Typical External Energy Sources
The Sunny Island enables switching over to the external energy source grid and disconnection from the grid. External energy sources are voltage sources and determine the voltage and frequency of the electricity grid. Typical external energy sources are generators and the utility grid.
Generators as an external energy source
A generator is used as an energy reserve in the off-grid system. If there is insufficient energy available for the loads from AC sources in the stand-alone grid (e.g. PV inverter), the Sunny Island can use the energy provided by a generator.
Possible generators | Explanation |
|---|---|
Autostart generators | These generators are started and stopped with a single contact. This means that the Sunny Island can control the generator directly. |
Generators without an autostart function | These generators do not have electric starting devices. These generators are started via a cable pull or a crank, for example. |
Generators that can be remote-started electrically and do not have their own control system | These generators have 2 control contacts: one contact for the starter and one contact for ignition or for preheating. An external generator control device is necessary. |
The utility grid as an external energy source
With the Sunny Island, you can use the utility grid in various ways:
As an energy reserve
As the main supplier of loads in the stand-alone grid
If the utility grid is the main supplier of the loads, then this is a battery-backup system. If the utility grid fails, the Sunny Island disconnects the stand-alone grid from the utility grid and switches to stand-alone mode. In stand-alone mode, the Sunny Island supplies the stand-alone grid with energy from the battery.
Generators and the utility grid as external energy sources
The utility grid and a generator can also be connected to the off-grid system in combination. This is particularly useful in the event of long-term grid failures where the battery capacity is no longer sufficient to bridge the grid failure after a period of time. In the event of long-term grid failures, you can switch to the generator.
The generator and utility grid cannot feed electricity into the off-grid system at the same time. Therefore, switching between the generator and utility grid operation must be possible. Since the Sunny Island does not have an integrated automatic transfer switch, an external automatic transfer switch is necessary in systems with both a generator and the utility grid connected as external energy sources.
In multicluster systems with the Multicluster-Box 12 (MC-BOX-12.3-20), for example, the Grid-Connect-Box takes on the role of the automatic transfer switch.