I would like to compare my domestic electricity consumption with my electricity production from a 5kW wind turbine, and be able to display the information graphically in my home.
The SMS wind turbine inverter is grid connected and located adjacent to the utility meter in a shed.
Since the inverter is 8yrs old, SMS do not support wireless connection or home monitoring packages, so I am looking to OpenEnergy Monitoring for help.
There is a power socket in the shed, but it is supplied from a separate utility supply from the domestic supply which I am hoping to monitor.
Should I order “emonPI-solar pV Bundle, with optical utility meter pulse sensor”?
What do you want the optical pulse sensor for? It’s a loaded question, because the optical pulse from a meter can’t determine the direction of energy flow, so it’s only useful on the wind meter (if you have one), it won’t tell you anything very useful if you put it on the main (grid) meter. (And even then, I’d expect your inverter to have a small consumption when there’s nil wind, and the pulses on that meter won’t show that.)
Fundamentally, I can’t see any difference between what you have and the ubiquitous P.V. installation.
You’ll need access to a single core cable at each point where you will attach the current transformers - I mention this because the inverter might well not be wired in single core (like your main meter) and you’ll need to get in to the consumer unit to find one.
That shouldn’t matter as long as the voltage is the same (or very nearly so) and the two are on the same phase. You are unlikely to have more than a single phase unless you are or were a big consumer. You can normally tell from your meter - see the pictures a little way down this page.
So subject to those things, I think the Solar PV bundle should be OK. I question whether the pulse sensor will be useful to you.
Thanks Robert for your useful input,
further careful examination showed that the utility meter is not optical. So bang goes that idea!
I will have to examine the cables carefully to make sure that they are both single core. The incoming main is a bunched cable, and I remember the electrician suggesting that he would install the same type back to the house. I suppose there might be some writing on the cable if I am lucky. Would you class single phase, bunched as single core?
I think the one from the inverter is single core.
Re. the plug socket:
The main coming in to the farm comes from 2 phases which have been bunched, so they act as one I believe. This supply is then fed to two independent utility meters. My guess is that they are in phase with one another, as they were bunched on arrival at the premises. The difference in voltage between the two supplies will relate to the output from the 5kW wind turbine, and use of cooker, kettle, heat pump in the house. I tested the fall in house voltage from using the cooker and kettle just now, and found that the voltage fell from 239V to 231V. Do you think this matters? This voltage drop would presumably feed back to the other utility meter, what with them both being on the same phase.
Many thanks again for your response.
Mrs. Helga Irvine
I don’t quite understand your cable arrangement - if you could post a picture, that would be helpful. (Just drag and drop into the box you type in.) There’s a picture here that shows a c.t. on a single core cable on the left, on on a flat twin on the right.
If you’re up to it, you can test whether the two “phases” are actually one, if you measure the voltage between the two lines (the brown wire). If it is low - around 10 V or less, they are the same phase. But if they are not, you will see about 415 V, so be very careful.
That 9 V difference will affect the power reading, so you need to decide whether to accept an error of up to a bit over 3%, or whether it’s worth having another socket installed. As you’ve said that you want to compare your consumption against generation, I think you probably need to measure the voltage at the point where the inverter joins the house supply, and if I understand correctly, that means a new socket.