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The off grid inverter is the interface between the DC side of the off grid power system and its AC side. Clean energy generators, namely solar electric panels and small wind generators generate DC (Direct Current) electrical power. The off grid home appliances, lighting, air conditioners and heaters are connected to AC (Alternate Current) supply. The inverter, in most cases a pure sine inverter converts the DC power to standard AC power (115V 60 Hz in the US, 230V 50 Hz in Europe).
The off Grid Power System
A basic off-grid system components are:
A renewable energy source (DC power generator)
An inverter; the inverter does not merely convert DC power to AC power, a “smart inverter” also serve as a battery charge controller and as the brain of the entire off grid system. The inverter, on its AC side can be connected to a back-up diesel generator and automatically start the generator and initiate a recharge cycle when the battery bank is depleted, or when the house current consumption is excessive. A good inverter monitors the DC current and voltage as well as the AC current, voltage and delivered power.
The inverter is a cardinal element for the smooth and reliable operation of the off grid system. Choose carefully the inverter from the offering from a well known reputable manufacturer. Look into the following lines in the inverter data sheet:
DC voltage rating: should fit the DC voltage rating of the clean energy source
DC current rating: should be more than the maximum current the renewable energy source can deliver.
Efficiency: should be greater than 90%; a lower efficiency inverter will force you tom buy more solar panels to compensate for the wasted energy. The added solar panels are more expensive than the added cost of a higher efficiency inverter
It is desired to have the battery charge controller integrated into the inverter; it saves external DC wiring and the system is more reliable
It is desired to have more than one DC inputs
It is desired to have a AC connection to the backup diesel generator and to have a command (start up/ shut down) on the generator
It should be possible to monitor all the voltages, currents and power from the inverter front panel and to have automatic protection for over voltage, over current and other mishaps.
It is desired to have a connection to a data link for remote control, remote monitoring and logging
