Power metering a single solar panel


I'm happy to have found this project. I'm not really in the electricity field so please apologize for my question. I wasn't able to find a complete answer on it. This is my situation : for a project, i would like to remotely log solar electricity production.

I have a single panel announced at 210 W max power output and an inverter. Will it be able to log energy produced ? Or the current won't be enough to be detected by the clamp ? Will I need to choose another clamp ?

I've read http://openenergymonitor.org/emon/buildingblocks/measurement-implications-of-adc-resolution-at-low-current-values and http://openenergymonitor.org/emon/buildingblocks/report-yhdc-sct-013-000-current-transformer but it can't answer my question.

I would be glad if somebody can help me

stuart's picture

Re: Power metering a single solar panel

Does the inverter have any sort of control output that can give you these readings instead?

Sfimx's picture

Re: Power metering a single solar panel


Sadly not, you answer makes me think it won't work :/

Robert Wall's picture

Re: Power metering a single solar panel

What current does 210 W represent? (You don't say what your voltage is! And you don't say where you are so I cannot guess!)

Unless it is a very low voltage system, at best it is a couple of amps, so the standard 100 A current transformer is almost useless. You need to search for a CT with a very low primary current rating, and those are difficult to find.

Because the current is so small, you will be able to use a wire with a small cross-section. You can multiply the current by winding a multi-turn primary winding for a 20 A CT. If you pass the wire through 10 times, and the current is 1.75 A, you will effectively get 17.5 A, so a 20 A CT will be suitable. I believe Robin Emley uses either the 20 A version here: http://www.yhdc.com/en/product/425/ or this 20A:10mA one http://eppep.com/?action-viewnews-itemid-140364 from http://www.ebay.co.uk/itm/281436762683?_trksid=p2059210.m2749.l2649&ssPa...

Because I'm a moderator here, I could look up your email address - so I think your mains should be 230 V, 50 Hz (but you didn't make it easy).

So you are looking at a bit less than 1 A - you need a 20 turn primary winding for your CT. You might just get 20 turns of 1.8 A wire (diameter 1.2 mm), but if not, use as many as possible.

Sfimx's picture

Re: Power metering a single solar panel

I'm sorry, I read so much topics here with the question "what's your voltage", and really, apologize me please. You' are perfectly right, i'm on 230V/50Hz. In addition you perfectly answered my question, so thanks.

So from now, I guess I'm ready to start.

Thanks again for the quick replies :)))

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