Blog - Micro-Inverters

FAQ:  Regulating the power from a single MicroInverter

Question: In my household installation the minimal consumption varies during the day. I have a typical consumption of 80W. At the lowest point I consume only 40Watts. When I have 1 solar panel with 240Wp, this is too much power for me during the full sunshine. During cloudy days however, one panel is not enough. In full sunshine I have an over supply that goes back to the grid. I wish to avoid this. In cloudy days I wish to have more panels to get enough energy to compensate the consumption. My goal is to get to nearly zero consumption from the grid. What do you suggest?

Answer: One solution is to have multiple solar panels connected over DC relays to one MicroInverter. (See the picture.) This way it is possible to regulate the output power coming from the MicroInverter.  During the full sunshine it is possible to connect just one or two panels to get a lowered power output. During cloudy days, it is possible to connect more panels to get enough power from the MicroInverter.

Note: This is the principle of the operation. In order to work automatically it is necessary to monitor the consumption and to have a central switching circuit with some logic to turn on/off the relays at the panels. Also it may be good to have some sunshine measuring (photo resistor) to estimate the production from the panels and to decide how many panels to turn on/off. As of Oct 2013, GWL does not produce this kind of a central switching circuit. At this moment we also do not know about any projects of our customers who would develop this kind of circuitry. We think this is a good potential for a small project development by an individual or small companies.