Off-Grid Systems
Off-grid systems are autonomous utility grids that are fed with energy from various energy generators.
Off-grid systems can consist of the following components:
Components | Description |
|---|---|
PV arrays | A PV array consists of several PV modules that produce direct current from solar energy. |
PV inverter | The PV inverter (e.g. Sunny Boy or Sunny Tripower) converts the direct current produced by the PV array into grid-compliant alternating current and feeds this into the alternating current grid. The PV inverter and the PV arrays must be dimensioned according to the chosen power ( > PV System Design). |
DC/DC charge controller | In an off-grid system, the direct current provided by the PV arrays can be used to charge a battery directly. A charge controller is necessary for this. |
Batteries | Batteries store electrical energy and support the grid when other energy generators are not producing sufficient electricity. If more energy is produced than is consumed, the batteries can be charged again. The capacity, nominal power and battery type must be taken into consideration when designing the batteries ( > Battery-Storage System Design). |
Battery inverter | As a voltage source, the battery inverter (e.g Sunny Island) forms the stand-alone grid. The battery inverter regulates the balance between the energy that is generated and the energy that is used and incorporates a battery, PV array and load management system ( > Working Principle of the Sunny Island Inverter). |
DC fuse | The external DC fuse protects the battery connection lines of the battery inverter. Furthermore, the DC fuse enables DC-side disconnection of the battery inverter. |
Generators | Fuel powered generators (e.g. diesel generators) are often installed to supplement the energy supply when the state of charge of the batteries drops and there is insufficient energy being supplied by the PV array. These generators supply alternating current directly. |
Wind turbine systems | Wind turbine systems convert wind energy into electrical energy and supply alternating current directly. |
Hydroelectric power plants | Hydroelectric power plants use the kinetic energy of water to produce electrical energy. The hydroelectric power plant generators supply alternating current directly or are equipped with inverters to convert direct current into alternating current. |
Off-grid systems can supply individual houses, settlements or even entire villages with electricity.
Various underlying conditions have to be taken into consideration when planning, designing and selecting an off-grid system. The optimum design of an electricity supply system depends on the following factors:
Necessary connected rating
Energy consumption
Type of loads
Utilization period
Underlying meteorological conditions