Remote PV monitoring

Emoncms
1

Hello and thanks for your help. I have a 4kWp PV system installed on my garage at the bottom of the garden with SMA inverter. The garage has a hardwired CAT6 cable connected to an access point to give extended wifi coverage. I would like to monitor the PV generation, export and electric consumed. I am also looking at the possibility of EV and battery storage in the garage together with a air source heat pump in the house if funds allow. As an electrician I can do all the hard wired parts but when it comes to programming I’m completely lost. Can you point me in the right direction for a starter kit that will set me on the right path. I have looked but not sure on the set up with the garage being remote from the house. Thanks

2

Welcome to the OEM forum, Mark.

Looking at your wish list, you want to monitor:
In the Garage

  1. PV Generation
  2. EV use
  3. Battery in/out

In the house

  1. Export
  2. House use
  3. ASHP

That’s awkward at 3+3. Had it been 2+4 it would have been a little easier/neater

There’s no “Starter Kit” as such that would suit what you want, so it’s got to be put together. An emonPi isn’t a good idea as it has only two current inputs, so I think you need two emonTx’s and one Raspberry Pi to run emonCMS on, plus either an ESP8266 or (preferably) a Pi Zero W. Each emonTx has 4 inputs (3 × 100 A & 1 × 18 A). I suggest co-locating the RPi with one of the emonTx’s and using a wired serial input to connect them (or you could have the RFM69Pi module on your RPi - converting it into an emonBase and use the radio if you prefer), with the other emonTx similarly connected serially to the ESP8266/Pi Zero W. Both would connect to your LAN via the router or AP, the ESP/Pi Zero by WiFi and the emonBase either WiFi or Ethernet. Which way round you have them (house or garage) is up to you.

So it looks as if your shopping list is
2 × emonTx
6 × c.t.
2 × a.c. adapter
1 × RPi (latest) + PSU
1 × RFM69Pi (only if you want to use radio to connect the emonTx to the RPi)
1 × Pi Zero W + PSU (not OEM supply, sorry) OR ESP8266 (OEM supply)
2 × SD card (2 blank, or 1 blank, 1 pre-programmed)
1 × programmer
leads as necessary
Cases for the RPi and Pi Zero W (if you use that)

Programming the Base RPi amounts to downloading the image and flashing an SD card (if you didn’t buy the pre-programmed one), plugging it in and then configuring the software, for which there are the Guides, or if/when those fail, we can steer you through. I’m not sure of the position with the Pi Zero W, but again we can help, and the ESP8266 comes pre-loaded with its software.

You shouldn’t need the programmer, but it’s indispensable if something goes wrong or you want to do something that’s not catered for, so we recommend you get one while you’re ordering.

3

Thank you very much for your quick reply.
As the ASHP could be last on my list I could discount that for the moment and just get used to setting up the other parts. Sorry to be a pain but can you list the parts needed without ASHP requirement so I know I’m on the right track. I do have a Raspberry Pi 3 which was bought for my son to play with but never got used and I don’t know what to do with it either so I’m on a big learning curve.
Regards
Mark

4

Hi Robert

Looking around your web site also got me thinking about another problem, As an electrician I am having to consider DC leakage current from solar PV/battery banks/ SMPS etc affecting type AC RCD’s, is there some way I can use your equipment to monitor mA DC current present on a 230VAC waveform, to provide reliable operation maximum DC on a type A RCD is <6mA and on a type F RCD <10mA.

Regards

Mark

5

When I put that list together, I was assuming that you’d have Henley Blocks where the garage feed comes off the main meter tails - is that correct? If so, and assuming you’ll never want to monitor anything else in the house, you could put an emonPi by your meter instead of the RPi and an emonTx. But I rather thought you’d probably want to monitor some other sub-circuits in the fullness of time.

Removing the ASHP takes one c.t. off the list, and you can certainly use the Pi 3 for your Base with emonCMS running on it, or you can buy the components for an emonPi less the RPi, and put your Pi 3 in that. That would be the most economical route, but it means house use will be calculated from the maths rather than measured independently when you add the ASHP.

We use c.t’s, so they obviously don’t pass d.c. As far as the EV is concerned, the OpenEVSE does of course monitor for d.c. @glyn.hudson is the best person for that. I’ve got to make one thing clear - we do energy monitoring, you can’t use our gear for protection.

6

Hi Robert

I’m completely new to the world of RPi and to be honest a bit scared of getting out of my depth but also feel I need to keep upto date with modern technology or I’ll get left behind. I will order the parts you have suggested and hopefully it will all fall into place when it’s in front of me.
The main electric supply is in an external meter box with sub main to a main distribution unit in the house. The garage is a sub main from the main distribution board in the house to a distribution board in the garage where the PV is connected. EV and battery storage is planned for when funds allow. I think once I have got to grips with the technology I will want to monitor everything!
As far as the DC current monitoring is concerned it was out of a matter of interest rather than providing protection. There is a lot of talk in the electrical world of DC leakage current from affecting the operation of RCD’s but I have no way to measure DC current on an AC waveform so was looking for a way the DC could be measured accurately over a period of time. As a minimum I only install type A RCD’s on general circuits with type B being installed for PV installations.
Thank you for your time
Mark

7

I think I saw that coming. :grinning:

That means you can’t measure your house consumption directly, then. What you’ll need to do is measure the nett grid infeed and the nett garage infeed, and that’s the house consumption. The maths can be done in emonCMS (both will be signed, indicating the direction of power flow).

I think the only way would be a shunt (with the implications for isolation), a Hall effect device or a Rogowski coil - and I’m not sure of the long-term stability of those.

8

Unfortunately I think the Rogowski coil only measures AC current and the hall effect sensor while measuring DC will also be affected by the current on an AC waveform. From what I have read I could separate AC and DC on an oscilloscope but that is going beyond my knowledge.

9

Hi,

to add my 2p’s worth as you have a Pi already if you make up the standard “solar” emonpi package using your own Pi this will give you a good start. As you add other devices you can either use an emontx or if the device outputs MQTT information as the emonpi has a MQTT broker running on it it can pass this data onto emoncms. As you have said once you start monitoring things it can get a bit addictive :slight_smile:
John

10

Hi John

I fear I’m in for a very steep learning curve and on top of all the changes to electrical regulations my brain is on overload, if I could only get my 12yr old lad to do something constructive on the computer instead of playing games all the time. I’ve ordered what has been suggested and will come crawling back for help very soon. Is there a place I should look for dummy guidance before I get started. Thank you for your input.
Mark

1 Like
11

I was in a similar position and wished my son would do the same. My experience suggests that you are about to learn a lot about arduino and RPi programming but I for one am confident it will be successful as the monitoring bit is quite addictive. :slightly_smiling_face:

12

If you scroll back to the top of this page, you’ll find a couple of banners with links. The light blue one has the FAQ - always worth a look because it’s what it says, and the magnifying glass is a search for this forum. The dark blue bar is the more interesting. ‘Guide’ is step-by-step instructions to get things working. ‘Learn’ is the basic (and sometimes not-so-basic) theory and practice. ‘Resources’ is a list of links to places where the nitty-gritty details are. The ‘Search’ here is much wider than the one below it - it will reach the whole site, including the archived forum that preceded this one.

13

This thread has continued here; Emontx connecting to RPi 3