Inverters

Three factors for consideration when choosing an inverter are:

• Input Vdc - the inverter DC input voltage must match the battery bank voltage;

• Continuous Power - the maximum continuous load run by the inverter;

• Surge current – some loads, such as electric motors, demand more power when they start. All inverters consume energy (tare loss). To counteract tare loss, most inverters offer a sleep mode or low power mode to save energy consumption.

Pure Sine Wave Inverters

Depending on the model, the AC output of an inverter is either a modified or pure sine wave. Modified sine wave power is
suitable for some loads but not for electronics such as home theater systems, high-end televisions and computers. Pure sine
wave output is ideal for sensitive electrical devices due to the low electromagnetic interference level.

All inverters in this section produce 120 Vac, 60 Hz. Some of the inverters may be stacked to power 240 Vac loads or a 120/240 transformer can be used to power 240 Vac loads from a single 120 Vac inverter.

Single Purpose Grid-Tie Inverters

An inverter converts DC or direct current produced by solar modules into AC or alternating current to operate standard household appliances. Besides changing the current, some inverters manage the flow of electricity into and out of batteries.
Single purpose grid-tie inverters do not interact with batteries. They change DC to AC and also disconnect the entire solar system from the utility in the event of a power outage. This is a safety precaution enabling workers to fix the utility lines. Grid-tie inverters are designed to produce high quality, utility-grade AC electricity, offer high efficiency and high reliability.

Multi-Purpose Grid-Tie Inverters

In addition to converting solar power into utility grade electricity for local loads and export, a multi-purpose inverter provides back up power capabilities when utility failures occur. These inverters use batteries for energy storage.

Backup capacity is limited by the size of the battery bank installed with the system. We recommend a minimum 200 Ah @ 48 Vdc battery bank for any multipurpose grid-tie system. Each 100 Ah @ 48 Vdc stores approximately 3.5 kW/hr of usable energy.

In most cases, the back-up power capability of the inverter(s) will not be sufficient to power the entire home. Generally, the most important loads such as communications, refrigeration, lighting, etc., will be re-wired to a sub panel powered by either the utility or the inverter.

Multi-purpose grid-tie systems are complex because batteries, MPPT controller(s), high current switch gear, and changes to a home's AC electrical distribution panel(s) are required.

In addition to the inverters listed here, Alternative Energy assembles complete Power Centers for grid-tie backup.

Off-Grid Inverters

Inverters manage the flow of electricity into and out of the batteries to provide an automatic supply of utility grade AC electricity. Some inverters include a battery charger and transfer switch to charge a battery bank when utility or generator power is available.

Once the batteries are charged, the inverter automatically disconnects from the power source and begins providing AC power to run the loads from the battery bank. The peak load determines the size of the inverter used in a system. For example, 50 amp service at 110 Vac requires a 5500 watt inverter. Several inverters may need to be stacked to provide the required service.