67King
New Member
Building a house, breaking ground on June 1. In east Tennessee, near Knoxville. Have given up on solar shingles, but the good news is that we have space and a few locations where we can put arrays. We are too early to have any sort of loading numbers, so the only thing I have to go by is benchmarking out current house. This one will be abotu 20% larger, but there are some major differences. First, it is on the lake, so we'll have a lot more windows. That and the sizing will increase the loading requirements. Our average electricity usage here is 2250kw-hr. We have some gas appliances that add 77 therms. That direct calculation doubles the loading; however, when I benchmark electric vs gas, the 29.31kw-hr/therm doesn't really hold. So if I use a modified version, I add a bit under 1000kw-hrs. So this house would have a fully electric load of call it 3250kw-hr per month on average.
A big unknown at this point is if I'll put in a lap pool. Really hoping to, as we're a big swim family (all 3 kids swim competitively, one is a D1 swimmer, and I do, as well). That would stand to take a lot more juice, especially if I heat the pool for a few months out of the year.
WOrking the other way. Going to try to avoid gas if at all possible. Natural gas utilities do not support the area, so we'd be looking at a buried LNG tank. That stuff is about 4 times more expensive than utility provided. We wanted to use induction cooktops anyway. Given the site, geothermal HVAC is ideal, so by going with that, we are fine with a straight up heat pump, rather than a dual fuel system (well, multiple - 2 level plus walkout basement home, a bit under 5000SF of heated space). That'll be a huge step in the right direction, but at this point, I cannot quantify it. Tankless water heaters will be another. Going with a metal roof with a radiant heat barrier. Will used closed cell foam insulation in strategic parts of the house. More generally speaking, this house will be newer, nicer, and much better built than the benchmark one. The plan here is for this to be our last home, so we will spend the money upfront to have a positive rate of return for >30 years (well.....hopefully, we'll both be 50 when we move in).
Main array will be very close to the house - if not for the terrain, I'd build an awning attached to the house. Will face SSE. Will use it as a "carport" to park a truck and 28' enclosed trailer. The length of that side of the house is 42 feet, so I have been limiting myself to that length. The goal is for the array to somewhat look like an awning against the house when viewed from the side (note that I'm going to space it off of the house by a few feet given the slope of the hill on that side, so I can have a step like feature, wall or not, then grade out a flat spot that would be appropriate for parking the truck and trailer). May be able to go longer, but that's the starting point. Structural support beams spanning 16 feet are kind of the end of the spectrum. So getting somewhere near a 42X20' covered area (accounting for overhang - and yes I may need to have some support for the overhanging portion of the panels if I go with longer ones).
So for now, I'm assuming I will have a 12X3 array. Best case is larger panels, something like a BlueSun460, which would give me a 12X3 array with a 16.5KW system. Something like a 400W Hanwha will also give me a 12X3, but a slightly lower capacity 14.4KW system.
That's teh straightforward part. Main panel, going to the house, use optimizers to get DC to an inverter in the house, supplying about 3 batteries (best case, Tesla Powerwall+ system, if those jackholes - and I drive a Tesla - ever let me buy the system, rather than forcing me to pay a 100% markup by going through a supplier in this area). Well......I *think* that's the straightforward part, anyway.
Here is where teh questions come in. Let me start out by saying we aren't going to mount on the roof of the house. However, there are two other areas where mounting panels will be an option. One is that I'm going to build a shed, about 12x16. It will have a 12/4 pitch, so I can probably get good use out of both sides. That's a pair of 4X1 arrays, giving me an additional 3200-3680KW. I am not entirely sure where on the property this will be. May be by the dock, may be far from it, depends on what TVA has to say, I suppose. Ideally for what we are using it for, it will be oriented so the panels would face ESE/WNW.
Boathouse/dock. I'm not sure how big that will be. There are piers there now, which appear to be abotu 30' wide (I can't recall the exact width, I will try to update this when I measure them). Probably 38' deep, as well. They, too, would have panels facing ESE/WNW. COuld have an 11X2 array on each side, giving a total of 17-20KW. Do need to point out that the horizon is lower on the WNW side than the ESE side, so I'm not sure which direction would see more sunlight.
Anyway, so between the 3 places, I'm assuming I should ahve enough to have a completely self sustaining system. Still likely will tied to grid, but just for convenience, not necessity.
What's the best way to handle this, in y'all's opinion? Main grid, like I said, appears easy. Optimizers to keep DC to send to batteries, then inverter, then one of the main panels (will have two 200A panels). Given the run required from the boathouse to the main panels, should I plan on a battery(ies) there, inverter, then send AC to the house? Or should I just plan on having that setup be a supplemental AC power supply to tie directly to the panel without battery backup? Figure I could send a pair of cables, maybe one for each panel, to a 50A breaker in each box, to supply juice only while sun is out? I am assuming since I don't own stock in any copper mines that I'd want to avoid running DC over such a long distance. Guess I could also put the more critical components on one of the panels, and the less critical on another, and have all my battery backup for the primary panel, and the supplemental to the secondary?
Is there such a thing as a rectifier in solar? Meaning could I run microinverters on the boathouse/shed arrays, and send AC to the house, into a rectifier, and then merge it with the DC source from the main array going into battery storage?
I know that's a whole lot going on. I'm trying to figure out the best strategy. I have time to sort out all fo this, but most of what I find out there is for more conventional/straightforward systems.
A big unknown at this point is if I'll put in a lap pool. Really hoping to, as we're a big swim family (all 3 kids swim competitively, one is a D1 swimmer, and I do, as well). That would stand to take a lot more juice, especially if I heat the pool for a few months out of the year.
WOrking the other way. Going to try to avoid gas if at all possible. Natural gas utilities do not support the area, so we'd be looking at a buried LNG tank. That stuff is about 4 times more expensive than utility provided. We wanted to use induction cooktops anyway. Given the site, geothermal HVAC is ideal, so by going with that, we are fine with a straight up heat pump, rather than a dual fuel system (well, multiple - 2 level plus walkout basement home, a bit under 5000SF of heated space). That'll be a huge step in the right direction, but at this point, I cannot quantify it. Tankless water heaters will be another. Going with a metal roof with a radiant heat barrier. Will used closed cell foam insulation in strategic parts of the house. More generally speaking, this house will be newer, nicer, and much better built than the benchmark one. The plan here is for this to be our last home, so we will spend the money upfront to have a positive rate of return for >30 years (well.....hopefully, we'll both be 50 when we move in).
Main array will be very close to the house - if not for the terrain, I'd build an awning attached to the house. Will face SSE. Will use it as a "carport" to park a truck and 28' enclosed trailer. The length of that side of the house is 42 feet, so I have been limiting myself to that length. The goal is for the array to somewhat look like an awning against the house when viewed from the side (note that I'm going to space it off of the house by a few feet given the slope of the hill on that side, so I can have a step like feature, wall or not, then grade out a flat spot that would be appropriate for parking the truck and trailer). May be able to go longer, but that's the starting point. Structural support beams spanning 16 feet are kind of the end of the spectrum. So getting somewhere near a 42X20' covered area (accounting for overhang - and yes I may need to have some support for the overhanging portion of the panels if I go with longer ones).
So for now, I'm assuming I will have a 12X3 array. Best case is larger panels, something like a BlueSun460, which would give me a 12X3 array with a 16.5KW system. Something like a 400W Hanwha will also give me a 12X3, but a slightly lower capacity 14.4KW system.
That's teh straightforward part. Main panel, going to the house, use optimizers to get DC to an inverter in the house, supplying about 3 batteries (best case, Tesla Powerwall+ system, if those jackholes - and I drive a Tesla - ever let me buy the system, rather than forcing me to pay a 100% markup by going through a supplier in this area). Well......I *think* that's the straightforward part, anyway.
Here is where teh questions come in. Let me start out by saying we aren't going to mount on the roof of the house. However, there are two other areas where mounting panels will be an option. One is that I'm going to build a shed, about 12x16. It will have a 12/4 pitch, so I can probably get good use out of both sides. That's a pair of 4X1 arrays, giving me an additional 3200-3680KW. I am not entirely sure where on the property this will be. May be by the dock, may be far from it, depends on what TVA has to say, I suppose. Ideally for what we are using it for, it will be oriented so the panels would face ESE/WNW.
Boathouse/dock. I'm not sure how big that will be. There are piers there now, which appear to be abotu 30' wide (I can't recall the exact width, I will try to update this when I measure them). Probably 38' deep, as well. They, too, would have panels facing ESE/WNW. COuld have an 11X2 array on each side, giving a total of 17-20KW. Do need to point out that the horizon is lower on the WNW side than the ESE side, so I'm not sure which direction would see more sunlight.
Anyway, so between the 3 places, I'm assuming I should ahve enough to have a completely self sustaining system. Still likely will tied to grid, but just for convenience, not necessity.
What's the best way to handle this, in y'all's opinion? Main grid, like I said, appears easy. Optimizers to keep DC to send to batteries, then inverter, then one of the main panels (will have two 200A panels). Given the run required from the boathouse to the main panels, should I plan on a battery(ies) there, inverter, then send AC to the house? Or should I just plan on having that setup be a supplemental AC power supply to tie directly to the panel without battery backup? Figure I could send a pair of cables, maybe one for each panel, to a 50A breaker in each box, to supply juice only while sun is out? I am assuming since I don't own stock in any copper mines that I'd want to avoid running DC over such a long distance. Guess I could also put the more critical components on one of the panels, and the less critical on another, and have all my battery backup for the primary panel, and the supplemental to the secondary?
Is there such a thing as a rectifier in solar? Meaning could I run microinverters on the boathouse/shed arrays, and send AC to the house, into a rectifier, and then merge it with the DC source from the main array going into battery storage?
I know that's a whole lot going on. I'm trying to figure out the best strategy. I have time to sort out all fo this, but most of what I find out there is for more conventional/straightforward systems.
