Measure divert energy


I want to measure the diverted energy of my solar system. I use an EmonPi with 2 CT sensors to measure both the use and the solar power.

Would I need an emonTx to measure the diverted energy?

If your export meter has an LED that flashes to indicate exported energy, then you could use the optical pulse sensor and feed that into your emonPi. If it has not, then yes, you will need a new emonTx because there’s no way to infer the information you want from only those two c.t’s.

The next question - what sort of diverter do you have? If it’s burst mode and you use an emonTx and c.t/v.t combination, you’ll need to use the CM library & sketch, and you might benefit from monitoring the Grid connection with that too. This is because the DS (discrete sample) emonLib and sketch is not suitable for use with something that is switched rapidly.

Are you on a single phase or three phase where you live?

Yes, my import/export meter has a LED that flashes to indicate the energy that is measuring. If I understand it well, you propose to use an optical pulse sensor to measure the imported/exported energy, and the 2 c.t. to measure both the solar energy and the diverted energy. It is a good idea, thanks.

I have a home made diverter, using an arduino and a solid state relay. It switch really rapidly, so if I understand it well it won’t be possible to measure it with an emonTx. Can the MK2 PV Diverter be measured with the emonTx?

I’m on a single phase.

Thanks for all the help, and sorry for my bad english…

Don’t say sorry for your English - it is much better than my Spanish.

Sorry, I asked the wrong question - I should not try to do two things at the same time. What I wanted to know is if the meter that measures only your PV Generation has an LED that flashes to indicate generated energy?

No diverter that switches rapidly can be measured with the standard emonTx, nor with the emonPi, because both use almost the same sketch and emonLib - and the reason is because that measures for 200 ms every 5 s for the emonPi, or every 10 s for the emonTx.
Therefore, if the diverter happens to be ‘on’ for those 200 ms, it assumes it is on for the whole 5 s or 10 s, and if it is ‘off’ for those 200 ms, it assumes it is off for the whole 5 s or 10 s.

But if you have the emonTx and upload the Continuous Monitoring (‘CM’) sketch and emonLibCM, then that measures continuously like your meter does, and therefore it will measure the rapidly switched diverted load accurately.

As yet, there is no equivalent CM sketch for the emonPi.

But note: If you can add a second c.t. to your Arduino, and put that on the diverter feed, then Robin’s sketch Mk2_RFdatalog_5a.ino will record and transmit the data by RFM.

[There’s a typo in the comment at the top of the sketch. It should of course read “Current is measured via Current Transformers at the CT1 and CT2 ports.”]

Thanks! In fact, my language is Catalan really :slight_smile:

Ok I understand. Yes, the meter that measures my PV generation has this Led, as has the meter that connects to the grid.

Ok I understand, thanks

Interesting! It can be a good option too, I can try to free a port

Thanks for all the information and support!

One thing that is worth checking is how the flashing LED on the import meter behaves when you are exporting power to the grid. On some meters the LED doesn’t flash for export, on others it does, exactly the same as when you are importing, and I believe on a few there is some way to tell. The behaviour can sometimes be configured, so it’s not enough to know the model number, you have to check what actually happens on your particular meter.

I think the favourite, if the Arduino can have the required hardware added, is to use the diverter to measure the diverted power. At the time I was asking about the meter LEDs, we didn’t have any details of what the diverter was, so it was necessary to explore all possibilities. Using meter LEDs is often the least preferred method, because the indication only comes after the event.

Exactly, in my case the meter behaves identically when I import and when I export. Using only the Led I can know the measure but I can’t know if it’s importing or exporting

Ok, I’ll try to measure the power using the diverter, adding a second c.t. on the diverter feed.