Inverters

An inverter is a very important component in the PV system. It does nothing less than change the DC (direct current) energy collected from your solar panels converting that energy to AC (alternating current). Inverters come in different configurations for different systems.

Off-grid PV or “stand alone” systems have no outside power, just the power the system generates. These are frequently called “Island Systems” because the main DC interconnects between the battery and the inverter and the charge controller are crucial to keeping the power at the correct levels, thus keeping the components at top condition. The DC batteries used are called “tolerant” as they are meant to charge and discharge many times. Be aware, however, that frequent overcharging may shorten the life of the battery.

A PV system more commonly in use is the Grid Tie. In this system the inverter can also be called a Synchronous Inverter, because part of its function is to allow excess electricity to flow back into the grid.

A grid tie inverter in this application is more straightforward because there is no need for the heavy battery cables, batteries or a large DC disconnect like the off-grid system.

The photovoltaic inverter changes DC from a solar cell array to AC, synchronizes with a grid and then feeds the energy back into the grid, typically to a public utility.

Using a grid tie inverter to sell power back to a local utility is a fairly new concept, and rules and inspection differ from utility to utility, and also from state to state. Many states and electric utilities require an exterior safety disconnect, so a utility inspection might also be required. You may also have to install a special electric meter that will total the electricity flow in both directions. Do be sure to check with your local utility and get a firm understanding of what is required before installing any solar system that will be designed to sell electricity back to the utility. Some state regulations are very strict and you would want to be legal and up to code before the inspection process begins.

However, let's not concentrate altogether on the outside of the house. Inside your house are many machines and appliances that make your life easier and more enjoyable, and basically every one of them runs on AC electricity. So, when you pick up your blow-dryer or turn on your television, of course it would be ludicrous to always send out a silent thank you to your faithful inverter. Maybe just once is sufficient.