Powering my house?

[d2dai00566]

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?

I meant power wall or server rack batteries. I haven’t looked into NEC 2020. My main reasoning for going off grid is not having to be tied down to permitting requirements to the T. However, I do plan on sending my entire design to an engineer for a final proofing so my system is safe.

 

[Ampster]

My main reasoning for going off grid is not having to be tied down to permitting requirements to the T.

It depends on whose permit you are referring to, your local building department or your power company?

 

[d2dai00566]

It depends on whose permit you are referring to, your local building department or your power company?

Both county and power. Power company will require crazy insurance for a tier 2 (above 10kw) PV system. They specify everything being UL listed. They have the right to inspect your system at anytime even in the future, they could come in your house and regulate something they don’t like or tell you to replace stuff. The county needs engineered designs and doesn’t like DIY in my area with this system size. Everything has been made so complicated trying to do a hybrid system and it makes it less cost effective because of the batteries I’ll be forced to use as well as inverters. And the engineering aspect. It’s made it so expensive. And for what? $100 a year net metered? I figured if I need more batteries to support my house I can always add on.

 

[Shimmy]

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?

At this point, I would recommend getting much more detailed information from them, including detailed BMS specifications, detailed cell information, confirmation of what testing/certification data they provide with each unit, fault current of each module, etc. A "3-5 year warranty" on such a monolithic system would scare me a bit.

Also, I would be less worried about getting an engineer to review the plans than to get someone experienced to help test and commission the complete system. (I say this as an engineer that sometimes does commissioning.)

I will say this much though: if you go with a 15kWh block, make sure you have a class-T fuse for each module before combining them onto a common bus, and for each inverter leaving the bus. These will have a lot of fault current and much of your equipment isn't likely to be able to interrupt it. The fuses provide a level of "series protection".

 

[d2dai00566]

At this point, I would recommend getting much more detailed information from them, including detailed BMS specifications, detailed cell information, confirmation of what testing/certification data they provide with each unit, fault current of each module, etc. A "3-5 year warranty" on such a monolithic system would scare me a bit.

Also, I would be less worried about getting an engineer to review the plans than to get someone experienced to help test and commission the complete system. (I say this as an engineer that sometimes does commissioning.)

I will say this much though: if you go with a 15kWh block, make sure you have a class-T fuse for each module before combining them onto a common bus, and for each inverter leaving the bus. These will have a lot of fault current and much of your equipment isn't likely to be able to interrupt it. The fuses provide a level of "series protection".

Wow that’s a lot of info. I’ll definitely look into all of that. Thank you for the guidance. And yeah I’ll definitely add the T fuses into the battery bank.

 

[lawJeff]

I have been studying “point of use power” solutions for for a couple of years now.
I installed a power monitor on my main panel to learn exactly what was going on. I am still trying to figure this whole thing out before I decide what to do, and how.

I quickly discovered that my home typically uses less than 2kwh - 3kwh most of the time, but when I looked at the second-by-second power consumption. There are brief peaks (5 to 10min.) that exceed 25kw. It is these brief peaks of consumption that you must size your system for. I don’t want to be taxing a system at or above it’s rated capacity. I learned early in life that running at maximum output is not a winning long term solution.

The next hurdle is the county & power company connection requirements. I am not interested in pushing power back to the grid, but would like to have utility power for times of low production. The problem with that is if you read their documents closely. That is not a winning solution in my situation. It is either all off-grid or nothing.

That brings me to my main question that seems to be eluding me. When we are talking about powering a home. Why are most of the inverters using 48v systems vs 380v systems? When you start talking about 30kw power systems for residential use. The conversation(s) abruptly end without logical explanations.

I realize that when you get that high with kw usage on a 48v system. The amps are in the 400a to 600a range causing high heat. So, that brings us to the 380v systems that are closer to the actual conversion voltage, thereby reducing wasted energy as heat.

The overall cost appears to be about equal between the two types of systems when you consider the addition of sub-panels and possible rewiring of loads. Why are there not more manufactures looking at better inverter solutions in the 380v range? What is it that I must be missing about these voltages?

 

[Ampster]

What is it that I must be missing about these voltages?

Could it be UL listing approval? I believe the Tesla Powerwall operated in those ranges but it is a self contained inverter/battery combination. It is UL listed.

 

[d2dai00566]

I have been studying “point of use power” solutions for for a couple of years now.
I installed a power monitor on my main panel to learn exactly what was going on. I am still trying to figure this whole thing out before I decide what to do, and how.

I quickly discovered that my home typically uses less than 2kwh - 3kwh most of the time, but when I looked at the second-by-second power consumption. There are brief peaks (5 to 10min.) that exceed 25kw. It is these brief peaks of consumption that you must size your system for. I don’t want to be taxing a system at or above it’s rated capacity. I learned early in life that running at maximum output is not a winning long term solution.

The next hurdle is the county & power company connection requirements. I am not interested in pushing power back to the grid, but would like to have utility power for times of low production. The problem with that is if you read their documents closely. That is not a winning solution in my situation. It is either all off-grid or nothing.

That brings me to my main question that seems to be eluding me. When we are talking about powering a home. Why are most of the inverters using 48v systems vs 380v systems? When you start talking about 30kw power systems for residential use. The conversation(s) abruptly end without logical explanations.

I realize that when you get that high with kw usage on a 48v system. The amps are in the 400a to 600a range causing high heat. So, that brings us to the 380v systems that are closer to the actual conversion voltage, thereby reducing wasted energy as heat.

The overall cost appears to be about equal between the two types of systems when you consider the addition of sub-panels and possible rewiring of loads. Why are there not more manufactures looking at better inverter solutions in the 380v range? What is it that I must be missing about these voltages?

As far as the voltage, I think it’s just a safety thing I believe. DC voltage at that high range can arc easier and stuff. It’s a lot to deal with. Here in the US DC isn’t as commonly used residentially so that high scares people off. Plus not many people are building PV arrays larger than 20kw. Others on here may have a better answer but that’s what I’m thinking.

When you are talking about second by second reaching kw ratings to 25kw. You said it’s sustained for 5-10 minutes? That’s a long time. All these inverters usually have a surge rating 3-4x their rated capacity but only sustainable for 30 seconds. So definitely something to consider. But that seems odd to be sustained for that long.

What size home? What area of US? How many hvac units? Any work shops heavy machinery? Just trying to figure out what could be causing a surge of 25kw or greater for sustained 10 min

 

[lawJeff]

I live in the south eastern US. Everything in my home operates on electricity, water (I have to pump it twice), air conditioning (7 tons total), cooking, washer & dryer, and the normal household stuff.

We do try to watch what we have on most of the time. When you have limited time on the weekend to perform all the weekly preparations. Things can add up very quickly. My other half is washing and drying clothes, cooking the weekly meals, and cleaning the house. Then, I may be working on something in the garage. It is that maximum KW usage that the system must be designed to handle. Not your monthly, weekly, or even daily, average.

The Emporia Energy monitor sure did open my eyes as to exactly what I was using, and when. I knew that I had a high demand for electricity and originality only wanted to reduce that consumption rate. The power company solar connection agreement threw cold water on that thought process very quickly.

So, it is to go totally off-grid. By that, I mean only use the utility to run some battery chargers when the demand exceeds the battery capacity.

I was waiting on the Sol-Ark 15k to come out before I made my purchases, but as I learn more. I am beginning to think using 48v systems is not the way to go for powering a home. I am not completely sold on thought just yet, but it is becoming more apparent day by day.

 

[Ampster]

I was waiting on the Sol-Ark 15k to come out before I made my purchases, but as I learn more. I am beginning to think using 48v systems is not the way to go for powering a home.

The Tesla Powerwall uses a high voltage battery for efficiency. It is a self contained unit that includes an inverter/battery and is UL listed. With the constraints of NEC2020 our choices may be limited for DIY installations.

 

[d2dai00566]

I live in the south eastern US. Everything in my home operates on electricity, water (I have to pump it twice), air conditioning (7 tons total), cooking, washer & dryer, and the normal household stuff.

We do try to watch what we have on most of the time. When you have limited time on the weekend to perform all the weekly preparations. Things can add up very quickly. My other half is washing and drying clothes, cooking the weekly meals, and cleaning the house. Then, I may be working on something in the garage. It is that maximum KW usage that the system must be designed to handle. Not your monthly, weekly, or even daily, average.

The Emporia Energy monitor sure did open my eyes as to exactly what I was using, and when. I knew that I had a high demand for electricity and originality only wanted to reduce that consumption rate. The power company solar connection agreement threw cold water on that thought process very quickly.

So, it is to go totally off-grid. By that, I mean only use the utility to run some battery chargers when the demand exceeds the battery capacity.

I was waiting on the Sol-Ark 15k to come out before I made my purchases, but as I learn more. I am beginning to think using 48v systems is not the way to go for powering a home. I am not completely sold on thought just yet, but it is becoming more apparent day by day.

Yeah I that’s why I am going off grid. Too many limitations and requirements when trying to go hybrid/net meter. Have you looked into paralleling the eg4 6500ex from signature solar? Such a great deal and a great inverter. Sol-ark is crazy expensive.

 

[d2dai00566]

I live in the south eastern US. Everything in my home operates on electricity, water (I have to pump it twice), air conditioning (7 tons total), cooking, washer & dryer, and the normal household stuff.

We do try to watch what we have on most of the time. When you have limited time on the weekend to perform all the weekly preparations. Things can add up very quickly. My other half is washing and drying clothes, cooking the weekly meals, and cleaning the house. Then, I may be working on something in the garage. It is that maximum KW usage that the system must be designed to handle. Not your monthly, weekly, or even daily, average.

The Emporia Energy monitor sure did open my eyes as to exactly what I was using, and when. I knew that I had a high demand for electricity and originality only wanted to reduce that consumption rate. The power company solar connection agreement threw cold water on that thought process very quickly.

So, it is to go totally off-grid. By that, I mean only use the utility to run some battery chargers when the demand exceeds the battery capacity.

I was waiting on the Sol-Ark 15k to come out before I made my purchases, but as I learn more. I am beginning to think using 48v systems is not the way to go for powering a home. I am not completely sold on thought just yet, but it is becoming more apparent day by day.

It’s hard to argue your numbers but at the same time it’s hard for me to believe the device is 100% accurate. There’s not one home powered by more than 48v inverters that I’ve heard of from all the solar forums I’m part of. Plus there’s tons of companies doing this and none I know of use higher volt inverters for their installs in residential. The voltage is really just to handle the runs from the batteries. Which are usually short runs right next to or under your inverters. You may be over thinking it. You should make this your own separate forum post and see what some of the real experts on here say.

 

[RV10flyer]

Totally off grid 4+ months. 20,640 pv, 134 kWh diy battery, two sol-ark 12k- output 18,000W, 10kw honeywell gen with auto start. Consume 50-80 kWh/day. 6.25T of hp's, all electric home. 12K's feed 100a sub panel then to 200a xfer sw then to house main panel. Works great. All Air Handler Electric heaters disabled via toggle switch.

 

[d2dai00566]

Totally off grid 4+ months. 20,640 pv, 134 kWh diy battery, two sol-ark 12k- output 18,000W, 10kw honeywell gen with auto start. Consume 50-80 kWh/day. 6.25T of hp's, all electric home. 12K's feed 100a sub panel then to 200a xfer sw then to house main panel. Works great. All Air Handler Electric heaters disabled via toggle switch.

That is awesome. Good job. What part of US are you in? Has your generator even needed to kick on? Did you build your own battery bank?

 

[RV10flyer]

That is awesome. Good job. What part of US are you in? Has your generator even needed to kick on? Did you build your own battery bank?

1000 mi north of you. Gen test once a week for 20 min and during my initial battery charge. I need about 6500W more pv for the dark, cold Dec-Feb and to max out the two SA (13,000W each). Installed all inverter or variable speed hvac (16-33 SEER) or soft starts before solar system.

Yes, 10 ea 280aH DIY batteries, all connected to 1/4" x 2.5" x 6' tin-plated copper bus bars. Max amps from/to SA: 370A or 37A per battery. That varies a couple of amps either way between each battery.

All 100' from house, cooled to 70F with a Fujitsu 9000, 33 SEER mini split hp.

 

[d2dai00566]

1000 mi north of you. Gen test once a week for 20 min and during my initial battery charge. I need about 6500W more pv for the dark, cold Dec-Feb and to max out the two SA (13,000W each). Installed all inverter or variable speed hvac (16-33 SEER) or soft starts before solar system.

Yes, 10 ea 280aH DIY batteries, all connected to 1/4" x 2.5" x 6' tin-plated copper bus bars. Max amps from/to SA: 370A or 37A per battery. That varies a couple of amps either way between each battery.

All 100' from house, cooled to 70F with a Fujitsu 9000, 33 SEER mini split hp.

Sorry I missed the “DIY” when you said the 134kwh. That’s a really awesome system. Thank you for the feed back. Your demands and use are very similar to mine. I don’t think I’ll need the the extra 6500kw pv. However, I may need to produce a bigger battery bank. Once you were up and running have you ever been below 40% battery usage?

 

[RV10flyer]

Sorry I missed the “DIY” when you said the 134kwh. That’s a really awesome system. Thank you for the feed back. Your demands and use are very similar to mine. I don’t think I’ll need the the extra 6500kw pv. However, I may need to produce a bigger battery bank. Once you were up and running have you ever been below 40% battery usage?

Yes, right after startup in March after three dark cloudy days it was down to 20%. My gen starts at 50.4V. It was close.

 

[RV10flyer]

I produced 125kWh on one May day. Second best, yesterday at 104 kWh.