Double PV on 3 phase and "remote" grid connection

I’m planning to monitor our PV system. We have 2 PV installation and the grid connection is “far” from them. So my plan is to use 2 x 3phase emonPi2 and 1 x emonBase.

  1. One emonPi2 will monitor the connection with the grid and will have the 3phase emonVS installed.

  2. The second one will monitor the production of both PV implant 3phase for each (I don’t think I need a second emonVS here, am I wrong?).

  3. emonBase will receive data from both.

Are there any critical aspects I should be worried about?

Welcome back!

Are the two PV installations far from each other as well as being far from the grid connection, and are all three “far” from your house?

Where do the various cables from the grid, each PV inverter and your house come together?

How far is “far” in each case, both in a straight line between all four places, and each cable to the place where it joins another?

Unfortunately you are wrong. The emonVs provides both power and a voltage sample to enable real (or active) power to be calculated. Without it, all you can know accurately is the current, you can guess the apparent power but it will only be as close as the voltage is to the value you must also guess. Even if this is acceptable, the 3-phase software inside the emonPi2 is not designed to work without the voltage sample, which it needs to know where one mains cycle begins and ends.

You might not need the emonBase. If both your emonPi2s are within Wi-Fi range of your router, then I think I am right in saying that either can operate as the “overseer” and the other can send its data to it, rather than both sending their data to a third Raspberry Pi running another emonCMS.

But, is there another way to get the data from your PV Inverters? Do they have a data connection, for example Modbus, which you can use instead?

As I wrote, A good Wi-Fi signal at both PV Inverters - this would be my preferred way to connect; and if you do not have Wi-Fi, do you have a clear path for the 433 MHz ISM band radio signal from each emonPi2 to the emonBase? Much safer but harder to install - would wired Ethernet be possible?

Thanks! Happy to be here again!

Between the node Wi-Fi is not a reliable solution, mostly because of the distance from the AP.
Ethernet would be my preferred choice but it is not an option, and power line network are not working too.

The PV inverters are all close together but not all of them are easy to monitor (there are 4 different inverters). I’ll probably use the onboard monitoring system of both fronius, but I’m not going to use the aurora interface again. I’ve used it in the past over RS485, but I’m not going along that path again.

Using an emontx is the most agnostic and at the same time homogeneous solution. And probably easiest to maintain over time. Adding an emonVS close to the inverters is not a problem.

So maybe I can avoid the emonbase and use the emonPi2 close to the inverters to receive the data from the “grid” emonPi2. That would be nice, also because I’ve the intention to send everything to a self-hosted cms anyway (maybe a docker app on TrueNAS SCALE? Will start on a VM first!).

An Ethernet connection will be available close to the PV monitoring node, and I think I could achieve a good connection over 433MHz, in the worst case bringing an external antenna from the board.

So I think a good solution could look like:

emonPi2GRID + emonVS (grid monitoring over 433MHz transmission to emonPi2PV)
emonPi2PV + emonVS (PV monitoring 6 phases, reception of data from emonPi2GRID over 433MHz, upload overt ethernet on remote cms)