Inverters use DC power and convert it to 240 V AC ready for use by your household appliances.

Off Grid solar PV systems are traditionally called Remote Area Power Systems (RAPS), and are installations that are typically not connected to the electricity grid. Unused DC power from the solar modules is stored in batteries for use at night time or when the electricity demand is more than what the solar modules are producing (eg peak demand times). All switching and charging is done automatically, although the battery bank may need some occasional maintenance/inspection.

Advantages of an Off Grid system are:

  • No need for batteries, as electricity is not stored but either fed into, or drawn from the electricity grid
  • You will not experience power failures due to the electricity grid going down

Things to be aware of:

  • Batteries may need some regular maintenance and/or inspections
  • The system must be large enough to cater for peak loads - for small systems, this may mean adjusting the way you operate your appliances (change in lifestyle)
  • Peak loads that are much higher than your normal usage (eg welders) can be run by supplementing the system with a generator
  • Off grid systems can also be connected to the electricity grid (if available), and the grid treated like a generator (power input only) - this is not often done as its typically not financially viable
  • BACKUP inverters are also available - these allow a Grid Connect system to operate normally until a grid power failure happens, when the Backup unit instantaneously supplies the loads and switches the grid connect inverter to its own power (off grid) - thereby automatically switching between Grid Connect and Off Grid configuration. The result is a constant uninterrupted power supply for a Grid Connect system.

 

When setting up Off Grid (Remote Area Power Systems, RAPS) systems, several components are requried, these being the PV solar modules, batteries, DC-AC inverter and battery charger. The way these components are connected can differ between Latronics and SMA systems.

Latronics setup functions like this:

  • The PV solar modules charge the batteries through a separate regulator
  • A battery bank stores solar energy during the day for use at night time
  • An AC battery charger is used to charge the batteries from the generator
  • The DC-AC inverter provides power to household appliances


The SMA setup is slightly different to that of Latronics, in that the solar energy produced by the PV modules is converted to 240 V AC power for immediate use or to charge the batteries via the Off Grid inverter which doubles as a battery charger (effectively, the DC-AC inverter is run in 'reverse' to give AC-DC, ie a battery charger).

  • The PV solar modules are coupled to a Sunny Boy or Mini Central to give 240 V AC power
  • The Sunny Island Off Grid inverter/charger either provides AC power (if the PV modules don't produce enough power to supply the loads), or charges the batteries using excess power produced by the PV modules/Sunny Boy or Mini Central system.
  • A battery bank stores solar energy during the day for use at night time
  • The batteries can be charged by a generator by simply connecting it to the Sunny Island.
    This setup means that a separate battery charge regulator and separate AC battery charger are not required.


Both systems work well. SMA caters for very large systems (above 7 kW as numerous inverters can be used in parallel), and also has more options in terms of linking the units with computers for viewing performance data and remote diagnostics. Also, both manufacturers offer wind turbine controllers/inverters for hybrid systems (please contact us if you require these).