Powering my house?

[d2dai00566]

Hey guys I'm new to this forum. Thank you for the add. I have posted questions about my system and people in facebook groups always tell me I need to speak to engineers because of my system size which is why I put it in this section. Finding an engineer to consult seems easier said than done. No engineer I've called wants to work with a DIY'er without charging over $5000-$15000 for consult and plans. So I'll explain my system and my current hiccup. I am building a 21kw array. 550w trina bifacial panels. I'll be using 4x MPP LV6548 inverters. I'm going to either buy a bank that has 90KWh storage or build one. I'm still deciding. This is going to be an off grid system. My house is large and I have a few workshops and ac's I need to power here in south florida. My house is fully grid tied right now but I am going to change that and go fully off grid. I've searched high and low and everything I see just doesn't solve my issue. I understand all the typical house wiring. I understand all the pv wiring and disconnects. I understand how to wire up the batteries with bus bar's and a bms. What I'm struggling with is connecting this to my house. I currently have a 200 amp main panel. I'm in USA so its split phase 120/240v. I have a sub panel in my house that is 150 amp in the addition that was built. Then I have 2x 70 amp sub panels in the shops. Obviously I just need to power the main panel to supply the rest of the house? However, my main issue is how the heck to I connect to the main 200amp panel? I see everyone connect by back feeding subpanels with double pole breakers. But everyone does this with smaller amperage breakers. And I don't think using 4x 50 amp breakers to feed the panel would be safe (one breaker for each inverter). I know that my main service is 2/0 wire in the main lugs. However, the inverters only support a smaller gauge wire for AC output. What am I missing? The only possible thing I could think of would be using a copper bus bar and connect all the smaller gauge wire from the inverter AC outputs into that bus bar and bring 2/0 wire from that bus bar to the main breakers in the panel. This is a complete guess. My knowledge of solving problems is extremely limited. I'm just basically skilled at the necessary labor and can follow plans. If anyone could help that would be great or point me to an engineer that is willing to consult for free or a reasonable price then I'm totally willing to speak with a professional as well.

 

[A.Justice]

Personally, I would hire an electrician for the grid hookup, solely to shift liability in the event of an accident (and have it done properly, if course). If the power went out and I zapped a lineman with my DIY setup, not only would I be held financially liable, I'd feel pretty shitty.

If you eff up something in your own home, the only people you could potentially hurt are you or your family. If you eff up something tied to the grid, there's numerous ways that could kill somebody miles from your house.

If it were me, I would install the entire system myself, then have a competent electrician familiar with DC and solar come by to check everything over, and actually hook it into the grid.

 

[Shimmy]

Are you working with your existing (utility) load data; do you know your peak load?
Are you wanting to entirely remove the possibility of grid connection?
Do you need generator provisions?

Simplifying things, if the answers to the last two questions is "no," then you just have the utility company disconnect service, remove their meter, and hook up the 200A downstream of the meter. Adding a bit more detail, the common approach is to use a "generation" panel upstream so you can tie in your four inverters and have a single output breaker going to the main panel. You can simplify it a little if your main panel has plenty of spare breakers and tie in the inverters there, but I personally wouldn't recommend it.

If you do want the ability to tie in grid or generator then you are going to need either a manual or automatic transfer switch upstream.

For my house which does not have a 200A main breaker ("6-disconnect rule"), my plan is to eliminate the "main" panel and provide a new main panel that re-feeds the existing loads and is the tie-in for my existing AC-coupled PV and new hybrid inverter. The old main panel will just have an auxiliary EV charger breaker, an inverter input breaker, and an inverter bypass breaker. (I am staying grid-tied.)

Your real challenge is going to be in finding a way to do the 90kWh energy storage system in a residential setting; that is likely the problem you should solve first and then the tie-in requirements to your existing electrical distribution will become more clear.

 

[d2dai00566]

Are you working with your existing (utility) load data; do you know your peak load?
Are you wanting to entirely remove the possibility of grid connection?
Do you need generator provisions?

Simplifying things, if the answers to the last two questions is "no," then you just have the utility company disconnect service, remove their meter, and hook up the 200A downstream of the meter. Adding a bit more detail, the common approach is to use a "generation" panel upstream so you can tie in your four inverters and have a single output breaker going to the main panel. You can simplify it a little if your main panel has plenty of spare breakers and tie in the inverters there, but I personally wouldn't recommend it.

If you do want the ability to tie in grid or generator then you are going to need either a manual or automatic transfer switch upstream.

For my house which does not have a 200A main breaker ("6-disconnect rule"), my plan is to eliminate the "main" panel and provide a new main panel that re-feeds the existing loads and is the tie-in for my existing AC-coupled PV and new hybrid inverter. The old main panel will just have an auxiliary EV charger breaker, an inverter input breaker, and an inverter bypass breaker. (I am staying grid-tied.)

Your real challenge is going to be in finding a way to do the 90kWh energy storage system in a residential setting; that is likely the problem you should solve first and then the tie-in requirements to your existing electrical distribution will become more clear.

Man I'm so sorry guys. I assumed this would email me that I got a response. I haven't gotten any emails, so I assumed no one responded.

Okay to answer your questions. I am working with my existing utility load data. I've only been here for 6 months at this house. But I have my monthly KWh used. I also called and they told me the average yearly KWhs used for the past 5 years. I would calculate my max KW usage around 20kw if everything starts up at the same time (highly unlikely). My daily KWh's used in the peak of South Florida summer heat are around 85. My cooler months are 70. I am wanting to totally remove the grid connection. I am going to start with out generator provisions. Given the battery bank and Florida always being sunny, I'm pretty positive I wouldn't need it.

I'm looking into "generation" panel. Not much is coming up. I'm just seeing info on PGF (panel generation panel). I also see generator panel. Could you send me a link of what you mean?

Why do you say the 90kwh battery system will be the most difficult part? Size? Space? Or is there another factor I'm not considering here?

 

[Shimmy]

A 90 kWh battery bank would cost you at least $35,000, and if off-grid you would want at least a 20kW PV array for another $40k with inverter... plus your installation cost. Oh, and you are also going to want to have a generator because sometimes the sun doesn't shine, even in Florida-- extra $10-15k for a fixed system. Are you willing to spend that much money? If so, an extra $3-5k is not a big deal in terms of house re-wiring to accommodate the system.

90kWh battery can fit in a space about 6'x2' with front access only, so that isn't a huge issue in relative terms. The big issue is $$$-- the $35k number is using "cheap" components, and "nice" stuff would be about 2x. The 20kW PV array needs about 2,000 square feet of south-facing roof (southeast and southwest can contribute to that), or equivalent ground-mount area.

 

[d2dai00566]

A 90 kWh battery bank would cost you at least $35,000, and if off-grid you would want at least a 20kW PV array for another $40k with inverter... plus your installation cost. Oh, and you are also going to want to have a generator because sometimes the sun doesn't shine, even in Florida-- extra $10-15k for a fixed system. Are you willing to spend that much money? If so, an extra $3-5k is not a big deal in terms of house re-wiring to accommodate the system.

90kWh battery can fit in a space about 6'x2' with front access only, so that isn't a huge issue in relative terms. The big issue is $$$-- the $35k number is using "cheap" components, and "nice" stuff would be about 2x. The 20kW PV array needs about 2,000 square feet of south-facing roof (southeast and southwest can contribute to that), or equivalent ground-mount area.

Got ya. Okay yeah as far as cost, I've already sourced everything. You'd be surprised how good of pricing you can get when you work with local wholesalers that sell to the big dogs. Outside of batteries, I'm only gonna spend 22k on my roof. I'm using 530w bifacial Trina panels so I don't need 50 panels taking up so much roof space. But yes all that stuff I've calculated and drew it out on my roof using a program. I have a large south facing roof so I have a perfect set up.

 

[d2dai00566]

Speaking batteries, I am still debating if I will build my own bank or use power walls. If I do a power wall style battery, I am going to use felicity solar batteries. I've only heard one review on them and it was really good. Has anyone else used them?

 

[Quattrohead]

A small sub panel with 4x 50A breakers is ideal to combine your 4 LV6548 inverters and hence connect to your main panel.
It is surprising how much the sun does not shine here in Florida, those pesky afternoon storms start building by midday and cause serious cloud cover if you get caught under them....but it's still hot and muggy as hell.

Conservation is WAY cheaper although not as sexy. Maybe start with a smaller system that can be expanded later. Live with it for a year and find out what it actually does for you, WAF etc.
Good luck.

 

[polar ape]

90kWh battery out of quality (factory tested automotive grade) cells should cost less than 30k if you DIY.

7 x 16 EVE LF280K@200USD=22400USD
7 x Seplos Mason case with 200A BMS@500USD=3500USD
Add postage and You have 98kWh battery that should last 20-30 years

 

[d2dai00566]

A small sub panel with 4x 50A breakers is ideal to combine your 4 LV6548 inverters and hence connect to your main panel.
It is surprising how much the sun does not shine here in Florida, those pesky afternoon storms start building by midday and cause serious cloud cover if you get caught under them....but it's still hot and muggy as hell.

Conservation is WAY cheaper although not as sexy. Maybe start with a smaller system that can be expanded later. Live with it for a year and find out what it actually does for you, WAF etc.
Good luck.

Ahhhhhhh okay. So I use a 200amp sub panel and once I combine 2 inverters on each leg (4 total) then I can run the 2/0 from the main lugs of the sub panel to the main lugs of my main panel? Each leg providing 100 amps and roughly 10000 kw?
And yeah I know I’ll have low days. That’s why I was thinking such a high battery bank. Have a big enough bank to at least run 1 day of autonomy if the sun was fully gone.
I have been considering conservation as well. Maybe start with a 45kwh bank then go from there.

 

[d2dai00566]

90kWh battery out of quality (factory tested automotive grade) cells should cost less than 30k if you DIY.

7 x 16 EVE LF280K@200USD=22400USD
7 x Seplos Mason case with 200A BMS@500USD=3500USD
Add postage and You have 98kWh battery that should last 20-30 years

Yeah if I can build the entire system for 50k, and use it for 25 years, it would save me 40k assuming my power would never change in price (yeah right). So I think it’s worth it. Plus I’ll have power through thick and thin.

 

[Shimmy]

Speaking batteries, I am still debating if I will build my own bank or use power walls. If I do a power wall style battery, I am going to use felicity solar batteries. I've only heard one review on them and it was really good. Has anyone else used them?

Hadn't heard much about them; the products generally look compelling (although the 15kWh battery is only rated for 80A nominal charge/discharge). I tend not to trust companies that aren't giving more technical details of their products though. (Free shipping would be nice though!)

The only issue with a DIY battery is if you need UL. I am torn on the price delta.

 

[Ampster]

Speaking batteries, I am still debating if I will build my own bank or use power walls. If I do a power wall style battery, I am going to use felicity solar batteries. I've only heard one review on them and it was really good. Has anyone else used them?

DIY you might be able to bring them in at $200 per kWh. I do not know what a power wall style battery is unless you are talking about thousands of small cylindrical cells? The most popular cells here are 280 to 320 Ahr prismatics from EVE or CATL. Have you looked into NEC 2020 and how that might affect your battery plans?

 

[richwolf]

I wouldn’t try cutting the cord until you get your system in. What is the monthly minimum hookup charge?
Also if you need to sell buyers may be reluctant to buy something totally off grid.
And if something happens to your system why not have another backup?

 

[Ampster]

I wouldn’t try cutting the cord until you get your system in. What is the monthly minimum hookup charge?
Also if you need to sell buyers may be reluctant to buy something totally off grid.
And if something happens to your system why not have another backup?

Not to mention that many building codes require a utility connection for safety reasons. There is no requirement to use that connection. Maybe the monthly minimum would be a good insurance policy until you survive a week of cloudy weather with very little solar production.

 

[Danke]

You can get server rack 100Ah or 200Ah batteries. For 90kWh size, around $23,000.

Since you are building such a large system, have you looked into the new Sol-Ark 15k Inverters?

 

[Nobodybusiness]

A 90 kWh battery bank would cost you at least $35,000, and if off-grid you would want at least a 20kW PV array for another $40k with inverter... plus your installation cost. Oh, and you are also going to want to have a generator because sometimes the sun doesn't shine, even in Florida-- extra $10-15k for a fixed system. Are you willing to spend that much money? If so, an extra $3-5k is not a big deal in terms of house re-wiring to accommodate the system.

90kWh battery can fit in a space about 6'x2' with front access only, so that isn't a huge issue in relative terms. The big issue is $$$-- the $35k number is using "cheap" components, and "nice" stuff would be about 2x. The 20kW PV array needs about 2,000 square feet of south-facing roof (southeast and southwest can contribute to that), or equivalent ground-mount area.

Unless the price of lithium cells has gone up significantly then $35,000 for 90kwh is a bit high.
Even buying EG4s server rack batteries would only cost you $27,000 for 90kWH. I have over 200KWH DIY for about $23,000.

 

[Shimmy]

Unless the price of lithium cells has gone up significantly then $35,000 for 90kwh is a bit high.
Even buying EG4s server rack batteries would only cost you $27,000 for 90kWH. I have over 200KWH DIY for about $23,000.

I'm referring to an all-in cost, FWIW. Racks, cables, etc. Also, since 90kWh exceeds the limit of 15 EG4s you need to split the system, which adds some complexities and likely requires greater investment. Plenty of ways of skinning the cat, but ultimately you will spend more doing it (either in time or money). Oh, and for ~1,000kg of batteries I would spring for a lifting cart.

 

[d2dai00566]

Hadn't heard much about them; the products generally look compelling (although the 15kWh battery is only rated for 80A nominal charge/discharge). I tend not to trust companies that aren't giving more technical details of their products though. (Free shipping would be nice though!)

The only issue with a DIY battery is if you need UL. I am torn on the price delta.

So they did give me a little more info. And send me the battery catalog. The one I would get would be the LPBF series. It’s a little better specs. Also, they use BYD battery cells. They said it’s a new battery being used for electric cars over there. Anyone have experience with these cells?

 

[d2dai00566]

You can get rack 100Ah or 200Ah batteries. For 90kWh size, around $23,000.

Since you are building such a large system, have you looked into the new Sol-Ark 15k Inverters?

I have. But the cost of those just make it not doable for me. I talked to solar installers using them and said they are having a lot of technical issues and call backs. I see the diy community has nothing but praise for the sol-arks so maybe the companies are doing something wrong on install. Using the MPP LV6548, or EG4 6500EX would keep my inverter cost at $5000.