micro inveter based, I just skimmed that section before, but I seem to recall that everything needs to be in steel conduit and I need HIGH DC VOLTAGE warning stickers every 10 feet or something like that on all exposed conduit.

[bcroe]

This is a bit off topic but... Bruce, it is good to see charting is not a lost art but, if you want, I will create a spreadsheet doc that will generate those charts for you. You could open it and make the data changes from excel or google sheets. Nothing wrong with your charts but they are so much easier to make when the data is in a spreadsheet or database.

Yes a formal presentation would need such a big cleanup effort. I'm not there yet, and more
worried about some concrete just now. But maybe that will happen later. thanks, Bruce Roe

[DrLumen]

This is a bit off topic but... Bruce, it is good to see charting is not a lost art but, if you want, I will create a spreadsheet doc that will generate those charts for you. You could open it and make the data changes from excel or google sheets. Nothing wrong with your charts but they are so much easier to make when the data is in a spreadsheet or database.