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AC to DC Inverters
The inverter is the heart of your AC solar energy systems. It is an electronic device
that converts direct current (DC) power from batteries or solar panels into alternating
current (AC) power the same as supplied by a utility company. This power is used
to operate lights, appliances or anything that normally operates on power supplied
by the utility company. Inverters come in many varieties, sizes and qualities and
offer various features that specialize them for particular applications.
Inverter types include
Grid-Tie
Grid-Interactive with built in Battery Charging
Stand-Alone Sine wave with built in Battery Charging
Stand-Alone Sine wave
Stand-Alone Modified Sine wave with built in Battery Charging
Grid-Interactive and some Stand-Alone or Off-Grid inverters will have built-in battery
chargers.
Grid-Tie and Grid-Interactive Inverters
Grid-Tie inverters are inverters which will sell electric directly back to your utility
company. Grid-Interactive Inverters sell back to your utility company but also have
battery back up so you will have some electric while your utility company is blacked
out.
There are four ways to approach grid-tie
String Inverter Systems. This is the most efficient, both energy wise and financially
per kilowatt produced. However it is the most expensive to get started with as you
have to buy the inverter and the matched strings of solar panels all up front.
Battery Based Inverter Systems. These systems are less efficient, however they will
provide you with a back up should you loose utility power. Also by shutting down
the utility to the inverter, you can generate your own electric at night to the items
connected to the inverter. Plus, you can add additional solar panels to up your selling
ability.
Micro Inverters. This is the least expensive as you can start off with as little
as one solar panel and one micro inverter at a time. Each time you want to expand,
you add another panel and inverter. These are tied into a combiner box and fed to
your distribution center.
Hybrid Systems. This is where you start with a Battery Based System and later add
a String Inverter System or Micro Inverters to grow you selling capacity.
Stand-Alone Inverters
Stand-Alone inverters are used in Off-Grid applications. The high end inverters will
include a battery charging mode for when the batteries become too low. When this
happens the inverter searches for a utility AC source, if it does not find one it
will attempt to start a standby generator in order to charge the batteries. Almost
all of these inverters are sine wave, however there are some modified sine wave inverters
still available. Since we all seem to use modern day electronics it is advisable
to use a sine wave inverter as opposed to using a modified sine wave inverter. The
only advantage the modified sinewave inverter has is that they are less costly.
Brands we represent...
APOLLO SOLAR · CT SOLAR · ENPHASE · EXELTECH · FRONIUS · KACO · MAGNIUM
Intertie inverters convert DC power from PV modules into AC power to be fed into the utility grid. There are two major types of utility inverters; string inverters and low voltage input inverters. The SMA Sunny Boy, Fronius and Xantrex GT-3 inverters are referred to as 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 guage wire. DC voltage this high can be deadly, so string inverters should be installed and serviced by qualified electricians. A utility-tie PV system uses the utility company as a storage battery. When the sun is shining, your electricity comes from the PV array,
via the inverter. If the PV array is generating more power than you are using, the excess can be sold to the utility (power company) through yor electric meter. If you use more power than the PV array can supply, the utility makes up the difference. This type of system makes the most sense if 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.
Using a multi-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 Outback GFX and Xantrex SW series are primarily stand-alone inverters that can function as an intertie inverter at the same time, but with a slightly lower efficiency than an inverter designed for intertie only. The Outback PS1 and Beacon Power M5 are intertie inverters that are 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, the utility power lines, a standby generator 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.
Stand-Alone 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 stand-alone inverters are available in sizes from 100 watts, for powering notebook computers and fax machines from your car, to 60 kilowatts, for powering a commercial operation. The size of an 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 owner’s 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. Stand-alone inverters are available with two basic power output waveforms: modified square wave (often called modified sine wave) and sine wave. Intertie, multifunction inverters and utility companies deliver a sine wave. Xantrex DR series and Samlex PSE inverters have modified sine wave output with harmonic distortion of around 40%. They are an economical choice in power systems where waveform is not critical. Their high surge capacity allows them to start large motors while their high efficiency makes them economical with power when running small loads like a stereo or a small light. They can power most lighting, televisions, appliances and computers very well. Unfortunately, this type of inverter may destroy some rechargeable tools and flashlights, and laser printers and copiers. They may not allow many laser printers, copiers, light dimmers and some variable speed tools to operate. Equipment with silicon controlled rectifiers (or SCRs) will not operate. Some audio equipment will have a background buzz that may be annoying to music connoisseurs. Exeltech, Xantrex SW Series, SMA Sunny Island and Outback FX inverters are sine wave inverters. Sine wave inverters have a higher cost, but they can operate almost anything that can be operated on utility power. Exeltech sinewave inverters are an excellent choice for power systems running audio or telecommunications equipment and other electronics that are waveform-sensitive. The Outback and Xantrex SW series inverters can be ganged together for up to 36 kW of output and can operate off-grid or intertied. We now carry Samlex Sine Wave PST inverters for a lower cost, small system Sine Wave alternative. Stand-Alone Inverters come in several configurations....
