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Author Topic: hybrid or GT inverter with battery and maximise self consumption  (Read 1026 times)
olly12383
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« on: April 09, 2020, 09:28:02 PM »

I am building a passive house in suffolk.
I have an existing 4kW fit array on an outbuilding (low rate fit but would like to avoid affecting it)
I have 12kW of PV on the new house roof.  Ite relatively unshaded and about 30 deg E of S.
I will probably fit a battery.
I have 3 phase but only use 1
Its all electric cooking so I doubt I will be able to run the cooking or the EV charger off the battery.

Hopefully I will get G100 and be able to export but I realise I may have to limit the new install to 2x 3.68kW export.
the grid does go high volt sometimes (big solar and wind farm nearby) knocking out the existing inverter (I haven't messed with the settings I believe there is a way to raise the cutoff with installer menu)

So I would rather have my 12kW array on 2x single phases (avoids knocking out the fit PV on the 3rd phase and also avoids losses if one phase goes high V because the 3ph inverters always throttle all 3 phases at once)

I run a marine electronics company so I know a lot about off grid stuff.
Inverter - GT with the battery AC coupled will be most flexible (and allow me best storage potential across all 3 phases)
Hybrid will be more efficient to the battery (but only for the phase its on)
It doesn't seem like you can connect more than one inverter to a lithium battery.  Does anyone know anyhting different?
I've pretty much discounted lead due to the inefficiency.
The problem is with hybrid there's no way to get the power from the other 2 phases into it.
If I go GTI with seperate inverter/charger then it looks like I will need to do some inventing of an interface to get the net import/export of all 3 phases (easy to get with inexpensive Modbus meter, but hard to work out how to feed that into the inverter/charger).
Has anyone tried making such an interface?  Or found one to buy?  Arduino / raspi I guess.
I have 2x EV with zappi (although of course they are usually absent during the day) and will dump the rest into a 1000l DHW tank.

Inverters - Sofar have 10yr warranty and are good on the price but are they too budget?  Growatt seem good but don't make a 1ph unit big enough.  I have got Solis in the shed and it seems OK but they only 5yr warranty.

Any thoughts on this?

Within reason, I'm not too bothered about payback, but I would like it to pay for itself eventually because I believe that if it doesn't pay for itself economically, there's a good chance it isn't going to environmentally either...

Ideally the battery would be 24V but I expect it will be 48V.  I say 24V because I have all DC lighting plus other 24VDC loads like the grey water system.  Which can all run right off the battery, thus avoiding the inverter loss plus the SMPS loss in each luminere.


Thanks
Olly
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RIT
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« Reply #1 on: April 10, 2020, 12:01:42 AM »

I've never used it, but you may find it is worth reading up on what is now known as the Iconica hybrid range as it will at least give you an idea of what is possible from lessor brands.

    https://www.photonicuniverse.com/upload/file/Manuals/Iconica/IC-KMS/IC-KMS5000-24/IC-KMS5000-24_user_manual.pdf

Things that the range offers includes

   - 24V operation
   - Array configuration
   - Common battery bank across the array
   - Array can be spread across different phases
   - Can be used in off-grid/UPS configuration.

Apart from the lessor brand issue, these are designed to work with Lead-acid batteries as the array handles the charge management.
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olly12383
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« Reply #2 on: April 10, 2020, 08:07:56 AM »

Thanks for your reply.  Unfortunately their MPPT can't handle my string voltage ~450V VOC. 
But otherwise looks intersting with a better written user manual than a lot of the 'big brand' solar kit!
Cheers
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RIT
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« Reply #3 on: April 10, 2020, 12:27:04 PM »

Thanks for your reply.  Unfortunately their MPPT can't handle my string voltage ~450V VOC. 
But otherwise looks intersting with a better written user manual than a lot of the 'big brand' solar kit!
Cheers

As you would need an array of inverters to handle a 12kW panel array would you not be able to wire up a number of smaller lower voltage strings?

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billi
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« Reply #4 on: April 10, 2020, 12:52:42 PM »

Well , as you are involved in marine electronics , you should find a good partner for equipment  from Victron

And why not cook electric , if Inverter and battery is big enough

A 100 kWh  deep cycle  battery cost about 6000 GBP (just an example , size-wise)

As well there is  the option perhaps to  split the total Pv and use half of it  via Mppt charge controller

As well there are  small heat-pumps to heat  hot water ( good to hear you have a 1000 l water battery)

Well it sounds an investment upfront , but  while you have 2  electric vehicles  already , it might calculate and payback  ok.... ish

Don t know, if the renewable heat incentive is still around  ??

Regards Billi
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
kdmnx
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« Reply #5 on: April 10, 2020, 01:33:36 PM »

Many brands of inverter can be linked, I'd split the array into three 4kWp arrays, with one inverter for each phase. You should investigate if the inverters can share a single battery pack.

Eg i know LuxPower inverters can work on three phases and there is an option in the GUI for a shared battery pack, so I guess that'd work.
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billi
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« Reply #6 on: April 10, 2020, 09:46:15 PM »

Many brands of inverter can be linked, I'd split the array into three 4kWp arrays, with one inverter for each phase. You should investigate if the inverters can share a single battery pack.

Eg i know LuxPower inverters can work on three phases and there is an option in the GUI for a shared battery pack, so I guess that'd work.


Well , ?   does DC power,  from a battery bank, give a care  about 3  phases AC !  ?
« Last Edit: April 10, 2020, 09:50:35 PM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
olly12383
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« Reply #7 on: April 12, 2020, 08:26:15 PM »

Thanks for your thoughts.

Well I have wired the panels in 2 strings of 10 and 2 of 9 to suit best the potential winter shading.  So can't really do DC MPPT now.  Thats hard to change because the scaf is gone and the lower part of the roof is slated.
Also during the time the car, the house batt, and the tank is full (probably by 10am during the summer) I would be reliant on big inverters to export 10kW, and doubt the efficiency is better going PV-48V-230VAC, as opposed to 400V PV - 230VAC.
 
I was concerned about the cooking via inverter as it means I need nearly 10kW of inverter, even allowing for it being unlikely that everything would be on at once.  And this is quite a cost especially given the likelihood of a fault over 10yrs and maybe it wouldn't pay for itself (economically or environmentally) due to the relatively small quantity of energy the cooking takes, despite its high rate.
I can't be independent of the grid for a number of reasons (not least of which the need to charge the vehicles during a winter night)

I guess they are probably more reliable on land but there aren't many boat ones which are >10yrs old.  Victron seem to be about the best.

I will have a look at Luxpower.

The reason for the 3 phase is so I can export the excess power.  It wouldn't be possible on 1ph.  And even at 5.5p/kWh, it still could be of the order of 8000units I export which at 5.5p is 440 a year, which should increase as energy prices do.

Billi do you mean 100kWh of lead @ 6k?  I had pretty much discounted lead due to inefficiency (not to mention size and maintenance) although I like it recyclability.

I would retain the option of dumping the house bat into the vehicle overnight if I knew it would be sunny the following day (or if I go on Octopus Agile or similar I guess I could dump the battery into the grid at peak time and either recharge it on the off peak overnight or wait til the following day)
Maybe another reason I need a raspberry pi based control system - could check the weather forecast for the following day and decide how much to dump to grid...  Not to mention check our calendars to see if the vehicles will be at home during the day!
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billi
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« Reply #8 on: April 13, 2020, 10:20:40 PM »

well , that might be true that lead acid is,  when cycled , a few percent less efficient , but on the other side , one can afford 3-4 times the size , than lion , that then results in a higher capacity  to avoid imported units or , avoid export for low  fit return or heating water ,  so the overall efficiency  depends on the setup and the requirements too

surely charging a car from a stationary battery sounds not really efficient , but , if the  discharge amps are not too high  , why not  do that with a bigger stationary bank

I allways thought , the limitation to  4 kw for PV is   a bit  sad , but i understand the technical rules involved ,  and   if land and roofs allow  i estimated a 10 kW PV would be good for houses , sure now EV s are getting more popular, so  its getting easier to self-consume ,  and heating is shifting to electric too,


We should work nightshift , and enjoy the sun and charge during the day  norfolk whistlie
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
echase
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« Reply #9 on: April 20, 2020, 11:18:48 AM »

Many brands of inverter can be linked, I'd split the array into three 4kWp arrays, with one inverter for each phase. You should investigate if the inverters can share a single battery pack.

Eg i know LuxPower inverters can work on three phases and there is an option in the GUI for a shared battery pack, so I guess that'd work.


Well , ?   does DC power,  from a battery bank, give a care  about 3  phases AC !  ?
I have a 3 phase 15kW UPS with one battery and am fairly sre its the standard way to do 3 phase systems.   

It is old and free to me so am thinking of doing some battery storage with it using DC charging off my PV. Anyone aware of a post here on use of UPSs to do a battery storage function cheaply as don't want invade this post with my questions?
« Last Edit: April 20, 2020, 11:20:26 AM by echase » Logged
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