Standalone PV for showcase at University

I’m currently building a standalone PV solarstation at my University (Clemson University, if you were curious). Basically, It will consist of a table with an “umbrella” of solar panels connected to a charge controller, which leads into a battery system. The batteries will then connect to an inverter and provide AC power to a GFCI outlet. This system has already been implemented somewhere else on campus. The one I’m building will differ a bit as I hope to have some sort of energy monitor on it. One that measures the incoming power as well as the outgoing power. I came across the Emonpi and wanted to ask if this will work. It is not connected to the grid and doesn’t have a meter to go along with it, so I’m not sure if this will work well with my requirements. Does anyone have any info on this or perhaps a link to something else I can look at?


Based on what I understand you want to do, the emonPi is not likely to be suitable. I think you’re saying that you need to measure the d.c. power out of the solar array before it hits the inverter, and compare that with the, presumably a.c, outgoing power. In other words, you want to demonstrate the efficiency of the complete system. The emonPi will certainly do the second part, but without serious modification - which will be tricky given the confinements of the enclosure - it cannot do the d.c. part.

What do you mean by

Are you observing a fact, or asking for an instantaneous analogue display using a meter movement? The emonPi will give you a display via a nearby router and WiFi to a computer, tablet or smartphone.

I just noticed a lot of posts regarding a meters for houses etc. and I was unsure if you would absolutely need one in order to implement the system. And you exactly right, I’m just trying to find a way to demonstrate the efficiency of the project. Do you have Any ideas as to how or what I can do in order to accomplish this task?

You don’t need a commercial meter (but you could use a DIN-rail one with serial output if you wanted).
I’d suggest an Arduino with either the emonTx Shield (for the a.c.) or copy the design of the shield for just one each a.c. current and voltage channel onto your own p.c.b, and add whatever signal conditioning you need for one each d.c. current (from a shunt or Hall effect device) and voltage channel. You can use emonLib to calculate the a.c. output power, and the sums for the d.c. are trivial. If you need a display, there are LCD’s that accept serial input. There’s a lot in the ‘Learn’ section here that will help you.

Or if you really wanted to use a Raspberry Pi, you’d do much the same but adding an 4+ channel ADC and your own signal conditioning pcb as a front end.