Dual solar inverter integration and diversion to smart plugs

Getting Started
1

Hi,
I am looking to build a shopping list for my setup and I would be grateful for a bit of help.

I think I can work out how to integrate the bits but I am not entirely sure whether I have all the information I need to go ahead.

I have two solar installations, 1.2kWh and 3.68kWh, through separate grid tied inverters. The panels are setup with different orientations.

I have multiple small electric heaters we use to offset gas heating usage and these run off very old smart plugs.

I have an old “Total Power” system, about 10 years old that sort of works but it does not pick up all the solar power and has only 1 ct for the mains which is bidirectional, that is, it can’t tell whether I am a generator or a consumer. It has another CT that sits on the main solar input.

The way it works is to detect the output power from the solar and if it exceeds the power consumed by the house, it will turn on a device in a smart plug. It monitors the power consumed and if there is more solar available it will turn on the next device and so on until it consumes available power or the sun goes in.

I want do the same kind of thing a bit more accurately and pick up the solar power from both inverters not just one.

I have read the documentation and I think the emonPI with the two CT’s which can sense directional flow on the same conductor could do what I want in terms of monitoring power consumed and power generated and net the two. (The cable to my meter smart meter).

What I can’t get clear in my mind is whether the emonPi can look at the difference in flow and switch on devices, wait to sense power consumed - or better still read it from the smart plug then start to turn on additional sockets if power is available.

Should I use Sonos sockets like in the documentation, would this work with what I want?

At a later date I may want to monitor the solar setups separately, if I get a bit more adventurous and net the two for the decision to turn on some sockets round the house.

But initially I am happy to have a combined result.

Everything is located on the same wall except the remote sockets of course.

I’d be grateful for any advice.

2

Welcome, Gordon, to the OEM forum.

I’m no expert on what you can and can’t do with the various home automation systems available, so I can’t answer what the emonPi can do with those things.

But it might be worth pointing out that, if the single feed cables from the two PV inverters come close enough together, you can pass both through the same c.t. and thereby measure the sum power produced. This would apply both to the emonPi and to your old system.

The emonPi will measure two powers (on the same phase - presumably you have a normal UK single phase supply) and you can do whatever sums you like to get total, difference, import, export etc. With a bit of ingenuity, it might even be possible to do greater/less than. What it won’t do directly within emonCMS - which is really only a monitoring application - is control your heating loads. That’s where the other home automation packages come in.

What worries me from what you’ve written is the emonPi has only two inputs, so it can’t monitor individual inverters and house consumption (3 measurements). If you really want to sop up every last drop of excess generation, it’s Robin Emley’s Mk2 PV Router that you need. That looks only at the nett grid power and exactly balances the load to reduce the export to zero - while it can, of course. But it would need it’s own ‘smart’ receivers to control many remote heaters plugged into your ring main, so it’s probably not practical.

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Robert,
Thanks for your comment. My current system CT is a tight fit on the current cable and I could not get another cable in it at the moment. I am not sure about replacing just the CT on this system.
Your assumption is correct in that I have a single phase UK supply.