Solar Power Systems: The basics (Page 3 of 3)

The simplest system is the “Grid Intertied Solar Without Batteries” seen above. This is a basic net metering arrangement, where the solar system may put power into the grid when you don’t need it, and you will use grid power when the solar system is not providing enough capacity. All you need is the panels and the inverter to produce AC power, as shown, and the metering on the utility connection measures which way and how much electricity flows.

The next solar power system (seen above) builds on this system, adding batteries for energy storage. This is the sort of system you would have if you wanted protection from losing your power supply to the house, and this is called “Grid Intertied Solar With Battery Backup”. Note how the solar panel output is routed to the charge controller, which controls how much power the batteries can take. The panels are not directly connected into the inverter, as in the first system, but the batteries provide a buffer for the power. The DC from the battery bank goes to the inverter, and makes AC electricity, as in the first case. Note also that there is an arrow both ways between the batteries and the inverter – this denotes that power from the grid can charge the batteries, if needed.

Finally, as you can see above, we go back to the previous solar and battery configuration, but without any connection to the utility grid. The “Off-Grid Solar” system shows an arrangement that would allow you to run your house even if you didn’t have a supply from your local utility company. This would also be suitable for your weekend cabin in the mountains. It functions in the same way as the second scheme, and shown in this case is an optional generator in place of the utility connection. While not completely necessary, if you want your power supply to be reliable you need to have an alternative way of generating power. This covers you for long periods of overcast weather, and also helps avoid having more batteries to carry you over those times.