avoid injecting into the grid

freshter

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Hi,

I'm considering installing solar panels, but I'd like to avoid injecting power into the grid. I still want to be connected to the grid though. Is there any way I can install panels and just connect my house in such a way that any power provided by the solar panels is consumed first and whatever shortage there is in the solar panels performance is taken from the grid, without ever injecting any power into the grid?

Power generated by the solar panels that cannot be consumed at the time would be charged into a powerwall, still to be built.

My grid connection is 3P+N (3*380V + N).
 

Redpacket

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freshter said:
Is there any way I can install panels and just connect my house in such a way that any power provided by the solar panels is consumed first and whatever shortage there is in the solar panels performance is taken from the grid, without ever injecting any power into the grid?

This is basically how a "normal" grid-tied solar system works - whatever you use doesn't go to the grid. If you use more that you're making, you draw from the grid.
When you add batteries, I think there's a few others here that have implemented current measuring + control systems that manage when power is drawn from the grid.
 

daromer

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You still need approval to hook a system like this. No matter if you inject to the grid or not. As soon as a system that have that capability is hooked up you need a permit in almost all places around the globe.

There are basically 3 routes

1. Go the legal route and get approval and then you get any grid-tie inverter that have 0limiting/offset feature.
2. Go the not so legal part and get one as above and install
3. Go offgrid where you swap over some of the appliances to use from a battery bank and solar. You can still charge from the grid to that battery bank but of course it wastes more energy. Most people here does that in some way or another.

I have the #1 in my home but hybrid path with battery system. I use battery and solar 9/12 month to 100% meanwhile rest is shared. I still sell all excess.

If you just want something cheaper that works the GTIL have become known as a system used fr 0meetering from solar or even battery. Note that in some countries the hw isnt approved meanwhile it can be approved.

Even my inverter from MPP can do 0metering but with extra meter.
 

Korishan

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Redpacket said:
This is basically how a "normal" grid-tied solar system works - whatever you use doesn't go to the grid. If you use more that you're making, you draw from the grid.
When you add batteries, I think there's a few others here that have implemented current measuring + control systems that manage when power is drawn from the grid.

daromer said:
You still need approval to hook a system like this. No matter if you inject to the grid or not. As soon as a system that have that capability is hooked up you need a permit in almost all places around the globe.

Agreed on both points. This is why you don't cheap out and go with a cheap chinesium or low quality build, AND you make sure, or to install, a cut off that when grid power is not present, the unit is OFF. A good grid-tie inverter (GTI) will do this. Some of the cheapo units may not do this. This makes it VERY dangerous if there are linemen working on the power lines. So make absolutely sure that the device you choose has auto disconnect/cutoff.
 

daromer

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Easiest is just to make sure its legal from the start. Since it no matter what requires permit to install ;)
 

OffGridInTheCity

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freshter said:
Hi,

I'm considering installing solar panels, but I'd like to avoid injecting power into the grid. I still want to be connected to the grid though. Is there any way I can install panels and just connect my house in such a way that any power provided by the solar panels is consumed first and whatever shortage there is in the solar panels performance is taken from the grid, without ever injecting any power into the grid?

Power generated by the solar panels that cannot be consumed at the time would be charged into a powerwall, still to be built.

My grid connection is 3P+N (3*380V + N).

Per your definition - I would say my off-grid + ATSsolution might meet your requirements. When my panels produce power, they begin to charge the battery bank. As the battery bank voltage rises a bit, the inverters are turned on which trip the ATSs... so that the house consumes power from the Solar system. Later, once the sun goes down and the battery drains the inverters shut-off and the ATSs go back to grid. All automatic.

So I 'have grid' but never feed back to the grid. A coupe of keydownsides
* Need UPSs to smooth the ATS switch overs
* Cannot feed excess power to grid and it's lost. This is very small for me (couple of weeks in thespring I loose 10% of my PV power) as I've sized the system right to this limit - and I'm out of space for more panels anyway :)

A couple of key upsides
* System is functional if the grid goes down / no interaction with Power Company
* To work on the system - all I have to do is manually turn off/disconnectthe inverters so the ATSs never switch over to solarand the house runs off grid as it did pre-solar.
 

daromer

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The ups part can be skipped if the inverter is of the type that syncs like an MPP PIP inverter.
 

OffGridInTheCity

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daromer said:
The ups part can be skipped if the inverter is of the type that syncs like an MPP PIP inverter.

Is this an example PIP-3048LV-MK 3kW 48V-https://www.ebay.com/itm/USA-support-PIP-3048LV-MK-3kW-48V-Solar-Inverter-4kW-PV-MPPT-split-phase/254725766854?hash=item3b4ed6bec6:g:-UIAAOSwGAVewwRT It specifically lists "Built in UPS / Power transfer as explained above" in the features.

If so, I think I'll try it with my cargo trailer -> camper conversion. It will have a couple of computers (for example) that will need UPS.
 

daromer

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Yeah they can sync and you can set them in 2 modes where one is UPS or inline. Where the ups have less than 20ms transfer time meanwhile the other is higher.. Think it was 10 vs 20... How they do that with mechanical relay i dont know though.. Normal mechanical transfers are around 15-25ms. Good enough for most transfers except some lights will flicker.

But they are syncing since they have built in transfer. I guess that can be related to the UPS vs inline setting.
But if you switch to UPS setting there is some other settings that is removed... But it was like 3+ years since i worked on them.
 

not2bme

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The PIP acts exactly like a line-interactive UPS. There's no reason to have another UPS after that. Mine switches back and from AC all the time and most of the time I won't even notice it. I think I have it at the appliance setting and not even the UPS setting. Works fine and all my PCs are still running after 2+ years. Some of the versions of the PIP are online UPS capable, which means it's doing a double conversion going from AC->DC and DC->AC and so when it switches to grid utility it technically never 'switches'. So the transition is instataneous. The cavaet of these modes is that it loses a lot of efficiency. So line-interactive is better as far as efficiency goes.
 

OffGridInTheCity

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Thanks guys. I just ordered one -https://www.ebay.com/itm/USA-support-PIP-3048LV-MK-3kW-48V-Solar-Inverter-4kW-PV-MPPT-split-phase/254725766854?hash=item3b4ed6bec6:g:-UIAAOSwGAVewwRT

Typically these are mounted vertically... does anyone know if they can mount horizontally and not burn up? (space in a cargo trailer is severely limited and I'm wondering about my options:))
 

Korishan

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OffGridInTheCity said:
Typically these are mounted vertically... does anyone know if they can mount horizontally and not burn up? (space in a cargo trailer is severely limited and I'm wondering about my options:))

Could always add a fan with a temp sensor. There are 48VDC models available so you wouldn't need to do any function DC-DC conversion. I have a few if you'd like to get one.
 

freshter

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daromer said:
Easiest is just to make sure its legal from the start. Since it no matter what requires permit to install ;)

Definitely. I already contacted the grid company to ask what's possible and legal of course.

OffGridInTheCity said:
Per your definition - I would say my off-grid + ATSsolution might meet your requirements. When my panels produce power, they begin to charge the battery bank. As the battery bank voltage rises a bit, the inverters are turned on which trip the ATSs... so that the house consumes power from the Solar system. Later, once the sun goes down and the battery drains the inverters shut-off and the ATSs go back to grid. All automatic.

So I 'have grid' but never feed back to the grid. A coupe of keydownsides
* Need UPSs to smooth the ATS switch overs
* Cannot feed excess power to grid and it's lost. This is very small for me (couple of weeks in thespring I loose 10% of my PV power) as I've sized the system right to this limit - and I'm out of space for more panels anyway :)

A couple of key upsides
* System is functional if the grid goes down / no interaction with Power Company
* To work on the system - all I have to do is manually turn off/disconnectthe inverters so the ATSs never switch over to solarand the house runs off grid as it did pre-solar.

How does it respond when the load of your house is higher than what the panels can provide? let's say there's a load of 5kW, but the panels can only provide 3kW?
 

OffGridInTheCity

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freshter said:
How does it respond when the load of your house is higher than what the panels can provide? let's say there's a load of 5kW, but the panels can only provide 3kW?
This is where the battery bank comes in serving as a buffer.

The inverters are set to turn onat 51.5v(3.68v/cell) and turn offat 49.5v(3.54v/cell). It takes a few kwhs of incoming power (2-9 depending on sunny or cloudy or severe cloudy)to raise the battery from 49.5v to 51.5v ... so there's a buffer. The varianceis due to theMidnite Classic charge controller's charge voltage which is much more aggressive (hits 51.5v quickly)infull summer sun and milder incloudy winter.

If the PV power islower than home demand after the inverters comeonat 51.5v the batterywill sink back to 49.5v after a few hours.

These settings are custom for my system with an eye toward theinverters turningon and offonce/day. I get a couple times a year in spring/extreme weatherwhere the inverter will come on/off twice in aday - e.g. maybe sunny for 1st 2hrs then storm/severe-clouds then clear again. Also around 25 days/year in the winter where it takes 2 days to reach 51.5v and 4 times it took 3 days to reach 51.5v.
 

freshter

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Well, that makes sense. Thanks for the knowledge :)

Is there any inverter you guys can recommend to me that would be compatible with my grid connection? Like I said, I have a 3 phase + neutral grid connection, so between neutral and each phase there's 230v, but between phases there's 380v.

I'm not looking for the cheapest device, but more for a reliable device that I hook up all the future gear to.
 

daromer

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Look at Victron devices as an example. They have everything you ever would need ;) But the price tag is higher.
 

freshter

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I had someone come by to make an offer for an installation. They're offering Q Cells Q-Peak BLK G8+ 340 W panels (30 panels). All panels would have optimizers connected.

I'd have 14 panels oriented east 336 degrees and 16 panels oriented west 157 degrees. Roof inclination is 38 degrees. I'm at longtitude 4.8547 latitude 50.837.

They're also proposing a SolarEdge 3 phase inverter either SE 5K or SE 7K.

In this setup I would inject back to the grid for at least 15 years as my meter would turn backwards. That gives me 15 years to come up with a solution for a powerwall :) I'd have 25 years warranty on the full setup.

How should I size the inverter? I'd have a yearly fee of 87 euros per 1kw maximum inverter output so I better don't size it too large.
 

OffGridInTheCity

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Got my newPIP running in test mode using 2 of my APC 7s7p batteries in series for 48vand its working. Iparticularly like the UPS aspect as discussed here.

image_uyhggn.jpg

This will go in myCargo Trailer, which will be great when I'm using it BUT for 9months of the year the trailer will sit by the house with 120v power.The trailer battery is a 14s100p(s) of same design as house battery bank and I plan to parallel itin as a 7th battery during those 9 months of idle time bringing the house up from 81kwh to 94.5kwh.

Seems like I should just do some plug/sockets and bypass this unit (disconnected it from120v in/out + disconnect thebattery / turn it off) for those 9 months.Batrium will continue as BMS. I don't get what ECO Mode and/or Bypass function does. Can the unit somehowjust act as a pass-thru for the 120v, ignore the battery,and not wear itself out? (e.g. fans running etc).

image_mfojxt.jpg

Bottom line -Do you think I should leave it live 24/7 for those 9 months the trailer is sittingidle next to the house?
 

not2bme

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OffGridInTheCity said:
Seems like I should just do some plug/sockets and bypass this unit (disconnected it from120v in/out + disconnect thebattery / turn it off) for those 9 months.Batrium will continue as BMS. I don't get what ECO Mode and/or Bypass function does. Can the unit somehowjust act as a pass-thru for the 120v, ignore the battery,and not wear itself out? (e.g. fans running etc).

Bottom line -Do you think I should leave it live 24/7 for those 9 months the trailer is sittingidle next to the house?


Don't have this model, but I assume the ECO mode is the line-interactive mode and the other the online mode. Bypass is as it suggests, it will bypass the battery, therefore pass-thru the 120v. The only strange thing on mine is that even in bypass mode, it draws the 40W self-consumption from the battery. But to counteract this, on mine I would set the charging amps to 2A.

If you keep it running you would be wasting the power keeping it running idle and wearing it out. Just power it down and your batteries are lithium so unless you plan on not using for over a year it should keep stable as long as there's no draw.
 

daromer

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As long as the unit is "ON" it will draw power. Bypass only switches the grid in bypass. Same on all those units

Offgridinthecity: No, I wouldnt have it turned on 24/7 if not used. Disconnect the unit and bypass with ATS and disconnect the battery. Note that if you have a BMS on you need to charge it every now and then.
 
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