Next Project is this the correct way of thinking?

So i set up my small array to handle essentials, I only went with two 380w panels mainly for the voltage as this was a greater PV power production than I actually needed.

Now there's talk in the house of a larger system to power everything but grid tie is more trouble than it's worth here so I'm thinking of sticking with off-grid hybrid.

Total peak draw is around the 4kw mark (adding more power monitoring in the coming weeks to cover the outbuildings as I only have monitoring on the main house to know for sure) so I'm looking at a daye 5kw system average draw is only about 1-2kw so I'm guessing I should look at just enough panels to cover that rather than peak and let the grid take care of any spikes is this a correct way of thinking?
Because of the heat I lean towards flooded deep cycles, also I'm not planning on using batteries regularly only as backups in case of outage which brings me to my next question.

As were planing on using Grid at night I'm thinking of a changeover switch so we're drawing from the grid directly rather than going through the inverter is this silly thinking any suggestions on how I would wire this? I'm thinking contactor on the grid side I control with the PV panel output, so grid as primary source & solar as secondary meaning either I switch off the grid or we get a power cut it swaps to PV/battery.

Run it through the inverter, there’s no efficiency loss, and then it’s automatic. I assume it can be set up for Solar-Utility-Battery priority or Zero Export or such.

wpns said:

Run it through the inverter, there’s no efficiency loss, and then it’s automatic. I assume it can be set up for Solar-Utility-Battery priority or Zero Export or such.

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Running through my current inverter on ups mode there's about a 15% efficiency loss, not sure if it's the same for other modes but I guess I won't know untill I have the unit.
I wasn't planning on manually switching a contacter at dusk the whole thing would be automated.

ThaiTaffy said:

Running through my current inverter on ups mode there's about a 15% efficiency loss, not sure if it's the same for other modes but I guess I won't know untill I have the unit.
I wasn't planning on manually switching a contacter at dusk the whole thing would be automated.

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Usually there's grid pass thru with no losses but depending on the inverter there may be standby losses (I e with zero load). Hopefully with a Deye it's less than say 50W?

Brucey said:

Usually there's grid pass thru with no losses but depending on the inverter there may be standby losses (I e with zero load). Hopefully with a Deye it's less than say 50W?

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I think as its in UPS mode the AC is being converted to DC so it can switch between grid or battery without any downtime rather than pass-through, that probably explains the efficiency loss.
It isn't a big problem to fix after i install everything i just need to draw the circuit down and think about it.
I'm more interested in trying to size the system first, the outside lights i wouldn't think consume too much but theres two more inverted AC units that aren't shown on the below graph so until i can work out how much they use i wont know if my planned 5kw system is going to handle everything.

the spikes are mainly from the kettle i believe.

ThaiTaffy said:

I think as its in UPS mode the AC is being converted to DC so it can switch between grid or battery without any downtime rather than pass-through, that probably explains the efficiency loss.

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This is called double conversion and is not a common mode for a hybrid or AIO, since they use an inverter/charger circuit that can only do one of the two at a time, not both.

If you do not have standard style solar equipment you should be careful about over generalizing

zanydroid said:

This is called double conversion and is not a common mode for a hybrid or AIO, since they use an inverter/charger circuit that can only do one of the two at a time, not both.

If you do not have standard style solar equipment you should be careful about over generalizing

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It is standard i was just being uninformed and overthinking things i just took a good look and my efficiency code calculations and the logs coming from the controller and worked out the loss was coming from the charging circuit. Seems even though I limited the grid charging to 2amp the system doesn't want to listen and is drawing around 70w which is more like 5amp on a 12v system.
Sorry for the confusion.

Ok glad that is cleared up.

Does your local grid operator care about unintentional backfeed? That is starting to be a concern in the U.S.; we are now catching up to EG South Africa of 5 years ago, with respect to power company policing people with unapproved equipment leaking back to grid

wpns said:

Run it through the inverter, there’s no efficiency loss, and then it’s automatic. I assume it can be set up for Solar-Utility-Battery priority or Zero Export or such.

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Sorry you are indeed correct I hadn't accounted for grid charging in my efficiency entity.

zanydroid said:

Ok glad that is cleared up.

Does your local grid operator care about unintentional backfeed? That is starting to be a concern in the U.S.; we are now catching up to EG South Africa of 5 years ago, with respect to power company policing people with unapproved equipment leaking back to grid

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They may do in the future but Thailand is the wild west and we still use dial meters here, everyone has awful power factors because of the massive amount of poor quality motors being used to power everything from pumps to processing equipment the backfeed is likely low on their priorities.

ThaiTaffy said:

They may do in the future but Thailand is the wild west and we still use dial meters here, everyone has awful power factors because of the massive amount of poor quality motors being used to power everything from pumps to processing equipment the backfeed is likely low on their priorities.

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LOL.

BTW there are two or three forum members from Thailand, you can try searching for their content.

So you can basically use any equipment you want and operate in grid assist/parallel mode without worrying. Just use the internal transfer relay in the equipment, with external contactors and bypass switches for servicing or if the programming isn’t to your liking.

There might be some folks on GTIL forums with info on how well batteryless works in your situation. I’m thinking solar panels can take a big chunk of power off the AC costs in Thailand, they were doing a ton of work when I was in Thailand in ”winter” one time. Can’t imagine what it’s like in the summer. The grid assist will let the grid handle the start surge and insufficient power situations.

ThaiTaffy said:

Running through my current inverter on ups mode there's about a 15% efficiency loss, not sure if it's the same for other modes but I guess I won't know untill I have the unit.
I wasn't planning on manually switching a contacter at dusk the whole thing would be automated.

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I guess it depends on the inverter. Switching a transfer switch will cause power glitches, which may not be good for all of your loads.

wpns said:

I guess it depends on the inverter. Switching a transfer switch will cause power glitches, which may not be good for all of your loads.

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Anything sensitive has redundancies and due to the excellent 3rd world power here we have multiple spd`s i had a spike of 900v only a few weeks ago and 11kv sometime last year when a drunk decided to play chicken with a power pole, didn't know you could fold a 2ft square concrete pole with a pickup and somehow survive.

Placement is kinda another issue we're planning on a new building(no walls for now just a roof, technically not our land but it's family so np) to put the panels on, which is about 500ft from the house.
I was thinking of just going max voltage with smaller wattage panels and running from said building to the main house with DC but the well pump is half way between and fed from the overhead line coming down to the house so maybe I should just ask nicely and add a room for the inverter/batteries at the new build closer to the main pole so I can feed the existing main line. Then if need be run a secondary main line for my big tools, it's likely the aluminium overhead cable we use here is cheaper than DC cable anyway.

You can check with local rules to see how high you can push the DC, most DIYers in the US stop at 600V but 1000V is another class that has plenty of equipment internationally and for commercial.

You can probably backfeed into that well pump AC cable, though it would be awkward to mount export limiting CTs if there are batteries involved later.

zanydroid said:

You can check with local rules

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Rules? I had a scan through the building regs years ago it pretty much said "don't start a fire".

The inverter I'm looking at wants about 370v to be happy so I'll try to get as close to that and 2500w as I can in whatever combination of a single string then if we decide to export I can add a second.

I'm leaning towards put the inverter in some form of accessable outbuilding near the panels as I'm guessing my brother in-law eventually wants most of the actual building as some form of car showroom.
I would have liked to place it all at the house so I could feed AC air at it, as we will likely run them alot when it's hot if they cost us nothing. The Colder climate would have also given us the possibility of lithium but without it I'm guessing 55°c+/130°f+ temps might be a tad scary.

370V is usually for max efficiency from the angle of the inverter. That is just one aspect of efficiency, if you push 370V down a really long DC circuit and lose 5% of it in the wire, you could also have gone higher voltage and matched the same efficiency. I guess if it is a hot climate you may not want the extra heating in the inverter from the less efficient higher voltage shift ratio.

Solar panels are cheap IMO, esp where you are I imagine, being next to China and on the export routes for a lot of creatively repackaged solar panels. So another approach is to start with the panel layout.

Did you see fmeili1’s setup with a ton of minisplits blowing at his 6 inverters?

LFP inside a place people live, combined with weaker building code and product safety, I’m not sure about. What is the max temp LFP batteries have on their spec?

zanydroid said:

370V is usually for max efficiency from the angle of the inverter. That is just one aspect of efficiency, if you push 370V down a really long DC circuit and lose 5% of it in the wire, you could also have gone higher voltage and matched the same efficiency. I guess if it is a hot climate you may not want the extra heating in the inverter from the less efficient higher voltage shift ratio.

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yes it maxes out at 500v but i dont really want that many panels as its mainly going to be off-grid and with the heat here id like to stay as close to my average load as possible and just let the grid handle the spikes.

zanydroid said:

Solar panels are cheap IMO, esp where you are I imagine, being next to China and on the export routes for a lot of creatively repackaged solar panels. So another approach is to start with the panel layout.

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yep silly cheap about $70 a 550w bifacial atm and thats without any discount codes i can probably get 25% off that by buying 4 plus delivery is like $3

zanydroid said:

Did you see fmeili1’s setup with a ton of minisplits blowing at his 6 inverters?

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no ill try take a look

zanydroid said:

LFP inside a place people live, combined with weaker building code and product safety, I’m not sure about. What is the max temp LFP batteries have on their spec?

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broadly max temp is 60c but if its a hot day and your charging them its likely you could surpass that quite easily, though if they are temprature controlled i might be more inclined, my current inverter and battery are in a 6inch thick concrete box off the side of the house which i could have happily vented ac air into.

Thankfully we didnt follow thai building code when i built our house its mainly poured concrete, engneered brick and decent steel rather than bamboo and box section.