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INVERTERS & CHARGE CONTROLLERS
The inverter is the heart of all but the smallest power systems. It is an electronic device that converts direct current DC power from batteries or solar modules into alternating current AC power to operate lights, appliances, or anything that normally operates on power supplied by the utility grid. Inverters come in many varieties, sizes and qualities and offer various features that specialize them for particular applications.
SMA Sunny Boy
Xantrex
PV Powered
Apollo Solar
Fronius
Outback
3 Phase Commercial & Industrial Inverters
Xantrex
Solectria
SatCon
PV Powered
NEW!! Enphase Micro Inverter
Simplifies wiring and increases efficiency
Charge Controllers
IBE Chargers
Xantrex Truecharge
Inverter information:
Off-Grid Inverters
Off-grid, or standalone inverters convert DC power stored in batteries to AC power that can be used as needed. Select an inverter for your power system based on the maximum load you will be powering, the maximum surge required, AC output voltage required, input battery voltage and optional features needed. High quality standalone inverters are available in sizes from 100 watts, for powering notebook computers and fax machines from your car, to 50 kilowatts, for powering a commercial operation. The size of the inverter is measured by its maximum continuous output in watts. This rating must be larger than the total wattage of all of the AC loads you plan to run at one time.
Wattage of most AC loads can be determined from a tag or label on the appliance, usually located near where the power cord enters, or from the owners manual. If the inverter is expected to run induction motors, like the ones found in top loading washers, dryers, dishwashers and large power tools, it must be designed to surge, or deliver power many times its rating for short periods of time while these motors start. Standalone inverters are available with two basic power out waveforms: sine wave, and modified sine wave.
Some types of appliances, such as rechargable tools and flashlights, laser printers, copiers, light dimmers and some variable speed tools may not operate on modified wave inverters, and some could actually be damaged. Audio equipment could experience an annoying background buzz. True sine wave inverters are recommended for sensitive equipment.
Grid-Tie Inverters
Grid-tie, or utility intertie inverters convert DC power from PV modules into AC power to be fed into the utility grid. There are two major types of grid-tie inverters: string inverters and low voltage input inverters.
The SMA Sunny Boy, Fronius and Xantrex GT-3 inverters are string inverters. The name "string" comes from the way the PV modules are wired together, in series to achieve a higher voltage. These inverters are designed to run at voltages up to 600 VDC. String wiring is faster to install, more efficient and allows the use of smaller gauge wire. DC voltage this high can be very dangerous and life-threatening, so string inverters should be installed and serviced by qualified electricians only.
A grid-tie PV system uses the utility company, in effect, as its storage battery. When the sun is shining, your electricity comes from the PV array, via the inverter. If the PV array in generating more power than you are using, the excess is sold to the power utility company through your electric meter, by making the meter run backward. When you need more power than the PV array can supply, the utility makes up the difference. This type of system makes the most sense in most cases where you have utility power, because there are no batteries to maintain or replace. Unfortunately, if the utility power goes down, this type of inverter will go off, too, regardless of whether or not the sun is shining.
Dual-Function Inverters
Using a dual-function inverter allows you to sell excess power to the utility, and also maintain a battery bank for standby power in the event of a utility power failure. The Xantrex XW series and the OutBack GFX series inverters are primarily standalone inverters that can function as an intertie inverter at the same time, but with a lower efficiency than an inverter designed for grid-tie only. The new Xantrex XW is a grid-tie inverter designed to provide battery backup when the utility fails. The SMA Sunny Island inverter is designed to work with a Sunny Boy inverter to provide utility intertie with battery backup.
In a typical installation, the inverter is connected to a battery bank, a sub panel for critical loads that will be powered during a power outage and the house load center. If the utility is available, the inverter will supply the house loads from the utility. If the utility fails, the inverter will supply power to the loads from the battery. When the utility is available again, the inverter will switch the loads back to the utility and recharge the batteries. If the batteries become fully charged by another power source such as photovoltaic modules or a wind or hydroelectric generator, excess power may be sold back to the utility in locations where net metering is allowed.
