So these are my fist few days with OpenEnergyMonitor and Emoncms. Currently I'm running on a single clamp and the voltage AC adapter. I have a second clamp, but due to the physical location of everything I am currently only able to log from the main feed at the meter. Its going to be a while before I can move this to the fuse board.
I had a bit of a play at the weekend and managed to get it up and running and logging. I've attached a screenshot of my first full day of monitoring. Now I have some questions....
I can see there are lots of processes that can be applied to inputs, but as yet I'm not really sure how to use them. I would like to do a couple of things to start to build an understanding.
1) calculate current : I have power on one feed and voltage on another, so I this should be fairly straight forward?
2) count only positive or only negative flow : I have a 3kWp solar array. One area I want to learn more about is not only my net energy usage but how much has been imported or exported in absolute terms. I suppose this equates to the area above and below the '0' line on the graph. Regardless of what I have generated, I'd like a figure for what I have imported in a given period.
Thanks...
Re: Newbie questions...
You are apparently calculating power in your front-end instrumentation (is this an emonTx?). If you read up in Building Blocks about ac systems, you'll see that the relationship between voltage, current and power is not straightforward - it is complicated by phase and power factor. To get an accurate measure of current, you need to send that to emonCMS along with the other data. Afterwards, you can only extract an approximation of current if you know only power and voltage.
The concept behind emonCMS processing is a number is input, a process works on it and produces a result, that result is the input to the next process, the result from that is passed on to the next, etc. At any point, you can "Log to feed" and only then is the number saved to the database.
To extract only positive values, you can use "allow positive", followed by a "log to feed" and that will give you the positive import values. Now you have a problem, the negative values are lost. You need a bit of lateral thinking. Follow this with "allow negative", which effectively zeros the chain, then do a "+ input" to recover the original power value, followed by another "allow negative" and a "log to feed" to give you a feed of the exported power.
Re: Newbie questions...
Hi JetJackson, I have a 3kWp solar array, and I use 2 ct, there are installed in mode type1 (pv-solar line and home line total energy). with the 2 inputs and the processes list, I have calculated pv-solar production, total energy usage, grig import, grid export. In attach the printscreen of my system. Hope its help you.
Re: Newbie questions...
That's superb! I notice your export is zero .. :-)
Re: Newbie questions...
In a few stolen moments today I've managed to get my brain partially in gear and set up the my first inputs and feeds a bit better. I've also set up a dashboard, picture attached.
Quite happy with what I'm seeing so far.
Very cloudy today so PV output was low (hence the low export). The almost 4kW draw starting at 17.30ish is my electric car on charge.
:-)