diy solar

diy solar

Inverter with off grid capabilities WITHOUT battery

Ampster said:
I think what @timselectric is talking about is a GT inverter configured for Zero Export. It does not need a critical loads panel. It just needs current transformers on the custormer side of the meter so that the GT inverter can throttle back to avoid export. It is an alternative to going through all the paperwork with a utility if the NEM policy is not worth doing all that paperwork.
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He said offgrid inverter.
Yeah that’s what I’m referring to. GTI powered by batteries with zero export if needed
 
Ampster said:
I looked at a lot of alternatives but in my environment in California my system (see my signiture) was more cost effective and simpler than all the separate parts you listed. It all depends on where you are standing.
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Well the offgrid inverter/Charger can be in one nowadays. That AC coupling stuff is Cool with the hybrid inverter throttling the grid tie inverter.
 
Ampster said:
I think what @timselectric is talking about is a GT inverter configured for Zero Export. It does not need a critical loads panel. It just needs current transformers on the custormer side of the meter so that the GT inverter can throttle back to avoid export. It is an alternative to going through all the paperwork with a utility if the NEM policy is not worth doing all that paperwork.
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Off grid inverters
No export capabilities
But can share the loads with the grid
SUB mode (solar, utility, battery)
 
Cheap 4-life said:
He said offgrid inverter.
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If so, my point was that there are several ways to do that which do not require a critical loads panel. If he is truly off grid, of course there is no need for a transfer switch or critical loads panel. As he pointed out the capability to share the loads with the grid gives him flexability to handle surges or critical needs that he cannot live without.
:ROFLMAO:
 
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If I couldn't have backfeed/net metering, I'd consider a system like what I have, but zero export.
Sunny Boy GT PV inverter, AC coupled to Sunny Island battery inverter, undersize battery for backup.

Batteries are expensive and wear out. Keeping it small, and not cycling it (except during power failures), reduces cost.
Could buy a big battery later if there is a reason to unplug from the grid.
 
Ampster said:
I think he was just pointing out that in most cases you still are required to pull a building permit.
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Yep, in my area the home owner can pull the permit to do work on their own house. If I seen it correctly, Engineer775 sets the SolArks up for offgrid and has them inspected and then basically turns on grid tie zero export after inspection. So if an offgrid inverter with AC charging doesn’t need to be inspected in the area then a zero export GTI or hybrid doesn’t need inspection.
 
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Hedges said:
Batteries are expensive and wear out. Keeping it small, and not cycling it (except during power failures), reduces cost.
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I agree, The cost of my battery system varies between $0.20 and 0.27 per kWh so it still makes sense for me to use them to avoid $0.50 per kWh rates at peak times. I know you are on PG&E, but what rate plan are you on?
 
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My rates are something similar, I think they got changed without much fanfare and rate plans got bumped to something new a while back. I recall they trumpeted an "Even Better!" (less worse) plan.

Once you've bought a battery, you might find it costs $0.27 per kWh if you use it, and might die of old age without being cycled if you don't. In other words, you might get some of your money back if you charge from PV at low times and export at high times.

I ran numbers on those SS server rack batteries that claim 6000 cycles, and they appeared to be around $0.05/kWh.
 
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Hedges said:
I ran numbers on those SS server rack batteries that claim 6000 cycles, and they appeared to be around $0.05/kWh.
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i modified my post to say my battery system which includes my hybrid inverter. Just the batteries which cost $125 per kWh could be $0.05 per kWh if I get 2500 full cycles out of them or 5000 half cycles.
 
Cheap 4-life said:
Yep, in my area the home owner can pull the permit to do work on their own house. If I seen it correctly, Engineer775 sets the SolArks up for offgrid and has them inspected and then basically turns on grid tie zero export after inspection. So if an offgrid inverter with AC charging doesn’t need to be inspected in the area then a zero export GTI or hybrid doesn’t need inspection.
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So why doesn’t he set up for zero-export grid tie before inspection?
 
Ampster said:
i modified my post to say my battery system which includes my hybrid inverter. Just the batteries which cost $125 per kWh could be $0.05 per kWh if I get 2500 full cycles out of them or 5000 half cycles.
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With that cost, charging off peak to use on-peak makes sense, also to export on-peak. While we get 100% credit not the proposed 25% credit. Even at 25%, $0.125/kWh on-peak, $0.05/kWh batteries could earn you net power. Break-even at 1000 full cycles (3 years full, 6 years half cycles) for the battery, and adding more could be worthwhile if they are simply purchased. But if DIY they have a labor content too.
 
Hedges said:
Motor starting surge is about 5x operating current, and only lasts a fraction of a second. Too long for most capacitors to support, however.
A very small battery, but capable of high current, should let a system start then run much larger loads.

If lead-acid, you would want low battery cutout to be quite a high voltage, keeping SoC above 80% or 90%, so it can give 10 to 20 year life. Voltage will drop low at high current, so inverter needs to allow some seconds before shutting down if it doesn't understand Peukert.

Possibly super-capacitor bank would also work. But I think used automotive batteries from the wrecking yard would be an economical first implementation. Handy as spare or jump starter for your vehicles too.



One link somewhere around here had video of a contractor who installed 6kW Sunny Boys for a customer, and they demonstrated that Secure Power was able to start a large angle grinder. That looked like one that might draw 15A full load, so I think Secure Power may deliver surge well over the 2000W rating they quote. System is sized for 240Vrms output, so when buck converter is delivering 120Vrms the capacitor voltage can swing a lot to release stored energy.

I think solar with large loads in the daytime is a reasonable goal. I run my central A/C with a fraction of PV output.
DC or AC powered LED lights and communications could be powered 24/7 from battery. Much of the gear is 12V, so separate AGM battery and charger could be used.
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I might also wonder if the inverter would last longer using a small battery bank, because the main board would be able to supply itself with a steady power source instead of a fluctuating power source where it may not have a steady voltage bus to operate. While they work batteryless, it seems like it would be less optimal. So a battery would give a stable voltage bus for the main board to operate with and could allow it to last longer.

Also to note, most of these inverters (well all of the ones I've seen so far), only allow batteryless mode in single inverter topology, so if you ever decided to parallel stack them, you'd have to add batteries anyways. You'd also have to find one that offers split-phase in a single unit (if in North America)...
 
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