The inverter

An inverter converts direct-current (DC) electricity to alternating-current

(AC) electricity. DC is what most turbines produce with the wind (technically,

your turbine first produces wild AC, but it’s changed to DC); AC is what you

use in your house and what the grid supplies to you.

In a system that’s connected to the grid and that has battery backup, the

inverter effectively acts as the charge controller, selling excess energy to the

grid to maintain the battery bank at the set voltage when the utility grid is

available. In a grid-tied system without battery backup, the inverter sells all

the energy that it can to the grid, because it has no batteries to care for.

In a batteryless grid-tied system, the inverter lives and works between the wind

generator and grid. In a battery-based system, its home is between the battery

bank and the house loads and grid. With higher-voltage wind generators,

there may be power conditioning equipment between the wind generator and

the inverter or charge controller. This equipment keeps voltage from going

too high, so it’s often called a voltage clamp.

There are two basic types of inverters:

 ✓ Battery-based inverters: These inverters need batteries to operate.

They work in backup systems, the ones that give you protection from

utility outages, and in off-grid systems.

 ✓ Batteryless inverters: These inverters convert the wind generator’s

DC output to AC without batteries involved. These systems provide no

backup. When the utility grid is down, you can’t make any electricity, no

matter how much the wind is blowing.

 Choose which type of inverter system you want — battery-based or batteryless —

upfront. Changing your mind later is costly. If you’re off-grid or want outage

protection, your choice has to be a battery-based inverter. If you’re grid-tied

and don’t want or need batteries, buy a batteryless inverter. See Chapter 9

for more discussion of this important decision.