Our grid-tie photo-voltaic system went on line on October 20, 2007. The 22 solar panels on our roof are rated at 200 watts each. The theoretical potential of the total array is 4.4 kilowatts. Our system is a grid-tie system which means that any electricity generated in excess of what we are using is sold back to the utility by feeding it through a special meter back into the grid. Our utility is Florida Power and Light. They allow grid-tie systems like ours to feed back into the grid to be used by other customers.
The direct current electricity from the solar panels comes down from the roof and passes through two charge controllers that manage where that energy goes. If our backup battery bank needs charging the charge controllers direct energy to the battery chargers. A very sophisticated program built into the charge controllers manages the battery charging profile. The charge controllers send direct current electricity not needed by the batteries to the inverters that convert the direct current to 115 volt alternating current. That alternating current feeds many of the circuits in the house during the daytime or during times when the grid is down. These circuits, lighting, TVs, computers, and refrigerators make up our emergency circuits that are always on when the grid is down.
The output of the panels and status of the system is monitored by MySolarLog software running on a small netbook computer. The MySolarLog software was developed by Aren Slootweg in the Netherlands. More info can be found at his website, http://www.mysolarlog.com . Detailed info on the performance of our system using MySolarLog may be found at http://bbbrown.mysolarlog.com/
Here’s the histogram for last year’s daily percentage electricity from our solar panels. It gives a good overall picture of the characteristics of our system. The year started with unusually high consumption for a variety of reasons. Nevertheless, you can see that we had more days above 50 percent than below. With more increases in efficiency, I should be able to shift that peak some more to the right. You can mouse over the bars to display individual day values.