Here's the idea: unobtrusively measure the direction and intensity of power flowing along an a.c. line, and by unobtrusively I mean without a physical connection (e.g. clamp meter, Rogowski coils, ...), and the amount of power is not so important, just a relative value would be sufficient.
Why? ... Like a lot of others, I have solar panels on the roof. I also have a few high energy users such as a pool pump, and an airconditioner. Wouldn't it be great if I could immediately detect when I'm exporting power and flip on the pool pump? Or the aircon? And if it gets cloudy and I'm no longer exporting power, to turn off the pump?
If I could determine whether energy is flowing into my house or out of my house (on the mains active line) that would be fantastic. And if I knew how much (or even relatively how much) that would be even better. A centre-zero analog meter for a display would be sufficient.
But how to measure the direction in which energy is moving in an a.c. line? Phase angle doesn't do it. Some sort of directional coupler maybe?
One alternative would be to measure the power output of the solar array and the power consumption of the house, and calculate the difference - which would be either the power I am importing or the power being exported - depending on which is the larger of the 2 measured values. But this is not simple as I don't have easy access to the circuits feeding the house.
Another alternative would be to watch the meters in the meterbox and work out manually whether I'm importing or exporting - but this is time-consuming and doesn't provide an instantaneous indication of the situation.
Is anyone aware of a simple means to measure the direction in which energy is travelling on the a.c. feed to the house?
I sense a market opportunity here for a clever solution, if there isn't already something out there.
cheers,
Mark