Hi, I have a “split buildings” house case, wher the grid connection point, the distribution panel and house consumption are located in the main building, while the PV panels, inverter and battery will be located at a storage building, 50m across the street from the main house. The two locations are connected only with a 16A mains cable (3* 2.5sqmm), without possibility to drop any other cable. I want to have a small ESS, to cover part of electricity cost and it would be nice if this could serve as a backup source for outages.
Questions:
Can Multiplus II (or EasySolar II) work in grid parallel (on the 16A line) without power sense, i.e. without transformer or power meter, thus feeding all PV power (or even battery power, according to configuration) back to the grid? Like a microinverter case… The feed-in is not compensated (for now), neither is allowed (for now), but it is not detectable by grid op, either (for now).
In this grid parallel “not detecting grid” case, can the user manual switch to island mode, i.e. switch off the mains and instruct MPII (somehow, easy) to run in off-grid mode, feeding critical sources? Cannot use AC out, there is only one cable connecting MPII with main distribution panel.
Victron AI answered “no” to the above. What is the solution for the inverter to sense the consumption of the house, without having the option to pass another 50m cable (RS-485 or Ethernet) between the two buildings? Is it a power meter with a ZigBee pair, from meter to inverter? Or maybe an Ethernet connection over Powerline? If this is implemented, does the “response” of the remote meter can handle the feed-in of the inverter according to loads, with option for (almost) zero feed-in?
If you do Not have an external grud Meter, the MP2 used the internal one or direct attached Ct clamps.
Usually you set a “grid set point”, though the MP2 will try to keep a certain energy flow at the metering point, e.g. 1kW into your house on ACin.
The specific setting depends on operation mode e.g. ESS or others.
If you have only one cable, then you need to connect to ACin putting your MP2 parallel to grid and house loads. Offgrid/island is supported on ACout only.
Easiest way to connect a grid meter might be a network capable grid meter like the VM-3p75ct. The network can be transferred by a wireless lan bridge or mesh network for IP. In addition, this IP network will connect your Cerbo GX to the cloud for remote control.
The ACin limit (16A) seems not to be respected by power assist and grid limit. Use breakers for the line.
@DuivertNL Of course MPII (or EasySolar) will be within 1m of the battery! (and some 5-7m from the solar panels). But the (house) consumption is across the street, 50m away, with only a 16A mains connecting the two spots. I was thinking of a “micro-inverter” like operation, i.e. feeding whatever panel production (and battery, depending on configuration) to the grid, without throtling it (cannot, since there is no sense of power and direction). I was thinking also of some smart meter/switches, to automate powering on loads (heater, dehumidifier, a/c…) whenever there is sun surplus. And of course, critical loads work only on AC1 out, so normally local to the MPII. In my (2) point above, I was thinking on outages to (manually) switch off mains switch and then reverse the connection to the MPII, from ACin to AC1out, while “programming” it in island (off-grid) mode - all of these somehow automated and secure!
@BjoernK Internal or external CT clamp is not an option, for 50m away from mains panel. I know about “grid set point”, I am using ESS in other installations and I would like to use ESS in this, “remote” case, as well. Yes, I buy your advice about setting an IP network (wireless or over powerline) for a power meter (one phase, my case) etc. There is the option also with Victron’s ZigBee twin kit (USB and RS-485). But I have no clue how fast those meters and fixture will respond to load demand.
That’s a very nice idea… I was thinking of something similar, you put down the numbers and wrapped up everything nice!
My concern was/is that the house is of very limited space, also I worry about the humming noise of MPII. The owner proposed to house everything (MPII, battery) outside, to build a mini weather protected shelf (like those that enclose the grid meters). Of course, all these (AC-PV, shelter) raise the cost, but I will propose to the owner. Having the MPII very close to mains panel, means grid metering, also controlling via ACout2 loads etc.
Maybe this is the solution, as you propose, something like 800-1600W PV-AC (HMS) on storage building, plus a 400W (12V) or 800W (24V) or 1200W (48V battery) PV-DC on house roof. Going for 48V LiFePo, I need at least 70V input to mppt, better 3 panels in series - which makes it complex, for that roof installation. Most pro I will forget the PV-DC for black start and work on something to trickle charge from mains the LiFePo.